TEXAS AGRICULTURAL EXPERIMENT STATION A. B. CONNER, DIRECTOR, College Station, Texas BULLETIN NO. s56 AUGUST 1944 THE UTILIZATION OF SKIM MILK IN THE ICE CREAM MIX WfS. ARBUCKLE, C. N. SHEPARDSON H. M. WALLING Division of Dairy Husbandry / LEW/QR?’ m M. CGLLEGE o; FEXAEi AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS GIBB GILCHRIST, President E04-844-4500-L180 [Blank Page: in Original Bulletin] bulletin presents information upon the preparation and use of a )1 ntrated skim milk product in the manufacture of ice cream. The '_ 0d which proved most successful consisted of coagulating skim milk temperature of 94 to 96°F. with dilute hydrochloric acid. The whey ‘k drained when suflicient acid had been added to produce an acidity in whey of 0.45 to 0.48 per cent. After the whey had been drained the was disintegrated by passing it through the screen bottom of the rack. The curd was dissolved by adding five pounds of sodium bi- w nate per 100 pounds of casein and heating to 150°F. for 3-9 minutes. milk was added to the dissolved casein to produce a finished product ‘taining 16 p-er cent solids. The product was standardized by the addition im milk to 16 per cent solids co-ntent according to the Pearson square i’ 0d or to a Baume reading of 7.2 at 60° Fahrenheit. The» method used f s from methods heretofore described in that the quality and composi- “' control was based upon the use of the acidity tester, a casein test and hydrometer. The preparation was simplified by completing the entire by the use of a cheese vat as the major piece of equipment. Dis- _; ation and heating the curd brought about more rapid dissolving. heating period reduced the bacterial count of the finished product to z thousand or less. The use of skim milk instead of water to stand- the finished product to 16 per cent solids content offered a means of rving additional non-fat milk solids. An analysis showed that the l ximate composition of the finished product was as follows: 84.0 per water, 16.0 per cent total solids including 13.8 per cent protein, 2.0 icent lactose and 1.5 per cent ash. The cost of manufacture excluding was approximately one and one-half cents per pound solids. _ e product prepared in this manner was used to supply 10 to 50 per of the serum solids content of various ice cream mixes. The data that 37.5 per cent of the serum solids can be supplied by the con- ted skim milk in a 10 per cent fat, 8 per cent serum solids ice cream 'ning butter as a source of fat. When cream was used as a source t, 10 per cent of the serum solids needed could be furnished by the i’ trated skim milk product in a 1.0 per cent fat, 8 per cent serum i»: mix. In a 12 per cent fat, 9.6 per cent serum solids mix, 20 per cent e serum solids could be supplied by the concentrated skim milk; and 12 per cent fat, 11 per cent serum solids mix, the concentrated skim _ could be used to furnish 50 per cent of the serum solids needed. CONTENTS PAG Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Plan of Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Manufacture of the Concentrated Skim Milk Product . . . . .. The Use of the Concentrated Skim Milk Product in the Ice Cream Mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Detailed Procedure for the Manufacture of the Concentrated Skim R Milk Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. The Results of Using the Concentrated Skim Milk Product in the Manufacture of- Ice Cream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 Discussion . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . THE UTILIZATION OF SKIM MILK IN THE ICE CREAM MIX W. S. Arbuckle, C. N. Shepardson and H. M. Wallingl The possibility of utilizing delactosed milk products as a source of solids in the ice cream mix has been recognized for many years especially in plants which do not possess the facilities for the conversion of skim milk into skim milk concentrates. Much of the ice cream produced in Texas is manufactured in small plants that carry on mixed operations-in which ,_skim milk is available at nearly all times. Nevertheless, many of these “ small plants continue to purchase the condensed milk and milk powder “purpose. Lack of acceptance of concentrated delactosed milk products by ‘ “the industry has been primarily due to inadequate methods of preparation and control. A satisfactory method would permit the more efiicient use of * surplus skim milk in human food channels rather than its present use for - feeding livestock.