LIB-MARY, ‘A & M cottzcz. CAMPUS. A45-538-6M-L180 TEXAS AGRICULTURAL EXPERIMENT STATION A. B. CONNER, DIRECTOR COLLEGE STATION, BRAZOS COUNTY, TEXAS BULLETIN NO. 562 MAY 1938 DIVISION OF HORTICULTURE Maturity Studies of Marsh Seedless Grapefruit in the Lower Rio Grande Valley ... . i‘; l-k a Y Agsiculwral i Mechanical College 0f Texas Collage Station, Texas. AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS T4 O. WALTON, President ‘cv w‘ ‘- A good quality grapefruit of full maturity is characterized by a relatively thin rind, regular segments, a large volume of juice, tender flesh, absence of bitterness, and a blending 0f solids to acids to give a tart to sweet taste. The percentage 0f rind was constant in the grapefruit during each of the two seasons investigated. The percentage of rag decreased, and the percentage of juice increased as the seasons advanced“ As the rag decreased, the juice increased. The total soluble solids, as degrees Brix, was approximately constant for all plats. Citric acid decreased, and the ratio of solids to acid increased as the season advanced. In a study of the seasonal changes in fruit from various loca- tions, fruit from widely separated orchards on dilferent soil types and under different soil management matured at approximately the same time. Other factors may possibly exert more influence on maturity of grapefruit than soil type, cultural practices, and increments of age from time of blossoming. The best measures of maturity of grapefruit found thus far are (1) the content of total soluble solids as determined in degrees Brix, (2) the ratio of solids to acids, and (3) the volume of juice. CONTENTS PAGE Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 The Texas Citrus Maturity Laws . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 Studies of Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6 Methods Employed . . . . . . . . . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Study of Criteria of Maturity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Amino Acid Determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 Naringen Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .' . . . . . . . . . . . . 9 Total Solids Determinations on Deaerated and Non-deaerated Juice 10 Variation in the Composition of Juice from the Stem and Blossom End of the Same Fruit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10 Variations Between Samples of Fruit from the Same Tree . . . . . . .. 11 The Electrynx as a Means of Determining the Maturity of Grape- fruit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Effect of Cultural Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 Soil Treatments . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 Varying the Amount of Irrigation Water . . . . . . . . . . . . . . . . . . . . . .. 20 Spray Materials . . . . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 The Effect of Age of Tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Seasonal Changes in Fruit from Various Locations . . . . . . . . . . . . . . . . . . 28 Physical Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Chemical Determinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 37 Summary and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39 BULLETIN NO. 562 MAY 1938 MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT IN THE LOWER RIO GRANDE VALLEY J. F. Wood, Horticulturist, Substation N0. 15, Weslaco, and Harold M. Reed, Horticulturist, Substation No. 3, Angleton. Early season grapefruit is often inferior in edible quality to that harvested in mid-season and later. Texas Citrus Maturity laws prior to 1936 have received considerable adverse comment because they allowed inferior quality fruit to flood the early markets. The‘ majority of the growers would willingly withhold shipments until the fruit is more palatable, but so long as some ship the unpalatable fruit, the industry_will suffer. Al- though early season shipments usually command a high price, the unpalata- ble fruit reduces the demand for the product and lowers the price for some time. Taking the industry as a whole, the first high prices do not offset the later low prices. Texas Citrus Maturity Laws The first citrus maturity law in Texas was passed in 1927. The require- ments for grapefruit were a minimum of 10 per cent total solids and a minimum ratio of solids to acid of '7 : 1 in the juice. This law required the testing to be done at the packing sheds (11). Considerable loss was occasioned to both growers and shippers when fruit already in the sheds was condemned. A new law was drafted in 1929 requiring testing on samples taken from the groves (12). This law, known as House Bill No. 500, set up the following legal standards: Juice of Seedy Grapefruit Minimum solids Minimum ratio (degrees Brix*) (Brix to acid) 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.5 : 1 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.0 : 1 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.5 : 1 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.0 : 1 Seedless grapefruit was required to have a minimum solids of 10° Brix and a minimum ratio of 7 : 1 until November 15, after which time the requirements were the same as for seedy fruit. All testing ended De- cember 15. During the first year of operation it was found that fruit meet- ing the requirements was often low in juice. Consequently the Commis- sioner of Agriculture, by the power invested in him by this law, set up the following juice requirements: *The terms Brix and Brix readings as used in this publication refer to the total soluble solids content of the juice. 6 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Fruit size ' (No. fruit per Fruit diameter Juice requirement standard box) (inches) per fruit (c. c.) 126 . . . . . . . . . . . . . . . . . . . . 3% . . . . . . . . . . . . . . . . . . . . 115 ' 96 . . . . . . . . . . . . . . . . . . . . 3% . . . . . . . . . . . . . . . . . . . . 135 80 . . . . . . . . . . . . . . . . . . . . 4 . . . . . . . . . . . . . . . . . . . . 145 70 . . . . . . . . . . . . . . . . . . . . 4% . . . . . . . . . . . . . . . . . . . . 150 64 . . . . . . . . . . . . . . . . . . . . 4% . . . . . . . . . . . . . . . . . . . . 170 54 . . . . . . . . . . . . . . . . . . . . 4% . . . . . . . . . . . . . . . . . . . . 190 46 . . . . . . . . . . . . . . . . . . . . A 4% . . . . . . . . . . . . . . . . . . . . 207 36 . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . 220 28 . . . . . . . . . . . . . . . . . . . . 5% . . . . . . . . . . . . . . . . . . . . 235 In the early part of the 1934 citrus season there was considerable criticism again of the shipping of immature fruit from the Rio Grande Valley. As a consequence, an amendment to House Bill No. 500 was drawn up and passed by the legislature in January, 1935 (13). This law put both seedy and seedless grapefruit on the same basis and set up the following re- quirements: Minimum solids Minimum ratio (degrees Brix) (Brix to acid) 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7.2 : 1 1O . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7.0 . 1 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.8 : 1 11.5 and above . . . . . . . . . . . . . . . . . . . . . .. 6.5 : 1 The juice requirements were increased 10 c. c. for the 126 size, 15 c. c. for the next four sizes, and 20 c. c. for the last four sizes. Slight differ- ences have been made in the juice requirements for seedy and seedless fruit in order to compensate for the space occupied by the seed in the first type. The maturity law as amended in 1935 is in effect at the present time (1937). The determination of such complex matters as taste and quality in citrus fruit is very difiicult. The changes which have been made in the Texas Citrus Maturity law, as knowledge was gained concerning tests of pala- tability of grapefruit, have reduced the percentage of fruit of inferior quality offered for sale. It is hardly likely that a maturity law can be devised that will entirely prevent the shipment of immature grapefruit. However, it seems possible that a law can be so devised that the percentage of imma- ture fruit ofiered for sale Will be negligible. Studies of Maturity During the seasons 1934-35 and 1935-36, studies were made (1) to accum? ulate fundamental data on the physical and chemical changes occurring in Texas Marsh Seedless grapefruit during the ripening season which might serve as criteria of maturity, (2) to investigate the effects of various MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 7 cultural practices on the maturity of the fruit, and (3) to substantiate or improve the existing maturity standards and tests. Methods Employed Ten fruits, two from each cardinal compass point of the tree and two inside fruits, were considered an adequate sample from a single tree. Thirty fruits, ten from each of three trees, were considered an adequate sample from a single plat. Check plats of comparable trees, in close proximity to their respective treated plats, were used for comparison. The data reported in this bulletin were secured during the 1934-35 an_d . 1935-36 fruit seasons. All’ analyses were made within twenty-four hours from the time the sample was taken. The juice was extracted with an aluminum hand- powered reamer and strained through cheesecloth. The fruit and various parts of the fruits xvvere weighed on a balance which was accurate to one gram. The specific gravity of the fruits was determined by calculation "from their displacement of water at room temperature. The volume of juice in cubic centimeters was measured and its weight was calculated from its specific gravity. Thickness in millimeters represented the aver- age of three measurements. The total soluble solids were determined by means of Brix hydrometers graduated in one-tenth divisions and_standard- ized at 175° C. Brix determinations were made on deaerated juice except in a few cases where comparisons were made with non-deaerated juice. The acidity was determined by duplicate titrations with standard sodium A hydroxide solution. Sugars in the juice were determined before and after inversion with hydrochloric acid by the Munson and Walker method (1). Sucrose was calculated by difference. Amino acid titrations were made ‘by the A. O. A. C. method of Sorenson (2) using formaldehyde. The pH ' and buffer indexes were determined with a Leeds and Northrup calomel _ electrode “acidity meter.” The buffer index was determined by the method , of Van Slyke (15.) The “electrolytic value” of the fruit was determined by means of a Westinghouse Electrynx. A tasting committee tasted each sample of fruit taken for analysis in an attempt to correlate all empirical J tests with edibility. 