r » 4 r" tarzi A Bfllluifi Statian, Texas The TEXAS AGRICULTURAL MECHANICAL COLLEGE SYSTEM ems GILCHRIST. Chczncejlior 7 v The Cover Picture A load of pint jars of blackeye peas is being removed from the canner. Three of the 16 jars were used for heat penetration tests. The thermocouple wires were inserted in the jars by means of the flat type stufling box soldered to the lid. One jar with a thermo- couple attached is on the table, another may be seen in the top layer in the canner and the third is in the bottom layer of the canner with only the thermocouple wire visible. The temperature inside each jar was re- corded at two-minute intervals by the instru- ment seen at the right. Preface A Blackeye peas are one of the favorite foods of Texans and many " e canned at home. The canning procedure used should prevent e growth of harmful bacteria and be carried out as quickly as is nsistent with safety. = This study was made to find the shortest safe processing periods _'ch would destroy the harmful bacteria and make home canned ackeye peas a safe food. The recommended procedure involves two eps: processing and cooling. ipProcessing: Place sealed containers in a pressure canner contain- ing one to two inches of boiling water. Process at 1o pounds pressure for the times required by size and kind of container. Processing times for glass jars (hot or cold pack) : Pints . . . . . . . . . . . g5 minutes Quarts . . . . . . . . .40 minutes Processing times for tin cans (hot pack only. sealing temper- ature 170° F. or above): No. 2 minutes No. 21/2 . . . . . . . .35 minutes No. 3 . . . . . . . . . .35 minutes i. ling: For glass jars, allow the petcock to remain closed until " the pressure returns to zero. Then open the petcock and remove the canner lid. Cool glass jars at room temperature away from drafts. For tin cans, open the petcock as soon as the fire is turned out. When the pressure returns to zero, remove the lid of the canner. Cool tin cans in several changes of cold water. C O N E N T S Y P8 4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i Experimental Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Peas Used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Hot Pack Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. % Cold Pack Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1:‘ Heat Penetration Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Inoculation Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1i Actual Processing Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. It Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Inoculation Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Calculation of Actual Process Values from Heat Penetration Data ll Calculation of Representative Process“ Values for Corresponding Process Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ Calculation of Safe Process Times . . . . . . . . . . . . . . . . . . . . . . . . . . . .. I Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . < Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Z ’ BULLETIN 707 DECEMBER 1948 Development of Safe Methods for Canning Blackeye Peas attHome I SYLVIA COVER, Professor, Department of Rural Home Research, Texas Agricultural Experiment Station = ANNIE B. SMITH, M. PATRICIA SHEPPERD and ELLEN G. CRAW- FORD, Agents of the Bureau of Human Nutrition and Home Economics, U. S. Department of Agriculture, located at College Station ONSIDERABLE research has been done in recent years on g developing safe methods for home canning of foods (Toepfer fat aL, 1946; Nelson and Knowles, 1940; Cover at aL, 1943). The {Bureau of Human Nutrition and Home Economics, in cooperation _with various agricultural experiment stations and departments of ifhome economics, is now engaged in a comprehensive study of home scanning problems. The Texas Station is cooperating with the Bureau n the work on vegetables. Vegetables are receiving attention because many of them are in he low-acid group of foods. If spores of C lostrizlium botulinum are resent, and the heat treatment during canning is not sufficient to - troy them, these spores may grow in sealed containers of canned w-acid foods and produce a toxin so poisonous that a tiny amount sufficient to cause death. The deadliness of this toxin may be re clearly understood when it is compared with that of other sons. Hull (1943) reported that the pure toxin of C l. batulinum 0 times as strong as cobra venom, 30o times as strong as strych- e and 10,000 times as strong as potassium cyanide. The toxin of Cl. lmtulinum may be present in a canned product _ich shows only slight indications of spoilage or decomposition. j is is indicated in a striking manner in the detailed reports of i“ ‘ histories from outbreaks of botulism. The habit of tasting food g pected of incipient spoilage has caused many women to die of tulism. A list of some foods which have caused outbreaks of botu- w and references to the original articles are given in Table I. As a ult of these and other studies, commercial canners were forced 0N adopt processing times which are adequate to destroy Cl. b0- 6 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION Table 1. Foods which have caused outbreaks of botulism Number of Bacteriologically Food outbreaks proven Reference String beans . . . . . . . . . . . . . . .. 21 Schoenholz, et al. 1923; ~ Geiger, et al. 1922; Dickson 1918 Corn . . . . . . . . . . . . . . . . . . . . . . . 12 6 Schoenholz, et al. 1923; Geiger, et al. 1922 Asparagus . . . . . . . . . . . . . . . . . . . 5 3 Schoenholz, et al. 1923; Dickson 1918; Geiger, et al. 1922 Spinach . . . . . . . . . . . . . . . . . . . . . 4 1 Schoenholz, et al. 1923; Geiger, et al. 1922 Apricots . . . . . . . . . . . . . . . . . . . . . 3 1 Schoenholz, et al. 1923; Dickson 1918 Pears . . . . . . . . . . . . . . . . . . . . . . . 3 1 Schoenholz, et al. 1923; Dickson 1918; Meyer and Gunnison 1929 Chili sauce . . . . . . . . . . . . . . . . . . 1 1 Schoenholz, et al. 1923i Chili peppers . . . . . . . . . . . . . . .. 