“ It would also facilitate the storage of temporary sur- a “pluses of skim milk for use in periods of shortages. This bulletin presents ‘such a method whereby small dairy plants can produce a concentrated _skim milk product for utilization in the manufacture of ice cream. LITERATURE CITED Experimental work conducted upon the manufacture of delactosed milk solids for use in ice cream indicates that this product offers a possible 11 Qmethod for utilizing skim milk solids. Several methods for the preparation of a low lactose skim milk product have been suggested, but no simple “rstandard method for its preparation and use has been developed. Hall and Houtz (4) were apparently the first to study the possibilities = of the use of acid casein as a source of serum solids in ice cream. The object of their investigations was to develop a method for raising the “serum solids content of ice cream Without the development of sandiness. They found that moist acid casein dissolved with sodium bicarbonate could be used in ice cream with satisfactory results. Turney and Turney (7) patented a process for producing a casein ice cream filler. The casein curd was precipitated by pepsin, rennin or acid, and then semi-dissolved by “i the addition of lime, soda bicarbonate and sugar. Zoller (9) patented a process for the preparation of an unhydrolized alkali caseinate to be used with the regular mix ingredients. Corbett and Tracy (2) produced a low lactose milk by the addition of Hygell, a carbo bean derivative, that caused the separation of the curd and ‘whey in skim milk. Bird, Sadler and Iverson (1) found that ice_ cream mix made with sodium ~ caseinate supplying from 2.5 to 5 per cent serum solids whipped more 17“1Dr. W. S. Arbuckle, Associate in Dairy Manufacturers. Prof. C. N. Shepardson, Head, Dairy Department, Texas A. & M. College. H. M. Walling, Creamery Supt., Texas A. & M. Creamery. I Iused in ice cream mixes rather than utilize available skim milk for this’ 6 BULLETIN NO. 656, TEXAS AGRICULTURAL EXPERIMENT STATION rapidly to a higher maximum overrun, had a smoother more desirable body and texture, was more uniform in melting and had slightly better flavor than ice cream made with other serum solids concentrates. Watts (8) found that the use of 4 per cent casein solids in the mix gave more satisfactory results from the standpoint of flavor, body and texture, whip- ping ability and melting quality than higher casein contents. He reported that the whipping properties of the ice cream mix were greatly increased _ by the use of casein solids. Teichert (5) made an extensive study of the manufacture and use of acid casein in ice cream and concluded that acid casein could be used as a desirable source of serum solids for the manu- facture "of ice cream. In an 11 per cent serum solids ice cream mix, as much as 4 per cent serum solids could be supplied as acid casein with satisfactory results. Teichert, et al., (6) in a preliminary study, described a method for the x preparation of acid casein for use in ice cream. Dilute hydrochloric acid was added to skim milk to form an acid curd. The curd thus formed when washed and drained contained 29 to 32 per cent solids. The curd was dis- solved for use in the ice cream mix by the addition of sodium carbonate or sodium bicarbonate. The most satisfactory results were secured when the pH of the dissolved curd was adjusted to 6.5 to 7.2. Studies indicated that this product could be used to supply up to 40 per cent of the serum solids content of an average commercial mix. The mixes showed exceed- ingly rapid whipping ability and a high maximum overrun. The finished ice cream possessed a slight curd flavor, and the body was criticized as being gummy. Freeman (3) made suggestions for the use of casein in the ice cream mix, as prepared by the method described by Teichert, et al., and suggested that the casein could be held at 45°F. for 3 to 5 days, and that the addition of 0.2 per cent sodium propionate as a preservative made possible storage at 45°F. for 3 to 4 weeks. The recommended method of incorporating the casein into the ice cream mix was to prepare a 20 per cent solids product by mixing the casein in sufiicient water to which had been added 0.25 pound of baking soda for each 10 pounds of curd used. Several hours were required for the casein to dissolve, and then it was added to the balance of the mix at 120°F. as the mix was being pasteurized. Objections to the use of casein to supply more than 40 per cent of the serum solids were: an impaired flavor, a chewy or pasty body and difiicult control of overrun due to excessive rapidity of whipping. PLAN OF INVESTIGATION The general plan of this investigation was to design an economical, simple and rapid method for the production of a concentrated skim milk solids product of uniform composition and desirable flavor for use as a source of serum solids in ice cream. Also a comparison of various testing procedures was made in order to establish a simple practical method of determining the solids content of the concentrated product. A study was made to determine the extent that the concentrated skim milk could be used as a source of solids for various ice cream formulas, and also its ..»