1p A study of the effects of various cultural practices on maturity was made 3' during the 1934-35 season, and a study of the seasonal changes of fruit ;_. from various locations in the Lower Rio Grande Valley was made during K: the 1935-36 season. A description of all of the plats on which the fruit was grown is given in Table 1. t: STUDY OF CRITERIA OF MATURITY Amino Acid Determinations p Amino acid determinations were made on the juice of several grapefruit ~ of varying maturity (Table 2). The highest quantity was obtained on the i juice from the greenest fruit and the lowest quantity on the juice from . the ripest fruit. These results indicated that the test might be of value in 8 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION .00 0202i . . . 0.62.03 E02 200mm MHZ r05 i000 .2. .006 mmmfi mm >02 00009.52 mm 28 032003 200.02 a 00¢ 00000.5 -000 flGQJQMGm 200cm .0 8 mmfi . . 5000009 cmfifimcm . h .003 .3 .000 00020 0mm, 0% 00000000000050.0010“ h 0 . . . 03 000m 030E002 dmmfi r52. .005 32000» E02 > 00w 00 fiawfi hbwnm .000 0200550 20 0002200 .02 mhd ow 200m 532005 >02 b 0cm 0 202$ LO H 2E K .3 =03 002 . . . . . . . . . . . . 02022 0.922002 00c 00060000: 0030.5 EEG 000000080000 000.3 .0003 >03 0032005 .02: E 055E000 .00 05:2. 0020 200E E02 LEE 00 200m Q0000sm .m A. $025050 $20000 00000:: 0Z mm Jsmuw 0023b 20.52 3 >20 01002? 0Q M0 E 2E X $00M 00G mmmfi . . . . . . . . . . . .0€0.m 0Q 0000b mmmfi m2 flwfiwwkM/wwflwwwswmfiwtfimrrAmwmflfi 0000090» 05w E02 h 00m &mc?m2.mwfiiwow~k0a7m 000m i0 00D 0000005 :80 0.60 000 0000 w mw 032002 .0302 20.82 m2 00c ommwwwmi .20 u)? 2E m0. ~ 220% .5 E mmmfi . . . . . . . . . . . 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Total Acid and Amino Acid titrations on juice from fruit of varying size and maturity . (10 cc. sample used; determinations made in duplicate.) _ _ Amino acid Ratio titratable Description of fruit Acid titre titre acid to (cc.) (cc.) amino acid About 2 inches in diameter, green and hard . . . . . . 24.25 1.83 13.2 : 1 About 3 inches in diameter, green and hard . . . . . . 18.75 1.48 12.7 : 1 About 3 inches in diameter, green and hard . . . . . . 18.23 1 .50 12.1 : 1 About 3 inches in diameter, but partially colored and less hard . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17.16 1.38 12.3 :1 Naringen Tests Naringen is the bitter principle of grapefruit. Since the bitterness disappears as the season advances, it was thought that a simple test for naringen might be of use in determining maturity. The reaction of chemically pure, powdered naringen dissolved in water, in water, acidified with citric acid, and in 47.5% alcohol acidified with citric acid was tested with various reagents (Table 3). None of the reactions were characteristic enough to be of any value. Baier (3), working with California and Arizona Marsh Seedless grapefruit, concluded that neither amino nitrogen nor naringen content held any promise as criteria of maturity. Table 3. in three difierent solvents (1934-35) The ‘visible reaction obtained with various reagents acting on naringen in solution \Vater 47.5% alcohol Reagent Water acidified with acidified with citric acid citric acid Hydrochloric acid . . . . . . . . . . . . none none none Sulfuric acid . . . . . . . . . . . . . . . . . none none none Nitric acid . . . . . . . . . . . . . . . . . . none none none Ammonium hydroxide . . . . . . . . lemon yellow color lemon yellow color lemon yellow color Starch . . . . . . . . . . . . . . . . . . . . . . none none none Starch-iodine ._ . . . . . . . . . . . . . . . decolorized none none Ammonium nitrate. . .. . . . . . . . none none none Calcium acetate . . . . . . . . . . . . . none none none Potassium sulfate . . . . . . . . . . . . none none none P1cr1c acid Methylene blue . . . . . . . . . . . . . . Methylene blue + hydrogen peroxide Ferrous sulfate . . . . . . . . . . . . . . Ferric sulfate . . . . . . . . . . . . . . . . Oxalic acid Tannic acid . . . . . . . . . . . . . . . . . Lead acetate . . . . . . . . . . . . . . . . Zinc + hydrochloric acid . . . . . . Magnesium nitrate . . . . . . . . . . . Stannous chloride . . . . . . . . . . . . yellow color faint blue color none light brown color light brown color none none none none none none yellow color faint blue color none light green color light green color none none _ vvhite precipitate none none none yellow color faint blue color none light green color light green color none none _ vvhite precipitate none none none 10 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Total Solids Determinations on Deaerated and Non-deaerated Juice Total solids determinations were made on nine samples of juice before and after deaeration. It was assumed that the determination on the dea- erated juice was the more nearly correct since the buoyant effect of the entrapped air was eliminated. Brix readings of the non-deaerated juice were sometimes higher and sometimes lower than those of the deaeratedfi juice, ranging from 4.20 to +.10 degrees Brix (Table 4). These results indicate that the slight variability of the determinations of the Brix of non- deaerated juice may just as likely be due to the error in reading the Brix v hydrometer as to the buoyant effect of the entrapped air. However, care should be exercised in extracting the juice to avoid excessive whipping and consequent entrapping of air. For this reason it is advisable to use hand- powered rather than motor-driven juice extractors. Table 4. Determination of Brix on deaerated juice and non-deaerated juice (1934) Sample Date Dejaliaircéetcd Non-iiueiizrated Difference (degrees Brix) (degrees Brix) (degrees Brix) 35 October 22 . . . . . . . . . . . . . . . . . .. 10.80 10.65 ——.15 37 October 22 . . . . . . . . . . . . . . . . . .. 10.70 10.60 ~—.10 39 October 22 . . . . . . . . . . . . . . . . . .. 10.90 10.98 +.08 14A October 29 . . . . . . . . . . . . . . . . . .. 11.30 11.30 0.00 16A October 29 . . . . . . . . . . . . . . . . . .. 11.30 11.20 ——.10 18A October 29 . . . . . . . . . . . . . . . . . .. 11.00 11.00 0.00 35 November 6 . . . . . . . . . . . . . . . . .. 10.80 10.90 +.10 37 November 6 . . . . . . . . . . . . . . . . .. 10.90 11.00 +.10 39 November 6 . . . . . . . . . . . . . . . . .. 11.20 11.00 —.20 Variation in the Composition of Juice from the Stem and Blossom End of the Same Fruit Grapefruit from Plat Y were picked on two different dates, halved, and the juice of each half analyzed separately (Table 5). Taking an average of the analyses for the two dates, the juice from the blossom end of the fruit was higher in solids, in ratio of Brix to acid, in sugar content, and in pH; but it was lower in acid and in buffer index. In addition it was slightly more sweet to the taste than the juice from the stem end. Haas and Klotz (9) found that under California conditions, the juice from the blossom end of oranges, grapefruit, and lemons, contained more total sugars than that from the stem end of the fruit. Baker (4), working with Texas grapefruit, found the same relation and also reported that the juice from the center portion of the fruit was higher in acid and Brix than the juice from the outer portion of the fruit. MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 11 Table 5. Chemical composition of juice from the stem-end and blossom-end of fruit. (Plat Y-—untreated, 10 years old, 1934.) _ Stem-end Blossom-end Both Determination ’ Av. Nov. 8 Nov. 22 Av. Nov. 8 Nov. 22 Av. Soluble solids (degrees Brix) . . . . . . . . . . . . . .. 11.00 10.95 10 98 11.00 11.05 11 O2 11.00 Citric acid anhydrous (%). 1.70 1.64 1.67 1.49 1.44 1 46 1.56 Brix to acid ratio . . . . . . . . 6.47 6.68 6.57 7.38 7.67 7 55 7.05 Invert sugar (%) . . . . . . .. 4.20 4.20 4 20 4.48 4.30 4 39 4.30 Sucrose (%) . . . . . . . . . . . .. 2.66 2.52 2.59 2.76 2.76 2.76 2 68 Total sugars (%) . . . . . . .. 6.86 6.72 6.79 7.24 7.06 7 15 6 90 pI-Il . . . . . . . . . . . . . . . . . . .. 3.20 3.15 3.18 3.20 3.20 3.20 3 19 Buffer indexl . . . . . . . . . . . . 1.013 1.140 .076 1.013 1.073 1.043 058 Taste*1 . . . . . . . . . . . . . . . . . SS-S A-T T-SS SS-S SS SS-S SS-S VSB NB VSB-N VSB NB VSB-N VSB-NB Invert sugar to acidl (ratio)... . . . . Sucrose to acidl (ratio). . . Total sugars to acidl (ratio) . . . . . . . . . . . . . . Invert sugar to sucrosel (ratio) . . . . . . . . . . . . . . Citric ac'd anhydrous? (%) Invert sugar? (%) . . . . . . . . Sucrose? (%) . . . . . . . . . . . . . . . . . . . . Total sugars? (%)........ 62.36 64.83 63.60 05.82 63.89 64.86 64.22 . 2.56 2.51 . 2.99 3.01 2.76 .56 1.54 1.55 .85 1.92 1.89 1.72 4 4 3 1 .10 4.06 4.86 1 13 KOO-Ni QOOUF‘ vb i-‘M >P~ U! \—l r5 Q0 O0 v-k U1 [Q N) 1On wet basis. 20m dry basis. _ _ *A-acid, SA-slightly acid, T-tart, SS-slightly sweet, S-sweet. B-bitter, SB-slightly bitter, VSB-very slightly bitter, NB-non-bitter. These results indicate that the composition of the juice from grapefruit is not uniform throughout the fruit and that all of the_juice from both halves of the cut fruit must be used in order to obtain a representative sample of juice for analysis. Variations Between Samples of Fruit from the Same Tree Ten-fruit samples were picked from each of the cardinal compass points of a tree, and one ten-fruit sample from the inside of the same tree. The acidity, volume of juice, Brix and Brix to acid ratio determined from each of these, were compared to a check sample consisting of two fruits from each of the cardinal compass points and two fruits from the inside of the same tree (Table 6). Table 6. Maturity tests on juice of fruit picked from difierent locations on same tree. (1935-36) Number Juice in Acid Brix to_ Location on tree of fruits 3,(frui)ts Brix (per cent) acid ratio cc. Inside . . . . . . . . . . . . . . . . . . . . . . . . . 10 496 9.30 1.38 6.74 North side . . . . . . . . . . . . . . . . . . . . . 10 504 9.45 1.50 6.30 South side . . . . . . . . . . . . . . . . . . . .. 10 418 9.90 1.50 b 60 East side . . . . . . . . . . . . . . . . . . . . . . 10 500 9.50 1.51 6.29 West side . . . . . . . . . . . . . . . . . . . . . . 10 494 9.50 1.46 6.51 Average of five locations . . . . . . . . . . . . . . . . . . . 428.4 9.53 1 .47 6 48 Average sample——8 outside, 2 in- _side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 496 9.80 1.52 6.45 'V8!