1 1 Hall 1936 Cauliflower . . . . . . . . . . . . . . . . .. 1 1 Hall 1936 Tomato-onion-chili sauce. . . . . 1 1 Cutter 1922 Tomatoes . . . . . . . . . . . . . . . . . . . 1 1 Slocum, et al. 1941 Okra . . . . . . . . . . . . . . . . . . . . . . . 1 1 Tucker and Swanson 1939 Beets . . . . . . . . . . . . . . . . . . . . . . . 1 0 Schoenholz, et al. 1923; Geiger, et al. 1922 Beets and turnip tops . . . . . . . . . 1 0 Schoenholz, et al. 1923 Pimento . . . . . . . . . . . . . . . . . . .. 1 Not tested Geiger 1924a Figs . . . . . . . . . . . . . . . . . . . . . . . . 1 Not tested Geiger 1924a Home canners in many parts of the United States, however, have i not been as aware of this danger as have the commercial canners,‘ nor have all of them been conscientious about using only those processing times which were known to be safe. Scarcity of recog-i niZed outbreaks and lack of familiarity with known cases of botu-,_ lism may have given home canners an unwarranted feeling of s‘ security which the commercial canners were forced to abandon long 3 ago. The wide geographic distribution of Cl. botuliuum is indicated; by its isolation in 44 of the 48 states either from soil samples or i from outbreaks of botulism. Texas is among the 44. Much of this i work was done by Meyer and Dubovsky (1922a and 1922b) but some reports were made also by Thom at al. (I919), Nevin (1921), Cutter (1922), Geiger (1924b), Damon and Payabal (1926), Hay- hurst (1926), Meyer andGunnison (1929), Hall (1933 and 1936), Slocum et al. (1941) and Parry (1946). Although the spores have DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 7 7" n foundmost frequently in the Western States, they a.re so xvidely‘ istributed in nature that n0 area may safely be assumed t0 be free i}; them. _ With these facts in- mind, it is a wise precaution to use only ose canning methods which provide heat treatments sufficient to troy the spores of CZ. botulinunz. Low-acid foods. for this reason. ould be processed only under steam pressure, never in an oven or “tiling water bath. This makes the pressure canner indispensable to i e safe processing of home canned low-acid foods. Other losses from spoiled food are also important. The time and in involved in preparing and preserving the food are too great risk spoilage by using inadequate processing times. In times of fol scarcity or high prices. the loss of the food itself is an impor- i tconsideration. Because of the lack of information on adequate heat treatments p er home conditions. quite long processing periods in the pressure ner were recommended in the past. ‘Many factors must be considered in determining the lowest safe }_ocessing periods. The heat resistance of thelspores is not the same ‘all foods. Differences in composition and acid reaction cause some s to need longer heat treatments than others. Heat penetration, reover, varies with the size of the container and also with the _] sistency of the food; thick or solid packs need longer processes watery or loose packs. Thus. the processing time of each food ést be studied separately in each of the various sizes and kinds of “tainers. z‘,- he present cooperative study between the Texas Agricultural riment Station and the Bureau of Human Nutrition an.d Home - omics reports the development of a safe home canning method iblackeye peas. a popular variety of Southern peas (edible J'- Experimental Procedure he lowest safe processing times for blackeye peas were (leter- f}: by procedures essentially the same as those (lescribzrrl by ipfer, Reynolds, Gilpin and Taube (i946) for other vegetables. ‘l procedures made use of heat penetration records and inocu- . jars. t» Peas Used "iesh blackeye peas were obtained from a wholesale produce any, grocery stores and local farms and gardens. The size a“ I rity of the peas used in the study were: 8 TBULLETIN 7O7I1TFIXAS AGRICULTURAL EXPERIMENT STATION I. immature green-JP he entire pods were green. The peas were small, immature and green in color; they were 1’ difficult to shell, but the quality and flavor 0f the ca product were excellent. N OHCS . 3. Frey/z white matz-n'e———'I‘he pods were yellow. These peas fresh (not dry). large, very mature and white; they quite easy to shell. The peas were kept under refrigeration both before and g shelling until they were used. Every effort was made to use i; firm, sound peas of good color and of the desired maturity’. Hot Pack Method The canning procedure used in this study followed the re ,_ mendations given in the USDA leaflet AWI-93, “Home Cannin Fruits and Vegetables” (I944), with a few exceptions. The important exceptions were the method of standardizing the fil" the containers and the amount of headspace above the liquid Because the fill of the container and the level of the liquid in. it may influence the rate of heat penetration, preliminary runs made to learn what weight of peas, in grams, would give the i desirable fill after processing. The weight of peas used for p‘ maturity and for each size and kind of container is given in T Fresh mature——'l‘he pods were either yellowish green orig yellow streaks. The peas were fully grown but were a mi of reenimd white; they were easier to shell than the sm g . i‘ 2. The desirable fill obtained is shown in Figure I. just before canning, the peas were thoroughly washed in lots, drained and combined into one large lot. The peas for ._ Table 2. Weight 0f blackeye peas in each container .9 i Hot pack Cold Container Immature Fresh Fresh white Fry j green mature mature m: p Pint glass jars . . . . . . . . . . . . . . . . . . .. 255 245 24o z - Quart glass jars . . . . . . . . . . . . . . . . . . 570 540 . . . . . . . . . . . . 5T r No. 2 tin cans . . . . . . . . . . . . . . . . . . . . . 320 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .; No. 2% tin cans . . . . . . . . . . . . . . .. . . . . . . . . . . . . .. 41o . . . . . . . . . . . . . . . . . . .. No. 3 tin cans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 535 . . . . . . . . 