-\. THE UTILIZATION OF SKIM MILK IN THE ICE CREAM MIX 7 iiefiect upon the properties of the ice cream mix and the flavor, body and texture, melting properties, consumer acceptance and keeping qualities ‘of the finished ice cream. This investigation was conducted under con- trolled conditions which closely simulated those of the commercial plant. METHODS The Manufacture of the Concentrated Skim Milk Product p The method of manufacturing the skim milk solids used in this investiga- tion was perfected after observations were made of various procedures. Various lots of skim milk were placed in a cheese vat and adjusted to Qvarious temperatures between 90 and 100°F. in order to determine the ,most desirable precipitating temperature. The casein content of the skim milk was determined to provide a basis for the control of the composition Iin the finished product. A comparison was made of the characteristics of lithe curds produced by the use of hydrochloric, sulfuric, acetic and lactic "acids as precipitating agents. One volume of concentrated acid was diluted Iiwith nine volumes of water. The dilute acid was slowly added to the {imilk with gentle stirring until a clean separation of the whey and curd ‘had taken place. The acidity of the whey was adjusted to various levels {between 0.43 and 0.52 per cent, and a comparison was made with the pH '4 alues of the whey at each adjustment in order to determine the titratable idity at pH 4.6, the point of complete precipitation of the casein. When e desired acidity was reached, the whey was drained and the curd was ntegrated and different lots dissolved by the use of various amounts of erent dissolving agents. A comparison was made of sodium bicarbonate, ium carbonate and a commercial alkali for dissolving the curd. The idity of different lots of the finished product was adjusted to various els between 0.2 and 0.6 per cent, and the pH values were taken at ch adjustment in order to determine the acidity that produced the most irable product. he Walker casein test was used because it offers a simple method of xmposition control that can be used in any plant. In conducting this test 9 ml. sample of the skim milk was pipetted into a white cup, and one of a one per cent phenolphthalein solution was added. ‘This was titrated h N/ 10 sodium hydroxide until a fairly deep pink color was produced. i‘- two ml. of neutral 40 per cent formalin were added which turned sample white. The reading was taken from the burette, and then the fali required to turn the sample a fairly deep pink again after the addi- }_~- of the formalin was determined and recorded. One ml. of N/ 10 sodium ‘droxide was considered equal to 1.63 per cent casein in the milk. L The acidity determination of the Whey was made with the Mann’s acidity “t? in which the acid is calculated as lactic acid. A 17.6 ml. sample was l.» ted with N/ 10 sodium hydroxide using phenolphthalein as an indi- tor. The acidity on the finished product was made by the same method V h the exception that a 9 gram sample was weighed on a torsion balance the determination. i igpAccording m A.O.A.C. Methods of Analysis. Fifth Edition. 8 BULLETIN NO. 656, TEXAS AGRICULTURAL EXPERIMENT STATION The solids content of the finished product was determined by three difie . ent methods: the hydrometer method, a modified Bidwell Sterling meth and by drying the sample in a vacuum oven until constant weight reached. The hydrometer used had a Baumé scale for heavier than wa u, liquids, from 0 to 25,lgraduated to read at 60° Fahrenheit. The Bidwell Sterling solids determination was made by using a 10 gra sample and a receiving tube which was graduated from 0 to 10 ml. in 0. ml. divisions. A Five gram samples were used for drying in the vacuum oven until constant weight was reached. The procedure followed was that reco" mended by A.O.A.C. methods of analysis for condensed milk. The sampl were accurately weighed on an analytical balance into aluminum so dishes. The samples were placed in a vacuum oven at 100° C. until mo of the moisture was driven off. Then the samples were heated at 100° f under 25-inches vacuum until each sample had reached a constant weigh This method gave consistent results on duplicate samples, and the res » secured was considered the correct solids content of