‘l3l1l0I1 from average sample. . . . . . . . . . . . . . + 13.6 + .27 + .05 — .03 12 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION The variation among the five ten-fruit samples was greater than the variation between the average of these samples and the check sample. This is interpreted to mean that a ten-fruit sample taken in this manner is as reliable as a comparable fifty-fruit sample. Baker (4) found differences in maturity of fruit from the north and south sides of the tree and from the inside and outside of the tree. The above results indicate that the method used in sampling for the maturity tests gave samples which were fairly representative of the fruit on the tree. The Electrynx as a Means of Determining the Maturity of Grapefruit An attempt was made to determine by means of an “Electrynx” the relation‘ between the electrolytic value of the whole fruit and its maturity. This instrument, manufactured by Westinghouse, is described as a sensi- tive microammeter, which, when used with electrodes of dissimilar metals, is capable of measuring the relative electrolytic effect of the substance being tested. The instrument is equipped with these six electrodes given in the order of their electromotive force: aluminum, iron, nickel, tin, copper and silver. Aluminum, the most negative electrode, is considered zero, and silver, the most positive electrode, 2.047. The instrument scale read pl. from zero to 100. The readings, when divided by five, give the approximate number of microamperes. The electrodes were inserted to the same depth each time through the rind of whole grapefruit. The readings were taken one minute after insertion. The data are summarized in Table 7 . When a reading slightly exceeded the 100 mark on the scale it was recorded as 100+. It will be noted from the average value of fruit with a reading of 100 or less that there is no relation between the readings and the date of harvest. No relation was shown between the readings and any other factor studied. These results are in agreement with those of Baker (4), who concluded that the measurement of electrical conductivity of grapefruit juice as measured by a modified Wheatstone soil bridge offers little promise as a means of determining grapefruit maturity. Gordon (8), however, reported that the Electrynx could be used to measure the ripeness of sugar cane. A few readings were made on extracted grapefruit juice, but these were more variable than on the whole fruit. Table 7. Determinations on fruit by means of the Electrynx. (1935-36) i Per cent of Average value No. fruits with of fruits with Date Plat Electrodes fruits readings greater readings of 100 tested than 100 or less Dec. 9, 1935 Shary . . . . . . . Nickel and aluminum. 30 0.0 60.83 Jan. 2, 1936 Shary . . . . . . . Nickel and aluminum. 30 0.0 68.70 Dec. 9, 1935lEngelman. . . Nickel and iron . . . . .. 2e 50.8 92.66 Jan. 2, 1936 Engelman. . . Nickel and iron . . . . . . 3O 0.0 80.27 Dec. 13, 1935 La Feria. . . . Nickel and iron . . . . .. 3O 10.0 79.96 Jan. ' 6, 1936 La Feria. . . . Nickel and iron . . . . . . 3O (‘.0 79.57 MATURITY STUDIES or MARSH SEEDLESS GRAPEFRUIT ' i 13 EFFECT OF CULTURAL TREATMENTS Soil Treatments The various soil treatments had been applied in the spring, for two con- secutive years (1933 and 1934). Plats of five trees each, of Marsh Seedless grapefruit, were used and samples were taken from the middle three trees. - An untreated check plat in close proximity to the treated plats was used for comparison. Sulfur and 9-27-9 fertilizer were applied to the soil at the rate of 1O pounds per tree, iron sulfate at the rate of 5 pounds per tree, and manure at the rate of 20 tons per acre (Tables 8 and 16). The sea- sonal averages of the total solids, citric acid, and solids to acid ratio are based on 120 fruits, comprised of 4 samples of 30 fruits each. Table 8. Effect of soil treatments on the juice. (1934-35) Soluble Citric _ solids acid Brix_ to Date Plat Treatment (degrees anhydrous ac1_d Taste* Brix) (per cent) ratio Oct. 17 27B 5 lbs. 9-27-9 per tree . . . . . . . 10.75 1.56 6.89 . . . . . . . . . . Nov. 14 27B 5 lbs. 9-27-9 per tree . . . . . . . 11.51 1.43 8.05 T NB Dec. 17 27B 5 lbs. 9—27—9 per tree . . . . . . . 11.19 1.34 8.35 S NB Jan. 18 27B 5 lbs. 9—27—9 per tree . . . . . . . 11.35 1.30 8.73 S NB Av. . . . . 27B 5 lbs. 9—27—9 per tree . . . . . . . 11.20 1 40 8.00 SS-S NB Oct. 17 29B 5 lbs. iron sulfate per tree. . . 10.95 1 .53 7. 16 . . . . . . . . . . Nov. 14 29B 5 lbs. iron sulfate per tree. . . 11.01 1 .40 7.86 T-SS NB Dec. 17 29B 5 lbs. iron sulfate per tree. . . 11.19 1.40 7.99 . NB Jan. 18 29B 5 lbs. iron sulfate per tree. . . 11.35 1.24 9.15 S NB _ Av. . . . . 29B 5 lbs. iron sulfate per tree. . . 11.12 1.39 8.00 SS NB Oct. 17 31B 10 lbs. sulfur per tree . . . . . .. 10.88 1.59 6.84 . . . . . . . . .. Nov. 14 31B 10 lbs. sulfur per tree . . . . . . . 11.01 1.54 7. 15 T VSB Dec. 17 31B 10 lbs. sulfur per tree . . . . . . . 11.14 1 .42 7.84 NB Jan. 18 31B 10 lbs. sulfur per tree . . . . . .. 11 .20 1.37 8. 18 SS-S NB Av. . . . . 31B 1O lbs. sulfur per tree . . . . . .. ll .05 1 .48 7.47 -S VSB-NB Oct. 17 33B 20 tons manure per acre... . . 10.95 1 .58 6.30 . . . . . . . . . . Nov. 14 33B 2O tons manure per acre... . . 11.41 1 .46 7.82 T-VSB-NB Dec. 17 33B 20 tons manure per acre. . . . . 11 .39 1.36 8.38 N Jan. 18 33B 20 tons manure per acre... . . 11.55 1.35 8.56 S NB Av. . . .. 33B 20 tons manure per acre. . . .. 11.32 1.43 7.92 -S VSB-NB Oct. 17 35B Untreated check . . . . . . . . . . . . 10.65 1.55 6.87 . . . . . . . . . . Nov. 14 35B Untreated check . . . . . . . . . . . . 10.81 1.44 7.51 T-SS NB Dec. 17 35B Untreated check . . . . . . . . . . . . 11.05 1.37 8.06 . NB Jan. 18 35B Untreated check . . . . . . . . . . . . 11 . 15 1.32 8.45 S t; NB Av. . . . . 35B Untreated check . . . . . . . . . . . . 10.91 1.42 7.68 SS NB *A-acid_, SA-slightly acid, T-tart, SS-slightly sweet, S-sweet, B-bitter, SB-slightly bitter, VSB-very slightly bitter, NB-non-bitter. 14 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Table 9. Physical measurements on fruits from normally irrigated plats (Averages on 30-fruit sample, 1934-35.) Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan 7 Jan. 29 Av l" . . ' Weight fruit (grn.) . . . . . . . . . . 337.0 363 .5 358.5 407.5 409.5 422.2 421.2 388.48 Volume fruit (cc.) . . . . . . . . . . . 414.0 432.0 423.5 485.0 505.2 520.2 500.0 468.55 Thicknessrind(m1n.) . . . . . . .. 7.2 6.7 6.7 6.7 7.6 7.2 6.9 7.0 Weight rind (gm) . . . . . . . . . .. 89.1 91.0 88.6 101.4 114.6 111.8 109.7 100.88 Weight ofrag (gm) . . . . . . . .. 80.1 81.0 75.0 73.9 77.3 82.4 74.9 77.80 Volume of juice (cc.) . . . . . . . . 137.0 159.0 160.0 184.0 175.6 189 .3 200.8 172.24 Specific gravity fruit . . . . . . . .. 0.814 0.841 0.846 0.840 0.810 0.811 0.842 0.829 Specific gravity juicel. . . . . . . . 1.043 1.043 1.045 1.046 , 1.046 1.045 1.044 1.0445 Weight juice (grim) . . . . . . . . . . 142.89 165.83 167.20 192.46 183 .67 197.81 209 .63 179.90 Rind? %3) . . . . . . . . . . . . . . . .. 26.43 25.03 24.71 24.88 27.98 26.48 26.04 25.96 a 3) . . . . . . . . . . . . . . . . .. 23.76 22.28 20.92 18.13 18.87 19.51 17.78 20.02 Juice? (%3) . . . . . . . . . . . . . . . . . 42.40 45.62 46.63 47.23 44.85 46.85 41.92 46.30 17.5° C. lBased on temp. 0f €——— 17.5° C. 2These _d0 not total 100% because 0f loss of seeds. 33y weight. Table 10. Chemical analyses of fruits from normally irrigated plats (Averages on 30-fruit sample, 1934-35.) Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan 7 Jan. 29 Av Soluble solids (degrees Brix). . 10. 79 10.82 11.11 11.42 11.45 11.21 11.05 11.12 Citric acid anhydrous (%) . . . . 1.65 1.50 1.53 1.50 1.49 1.44 1 .30 1.48 Brix to acid ratio . . . . . . . . . .. 6.54 7.21 7.26 7.61 7.68 7.78 8.50 7.51 Invert sugar (%1) . . . . . . . . . .. 4.31 4.51 4.52 4.61 4.64 4.61 4.77 4.56 Sucrose ((701) . . . . . . . . . . . . . .. 2.58 2.60 2.47 2.73 2.73 2.66 2.62 2.62 Total sugars (701) . . . . . . . . . .. 6.89 7.11 6.99 7.34 7.37 7.27 7.39 7.19 Amino acid titra. as N (%1) . . . . . . . . . . . . . . . . . . . . 0.0242 0.0204 0.0229 0.0210 0.0239 0.0224 pH . . . . . . . . . . . . . . . . . . . . . . .. 3.10 3.20 3.10 3.10 3.10 3.20 3.40 3.17 Bufier index . . . . . . . . . . . . . . . . 1.014 1.140 1.140 1.140 1.140 1.111 0.909 1.084 Taste" . . . . . . . . . . . . . . . . . . . . A T-SS T-A T SS-S SS-S SS-S T-SS B V B NB NB NB NB NB VSB-NB Invert sugar to acidl (ratio). . 2.61 3 .01 2.95 3.07 3.11 3 .25 3.67 3.08 Sucrose to acidl (ratio) . . . . .. 1 56 1.73 1.61 1.82 1.83 2.17 2.02 g 1.77 Total sugars to acidl (ratio). . 4.17 4.74 4.57 4.89 4 .95 5.05 5.68 4.86 Invert sugar to sucrosel (ratio) 1 .67 1 .73 1.83 1 .65 1 .70 1 .32 1 .82 1.74 Citric acid anhydrous (%2). . . 15.29 13 .86 13.77 13.13 13.01 12.84 11.76 13 .88 Invert sugar(%2) . . . . . . . . . . . . 39 .94 41.68 40. 68 40.37 40.52 41.12 43 .17 41.06 Sucrose ('71,?) . . . . . . . . . . . . . . . 23.91 24.02 21.23 23 .90 23 .84 23.73 23.71 23 .47 Total sugar (%2) . . . . . . . . . .. 63.85 65.70 61.91 64.27 64.36 64.85 66.88 64.54 Amino acid titration as N2. .. . . . . . . . . . . . . . . . . .. 0.218 0.179 0.200 0.187 0.216 0.200 lOn a wet basis. 20m a dry basis. _ _ *A—acid, SA-slightly acid, T-tart, SS-slightly sweet, S-sweet, B-bitter, VSB- very slightly bitter, NB-non-bitter. MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT Table 11. Physical measurements of fruit from heavily irrigated plats (Averages on 30-fruit sample, 1934-35.) Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan. 29 Weight fruit (gm) . . . . . . . . .. 347.0 379.0 343.0 389.4 400.6 409.1 414.3 383.2 Volume fruit (m) . . . . . . . . . .. 432.0 457.0 411.5 465.8 494.0 508.5 495.1 466.27 Thickness rind (mm.)........ 7.5 6.9 6.6 6.8 7.5 7.3 6.9 7.07 Weight rind (gm) . . . . . . . . .. 94.5 97.6 87.4 99.4 111.7 110.9 108.6 101.4 Weightrag(gm.)........... 84.0 87.6 72.4 68.3 73.5 78.2 75.5 77.07 Volume juice ('00.) . . . . . . . . .. 134.0 161.0 149.0 178.0 167.5 183.7 196.6 167.11 Specific gravity fruit . . . . . . . . . 0.803 0.829 0.833 0.835 0.810 0.804 0.836 0.821 Specific gravity juicel . . . . . . . . 1.043 1.044 1.045 1.046 1.046 1.046 1.046 1.0451 Weight juice (gm) . . . . . . . . .. 139.76 168.08 155.70 186.18 175.20 192.15 205.64 174.64 Rind? (%3) . . . . . . . . . . . . . . . .. 27.23 25.75 25.48 25.52 27.88 27.10 26.21 26.46 Rag? (‘i703 . . . . . . . . . . . . . . . . .. 24.20 23.11 21.10 17.53 18.34 19.11 18.22 20.11 Juice? (%3) . . . . . . . . . . . . . . . .. 40.27 44.34 45.39 47.81 43.73 46.96 49.63 45.57 175° C. lBased on temp. of — 7 5° C ?These do not total 100% because of loss of seeds. 3B3‘ Weight. Table 12. Chemical analyses of fruit from heavily irrigated plats (Averages on SO-fruit sample, 1934-35.) Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan. 29 Soluble solids (degrees Brix).. 10. 72 10.91 11.24 11 52 11.53 11.34 11.35 11.23 Citric acid anhydrous (%). . .. 1.62 1.50 1.5¢7 1.51 1.50 1.41 1.31 1.48 4 Brix to acid ratio . . . . . . . . . .. 