4 Weight of peas packed, grams DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 9 container were then weighed, placed in individual two-quart sauce- pans and precooked separately by covering with boiling water and bringing to a rolling boil. Next, they were drained and placed in clean, numbered, hot glass jars 0r clean, numbered tin cans. Fresh, boiling water was added t0 the containers in accordance with the Bureau’s directions. (Certain bacteriologists insist that the precook- ing water be discarded because this reduces the spore load.) The headspace above the liquid level was one-half inch for jars and one-fourth inch for tin cans. Air bubbles were worked out with a knife blade. The mouth of each container was wiped with a clean, damp cloth. The jars were sealed with two-piece metal closures which had been given the recommended hot water treatment. The recorded sealing temperatures for tin cans ranged from 177° to 195° F., well above the minimum of 170° F. specified for tin cans by Toepfer, Reynolds, Gilpin and Taub-e (1946). Each container, as soon as it was packed and sealed, was placed in the hot pressure canner containing 1 to 2 inches of boiling water. Placing the con- tainers in accordance with a prearranged diagram insured that the containers with the thermocouples, the inoculated containers and the controls were arranged differently in each canner load. Two Figure 1. Desirable fill of jar. The peas come to the neck of the jar and the liquid covers them slightly. 10 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION persons working together completed the procedure from the start of the precooking to the sealing of the last container for a full canner load in approximately 20 minutes. Frequently, steam was issuing from the petcock by the time the canner lid was fastened. After steam appeared. the petcock was left open for a 10-minute steaming period, (luring which the amount of issuing steam was kept steady. When the petcock was closed. the flame was turned up until it covered the bottom of the Pressure canner, and an effort was made to bring the temperature of the pressure canner up to I15.5° C. ('24o° F., 1o pounds pressure) in approximately 1o minutes. Processing time was counted from the time the pressure canner reached 1o pounds pressure. .\t the end of the processing time, the fire was turned out and the canner left to cool on the open ring of the gas hot plate. \\'hen pint and quart jars were processed, the petcock was left closed until the tempera- ture of the pressure canner reached 100° C. (21.20 17., o pounds pressure). At that time the petcock was opened and the lid xvas removed. When No. 2, No. 2% and No. 3 tin cans were processetl. the petcock was opened immediately after the fire was turned out. and the lid of the pressure canner was removed when the tempera- ture of the canner reached 100° C. (212° F). The glass jars were allowed to cool at room temperature, away from drafts. The tin cans were cooled by being moved about in a sink filled and refilled with cold water. A continuous record of the internal temperature of the pressure canner and the three jars ( or cans) containing the thermocouples was secured at 2-minute intervals throughout the entire processing period. This record was continued for the containers until the tem- perature of the slowest cooling one reached 875° C. (I8o.5° After cooling, the bands were removed from the jars, and both jars and cans were cleaned, labeled and stored. A full canner load was processed each time. For pint jars and No. 2 tin cans, there were I6 containers in each canner load, but there were only II No. 2% tin cans, IO No. 3 tin cans and 7 quart jars. A Cold Pack Method Cold pack methods are easier to use than hot pack methods, but they may not produce as good a product because of inadequate vent- ing of entrapped air. However, Esselen and Fellers (I948) re- ported that glass jars, if tightly sealed with two-piece metal closures and processed at IO poundsipressure, will vent satisfactorily and t W I wmaqwtwwqwtmawn,tw-w .. l, < *- DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS. 11 will permit most of the entrapped air t0 be exhausted from the jars during the processing. This ventingcharacteristic makes glass jars suitable for cold pack canning. The determination of safe processing times for blackeye peas in glass jars using the cold pack method is, therefore, desirable. The cold pack method used with the blackeye peas followed closely the previously described hot pack method. The only difference in the two methods was that, in the cold pack method, the peas were not precooked; they were placed in the clean containers immediately after weighing, and fresh, boiling wa.ter was added to within one- half inch of the top of the jars. Preliminary runs were made, as before, to determine what weight of peas, in grams, would give the most desirable fill after processing. The weights selected are given in Table 2. Heat Penetration Tests The heat penetration tests were made by passing four thermo- couple leads from a recording potentiometer through the lid of the pressure canner. One was used to record the temperature in the, canner and one in each of the three containers of canned food. To prevent loss of steam, the thermocouple wires were passed through stuffing boxes attached to the lid of the canner and the lids of the containers of food. Two types of stuffing boxes were used, as shown in_ Figure 2. The shank type in the foreground) was attached to Figure 2. Stuffing boxes used for heat penetration tests. The shank type, in the foreground, was used on the lid of the pressure canner. The fiat type, in the background, was soldered to the lid of the container. " 12 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION the pressure canner by means of two gaskets and a nut. A hole had been drilled in the canner lid to allow passage of the shank con- taining the wires. One gasket was placed between the stufling box and the outside of the lid, the other between the inside of the lid and the nut. The flat