the product. The Use of the Concentrated Skim Milk Product in the Ice Cream Mix In order to determine the extent to which the concentrated skim m'i product could be used as a source of serum solids in commonly used i' cream formulas, a number of mixes of various compositions were prepar‘ The mixes used in this investigation were prepared from the same sour’ of ingredients, and the only difierence between mixes, within the sam series, was that variable increments of the concentrated skim milk produ i; were used as a source of serum solids. The total solids content was constan for mixes within each series. The mixes were made of cream or butter, =1 .the sources of fat, sodium alginate, as stabilizer, cane sugar, spray proce skim milk powder, skim milk and the concentrated skim milk produc’ Various amounts of the concentrated skim milk product were used to r": place milk powder as a source of serum solids. The following series mixes were studied. g Series I. Mixes in this series contained 10 per cent fat, 8 per cent seru solids, 15 per cent sugar and 0.3 per cent stabilizer. The fat was suppli by butter and the serum solids were supplied by skim milk powder if skim milk. The concentrated skim milk product was used to furnish 0, y‘ 37.5 and 50 per cent of the serum solids required. , Series II. In this series the mixes contained 10 per cent fat, 8 per cen, serum solids, 15 per cent sugar and 0.3 per cent stabilizer. The fat =I supplied by 40 per cent cream, and the serum solids were supplied b‘, skim milk powder and skim milk. The concentrated skim milk solids prod ‘l uct was used to furnish 0 and 10 per cent of the serum solids required. Series III. Mixes in this series contained 12 per cent fat, 9.6 per ce serum solids, 15 per cent sugar and 0.25 per cent stabilizer. The fat w supplied by 40 per cent cream, and the serum solids were supplied by ski‘ milk powder and skim milk. The concentrated skim milk product was us to furnish 0, 15, 20 and 25 per cent of the serum solids required. " THE UTILIZATION OF SKIM MILK IN THE ICE CREAM MIX 9 Series IV. This series of mixes contained 12 per cent fat, 11 per cent Yserum solids, 15 per cent sugar and 0.25 per cent stabilizer. The fat was supplied by 40 per cent cream, and the serum solids were supplied by skim lmilk powder and skim milk. The concentrated skim milk product was used to furnish 0, 25, 37.5 and 50 per cent of the serum solids required. The above mixes were made in 50 pound lots in 10 gallon cans and were pasteurized at 160° F. for 30 minutes. Each mix was homogenized at the pasteurization temperature with a single stage homogenizer set at 2500 LPOUIIdS pressure. The mixes were cooled to 40° F., and aged at this temperature for approximately 12 hours. A 40 quart batch freezer was Fused to freeze 45 pounds of each mix. Overrun determinations were taken rat one minute intervals, and the ammonia was turned off when the ice cream reached a temperature of approximately 25° Fahrenheit. ' Those mixes that proved most desirable when frozen on the batch freezer were prepared and frozen on a continuous freezer. The flavor, body and texture, melting properties, consumer acceptance, 7 dipping properties and keeping quality studies of the ice cream of different composition were made on samples drawn at 100 per cent overrun. l The viscosity of the different mixes was determined at 70° F. by the use Jof a pipette that delivered 100 ml. of water at 100° F. in 34 seconds. The viscosity was expressed in comparison with water. The ice creams were “observed for flavor and body and texture after the samples had been stored at 0° F. for o-ne week. Texture studies were made by breaking a half pint sample and observing the broken inner surface. The melting studies i were made by tempering a one pint sample of each ice cream at 0° F. for 24 hours, and then exposing it on a wire gauze to a temperature of 85° F. fora 60-minute period. At the end of the exposure period, the ice creams a were photographed, and the amount melted was determined by weight. ' The most desirable ice cream of each series was dipped after it had been g tempered at 6° Fahrenheit. The average weight per disher was calculated. lThe consumer acceptance of each ice cream was determined from the ‘flavor and body and texture preferences of a group of 15 consumers com- .posed>of housewives, food specialists and creamerymen. Samples of each ice cream were held at 0° F. and examined weekly for keeping quality. A . Those mixes that proved most desirable were manufactured and handled ’ on a commercial basis by the College Creamery. RESULTS The results presented in Table 1 show the effect of precipitating tempera-