6.62 7.27 7J6 7.66 7.69 8.04 8.66 7.58 Invert sugar (%>1 ......... .. 4.3L 4 .49 4.55 4.69 4.69 4.59 4.79 4.5a Sucrose (%)1 . . . . . . . . . . . . . .. 2.76 2.74 2.49 2.64 2.88 2.82 2.74 2.72 Total sugars (%)1 . . . . . . . . . .. 7.07 7.23 7.04 7.33 7.57 7.41 7.53 7.40 Amino acid t-itra. as N (%)1.. . . . . . . . . . . . . . . . . . . 0.1-29 0.0214 0 0231 0.0190 0.0243 0.0221 pH . . . . . . . . . . . . . . . . . . . . . . .. 3.10 3.20 ‘$.10 3.15 3.00 3.20 3.35 3.15 Buffer index . . . . . . . . . . . . . . .. 1.014 1.140 1.140 1.073 1.3 3 1.111 0.952 1.104 Taste“ . . . . . . . . . . . . . . . . . . . . A 1193 T-SS T-SS SS-S SS-S S T-SS B SB NB NB NB NB NB VSB-NB Invert sugar to acidl (ratio). . 2.66 2.99 2 .90 3.11 3.13 3 .26 3.66 3.09 Sucrose to acicll (ratio) . . . . . . 1_.70 1.83 1.58 1.75 1.92 2.00 2.09 1.83 Total sugars to acid‘ (ratio). . 4.36 4.82 4.48 4.85 5.05 5.26 5.75 5.00 Invert sugar to sucrosel (ratio) 1 .56 1 . 64 1 .82 1 .78 1.63 1 .63 1 . 75 1 .68 Citric acid anhydrous? (%). .. 15.11 13 .74 13.96 13.11 13 .01 12.43 11.54 13.27 Invert sugar? (%) . . . . . . . . . .. 40.20 41.15 40.48 40.71 40.68 40.48 42.20 40.84 Sucrose? (%) . . . . . . . . . . . . .. 25.74 25.11 22.15 22.92 24.98 24.87 24.15 24.27 Total sugars? ( . . . . . . . . . . . 65.94 66.26 62.63 63.63 65.66 65.35 66.35 65.12 Amino acid titration as N?(%) . . . . . . . . . . . . . . . . . . 0.204 0.186 0.200 0.168 0.214 0.194 1On a wet basis. 20m a dry basis. *A-aci_d, SA-slightly acid, T-tart, SS-sllghtly sweet, S-sweet, B-bltter, VSB-very slightly bitter, NB-non-bitter. 16 ‘BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Table l3. Physical measurements of fruit from lightly irrigated plats (Averages on SO-fruit sample, 1934-35.) Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan 7 Jan. 29 Av Weight fruit (gm) . . . . . . . . . . 359.0 339 .0 360.4 411.8 440.2 419 .9 394. 0 389 .18 Volume fruit (cc.) . . . . . . . . . . . 437.5 396.0 432.6 484.7 535. 8 511.7 470.5 466.97 Thicknessrind 7.1 6.5 6.9 6.8 7.6 7.3 6.9 7.01 Weight rind (gm.) . . . . . . . . . .. 91.3 84.0 93.0 102.3 119.6 111.6 104.2 100.85 Weight rag (gm) . . . . . . . . . . .. 82.6 66.5 73.1 77.9 84.0 82.3 71.9 76.90 Volume juice (cm) . . . . . . . . . . . 148.0 163.0 159.0 193.0 194.0 191.7 190.6 177.04 Specific gravity fruit . . . . . . . . . 0.820 0.856 0.833 0.849 0.821 0.820 0.837 0.833 Specific gravity juice‘ . . . . . . . 1.044 1.045 1.046 1.046 1.047 1.046 1.046 1.0457 Weight juice (gIIL) . . . . . . . . . . 154.51 170.33 166.31 201.87 203.11 200.51 199.36 185.13 Rind (%1 . . . . . . . . . . . . . . . .. 25.43 24.77 25.80 24.84 27.16 26.57 26.44 25.91 Rag (313) . . . . . . . . . . . . . . . . . . 23.00 19.61 20.28 18.91 19.08 19 .59 18.24 19.75 Juice (%1) . . . . . . . . . . . . . . . .. 43 50.24 46.14 $9.02 46.14 47.75 50.60 47.56 17.5° C. *Based on temp. of —-i— 17.5° C. lBy weight. Table l4. Chemical analyses of fruits from lightly irrigated plats (Averages on 30-min sample, 1934-35.) l0 ® wC/RO Q Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan 7 Jan. 29 Av Soluble solids (degrees Brix).. 10.92 11.17 11.54 11.52 11.62 11.54 11.45 11.39 Citric acid anhydrous (%). . . 1.65 1.64 1.64 1.53 1.58 1.52 1.43 1.57 Brix to acid ratio . . . . . . . . . .. 6.62 6.81 7.04 7.53 7.35 7.59 8.01 4.27 Invert sugarl (%) . . . . . . . . . .. 4.59 4.81 4.74 4.72 4.69 4.87 5.01 4.77 Sucrose1(%) . . . . . . . . . . . . . .. 2.40 2.47 2.50 2.66 2.83 2.70 2.46 , 2.57 Total sugarsl (%) . . . . . . . . . .. 6.99 7.28 7.24 7.38 7.52 7.57 7.47 7.35 Amino acid titra. as N1 (%). . . . . . . . . . . . . . . . . . . . 0.0235 0.0231 0.0221 0.0210 0.0243 0.02 p 1 . . . . . . . . . . . . . . . . . . . . . .. 3.10 3.10 3.10 3.10 3.00 3.20 3.20 3.11 Buffer indexl . . . . . . . . . . . . . .. 1.014 1. 03 1.140 1.140 1.303 1.111 1.111 1.16 Taste“ . . . . . . . . . . . . . . . . . . . . i A T‘LS SS SS SS-S SS-S cS-S T-S B SB NB NB NB NB NB VSB-N Invert sugar to acidl (ratio). . 2.79 2.93 2.89 3.08 2.97 3.20 3 .50 3. 4 Sucrose to acidl (ratio) . . . . . . 1.45 1.51 1.52 1.74 1.79 1.78 1.71 1 64 Total sugars to acidl (ratio). . 4.24 4.44 4.41 4.82 4.76 4.98 5.22 4.68 Invert sugar to sucrosel (ratio) 1.91 1.95 1.90 1.77 1.66 1.80 2.04 1.86 Citric acid anhydrous? (%). .. 15.11 14.68 14.21 13 .28 13.60 13.17 12 .49 13.79 gvert sugar? (8%) . . . . . . . . . . . 42.03 43.06 41.07 40.98 40.36 42.20 43.76 41.92 ucrose? ('70) . . . . . . . . . . . . . .. 21.97 22.11 21.66 23.09 24.35 2340' 21.48 22.58 Total sugars? ('70) . . . . . . . . . . . 64 .00 65. 17 62.73 64.07 64.71 65.60 65.24 64.70 Amino acid titra. as N2 (%).. . . . . . . . . . . . . . . . . . . 0.204 0.201 0.190 0.182 0.212 0.19 1On wet basis. 2On dry basis. *A-acid, SA-slightly acid, T-tart, SS-slightly sweet, S-sweet, B-bitter, VSB-very slightly bitter, NB-non-bitter. MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 17 Table 15. Chemical analyses of fruit from plats receiving different spray treatments (Average on 30-fruit sample, 1934-35.) Soluble Citric solids acid Brix Date Plat Treatment (degrees anhydrous to acid Taste* Brix) (per cent) (ratio) Nov. 14 20A 1.5% lime sulfur . . . . . . . . . .. 11.41 1.67 6.83 T-SS NB Dec. 17 20A 1.5% lime sulfur . . . . . . . . . .. 11.42 1.59 7.18 T-SS NB Jan. 18 20A 1.5% lime sulfur . . . . . . . . . .. 11.55 1.43 8.01 S NB Av... . . 20A 1.5% lime sulfur . . . . . . . . . .. 11.46 1.56 7.35 SS NB Nov. 14 22A Untreated check. . . . . . . . . . .. 11.21 1.63 6.88 SA VSB Dec 17 22A Untreated check . . . . . . . . . . . . 11.47 1.56 7.35 SS NB Jan. 18 22A Untreated check . . . . . . . . . . . . 11.55 1 . '10 8.25 S NB Av. . . .. 22A Untreated cheek . . . . . . . . . .. 11.41 1.53 7.46 T-SS VSB-NB Nov. 14 26A Soluble phosphate . . . . . . . . . . 11.31 1.62 6.98 NB Dec. 17 26A Soluble phosphate . . . . . . . . . . 11 .47 1.44 7.96 SS NB Jan 18 26A Soluble phosphate . . . . . . . . .. 11.45 1.46 7.84 NB Av. . . . . 26A Soluble phosphate . . . . . . . . . . 11.41 1.50 7.61 SS NB Nov. 14 28A Untreated check . . . . . . . . . . . . 11.51 1.66 6.93 T-A NB Dec. 17 28A Untreated check . . . . . . . . . . .. 11.57 1.64 7.05 SS-S NB Jan. 18 28A Untreated check . . . . . . . . . . . . 11.65 1.48 7.87 S NB Av. . . . . 28A Untreated check . . . . . . . . . . . . 11.57 1 .59 7.28 SS NB Nov. 14 30A Tank mix oil . . . . . . . . . . . . . . . 11.01 1.61 6.84 T VSB Dec 17 30A Tank mix oil . . . . . . . . . . . . . .. 11.02 1.53 7.20 SS NB Jan. 18 30A Tank mix oil . . . . . . . . . . . . . . . 11.25 1.47 7.65 SS-S NB Av... .. 30A Tank mix oil . . . . . . . . . . . . . .. 11.09 1.53 7.25 -SS VSB-NB Nov 14 32A Zinc sulfate and lime. . . .. . .. 11.11 1.49 7.46 T NB Dec 17 32A Zinc sulfate and lime . . . . . . . . 11.30 1.60 7.06 S NB Jan 18 32A Zinc sulfate and lime . . . . . . . . 11.35 1.45 7. 83 SS-S NB Av. . . . . 32A Zinc sulfate and lime . . . . . . . . 11.25 1.51 7.45 SS NB *A-acid, SA-slightly acid, T-tart, SS-slightly sweet, S-svveet, B-bitter, SB-slightly bitter, VSB-very slightly bitter, NB-non-bltter. 18 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Java ash... ..-._.-. . . . . . . . . . . . . . . . . - . . . . . ~ . - . - - . . - . . - 899T mmwo $.m+ Qqlwmgrr $4? mwf 5.3 m5o§moo+ fifiolwms £4 5 3 .. .30 3m?» Ewwwuwwmw W S o+ woélmmél m?» EA a: . . . . . 5555a ofiwbzw QEN Q miolfioslwowolmms mm; $0.: ..............=¢iEv_Ew_. om . . . . . . . . . . . . . . . . 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MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 19 The seasonal averages of the Brix on fruit grown on all of the treated plats were higher than that of the untreated plat (Figure 1). Manure gave the greatest increase and sulfur the least increase. There was an increase in the seasonal average of the Brix to acid ratio over the check plat on all of the treated plats with the exception of the sulfur plat which showed a decrease. It will be noted from Figure 1 that the Brix readings of all of the fruit from the treated plats were higher throughout the season than were those of the untreated plat. All of the samples contained more than the required minimum solids of 10 on the first date analyzed. The general trend of the solids was upward as the season advanced. The iron sulfate plat was the only one above the required 7 : 1 ratio on the first date analyzed (Fig- ure 2). On the second date, all treatments except sulfur gave a higher solids to acid ratio than the check plat and remained as high or higher throughout the season. - The data indicate that applications of 9-27-9 fertilizer, iron sulfate, and manure hastened maturity in this experiment, whereas sulfur retarded maturity. It is believed that the conclusions drawn are justified since the various treatments had a cumulative effect on the Brix and on the ratio as the season advanced. A study of the data in Table 8 shows that the Brix to acid ratio of the 9-27-9 plat was .02 higher than the check plat on the first date and .28 higher on the last date; iron sulfate was .29 higher 11.55 r Z r e/ “U ".45 - I \ ' y 4 F “1/ 11.35 - fl H25 - ll.|5 - ll.O5 - DEGREES BRIX I035 IQBS- I065 - - - OCT :7 NOV. l4 050.11 JANJB SAMPLING DATES FIGURE 1. Seasonal changes in the total soluble solids of juice as influenced by various soil treatments. 20 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION 9. 3O - . / e10 4”} 5.40 - '4“/ 9'} 'P‘ _,.__-__- __._.