type (in the background) was soldered directly to the lid of the containers; a small hole had been cut in the lid to allow passage of the thermocouple wire. With the lids for the glass jars, the soldering could be done before the hot food was placed in the container, but for the tin cans, the soldering had to be done after the container was sealed. Temperatures of canner and con- tainers were recorded automatically on the instrument chart. This equipment is shown in the front cover picture with a load of pint jars being removed from the canner. Because the place in the container which heats most slowly is the spot most desirable for the thermocouple, preliminary runs were made to determine the location of the “cold spot” in each of the different containers. This was done by inserting two or three thermo- couple wires of different lengths along a vertical axis in the center of the same container filled with peas and noting the differences in heat penetration. The “cold spot”was found to be near the bottom of the container. The length of the thermocouple wire was then adjusted to secure readings at that spot in each container. Inoculation Tests Spore preparations of Cl. botulinuflz fail to exhibit uniform heat resistance. For this reason, laboratories interested in commercial canning problems found that they needed an organism whose spores were similar to Cl. botulinuwz in their growth requirements, were near or slightly higher than the maximum of Cl. botulinunz for heat ressistance, but were of uniform heat resistance. Putrefactive An- aerobe No. 3679 was reported by Townsend, Esty and Baselt ( 1938) to meet these conditions. This organism has been and is widely used by the canning industry in place of C l. botulinunz for deter- mining safe processing times. Since outbreaks of botulism from eating commercially canned food have not occurred in recent years. P. A. No. 3679 was considered a satisfactory test organism and was used in this study. Inoculation tests were made only in hot pack pint jars. Only one size and kind of container and method of packing was needed because the inoculation tests were made to determine the heat resistance of the spores. The heat resistance is affected by the composition and acid reaction of the food, not by the rate of heat penetration. DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 13 _p i161 3 jars in each canner load not needed for heat penetration ts, were utilized for the inoculation tests. Four or 5 were kept controls, and the remaining 8 or 9 were each inoculated with i,ooo spores of P. A. No. 3679. Because no spoilage occurred the To st year even with short processing times, the precaution was "f en the second year to test the viability and resistance of the an at intervals during the canning period. The dilution of the ire suspension was adjusted to secure 10,000 viable spores per iilliliter of inoculum. Inoculation was made into the filled container i} st before it uzas.-.sealed. Spoilage in the inoculated jars was shown broken seals, gas bubbles, frothing and foul odor. The inoculated and control jars were stored in a constant tem- L-"rature room in which the temperature varied normally between 38° and 80° F. i’ Actual Processing Times 1; Variation in process times for the hot pack pint jars were planned i’ accordance with expected spoilage: complete spoilage with the ’ west process time, partial spoilage with the next, and none with e highest. Because quart jars, tin cans and cold pack pint jars were not inoculated, only one processing time was used. The time _ lecited was estimated to be long enough to prevent spoilage. The ieasons for this will be given later in the bulletin. Results and Discussion Inoculation Tests T ¢ Complete spoilage data were obtained for immature green black- jye peas and some data were secured with the other maturities. ata from the spoilage tests are given in Table 3. A Immature green bl-ackeyc peas: With the 10-minute processing, i mplete spoilage of the inoculated jars had been expected. In the canner loads processed. 4o of the 41 inoculated jars had spoiled ter 6 months’ storage, but none of the 22 control jars spoiled. The one unspoiled, inoculated jar contained no viable spores of A. No. 3679 when tested bacteriologically in the laboratories of ihe Bureau of Human Nutrition and Home Economics. With the 20 minute processing, some spoilage was expected. Four canner loads were processed. Of the 33 inoculated jars stored, conly I spoiled within 6 months, and no viable spores were found in any of the other 32 when bacteriological tests were made by the lBureau. None of the control jars spoiled. l4 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION Table 3. Spoilage in inoculated pint jars 0f blackeye peas after processing at 2 j and incubation at 78-80° F., 1947 data (hot pack) _ Mean No. of jars Spoilage in Date of No. of Process process stored inoculated jars processing canner time, value loads min. j o Control* jlnoculated Number j % Immature green 24 59 May l3. , 37 90 14, 15, 16, 5 10 4.68 22 41 38 93 and l9 39 95 40 98 May 17, 21, 4 20 7.87 17 33 1 3 22, and 23 l May 24, 26, Z 4 30 10.51 17 Z 34 0 0 27, and 28 j Fresh mature June 12, 38 93 13, 14, l6. 5 l0 4.30 22 41 39 95 and 17 41 100 Fresh white mature l May 28 l 10 3.79 j 4 9 9 100 *None spoiled. jAs the first step in these calculations, the time and temperature N0 spoilage was expected with the 3o minute processing‘. Four canner loads were processed for 3o minutes, and no spoilage oc-‘ curred in either the control or the inoculated jars after 6 months’. storage. F¢76Sh mature blackeye peas: Five canner loads were processed for p 1o minutes. All of the 41 inoculated jars spoiled within the first 3 months of storage. No Otllfiil‘ packs of this maturity were inocu-{ lated. i fiires/z white nzatare blackeye was: Only one canner load of peas of this maturity was available when the inoculation tests were made. They were processed for IO minutes. All of the nine inoculated jars spoiled within the first month of storage. ’ Calculation 0f Actual Process Values From Heat Penetration Data The heat penetration records, consisting of the internal temper- atures of the containers, were used to calculate safe process times. _ data for each container of food must be converted into terms of their destructive effect on the spores of the spoilage organism. The destructive effect of each temperature for each minute of time it is rraintaineld represents a definite fraction of the total destructionqi This fraction may be expressed as the lethal rate. i DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 15 The lethal ra.te at any given temperature is the ratio of the time in minutes needed to destroy the organism at 250° F. to the time in minutes needed to destroy it at the given temperature. This ratio is known as F/t. The equation for calculating F/t is usually given 250 — T as log t/F I ——————, where F is the time in minutes needed to destroy the organism at 250° F. 2‘ is the time in minutes needed to destroy the organism at the given temperature. 7.1 is the slope of the thermal-death-time curve. (‘z I I8 was used for the calculations in this study.) 250 is degrees Fahrenheit. T is the observed can or jar temperature in ° F. Using a table of logarithms, the antilog for log t/F is obtained. The reciprocal of this antilog is F/t. A table of lethality values was prepared from these calculations. Since the temperatures were recorded in degrees Centigrade, the table was made for the Centigrade readings and their equivalents in degrees Fahrenheit. As an illustration, the time and temperature data and the 13H values for one pint jar (hot pack) in one canner load are given in Table 4. A lethality curve was then constructed for each jar containing a thermocouple. 'l‘his was done by plotting lethal value against time on accordinate paper. Such a lethality curve is shown in Figure 3 using the data given in Table 4. The area under the lethality curve was then measured in square inches with a planimeter (Figure 4). This area represents the total lethal value of the heating-cooling" period and is referred to as the process value, or F0. The heating part of the area is referred to as FH and the cooling part of the area as F c. In order for the area under the lethality curve, in square inches, to represent the lethal value of the process directly in terms of F0. the scale of the figure was purposely designed so that, in one square inch, the product of the time and the sterilizing value (F/t) would equal I, as, for example, 2o minutes x .05 I 1.0 in Figure 3. A summary of the heating" and cooling data and the sterilizing value of the processes for blackeye peas is given in Table 5. 16 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION .25’ J0 LET/YAL/TY Wu. us (‘Z6 K 0 Z0 410 7701s uv Muvurss Figure 3. A lethality curve constructed from the data for a pint jar given in Table 4. Figure 4. The area under the lethality curve is being measured with a planimeter. DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 17 Table 4. Times, temperatures, and lethality values for one» pint jar of blackeye peas during processing at 240° F. (hot pack) Minutes Minutes Temperature Jar 6B from from inside pressure —’ fastening start of canner Jar temperature of pressure processing F/l canner lid time °c l °F °c I °F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 82.5* 1805* 0 . . . . . . . . . . . . . . .. ——28 . . . . . . . . . . . . . . . . . . .. 86.0 186.8 . . . . . . . . .. 2 . . . . . . . . . . . . . . . . ~26 . . . . . . . . . . . . . . . . . . . . 88.0 190 4 00049 4 . . . . . . . . . . . . . . . . ~24 . . . . . . . . . . . . . . . . . . . . 90.0 194 0 00077 6 . . . . . . . . . . . . . . .. ~22 91 0 195 8 91.5 196 7 00109 8 (S) . . . . . . . . . . .. —20 99 5 211 1 93.5 200 3 00173 10 . . . . . . . . . . . . . . .. —18 100.5 212 9 95.5 203 9 00275 12 . . . . . . . . . . . . . . .. ~ 16 100.0 212 0 97.5 207 5 00436 14 . . . . . . . . . . . . . . .. —14 100.5 212 9 98.5 209 3 00548 16 . . . . . . . . . . . . . . .. —12 100 0 212 0 99.5 211 1 00690 18 (D) . . . . . . . . . . .. ~—10 100 5 212 9 99.5 211 1 00690 20 . . . . . . . . . . . . . . .. —— 8 103 5 218 3 100 0 212 0 00774 22 . . . . . . . . . . . . . . .. —— 6 106 5 223 7 101 0 213 8 00975 24 . . . . . . . . . . . . . . .. ~ 4 108 5 227 3 103 0 217 4 0155 26 . . . . . . . . . . . . . . .. — 2 113 0 235 4 105 5 221 9 .0275 28 (P) . . . . . . . . . . .. 0 116 0 240 8 108 0 226 4 .0489 30 . . . . . . . . . . . . . . .. 2 115 5 239 9 110 5 230 9 0869 32 . . . . . . . . . . . . . . .. 4 115 5 239 9 112 0 233 6 1227 34 . . . . . . . . . . . . . . .. 6 115 5 239 9 112 5 234 5 1377 36 . . . . . . . . . . . . . . .. 8 115.0 239.0 113 5 236.3 1734 38 (0) . . . . . . . . . . .. 10 116.0 240.8 114 0 237.2 1945 40 . . . . . . . . . . . . . . .. 12 114 0 237.2 114 0 237.2 1945 42 . . . . . . . . . . . . . . .. 14 112.0 233.6 114.0 237.2 1945 44 . . . . . . . . . . . . . . .. 16 111 0 231.8 112.5 234.5 1377 46 . . . . . . . . . . . . . . .. 18 . . . . . . . . . . . . . . . . . . .. 111 5 232.7 1094 48 . . . . . . . . . . . . . . .. 20 107.0 224.6 110 5 230.9 .0869 50 . . . . . . . . . . . . . . .. 22 106.0 222.8 109 0 228 2 .0615 52 . . . . . . . . . . . . . . .. 24 104.5 220.1 107 5 225 2 0436 54 . . . . . . . . . . . . . . .. 26 103.0 217 4 106 5 223 7 0346 56 . . . . . . . . . . . . . . .. 28 102.0 215.6 105 0 221 0 0245 58 (R) . . . . . . . . . . .. 30 100.5 212.9 104 5 220 1 .0218 . . . . . . . . . . . . . . .. 32 1015 2147 0109 62 . . . . . . . . . . . . . . . . 34 . . . . . . . . . . . . . . . . . . . . 98 0 208 4 00489 64 . . . . . . . . . . . . . . . . 36 . . . . . . . . . . . . . . . . . . .. 93 5 200 3 00173 66 . . . . . . . . . . . . . . . . 38 . . . . . . . . . . . . . . . . . . .. 91 5 196 7 00109 68 . . . . . . . . . . . . . . . . 40 . . . . . . . . . . . . . . . . . . . . 88 0 190 4 00049 *Sealing temperature. Symbols S—Steam D—Petcock down P—Processing time begun O—Fire out R—Jars removed Estimated process values are sometimes necessary.’ In those tests which were run for heat penetration only, the processing time was continued for a period considerably beyond that at which spoilage would develop, thus permitting estimations of process values to be made for shorter times. First, the lethality curve was constructed as before, and the process value for the entire time was obtained“ in the usual way. Then, to obtain the process value of the shorter time, a vertical line was erected at the new process time until it intersected the heating curve. A second line was drawn horizontally from that point until it intersected the cooling curve. A third line was drawn perpendicularly between that intersection and the base line. The area t0 the left of the first new line is the new FH, and the area to the right of the third new line is the new Fe. The sum of the two areas is the estimated F0 for the new process time. The estimated process value for a still shorter process time may be BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION mm: ::.:: ::.N 00.» :NN N»: N: m." mvm: . . . . . . .0.:55: 500...: . . . . . . .0555: “:4 Nv.:: __ 5.0 0:: mNN 0v: m. , 00 02.. . . . . . 10:55: A095: ... . . 055.: _ W 0:00.: 0:00 :0: 00.2 00... i N“: ::N ::: N: w :v 0...: .0555: 05:3 500.0: :m.: :00: 00.: y 00.0. 000 2.. N: ,. :0 $0. . . . . . ..0...50:. 500...: 3.0000 0 .07: .0... 0:6: w v»: 2 .0. aNN :0: N: :0 $0. . . . . . 100.50.: 500...: 20:00 0.0 .07: ma: :m.:: 9...: 0.03:: NmN hm: :: :v 02: .......00..u 00.5055: 325.00 N .07: N0: 0:6: 00.0 00.0. mNN Nw: v: :0 $0. . . . . . . .0...50.: 500...: Nu: 00.0. 0v: _ N04": :NN :0: N: :0 02: .... .:00..u 00.5055: ..... .0555: . . . . . . . . 5.0 00.. mNN 000 00. 0 :: 2.0. 10:55: 05:3 500...: 0v: 004... ::.N ::.:: wNN Nw: 0. mv 00.: =0... ::.N ::.N wNN =0. m: :: $0. . . . . . 20:55: 500...: .0... 5.... $0 00.... mNN 02d N: ::.. N»: Nw.» v:.N 00... :NN m: N: :N 00.0 00... 00.0 00.0 wNN h“: b: :: $2 0a.: Na: 2... 2.0 mNN 00. N: 00 0»... 0N0 .3: :5: 000 S. N: :N .3... SYN ::.: 00.. .00 S. N: :: 0...: 13:00.0 00.5055: . . . . . . . .055: A: .0 0.: 0k 1K he m0 .52 0:05: 50:: h o:vN 005.00 o 1.: 550:. 05-000 55:00! 00:000.. :05? 0:055:00 0:55 :0 ..0::00 :05? :0 .07: 00000.»: 000w 50.5.0.5 00505.00 :05.5>0:. :0..0:0:.5w 00.50.» 00000:: :00:>: 00.50.0050: 00.5.5000 18 000: 0:00:05:- ..0.: 00000000.: :0 00.50.» M55500? 0:0 050:. M51000 0:0 55:00:: .m 030:. DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 19 Table 6. Actual and estimated process values for im- mature green blackeye peas in quart jars (ho-t pack) Actual process values Estimated process values i Number of canner loads l 60 minutes l 35 minutes l0 minutes ___-_ { .___ 7 --, l l; F0 ' F0 p .F0 1 . . . . . . . . . . . . . . . . . . . . . . . .¢ 15.55 . 8.51 1 1.44 . 15.48 8.53 1.59 15.32 8.37 f 1.54 1 . . . . . . . . . . . . . . . . . . . . . . . ... 14.45 8.05 e 1.53 ' 14.41 8.57 ; 1.85 14 92 ; 8.52 l 1.50 Y l 1 . . . . . . . . . . . . . . . . . . . . . . . ._ 15.54 8.48 g 1.77 4 15.32 7.25 i 1.42 l 15.23 8.28 .1 1.51 1 . . . . . . . . . . . . . . . . . . . . . . . ..§ 14.72 7.77 1.21 5 14.73 7.23 ; 1.10 ' 14.39 7.99 § 1.28 obuuned in :1 sunihn‘\vay. j\n ilhuuratuni of hourzni esfirnauxl process value was obtained is given in Figure 5, using data for a hot pack quart jar. Actual and estimated processes for one series of quart jars are given in Table 6. Thus, lay using two estimated processes, the number of process times needed for calculating" the regression line may be obtained from the heat penetration data for only one long‘ actual processing} time. v-y-rm-i-v-w L 4- runa/rr V4405 (1%) 77M: IN MIIVUTEJ Figure 5. A lethality curve, showing how an esti- rnated process value vvas obtained for a process tune of 10 rninutes. 20 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION Estimated process values may be slightly in error when they are i‘ obtained for very short process times. In experimentally obtained curves for short process times, the, temperature of the food may remain constant at the process temperature for a few minutes, or even rise slightly, before cooling. This would increase the area under the curve and so increase the process value. Thus, an estimated process value, which does not take this increase into account, may be slightly lower than one obtained experimentally. The error, how- ever, has the effect of increasing the margin of safety. Calculation of Representative Process Values for Corresponding Process Times The next step was to determine, from the many individual process values, processing times which will yield adequate sterilizing values for each size of container and method of packing. Uusually 12 separate process values were secured for each process time, and usually each one was a different value. The mean of these F0 values could not be used as the representative value because it would be greater than several of the determinations for the same process times, and the containers showing these lower F0 values would require longer process times to reach that mean F0. On the other hand, to use the lowest process value obtained in a series of I2 would not mean that the lowest value in that series is the lowest one possible for the given process time. In view of these objections to using either the mean or the lowest process value, statistics were employed to obtain the lower limit of process value. This makes use of a line of regression and its standard error of estimate. The line of regression shows the change of process value with process time. F0 values from at least three different process times must be obtained. The 12 F0 values for each of the 3 different process times for blackeye peas were obtained experimentally in some instances, but in others only the highest level was obtained experimentally while the 2 lower ones were obtained by estimation. as previously described. The I2 individual F0 values at each time level were used to calculate the regression line and its standarrl error of estimate. The equation for the line of regression is y! I a + bx, in which x equals the process time; y, the process value; a, the ordinate of the point where the line crosses the y axis (x I 0) and b, the slope of the line. The values for constructing the lines of regression for each size of container. maturity of peas and method of packing are given in Table 7. The standard error of estimate is a measure of the variation among all the different process values used for calculating the line _ VVi'Y*Y'*"Vr DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 21 Table 7. Regression equation and standard error of estimate of process value on process time Regression equation yr =a +bx i i l ‘ r Container Maturity ‘ size of peas i Year Standard i H error of 2.6 x I estimate St. E. of Est. Hot pack Pints. . . . Immature green 1946 —0.377 0.292‘ 0.79s 2.07 1 1947 ; 1.841 0.292 0.641 1.67 Fresh mature. .. 