—i-— 7.80 - 7.50 ~ IZO~ BPJX TO ACID RATIO Eager w uov‘. n4 050.17 JANEIB SAMPLING DATES FIGURE 2. Seasonal changes in the total soluble solids to acid ratio of juice as influenced by various soil treatments. to .70 higher, and manure .57 lower to .11 higher. The exceptional sulfur treatment decreased from .29 higher to .27 lower. The trends, though vari- able, are evident. The soil treatments were still having an effect at the time the tests were made; otherwise the changes in ratio would have had a tendency to be more nearly alike. This was not a static condition which caused one lot to start maturing sooner, but appeared to be in eflect throughout the season, as indicated by the fact that there was a spread in the ratio during the period of time covered by the tests. In the interpre- tation of the data throughout this bulletin, the seasonal averages of the Brix and Brix to acid ratio were used as criteria of maturity. Varying the Amount of Irrigation Water Three plats of five trees each were used in this test, samples being taken from the three middle trees. One plat received heavy irrigations,’ one plat light irrigations, and the check plat received normal irrigations. Although the water was not measured onto the plats, it is estimated from experience that a normal irrigation consists of three acre inches, that a light irrigation approximates one and one-half acre inches, and a heavy irrigation approx- imates five acre inches. The plats were irrigated May 19, June 30, August 16, and during the period December 6 to 1'7. The following physical meas- urements were made on each fruit of each sample: size, weight, rind thick- ness, weight of rind, weight of rag, volume of juice, and specific gravity of the whole fruit. In order to minimize the error incurred in sampling, the data on each fruit size and weight are not used comparatively. With the exception of the specific gravity, the remainder of the physical data "WYW"~1:“2fi"Y"'“'a"\j-rr ~-—- wv gyzwvvgwqnrik,» , .. . . . MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 21 are expressed in per cent by weight. Seven samples were taken from these plats at approximately two-week intervals from October 22, 1934, to January 29, 1935 (Tables 9 to 14 inclusive). The seasonal averages are based on the individual measurements of 210 fruits (Table 16). There was a slight increase in the average total solids of fruit from the heavily irrigated plat over those from the normal check and a very slight widening of the average Brix to acid ratio (Tables 9, 10, 11, 12), whereas fruit from the lightly irrigated plat showed an increase in average Brix but a narrowing in the Brix to acid ratio (Tables 9, 10, 13, 14). There was a slight increase in specific gravity 0n the heavily irrigated plat and a slight decrease on the lightly irrigated plat as compared with the check. Total solids, acid, and solids to acid ratio were affected very slightly by heavy irrigation. Light irrigation apparently deterred maturity to a cer- tain extent in this case. The lightly irrigated plat had less rind, less rag, and more juice than the check plat, whereas the heavily irrigated plat showed the reverse to be true. Fruit from all plats were above the solids requirement of 10 on the first date analyzed (Figure 8). With the exception of the first date, both heavy and light irrigations gave higher Brix readings throughout the season than did the check plat. The Brix of fruit from the lightly irrigated plat was consistently higher than that of the other plats. After December 21, the Brix readings on fruit from all plats were lowered, perhaps partly be- cause the only irrigations applied during the period of analysis were be- tween the December 4 and December 21 readings. H7O - ,fl'}\_~ X H5O F'-*- ——--——--'\\ L~___ E p» 4 i \ (Q A, Y?! z ~ ~z~ -——-——-—"-- m H.130 » ‘b (~94; m v +6 m O t! mo ,1’ /' o ’ ’ m / / 0 10.90- I!’ IOJO ‘ ‘, <-’ OCT Z2 NOV. G NOV l9 ADECA» DEC, 2| JAN. 7 JAN- 2.9 SAMPLlNG DATES FIGURE 3. Seasonal changes in the total soluble solids of juice as influenced by varying the amount of irrigation water. Figure 4 shows the general seasonal trend of the solids to acid ratio to be upward. None of the plats had reached the legal requirement of a ratio of 7 : 1 on the first date analyzed. On the second date fruit from the light irrigation plat was the only one with a ratio below 7 : 1. On the third date and thereafter to the close of the test, all plats showed ratios above 7 : 1. References to the ratings of taste in Tables 10, 12 and 14, show fruit from all three plats to be acid and bitter on the first date 22 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION analyzed. Fruit from all plats became less acid and less bitter on second date and by the third date bitterness had disappeared and was r‘ _ encountered again during the test. Fruit from the light irrigation p had the highest Brix and the lowest ratio throughout the season, with -; exception of the first date, and the acidity was consistently higher tha was that of the other plats. The increased acidity resulted in a ratio than that of either the heavy or normal irrigation plats, and it ma j, be assumed, in this instance, that light irrigation deterred maturity. Th effect of heavy irrigation, when compared to that of normal irrigation, w? so slight as to be negligible. i‘ 8.70 - 8.50 - 5.30 8J0 T 9O 7.70 - ‘Z50 7. 3O - 7.IO ' BPJX TO ACID RATlO 6. 9O 6.70 ember. zz NOV. c NOV. as 050.4 oclo. 21 JAN.7 JAfzs" SAMPLING DATES FIGURE 4. Seasonal changes in the total soluble solids to acid ratio of juice as influenced by varying the amount of irrigation water. The general seasonal trend of invert sugar was upward with the excep- l tion of the light irrigation plat which decreased slightly during the middle I of the season. The amount of sucrose in fruit from all plats was erratic V2 and did not show any definite seasonal trend. Total sugars were somcwhate variable but showed a general upward seasonal trend. Amino acid titrations ‘j were very erratic and did not show any seasonal trend. The pH determina- tions were variable with a very slight upward trend. The buffer indexes were approximately constant until near the end of the test and then in- i creased, with the exception of fruit from the lightly irrigated plat which decreased slightly. The ratio of invert sugar to sucrose was erratic and‘ did not show any definite seasonal trend. The ratios of invert sugar to acid, sucrose to acid, and total sugars to acid, though somewhat variable, showed general seasonal increases. Spray Materials The various spray treatments were applied with a power sprayer in October, 1934. Five trees were sprayed in each instance and data taken from the three middle trees. Lime-sulfur was applied in a 1.5 per cent solution. The soluble nitro-phosphate spray was made by dissolving 20 pounds of 11-48-0 fertilizer in 100 gallons of water. The zinc-lime spray was made by MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 23 dissolving 4 pounds of zinc sulphate and 4 pounds of hydrated lime in 100 gallons of water. The oil spray was of the tank-mix type and conformed to Smith’s grade 4 (10). It was applied in a two per cent solution. Two 5 untreated check plats in close proximity to their respective treated plats were used for comparison (Tables 15 and 16.) A spray consisting of 2 f pounds of iron sulphate in 100 gallons of water did considerable damage to l the foliage and fruit. The fruits from this plat were so severely injured that no attempt was made to analyze them. Fruit from the plats receiving tank-mix oil and zinc-lime sprays showed a decrease in the average Brix as compared with the check. The other treatments produced only slight differences in average Brix. The lime- § sulfur, soluble nitro-phosphate and tank-mix oil produced a narrowing in the average Brix to acid ratio, and the zinc-lime plat showed a xvidening. L Differences between Brix readings .for the lime-sulfur, soluble nitro- " phosphate, and their check plat (22 A) were even less than the difference between the two checks (Table 15, Figure 5). The tank-mix oil plat had the lowest Brix readings of any of the plats. All plats showed a total 7" solids of 11 or higher and met the required 6.8 : 1 ratio throughout the 5;; test. The ratio of total solids to acid on the zinc-lime plat was highest on November 14 and much lower on December 17 (Figure 6). The soluble nitro-phosphate plat had a high ratio on December 17 and a low ratio on a; January 18. The differences in ratios on the other treated plats and their respective check plats were small. From these data it was concluded that very slight if any effect on the maturity of the fruit was caused by the ‘i various spray materials. ll. 7O - i u. so ILSO - HAO - H.150 ILZO mo » _ /1 __J [LOO NOV. a4 ’ 0:047 JAaae SAMPLING DATES DEGRDEES smx —¢--1—-_—-u¢ FIGURE 5. Seasonal changes in the total soluble solids of juice as influenced by fall applications of various spray materials. 24 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION 8.40 - 6.20 - 7.60 r 7.40 - 720' BRlX TO ACID RATIO TOO - uoum » 050.»? JAEJB sAMPLlNG DATES FIGURE 6. Seasonal changes in the total soluble solids to ratio of juice as influenced by fall applications of various spray materials. THE EFFECT OF AGE OF TREE This test Was conducted in order to determine the effect of age of the tree on maturity of fruit. Three trees were used in each plat. Both physical and chemical measurements were made at two-week intervals from October 25, 1934, to February 6, 1935. The data obtained represent the measurement on the dates specified of 210 fruits, comprising seven samples of 30 fruits each. Neither plat of trees had received any differential treat- ment. One lot of trees, designated as “young,” was 10 years of age, and theother lot, designated as “old,” was 15 years of age. The two plats were located on the Experiment Station property in separate orchards ap- proximately one-fourth mile apart on the same soil type (Tables 16, 17a, 17b, 18a and 18b). Fruit from the 15-year-old trees averaged less rind, more rag, less juice, and a lower specific gravity than that from the 10-year-old trees. During the period of the test the seasonal average of the total solids, acid, and solids to acid ratio, showed that on any given date fruit from the older trees was more mature than the fruit from the younger trees. MATURITY STUDIES QF MARSH SEEDLESS GRAPEFRUIT 25 Table 17a. Physical measurements of fruit from trees 10 years old (Plat Y——averages on 30-fruit sample, 1934-35.) Determination Oct. 25 Nov. 8 Nov. 22 Dec. 13 Dec. 31 Jan. 15 Feb. 6 Av Weight fruit (gm) . . . . . . . . .. 295.0 349.0 360.0 392.0 431.0 385.0 417.0 375.57 Volume fruit (ca) . . . . . . . . . . . 357.0 414.0 423.0 471.0 531.0 461.0 502.0 451.28 Thickness rind (mm.) . . . . . . .. 6.5 6.5 6.3 6.8 7.2 6.5 7 1 6.7 Weight rind (gm.) . . . . . . . . . .. 76.5 88.5 92.0 101.0 114.5 101.0 114.7 98.31 Weight rag (gm. . . . . . . . . . .. 65.6 66.5 71.0 67.6 72.2 65.7 71.3 68.55 Volume juice (cc) . . . . . . . . . . . 127.0 163.0 166.0 183 .0 204.0 190.0 201.0 176.28 Specific gravity fruit . . . . . . . . 0.826 0.842 0.851 0.834 0.811 0.835 0.830 0.832 Specific gravity juicel . . . . . . . . 1.044 1.044 1.044 1.045 1.045 1.044 1.044 1.0442 Weight juice (gm) . . . . . . . . . . 132.58 170.17 173 .30 191.23 213.18 198.36 209.84 184.07 Rind o? . . . . . . . . . . . . . . . .. 25.93 25.35 25.55 25.76 26.56 26.23 27.50 26.17 Rag (7702) . . . . . . . . . . . . . . . . .. 22.23 19.05 19.72 17.24 16.75 17.06 17.09 18.25 Juice (%2) . . . . . . . . . . . . . . . .. 44.94 48.75 48.13 48.78 49.46 51.52 50.32 49 .01 17.5° C. lBased on temp. of — _ 17.5° C. lBy weight. Table 17b. Physical measurements of fruit from trees 15 years old (Plat 35—~averages 0n ISO-fruit sample, 1934-35.) Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan. 7 Jan. 29 Av. Weight fruit (gm) . . . . . . . . . . 337.0 363.5 358.5 407.5 409.5 422.2 ' 421.2 388.48 Volume fruit (cc.) . . . . . . . . . . . 