1947 1.371 0.269 0.770 2.00 | All 1947 pints... . . . . . . 1661i 0.267 0.849 2.21 ‘Allpintsnnnn . . . . . . .. 1.203!‘ 0.273 1.150 2.99 Quarts . . . . . Immature green 1946 —l . 279 0. 272 0.474 1.23 l Fresh mature. . . 1947 —0. 872 0. 280 0. 671 1 . 74 l i All quarts . . . . . . . . . . . . . . ~—1 . 039 0 . 276 0 . 680 1 . 77 No. 2 cans. . Immature green 1946 0. 488 0. 276 0 . 401 1 . 04 No. 2% cans Fresh mature. . . 1947 —0.538 0.275 0.544 1.41 No. 3 cans. .. Fresh mature. . . 1947 0.304 0.273 0.591 1 .54 Fresh white mature... . . .. 1948 —0.604 0.281 0.680 1.77 All No. a cans . . . . . . . . .. 0.254 0.2801 0.715 1.86 Cold pack Pints. . . . . Fresh mature. . 1948 0.481 0.302% 0.883 2.30 Quarts . . . . . . Fresh mature. . . 1948 ——0.897 0.312‘ 0. 460 1.20 of regression. The value to be assigned to each standard error of estimate is also arrived at by statistical calculations. The values for the standard errors of estimate are given in Table 7. Each regression line was then drawn on coordinate paper, and a broken parallel line was constructed below it at a distance of 2.6 times the standard error of estimate. This lower line was, the one used in determining adequate process times, because it is assumed that, with normal distribution of process values, the F0 values for a given process time would not fall below this lower limit more than once out of every 20o times. This was the method used by Toepfer, Reynolds, Gilpin and Taube (I946). As an illustration. the regression line and its lower limit are given for hot pack pint jars in Figure 6. ’ Calculation of Safe Process Times A safe process is one in which the heat treatment is adequate to destroy completely the most heat-resistant food poisoning organ- isms likely to be present in the raw product. Since the F value of the organism (the process value causing complete destruction) is ._ not the same in all foods, it must be determined by relating inocu- 22 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION 13 12 till??? Panacea Wu»: FF’) e3 as fifi as fi . a. as a 1 .3: i "833 an n 77M: 0v N/zvu 1's: Figure 6. A regression line and its lower limit». The lower limit is drawn at a distance of 2.6 times the standard error of esti- mate, and is used to determine adequate process times. lated pack data to heat penetration data. The process values (Fol for a series of inoculated packs are given in Table 8 together with the spoilage data. These data indicate that processes yielding Fa values of 8.0 will be adequate to destroy spores of P. A. 3679 in blackeye peas. Since spores of this organism are one and a half to two times as resistant to heat as are those of Cl. bozfzrliizzravz, processes with minimum F0 values of 8.0 may be expected to have good margins of safety. The processes recommended xvere chosen to pro- vide such sterilizing values. Table 8. Summary of heat penetration and inoculation tests in pint jars. 1947 data for immature green bla-ckeye peas l Inoculated jars containing spores not killed _ Process value Process time Spoiled Viable spores within l present after 1 Mean Range 6 months 6 months Minutes <7; <70 ' F0 F0 1o . . . . . . . . . . . . . . . . . . . .. 9s o ' 4.6a 3.71 to 5.63 20 . . . . . . . . . . . . . . . . . . . .. 3. 0 3 7.37 6.81m 9.41 30 . . . . . . . . . . . . . . . . . . . .. 0 § Not tested 10.51 9.30 to 11.20 ‘it DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 23 » Table 9. Calculated and recommended process times for blackeye peas Processing time at 240° F Container Maturity of peas Year Process Calculated size value Recom- Hot pack Cold pack mended F o Minutes Minutes Minutes Pints. . . . . .. Immature green... . . 1946 8.0 36 . . . . . . . . . . . . . . . . . . .. Immature green... . . 1947 8.0 27 . . . . . . . . . . . . . . . . . . . . Fresh mature . . . . . . . 1947 8.0 32 . . . . . . . . . . . . . . . . . . . . Fresh mature . . . . . . . 1948 8.0 . . . . . . . . . . 33 . . . . . . . . . . All 1947 pints . . . . . . . . . . . . . . . 8.0 31 . . . . . . . . . . . . . . . . . . . . All pints . . . . . . . . . . . . . . . . . . . . 8.0 36 33 35 Quarts . . . . . . Immature green... . . 1946 8. 0 39 . . . . . . . . . . . . . . . . . . . . Fresh mature . . . . . . . 1947 8.0 38 . . . . . . . . . . . . . . . . . . . . Fresh mature . . . . . .. 1948 8. 0 . . . . . . . . . . 33 . . . . . . . . . . All quarts . . . . . . . . . . . . . . . . . . 8.0 39 33 40 No. 2 cans... Immature green... . . 1946 8.0 31 . . . . . . . . . . 30 No. 2% cans Fresh mature . . . . . . . 1947 8.0 36 . . . . . . . . . . 35 Ne. 3 cans. . . Fresh mature . . . . . . . 1947 8.0 34 . . . . . . . . . . . . . . . . . . . . Fresh white mature. . 1948 8.0 37 . . . . . . . . . . . . . . . . . . . . AllNo.3cans....... . 8.0 36 . . . . . . . . .. 