414.0 432.0 423 .5 485.0 505.2 520.2 500.0 468.55 Thicknessrindhnm.) . . . . . . .. 7.2 6.7 6.7 6.7 7.6 7.2 6.9 7.0 Weightrind(gm.)........... 89.1 91.0 88.6 101.4 114.6 111.8 109.7 100.88 Weight rag (gm). 80.1 81.0 75.0 73.9 77.3 82.4 74.9 77.80 Volume juice (cc.) . . .. 137.0 159.0 160.0 184.0 175.6 189.3 200.8 172.24 Specific gravity fruit... ... 0.814 0.841 0.846 0.840 0.810 0.811 0.842 0.829 Specific gravity juicel . . . . . . . . 1.043 1.043 1.045 1.046 1.046 1.045 1.044 1.0445 Weight juice (gm.) . . . . . . . . . . 142.89 165.83 167.20 192 .46 183.67 197.81 209.63 179.90 Rind (%2) . . . . . . . . . . . . . . . .. 26.43 25.03 24.71 24.88 27.98 26.48 26.04 25.96 Rag (91-2) . . . . . . . . . . . . . . . . .. 23.76 22.28 20.92 18.13 18.87 19.51 17.78 20.02 Juice %2) . . . . . . . . . . . . . . . .. 42.40 45.62 46.63 47.23 44.85 46.85 41.92 46.30 bl 17.5° C. lBased on temp. of ——-—- 17.5° C. “By weight. 26 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Table 18a. Chemical analyses of fruits from trees l0 years old (Plat Y——averages on 30-fruit sample, 1934-35.) Determination Oct. 25 Nov. 8 Nov. 22 Dec. 13 Dec. 31 Jan. 5 Feb. 6 Av Soluble solids (degrees Brix).. 10.84 10.97 10.98 11.15 11.11 11.05 10.99 11.01 Citric acid anhydrous (%). . .. 1.64 1.60 1.54 1.55 1.44 1.41 1.32 1.50 Brix to acid ratio . . . . . . . . . .. 6.61 6.86 7 13 7.19 7.72 7.84 8.32 7.38 Invert sugar (9701) . . . . . . . . . .. 4.44 4.34 4.25 4.15 4.09 4.31 4.45 4.29 Sucrose (9701) . . . . . . . . . . . . . .. 2.44 2.71 2.64 2.76 3.05 2.83 2.56 2.71 Tot-al sugars (8701) . . . . . . . . . .. 6.88 7.05 6.89 6.91 7.14 7.14 7.01 7.00 Amino acid titra. as N (751).. . . . . . . . . . . . . . . . . .. 0.0240 0.0223 0.0189 0.0220 0.0217 0.0217 pHl . . . . . . . . . . . . . . . . . . . . . .. 3.15 3.20 3.18 3.20 3.20 3.25 3.40 ~ 3.22 Butler indexl . . . . . . . . . . . . . .. 1.073 1.013 1.106 1.013 1.111 1 176 0.909 1.057 Taste*1 . . . . . . . . . . . . . . . . . . . . A SS-S T T-SS T S SS-S T-SS NB VSB NB NB NB NB NB NB Invert sugar to acidl (ratio). . 2.71 2.71 2.76 2._68 2.84 3.06 3.37 2.86 Sucrose to acidl (ratio) . . . . .. 1.49 1.69 1.71 1.79 2.12 2.01 1.94 1.81 Total sugars to acidl (ratio). . 4.20 4.41 4.47 4.46 4.96 5.06 5.31 4.63 Invert sugar to sucrose-l (ratio) 1.82 1.60 1.61 1.50 1.34 1.52 1.58 1.58 Citric acid anhydrous (913). .. 15.13 14.58 14.02 13 .90 12.96 12. 76 12.01 13.62 Invert sugar (%‘3) . . . . . . .1 . . 40.95 39.56 38.70 37.22 36.81 39.00 40.49 38.96 Sucrose (%2) . . . . . . . . . . . . . .. 22.50 24.70 24.04 24.75 27.45 25.61 23.23 24.61 Total sugars (%2) . . . . . . . . . .. 63.45 64.26 62.74 61.97 64.26 64.61 63.72 63.57 Amino acid titration as N (%2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.218 0.200 0.170 0.199 0.197 0.196 lOn wet basis. 20m dry basis. *A-acid, SA-slightly acid, T-tart, SS-slightly’ sweet, S-svieet, ‘B-bitter, VSB~very slightly bitter, NB-non-bitter. Table 18b. Chemical analyses of fruits from trees 15 years old (Plat 35——averages on SO-fruit sample, 1934-35.) Determination Oct. 22 Nov. 6 Nov. 19 Dec. 4 Dec. 21 Jan. 7 Jan. 29 Av Soluble solids (degrees Brix). . 10.79 10.82 11.11 11.42 11.45 11.21 11.05 11.12 Citric acid anhydrous (%). . . 1.65 1.50 1.53 1.50 1.49 1.44 1.30 1.48 Brix to acid ratio . . . . 6.54 7.21 7.26 7.61 7.68 7.78 8.50 7.51 Invert sugar (%1) . . . . . . . . . .. 4.31 4.51 4.52 4.61 4.64 4.61 4.77 4.56 Sucrose (%1) . . . . . . . . . . . . . .. 2.58 2.60 2.47 2.73 2.73 2.66 2.62 2.62 Total sugars (%1) . . . . . . . . . .. 6.89 7.11 6.99 7.34 7.37 7.27 7.39 7.19 Amino acid t-itra. as N (%1). . . . . . . . . . . . . . . . . . . . 0.0242 0.0204 0.0229 0.0210 0.0239 0.0224 pHl . . . . . . . . . . . . . . . . . . . . . .. 3.10 3.20 3.10 3.10 3.10 3.20 3.40 3.17 Bufier indexl . . . . . . . . . . . . . .. 1.014 1.140 1.140 1.140 1.140 1.111 0.909 1.084 Taste“ . . . . . . . . . . . . . . . . . . . . A T-SS T-A T SS-S SS-S SS-S T-SS B VSB NB NB NB NB N VSB-NB Invert sugar to acidl (ratio). . 2.61 3.01 2.95 3 .07 3.11 3.25 3.67 3.08 Sucrose to acidl (ratio) . . . . . .. 1.56 1.73 1.61" 1.82 1.83 2.17 2.02 1.77 Total sugars to acid! (ratio). . 4.17 4.74 4.57 4.89 4.95 5.05 5.68 4.86 Invert sugar to sucrosel (ratio) 1.67 1.73 1.83 1 . 65 1.70 1.32 1.82 1.74 Citric acid anhydrous (%2). . . 15.29 13.86 13.77 13.13 13.01 12.84 11.76 13.88 Invert sugar (%2) . . . . . . . . . .. 39.94 41.68 40.68 40.37 40.52 41.12 43.17 41.06 Sucrose (%2) . . . . . . . . . . . . . .. 23.91 24.02 21.23 23.90 23.84 23.73 23.71 23.47 Total sugars (%2) . . . . . . . . . .. 63.85 65.70 61.91 64.27 64.36 64.85 66.88 64.54 Amino acid titra. as N (%2).. . . . . . . . . . . . . . . . . .. 0.218 0.179 0.200 0.187 0.216 0.200 1On wet basis. 2On d basis. _ *A-aci , SA-slightly acid, T-tart, SS-slightly sweet, S-sweet, _ B-bitter, VSB-very slightly bitter, N B-non-bitter. MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 27 Although the analyses of samples from the two plats were not made on the same dates, the time elapsing between analyses was relatively short, and it is believed that very little error is incurred by comparing the separate dates (Tables 17a, 17b, 18a, and 18b). The Brix readings on both plats were above the minimum requirement of 10 on the first dates analyzed (Figure 7). After the first readings in November, the Brix readings from the older trees remained higher than those from the younger trees. The general trend of the Brix on both plats was upward until the middle of December and downward after that time. SAMPLING DATES H 500411". 22 NOV. s NOV. l9 050.4 050.21 JAN.T JAN. 29 >< E n30 d) U) u; 11.10 - m a m i’) m noxao O lofro é oer zs wove NOV. zz Deena nectar LIAN.5 FEB.6 SAMPLING DATES FIGURE 7. Seasonal changes in the total soluble solids of juice as influenced by tree age. The Brix to acid ratios of both plats were below the minimum require- Ament of 7 : 1 on the first dates analyzed (Figure 8). On the second date and thereafter the fruit from the older trees passed the requirements. The fruit from the younger trees did not reach the requirement until the third date analyzed. With the exception of one date in January, the ratio from the old tree plat was consistently higher than that from the young tree plat. It may be concluded from these data that the fruit from the older trees matured first and was of relatively higher maturity throughout the test. Invert sugar in the fruit from Plat 35 (old trees) showed a general up- ward seasonal trend, whereas it showed a downward trend in the fruit from Plat Y (young trees) until the latter part of the season and then an upward trend. The percentage of sucrose was erratic and showed no definite sea- sonal trend. Total sugars in fruit from Plat 35, though somewhat variable, showed an upward trend, whereas fruit from Plat Y showed no definite seasonal trend. The amino acid titrations were quite variable with no trend shown. The pH showed a rather indefinite but slightly upward trend. The buffer indexes were approximately constant until near the end of the season when they decreased. The ratios of invert sugar to acid, sucrose to acid, and total sugars to acid, though somewhat variable, showed an upward trend. There was no definite trend in the ratio of invert sugar to sucrose. The bitterness disappeared from the fruit from the old-tree plat 28 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION SAM PLING DATES a agCT. Z2 NOV.6 NOV. l9 DEC. 4- DEC. 2| JAN.7 JAN 29 8.40 - 6.00 - 7.60 > "ZZO BR\X TO ACID RATIO 6.80 - 6.40 OCT. 2s NOVB NOV. 22 DEC. 1a 05oz: JAN.5 Fzas SAM PLING DATES FIGURE 8. Seasonal changes in the total soluble solids to acid ratio of juice as influenced by tree age. on November 19. Fruit from the young-tree plat, though not showing bitterness on the first date, was slightly bitter on the second date. The bitterness disappeared from this fruit before November 22. The acidity, as recorded by taste, tended to become less as the season advanced, although there was a variation in tartness during the latter part of the test. SEASONAL CHANGES IN FRUIT FROM VARIOUS LOCATIONS l Physical Measurements Plats designated as Alamo, La Feria, Mission, and Engelman were the ones used in this study for the 1935-36 season (see Table 1 for the location of these plats). The results of Plat Alamo are based on three determinations on the dates specified and represent the average of the individual measurements of 90 fruits (Table 19). Fruit from this plat was harvested by mistake before the work planned was completed; hence only three readings could be taken. The results of the other three plats are based on seven determinations on the dates specified and represent the averages of the individual measure- ments of 210 fruits (Tables 20, 21, and 22). In order to facilitate inter- pretation, the results from all plats are expressed in per cent by weight. MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 29 Table l9. Physical measurements of fruit from plat Alamo (Averages on 30-fruit sample, 1935-36.) Determination Oct. 18 Oct. 24 Nov. 1 Av. i‘ ei ht fruit (gm) . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 406.20 406.06 375.76 396.00 hic nessrind(mm.) . . . . . . . . . . . . . . . . . . . . . . . . .. 7.6 7.9 7.3 7.6 eight rind (gm) . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 110.33 110.46 104.09 108.29 u eight rag (gm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100.93 108.40 86.60 98.64 * oiume juice (cc_.)_ . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 168.80 163.33 174.16 168.76 epific gpavity Juicel . . . . . . . . . . . . . . . . . . . . . . . . . . 1.039 1.039 1.039 1.039 elght Julce (gm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175.38 169.69 180.95 175.34 in ('73) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27.16 27.20 27.91 27.34 ag ('76?) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24.84 26.69 23.04 24.90 u1ce(%2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.17 41.78 48.15 44.27 f' 17.5° c. i lBased on temp. of —-i— 1 17.5° C. E_ ZBy weight. Table 20. Physical measurements of fruit from plat La Feria A) (Averages on 30—fruit sample, 1935-35.) i Determination Oct. 18 Oct. 24 Nov. 1 Nov. 14 Nov. 25 Dec 13 Jan 6 Av _' tfruit (gm) . . . . . . . . .. 373.96 393.63 408.23 413.93 448.46 404.83 450.23 413.32 _= essrmd (mm. 7.2 7.1 7.1 7.1 7.4 7.0 7.4 7.18 rind (gm.) . . . . . . . . . . . 100.40 103.16 109.03 106.30 122.26 106.30 124.13 110.22 Bight rag (gm.) . . . . . . . . . . . 91.73 106.06 102.50 100.30 98.50 82.63 83.73 95 .06 olume juice (cc_.) . . . . . . . . . . . 153.13 160.40 168.86 184.23 206.56 195.23 216.87 183.61 1 ific gravity Juicel . . . . . . . . 1.040 1.040 1 .040 1 .040 1.040 1 .040 1.040 1.040 ‘eight Juice (gm) . . . . . . . . .. 159.25 166.81 175.61 191.59 214.82 203 03 225.54 190.95 y... (31,?) . . . . . . . . . . . . . . . .. 26.84 26.20 26.70 25.68 27.26 26.25 27.57 26.66 V; (%2) . . . . . . . . . . . . . . . . . . 24.52 26.94 25.10 24.23 21.96 20.41 18.59 22.99 ‘gm ' (%2) . . . . . . . . . . . . . . . . . 42.58 42.37 43.01 46.26 47.90 50.15 50.09 46.19 i 17.5° c .: lBased on temp. of ——— ‘ _ 17.5° C. ‘lBy weight. _ Table 21.‘ Physical measurements of fruit from plat Mission F (Averages on EEO-fruit sample, 1935-36.) Determination Oct. 14 Oct. 21 Oct. 28 Nov. 12 Nov. 22 Dec 9 Jan. 2 Av 'ht fruit ggm.) . . . . . . . . .. 310.15 306.13 317.23 326.33 356.73 374.26 365.90 336.67 s-w essrin (mm.). 10.4 9.4 9.5 8.6 8.7 8.9 8.6 9.15 i t rind (gm). .. 115.96 105.70 109.86 110.20 111.30 119.86 118.50 113.05 ght rag (gm). 84.93 85.43 86.60 83.60 84.63 76.23 71.00 81.77 .1: juice (cc.). . . . 99.53 91.93 99.43 118.66 134.33 153.10 153.10 121.44 = ific gravity juicel. 1.045 1.043 1.043 1.042 1.042 1.042 1.043 1.042 y; juice (g 104.00 95.88 103.70 123.64 139.97 159.53 159.68 126.54 =~ (%?). 37.38 34.52 34.63 33.76 31.20 32.02 32.38 33.57 ' (%2) . . . . . . .. 27.38 27.90 27.29 25.61 23.72 20.36 19.40 24.28 j ~- (%?) . . . . . . . . . . . . . . . .. 33.53 31.32 32.68 37.88 39.23 42.62 43.64 37.58 R i 17.5° c. lB-ased on temp. of ———— 17.5° C. YBy weight. ' 30 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Table 22. Physical measurements of fruit from plat Engelman (Averages on 30-fruit sample, 1935-36.) Determination Oct. 14 Oct. 21 Oct. 28 Nov. 12 Nov. 22 Dec. 9 Jan. 2 Av. Weight fruit (gm) . . . . . . . . . . 354.20 350.53 366.23 374.23 376.10 402 .46 387.53 373 .04 Thickness rind (mm.) . . . . . . .. 7.5 7.4 7.7 7.0 7.2 7.5 7.3 7.3 Weight rind (gm) . . . . . . . . . . . 100.06 99.93 107.66 103.10 105.03 111.46 107.47 104.95 Weight rag (gm.) . . . . . . . . . . . 72.76 82.13 83 .00 82 .50 77.73 75.63 67.60 77.33 Volume juice (cc.) . . . . . . . . . . . 145.66 143 .00 151.83 169.63 174.10 193.30 191.10 166.94 Specific gravity juicel . . . . . . . . 1.040 1.040 1.043 1.039 1.039 1.039 1.039 1.0398 Weight juice (gm) . . . . . . . . . . 151.48 148.72 158.35 176.24 180.88 200.83 198.55 173.58 Rind (£702) . . . . . . . . . . . . . . . . . 28.24 28.50 29.39 27.54 27.92 27.69 27.73 28.13 Rag (‘Z/Ifl) . . . . . . . . . . . . . . . . .. 20.54 23.43 22.66 22.04 20.66 18.79 17.44 20.72 Juice (%2) . . . . . . . . . . . . . . . .. 42.76 42.42 43.23 47.09 48.09 49.00 51.23 46.53 17.5° C. lBascd 0n temp. 0f 17.5° C. 28y weight. The seasonal average of the rind ranged from 26.66% for La Feria to 33.57% for Mission. The rag ranged from 20.72% for Engelman to 24.90% for Alamo. The juice ranged from 37.58% for Mission to 46.53% for Engelman. It will be noted that the La Feria plat, which received no irrigation, had the least rind and a high content of juice, which is in agreement with the irrigation tests previously discussed. The Mission plat This was to be expected since this plat bloomed two months later than the others and consequently showed the greatest rind and the least juice. was not as _far advanced. The proportion of rind was relatively constant with the exception of fruit from Plat Mission (Figure 9). This fruit had a consistently thick rind while that from Plat La Feria a consistently thin rind throughout the test. The general trend of the percentage of rag was upward on all plats from the first to the second dates, but downward thereafter (Figure 10). With the exception of one reading in December, fruit from Plat Mission had a consistently higher proportion of rag than fruit from the other plats. The proportion of rag of fruit from Plat Engelman was consistently lower than that of the other plats. The trend of the juice content was downward from the first to the second dates but definitely upward thereafter throughout the test on all plats (Figure 11). juice than the other plats. study, giving 24 paired comparisons. the rag was 23.064% with a standard deviation of 3.111. Plat Mission shows a consistently lower percentage of Plats La Feria and Engelman show relatively little difference in amount of juice throughout the season. The graphs suggest that a correlation exists between the decrease- in rag and the increase in juice; consequently the data for rag and juice for each date on all four of the above mentioned plats were used in this It was found that the mean value of The mean value of the juice was 43.378% with a standard deviation of 5.473. The correla- tion coefficient, (r), was ——0.751. and two variables, there were 22 degrees of freedom. Since there were 24 paired comparisons By the use of new. cam" RAG av weneur MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 31 SAMPLING DATES oer. m» ocT. z: 0012s uov nz uov. 22 oec. 9 JAN-‘Z a9 ' ' ' ' ’ ' 29 K\\ h’ MO \ EN6ELMAN r>% ,Z"“__' ' _ a mf- kve - 2 “~~ 7 k,__x'\\ llfi a__'\/ \‘L PER CENT RIND BY WEIGHT I Z5 a OCiIS oorz4 NO\/.| Noam Nov 25 DEC_I3 JANG SAMPLING DATES FIGURE 9. Seasonal changes in_the per cent of age of rind from various locations in » the Lower Rio Grande Valley. 5 AMPLING DATES aw: ozwra: ocrza - NOV. lz uov. zz 05o 9 JAPILZ l‘4sI~GI_'- ocirsa ootz4 noun Noam NOV. 25 DEC. \a JANG SAMPLING DATES FIGURE 10. Seasonal changes in the per cent of age of rag from various locations in the Lower Rio Grande Valley. 32 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION SAMPLlNG DATES Boer 14 ocrz» oer 2e uowz uouzz 050.9 JAMZ PER CENT JUICE BY WEIGHT ocrna 061124 NOV! Nov. 14 NOV. 25 _ 05c. 2s JAric SAMPLING DATES FIGURE 11. Seasonal changes in the per cent of age of juice from various locations in the Lower Rio Grande Valley. Wallace and Snedecor’s table of R, r and t (16), it may be seen that dis- regarding signs, the least significant value of r is .404 and the least highly significant value of r is .515. Since the value of r found in this case (—-.751) is well above this figure, we may safely say that a very definite negative correlation exists between the percentage of rag and the per- centage of juice, denoting a very real tendency for the rag to decrease as the juice increases. As a further check on the validity of this correla- tion under varying conditions, the figures for rag and juice content of each sample from the irrigation plats and from the 10 year old tree plat previ- ously discussed were examined. These gave 28 paired observations. The mean value for the rag was 19.67% with a standard deviation of 2.126. The mean value for the juice was 46.73% with a standard deviation of 2.857. The correlation coeflicient was —0.662. With 28 paired compari- sons there were 26 degrees of freedom. According to Wallace and Snede- cor’s table the least significant value of r is .374, and the least highly significant value is .478. Since the correlation coefficient of ~4).662? is well above the latter figure and is negative, it is in agreement with the other correlation study. ~ 1M a RiA. RY » MATURITY STUDI s BOF.MARSH EEQLE s P FR 33 a misiihim a Miami eiiiifa IllTTms Chemical Determinations The plats used for this test wgdma oleaug for the physical leasurements, and the data are presented in Tables 23, 24, 25, and 26. J e seasonal‘ average of the Brix ranged from 9.47 for Plat Engelman Vi. 10.65 for Plat Mission. The citric acid ranged from 1.34% for Plat lamo and Plat Engelnrian to 1.75% for Plat Mission. The Brix to acid tio ranged from 6.08 : 1 for Plat Mission to 7.37 : 1 for Plats La Feria _nd Engelman. Table 23. Chemical analyses of fruit from plat Alamo (Averages on 30-fruit sample, 1935-36.) Determination Oct. 18 Oct. 24 Nov. 1 Av. Qluble solids (degrees Brix) . . . . . . . . . . . . . . . . . . . . 9.81 9.77 9 .71 9.76 itric acid anhydrous (%) . . . . . . . . . . . . . . . . . . . . . . 1 .38 1 .35 1.30 1 .34 rixto acid ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7.11 7.24 7.47 7.28 . vert sugar1(%) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.86 3.98 4.13 3.99 ucrose1(%) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.68 2.63 _2.56 2.62 otal sugarsl (%) . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.54 6.61 6.69 6.61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.60 3.60 3.80 3.67 ufier index1.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.666 1.250 1.000 1.305 f‘! aste*1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VSA T-SS SA T-SS . NB NB NB NB vert sugar to acidl (ratio) . . . . . . . . . . . . . . . . . . . . . 2.80 2.95 3.18 2.98 ucrose to acidl (ratio) . . . . . . . . . . . . . . . . . . . . . . . . . 1 .94 1.95 1.97 1 .96 s otal sugars to acidl (ratio) . . . . . . . . . . . . . . . . . . . . . 4.74 4.90 5.15 4.93 avert sugar to sucrosel (ratio) . . . . . . . . . . . . . . . . . . 1.44 1.51 1.61 1.52 g itric acid anhydrous (%2) . . . . . . . . . . . . . . . . . . . . . 14.07 13.82 13.39 13.76 vert sugar (%2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39.35 40.74 42.53 40.87 ucrose (%2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.32 26.92 24.36 26.87 otal sugars (%2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66.67 67.66 68.89 67.74 lOn wet basis. 2On dry basis. *A-aci_d, SA-slightly acid, T-tart, SS-slightly sweet, S-sweet, B-bitter, SB-slightly bitter, VSB-very slightly bitter, NB-non-bitter. Table 24. Chemical analyses of fruit from plat La Feria (Averages on 30-fruit sample, 1935-36.) ‘, Determination Oct. 18 Oct. 24 Nov. 1 Nov. 14 Nov. 25 Dec. 13 Jan. 6 Av. 3 u_ble solids (degrees Brix).. 9.91 9.95 9.94 9.95 10.05 9 .98 9.85 9.95 fif- ic acid anhydrous (%). . . 1.45 1.43 1.41 1.34 1.30 1.30 1.25 1.35 j» toacid ratio . . . . . . . . . .. 6.83 6.96 7.05 7.42 7.73 7.68 7.88 7.37 _ ertsugar1(%)..._. . . . . . .. 3.96 4.00 3.94 4.06 4.03 4.10 4.06 4.02 y~ %) . . . . . . . . . . . . . .. 2.61 2.64 2.81 2.83 2.91 2.88 2.90 2.80 sugars1(%) . . . . . . . . . .. 6.57 6.64 6.75 6.89 6.94 6.98 " 6.96 6.82 “5 . . . . . . . . . . . . . . . . . . .. 3.50 3.40 3.90 3.30 3.50 3.50 3.60 3.53 .1,|i lndexl . . . . . . . . . . . . . . . 1.333 1.666 0.786 1.250 1.111 1 428 1.000 1 225 f *1 . . . . . . . . . . . . . . . . . . .. A A T A-T T-SS T-SS SS T-VSB _ _ SB VSB NB NB NB NB NB NB 4 rt sugar to ac1d1_ (ratio). . 2.73 2 .79 2.79 3 .03 3.10 3.15 3 .25 2 98 osetoacid1(ratio).._.... 1.80 1.84 1.99 2.11 2.24 2.22 2.32 2 07 = sugars to acidl (ratio). . 4.53 4.64 4.79 5.14 5.34 5.37 5.57 5 05 ’ e_rt sugar to sucrosel (ratio) 1.52 1.52 1.40 1.43 1.38 ~ 1.42 1.40 1 44 ,~< c acid anhydrous (702). . . 14.63 14.37 14.18 13 .47 12.94 13.03 12.69 61 y It sugar (%2) . . . . . . . . . . . 39.96 40.20 39.64 40.80 40.10 41.08 41.22 40 43 - » ose (%2) . . . . . . . . . . . . . . . 