35 Because the lower limits of the lines of regression indicate the minimum process values expected for specified processing times, the processing times required to give F0 values of 8.0 or higher may be obtained from the lower limit of each regression line. This procedure is illustrated in Figure 7 where a processing time of 36 minutes was obtained for all hot pack pint jars. Safe processing times were calculated in this way from the individual lines of re- gression for each size of container, maturity of peas, year and method of packing. These times appear in Table 9. It may be noted that the calculated processing times for hot packs were similar for a.ny one size of container irrespective of maturity of peas or year the data were obtained, except in the I946 pints. Nevertheless, separate calculations were made using the com- bined data for each container size. The safe processing times cal- culated in this way are also given in Table 9. These times were rounded off to the nearest 5-minute interval to give the recommended processing times for hot packs (Table 9). Thus, only one processing time is recommended for each container size. Cold packs in glass jars gave calculated processes of 33 minutes for both pints and quarts (Table 9). The recommended processing times, therefore, could be 35 minutes for each. However, it seemed safest to recommend the same processing times for cold packs as for hot packs. This increased the recommended time for quarts to 4o minutes. 24 BULLETIN 70-7, TEXAS AGRICULTURAL EXPERIMENT STATION Pacers: Wuuc l’) T: ME m Mmursa Figure 7. The regression line and its lower limit, showing how safe process times are read from the lower limits of the regression lines for an F0 of 8.0. Conclusions Recommended processing‘ times for hot pack blackeye peas are: pints, 35 minutes; quarts, 40 minutes; No. 2 cans, 3o minutes; No. 2% cans, 35 minutes, and No. 3 cans, 35 minutes. Cold packs in glass jars may be processed for the same times as hot packs. It is convenient that maturity of peas does not influence the recommendations. While the cold pack method of canning is much easier to do than the hot pack, there is no information yet as to which method gives the more palatable product or retains more of the vitamins. The hot pack method differs from the cold pack chiefly in its higher sealing temperature and the precooking in water which is discarded; there- fore, flavor and vitamin retention may be affected. These problems need to be studied before either hot or cold pack ca.n be recommended as the better method. DEVELOPMENT OF SAFE METHODS FOR CANNING BLACKEYE PEAS 25 Acknowledgments The authors wish t0 express their deep appreciation t0 Dr. O. B. Williams, University of Texas, for making the tests ‘for viable spores in the unspoiled containers which were canned in 1946, and t0 Dr. Howard Reynolds, Bureau of Human Nutrition and Home Economics, for the ones which were canned in 1947, and also for the viability tests of the spore suspension used in I947. They are grateful also for the spore suspension of Putrefactive Anaerobe No. 3679 supplied in 1946 by the National Canners’ Association and in 1947 by the Bureau of Human Nutrition and Home Economics. Literature Cited Cover, Sylvia, Turk, R. Dfand Kerns, A. H.: Development of methods for safe processing of home canned meats. Texas Agri. Exper. Sta. Bul. 63s, 1943- Cutter, j. B.: Death from food poisoning due to Bacillus botulinus. j. Am. Med. Assn. 79:825, 1922. Damon, S. R. and Payabal, L. B.: Distribution of the spores of Bacillus botulinus and Bacillus tetani in the soil. l. Maryland. j. infect. Dis. 391491-501, 1926. Dickson, E. C.: Botulism. A further report of cases occurring in the Pacific Coast States. Arch. Int. Med. 22483-495, 1918. Eisselen, W. B. jr. and Fellers, C. R.: Effect of different processing Ptoce- dures on venting and loss of liquid from home canning jars. Food Tech. 2:222-227, 1948. Geiger, j. C.: Status of bacterial food poisoning in the United States. Am. j. Pub. Health 14:3o2-308, 1924a. Geiger, j. C.: Possible danger of absorption of toxin of Bacillus botulinus through fresh wounds and from mucous surfaces. Am. j. Pub. Health 14 :3o9-31o, 1924b. Geiger, j. C., Dickson, E. C. and Meyer, K. F .: The epidemiology of bot- ulism. U. S. Public Health Service, Public Health Bul. 127, 1922. Hall, I. C.: Further outbreaks of botulism in the Rocky Mountain Region. Am. j. Hygiene 17:235-251, 1933. Hall, I. C.: New outbreaks of botulism in Western United States. Food Research 1:171-198, 1936. Hayhurst, E. "R.: Outbreak of botulinus poisoning in Solon, Ohio. Am. j. Pub. Health 16228-230, 1926. Hull, Thomas G.: Botulism. Hygeia 211566-567, 1943. Meyer, K. F. and Dubovsky, B. j.: Distribution of spores of Bacillus bot- ulinus in California. II. j. Infect. Dis. 31 :541-555, 1922a. 26 BULLETIN 707, TEXAS AGRICULTURAL EXPERIMENT STATION Meyer, K. F. and Dubovsky, B. j.: Distribution of the spores of Bacillus botulinus in the United States. IV. j. Infect. Dis. 31 :559-594, 1922b. Meyer, K. F. and Gunnison, j. B.: Botulism due to home canned Bartlett pears. XXXIX. j. Infect. Dis. 452135-147, 1929. Nelson, C. I. and Knowles, Darlene: Effectiveness of heat penetration in meat canned in glass jars in a pressure cooker. j. Agri. Research 61 :7 53-7 59, 1940. Nevin, Mary: Botulism from cheese. j. Infect. Dis. 28:226-231, 1921. Parry, E. Winifred: Prevalence of Clostridium botulinum in soils of central New York State. Food Research 11 :2o3-209, 1946. Schoenholz, P., Esty, j. R. and Meyer, K. F .: Toxin production and signs of spoilage in commercially canned vegetables and fruits inoculated with detoxified spores of Bacillus botulinus. XII. j. Infect. Dis. 332289-327, 1923. Slocum, Glenn G., Welch, Henry and Hunter, Albert C.: An outbreak of bot- ulism caused by home-canned tomatoes. Food Research 6:179-187, 1941. Thom, C., Edmundson, R. B. and Giltner, L. T.: Botulism from canned asparagus. Part I. j. Am. Med. Assn. 731907-912, 1919. Toepfer, E., Reynolds, H., Gilpin, Gladys L. and Taube, Katherine: Home canning processes for low-acid foods developed on the basis of heat pene- tration and inoculated packs. U. S. D. A. Tech. Bul. 930, 1946. Tucker, C. B. and Swanson, H.: Outbreak of botulism in Tennessee due to type B- Clostridiznn botulinum. Pub. Health Reports 54:1556-1560, 1939. U.S.D.A. Leaflet AWI-93: Home canning of fruits and vegetables. May, 19_44. P22-149-5M-L1 80