26.34 26.53 28.27 28.44 28.96 28 85 29.44 28.12 l sugars (%2) . . . . . . . . . .. 66.30 66.73 67.91 69.24 69.06 69 93 70.66 68.55 1On wet basis. 2On dry basis. *A-acid, SA-slightly acid, T-tart, SS-slightly sweet, S-sweet, B-bitter, SB- ightly bitter, VSB-very slightly bitter, NB-non-bitter. 34 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION Table 25. Chemical analyses of fruit from plat Mission (Averages 0n BO-fruit sample, 1935-36) Determination Oct. 14 Oct. 21 Oct. 28 Nov. 12 Nov. 22 Dec 9 Jan 2 Av. Soluble solids (degrees Brix). . 11.02 10 72 10.58 10.50 10.55 10.57 10.63 10.65 Citric acid anhydrous (%). . .. 1.89 1.89 1.93 1.72 1 .67 1.60 1.58 1.75 Brix to acid ratio . . . . . . . . . .. 5.83 5 67 5.48 6.10 6.32 6.61 6.73 6.08 Invert sugarl (%) . . . . . . . . . .. 3.11 3 84 3.79 3.82 3.80 3 .83 3.70 3.70 Sucr0se1(%) . . . . . . . . . . . . . .. 2.56 2 96 2.85 2.92 3.05 3.23 3.35 2.99 Total sugarsl (%) . . . . . . . . . .. 5.67 6 80 6.64 6.74 6.85 7.06 7 05 6.69 pHl . . . . . . . . . . . . . . . . . . . . . .. 3.50 3 40 3.60 3.75 3.90 3.95 3.80 3.70 Bufier index] . . . . . . ... . . . . .. 1.250 1 428 2.500 0.952 1.111 1.176 1.666 1.440 Taste*1 . . . . . . . . . . . . . . . . . . . A A A ‘A-T A A T T-A B VSB SB NB NB NB NB VSB-NB Invert sugar to acidl (ratio). . 1.65 2.03 1.96 2.22 2.28 I 2 .39 2.34 2. ll Sucrose to acidl (ratio) . . . . .. 1.35 1.57 1.48 1.70 1.83 2.02 2.12 1.71 Total sugars to acid] (ratio). . 3.00 3.60 3.44 3.92 4.10 4.41 4.46 3.82 Invert sugar t0 sucrosel (ratio) 1.21 1.30 1.33 1.31 1.24 1.18 1.10 1.24 Citric acid anhydrous (9/07). .. 17.15 17.63 18.24 16.48 15.83 15.14 14.86 16.48 Invert sugar (%2) . . . . . . . . . . . 28.22 35.82 35 82 36.38 36.02 36.22. 34.81 34.76 Sucrose (%2) . . . . . . . . . . . . . .. 23.23 27.61 26.94 27.81 28.91 30.56 31.51 28.08 ‘Total sugars ('75?) . . . . . . . . . . . 51.45 63.43 62.76 64.19 64.93 66.78 66.32 63.26 lOn wot basis. 2On dry basis. *A-acid, SA-slightly acid, T-tart, SS-slightly sweet, S-swect, B-bitter, SB-slightly bitter, VSB-very slightly bitter, NB-non-bittcr. Table 26. Chemical analyses of fruit from plat Engelman (Averages on 30-fruit sample, 1935-36.) Determination Oct. 14 Oct. 21 Oct. 28 Nov. 12 Nov. 22 Dec. 9 Jan. 2 Av Soluble solids (degrees Brix). . 9 .90 9 .85 10.75 9.70 9 .65 9.67 9.68 9.88 Citric acid anhydrous (%) . . .. 1.46 1.42 1.37 1.32 1.22 1.29 1.28 1.34 Brix to acid ratio . . . . . . . . . .. 6.78 6.94 7.12 7.35 7.91 7.50 7.56 7.37 Invert sugarl (%) . . . . . . . . . .. 4.02 3 .99 3 .94 3.94 3 .98 3 .93 3 .83 3.95 Sucrosc1(%) . . . . . . . . . . . . . .. 2.56 2.59 2.57 2.62 2.60 2.66 2.83 2.63 Total sugarsl (%) . . . . . . . . . .. 6.58 6.58 6.51 6.56 6.58 6.59 6.66 6.58 pHl . . . . . . . . . . . . . . . . . . . . . .. 3.50 3.50 3.80 4.00 3.70 4.20 4.05 3.82 Bufier index1..... 2.500 1.052 1.250 0.769 0.909 0.645 1.333 1.207 Taste“ . . . . . . . . . . . . . . . . . . . . SA A-SA SA '1‘ T-SS A-T T-SS T VSB NB VSB NB B NB NB VSB-NB Invert Sugar to acidl (ratio). . 2.75 2.81 2 .88 2 .98 3 .26 3.05 2.99 2.95 Sucrose to acidl (ratio) . . . . . .. 1.75 1.82 1.88 1.98 2.13 2.06 2.21 1.96 Total sugars to acidl (ratio). . 4.51 4.63 4.75 4.97 5.39 5.11 5.20 4.91 Invert sugar to sucrosel (ratio) 1.57 1.54 1 .53 1.50 1.53 1.48 1.34 1.50 Citric acid anhydrous (%2) . . . 14.75 14.42 12.74 13.61 12.64 13 .34 13 .22 l3 .53 Invert sugar (%2) . . . . . . . . . . . 40.61 40.51 36.65 40.62 41.24 40.64 39.57 39.98 Sucrose (%2) . . . . . . . . . . . . . .. 25.86 26.29 23.86 27.01 26.94 27.51 29.24 26.67 Total sugars (%2) . . . . . . . . . . . 66.47 66.80 60.51 67.63 68.18 6815- 68.81 66.65 1On wet basis. 2On dry basis. *A-acid, SA-slightly acid, T-tart, SS-slightly sweet, S-sweet, B-bitter, SB-slightly bitter, VSB-very slightly bitter, N B-non-bitter. The Brix of fruit from Plat Mission was consistently higher than that of the other plats (Figure 12). Plat Alamo shows the lowest Brix of the test for the period prior to November 1. The general trend of the Brix for all plats was rather erratic and was approximately constant. The Brix readings of Plat Mission were above 10° throughout the test. All other plats showed a Brix reading between 9° and 10° throughout the test. MATURITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 35 SAMPLING DATES octw, octz: ocr 2e NOV. l2 NOV. zz 05c. a JAN.Z n20 ' i Y v ' - lLOO 10.80 >( (I060 a: M’ 94m, I!) “I040 nu t! 0mm» u O W‘ --_ [Q00 \lkf,t_l§_ L‘ f _ - - _ “">-f> L-_ q‘ _$ . aao- l“ LAJ“ -g ° ‘$_ EneELlnAN g- .--i—v—i*ii-— 9,50 . . . . . . An OCTJB OCT 2A NOV.I NOV. l4 NOV. 2'5 DEC. l3 JAN.6 SAMPLING DATES FIGURE 12. Seasonal changes in the total soluble solids of juice from. various locations in the Lower Rio Grande Valley. The Brix to acid ratio of the fruit from Plat Mission was consistently lower than that of the other plats (Figure 13). Plat Alamo had the highest ratio during the first part of the season. Plats La Feria and Engelman were relatively close together in ratio. Although Plat Mission had a Brix above 10° throughout the test, the ratio did not reach the required 7 : 1 during the season. The other plats with a Brix between 9 and 10 are required to have a ratio of 7.2 : 1 in order to pass the maturity require- ments. Plat Alamo reached this requirement on October 24, the second date analyzed. Plats La Feria and Engelman did not reach the required ratio until the fourth date analyzed, November 12 and 14 respectively. The general seasonal trend of the Brix to acid ratio on all plats was upward. The readings on Plat Alamo showed that fruit to be more mature during the early part of the season than that of any other plat. Fruit from Plat Mission was less mature during this period. Plats La Feria and Engelman matured their fruit at approximately the same time. It should be borne in mind that these plats differed widely in their location, soil type, and orchard management (Table 1). There is an indication that some factor or set of factors exerts more influence on maturity of grapefruit than soil type and cultural practices. Plat Mission, which bloomed two months later than the other plats, had not made up for these two months in maturity by the end of the test. This indicates that factors other than increments 36 BULLETIN NO. 562, TEXAS AGRICULTURAL EXPERIMENT STATION SAMPLING DATES azféGT. s4 ocrz! OCT. as NO\/. a2 NOV. 22 050.9 JAN.9 Z80 h x LAFfiRJ§_i r- ’ ‘ ,_ , x \__E_~'=_Eer_~1____ q _ O C‘ 140 ggr/ f m’ %l Q —. ‘f’ U ~ ’ <1 Z ' 0 GLOr- “ F‘ 9\° vA\ K .._ 6.20 I! d) 5.80 5A0 i - L OCT. l8 OCT Z4- NOV. l NOV l4 NQV 25 DEC. l3 JAN. G SAMPLING DATES FIGURE 13. Seasonal changes in the total soluble solids to acid ratio of juice from various locations in the Lower Rio Grande Valley. ' of age from time of blooming are involved and exert their influence on maturity. These may possibly be soil, climatic conditions such as heat units, or the amount and intensity of sunshine. The Brix readings of all plats were approximately constant, and the Brix to acid ratio showed an upward trend as the season advanced. The trend of the citric acid was downward throughout the test. Chace and Church (6) showed that the soluble solids in Washington Navel oranges grown in California gradually increases and the acid con- tent gradually decreases during the season, resulting in a rapidly in- creasing ratio of solids to acid. These same writers have shown that the efiect is not so pronounced in grapefruit as in oranges (5). Traub, Fraps, and Friend (14), working in Texas, and Dominguez and Cady (7), working in Puerto Rico, reported that the chemical composition of grapefruit juice becomes relatively stable as the fruit reaches maturity. These writers also reported that the general tendency in grapefruit juice is for the total solids to decrease slightly or remain practically the same throughout the season, and for the acid content to decrease, which results in a gradual increase in the solids to acid ratio. These conclusions are in agreement with the tests herein reported. Total sugars showed a very slight upward trend throughout the sea- son. Invert sugar did not show any definite upward or downward trend, but remained approximately constant. Sucrose showed a slight upward trend. p The ratios of invert sugar to acid, sucrose to acid, and total sugars to MA'1‘URITY STUDIES OF MARSH SEEDLESS GRAPEFRUIT 37 acid showed general upward seasonal trends. The ratio of invert sugar to sucrose showed a rather indefinite downward seasonal trend. The pH showed an indefinite upward seasonal trend. The buffer indexes as determined from the pH were erratic and did not show any definite sea- sonal trend. These results are not in agreement with the work of Traub et al (14), since they found a consistent increase in pH during the course of the season, with a definite decrease in buffer capacity. Bitterness disappeared from most samples during the first two weeks of November. The fruit became less acid to taste as the season advanced. ACKNOWLEDGEMENTS Thanks are due Mr. J. L. Heid and Mr. W. C. Scott of the U. S. D. A. Citrus Products Station, who offered many helpful suggestions during the course of the experiments. The authors are indebted to the U. S. D. A. Bureau of Chemistry and Soils for the use of their laboratory and equip- ment at the Citrus Products Station, Weslaco. The Texas (Beta) Chapter of the Society of Subtropical Horticulturists sponsored the work and as- sisted in the organization of the project. Mr. L. E. Pratt, through the ' Maturity Division of the Texas State Department of Agriculture, furnished facilities and financial aid in conducting the experiment. The following individuals and organizations co-operated with the sta- tion in these experiments by furnishing fruit: E. H. Reichert and Sons, J. S. Shearer, who manages the George Ross grove, John H. Shary, and J. C. Engelman, Jr. ' SUMMARY AND RECOMMENDATIONS The quantity of amino acid was erratic throughout the season and did ynot show any definite seasonal trend. The human error in tasting is probably too great to be of use in deter- i mining the amount of naringen, or degree of bitterness, in grapefruit juice. Attempts to find a simple chemical reaction which would indicate the amount of naringen were not successful. Brix readings made on non-deaerated juice are sufliciently accurate for 7- practical use in testing for maturity, provided care is exercised to avoid ' excessive whipping and incorporation of air with the juice. The composition of the juice from grapefruit is not uniform throughout the fruit, and it is necessary to take all of the juice from both halves of the cut fruit in order to obtain a representative sample of juice for analysis. i 5. I: .. w -":1\,~