BULLETIN 239 SEPTEMBER 1933 The Use of Dry Skim Milk in the Manufacture of Cultured Buttermilk By E. E. ALLDREDGE AND A. D. BURKE AGRICULTURAL EXPERIMENT STATION OF THE ALABAMA POLYTECHNIC INSTITUTE M. J. FUNCHESS, Director AUBURN, ALABAMA ALABAMA AGRICULTURAL EXPERIMENT STATION STAFF Administrative Committee John Jenkins Wilmore, 13. M. E., M. E. Boiling Hail Crenshawv, M. E. Luther Noble Duncan, M. S. M. J. Funchess, M. S., Director of Experiment Station W. H. Weidenbiach, B. S., Executive Secretary P. 0. Dlavis, B. S., Agricultural Editor Mary E. Martin, Librarian Sara Willeford, B. S., Agricul~tural Librarian AGRONOMY AND SOILS: Professor of Agronomy -- ---- .Head M. J. Fuchiess, H. S. Professor of Soil Chemistry ----- . -------.__.-J. W. Tidmore, Ph. D. Associate Professor of Soil Chemistry Anna L. Somimer, Ph. D. -Assis tant Professor iof Soil Chemistry G. D. Scar eth, It. S. _______Assistant Professor of Soil Chemistry J. A. Nafteil, M. S. -Assistaiit Soil Cheniist -- ___ ___r. Ph. 1). ----R. E. Viii __________________ Associate Profcssor of Plant Blreeinig H. B. T1isdialie, M. S. Associate Professor of Agronomy J. T. Williamoin, 1.S5__. Proifessor of Agronomiy -Assistaint ------------------------R. Y .Itailoy, It. St. 1). G. Stuarkii, Ph. D. ---------------------------- Assistant Priofessor of Agronomy ---------- Assistant Proifess or of Agrononiy *F. L. Davis. M. A. --------- _--- _---Ass istant in Agronomy ---------It. S. **G. It.stic. ----------- Assistaiit in Agriinomy __ F'. E. Beirtrain, 13. S. ___ Assistant iin Agroniimy E. L. Maystiiii It. S. Assistant in Agriiniiiy _ J. W. Rtichairidson, 13. S. ---in Agronomy --- .Assistant J. It. Tayliir. It. S. ANIMAL HUSBANDRY, DAIRYING AND POULTRY: J. C. Grimes, M. S. ------ Head Professor of Animal Husbianidry, Dairying anid Piiultry ----- Eeseairch Profes~sor of Animal Niitrit ion W. D). Salimin, M. A. Assosiate Priife sor of Animal Niitritiiin G. A. .Schraiier, Ph. D. Associate Priifiessor oif Animal Nutrition It. A. C. 0. Picketti, Professor of P'oultry Husba~ndlry -_____ G. A. Trolloipis, 13. S. Assistant Professiir of P'oultry Hutsbilandry --------------------D. F. King, H. S. -______--Assistant Professor of Animal Husbianitry W. E. S,*sell. M. S. _---Assistant in Animal Huisbaindry G. J. Ctneir. M. A. Graduate Assistant in Animal Nutrition J. G. Gooidman, B. S. BOTANY . L. G. L. E. V. AND PLANT PATHOLOGY: SenaI, lbh 1). Fick, M. S. Smith, M. S. Head Priifessor of Botany and Plant Paithiology Assistant Professor of Botany and Plant Paitholiigy Assistant in Botany aind Plant Pathiilogy ___ -. Heaid Associate Associate ___Assistant _---.Professor Professor Professor Pirofessor . ._of of of iof Agricultural Economics Agricultural Economics Agricultural Ecioniomics Agricultural Eciinomics Statisticail Assioistn Engineeriiig U. S. D. A.) Esgineen'ring Engineering Eiigineerinig and Zoioliigy Entiimoilogy Eiitiimiiliigy Eiitomoliogy AGRICULTURAL ECONOMICS: J. D. Popije. M. S. It. 1". Akos rd, M. S. EK. 11. Merenss, Ph. 1)--lark, M. S. C. M. Eidith May .Slights ---- AGRICULTURAL ENGINEERING: eaid Pirofess.or of Agricultural t---M. 1.. Nichols, M. S. Agricultural Engineer (Cootp. ---J. W. ERandiolpih, M. S. --- ---- Assistant Professor of Agricultural A. Carsi s. M. S. Assistant Professor of Agricultural ..---------N. W. Wilsiii, B. S. Assistant in Agricultural ------------ . It. S. E. G. likler, ENTOMOLOGY: Head Professor of _ M. A. J1. M. Roini~soi, H-. S. Sswingle, M. S. ._____-Associate Associate ________--L,. L. English. Ph. 1). _Assistant --------- . F. S. Araint, M. S. SPECIAL INVESTIGATIONS: J. F'. D~uggair, M. S. _-----Research Entomology Priifessor of Priifessor of Professor of Professor of Special Investigaitions of of of of Horticulture Horticulture Horticulture Horticulture and Forestry anul Foirestry anid Forestry and Fiirestry HORTICULTURE AND FORESTRY: ---- Head 1L. M. Ware, M. S. __-----_ C. IL. Isbell, Ph. D. Assistant 0. C. Melo~ck, M. S. Assistant *'It. W. Taylor, M. S. Proufessor Professor Professor Pirofessor SUBSTATIONS: Fred Steswurt, It. S. __________ Supt. Tennessee Valley Substation, Belle Mina, Ala. Supt. Suind Miiuntain Siibstation, Crosssville, Ala. R. C. Christiipher, B. S. ______ J. M. Henidersoni B. S. --- _---Assistant to Suinud Mountain Substation Superinitenident J. P. Wilson, B. S. --------------- ___ Supt. Wiregrass Subistation, Healanid. Ala. K. G. liker, BI.S. ----- -- ---- Supt. Black Belt Substation, Marion Jsinctiiin, Ala. Assistant to Black Belt Suibstuation Sntperinte~nidsnt .--------.--C. L. Milntyre. B..S. Supt. Gulf Coast Subsstation, Faiirhiipe, Ala. Otto Btrown, M. S. Assistant to Gulf Coast Substation Superintendent Harold Yuites, II. S. * Assigned by the State Department of Agriculture and Industries. *Ons leave. Staff as of September 1933. * The Use of Dry Skim Milk in the Manufacture of Cultured Buttermilk By E. E. ALLDREDGE GraduateAssistant, Department of Dairy Husbandry A. D. BURKE Head Professor of Dairying BULTI 3 BLT 239 ^1 SEPTEMBER 1933 Contents Introduction Object4 Methods and Equipment5 The Effect of Different Total Solids Content and Temperatures of Breaking the Curd on the Physical Properties of Cultured Buttermilk Made from Dry Skim Milk --The Effect of Different Total Solids Content on the Flavor of Cultured Buttermilk Made from Dry Skim Milk -11 The Effect of Viscolizing Reconstructed Skim Milk Prior to Culturing on the Flavor and Physical Properties of Cultured Buttermilk The Effect of Air Incorporation on the Flavor and Physical Properties of Cultured Buttermilk Made from Dry Skim Milk The Effect of Pumping with Different, Types of Pumps at Different Temperatures on the Physical Properties of Cultured Buttermilk Made from Dry Skim Milk The Effect of Fineness of the Curd Prior to Pumping Through Different Types of Pumps on the Physical Properties of Cultured Buttermilk Made from Dry Skim Milk The Effect of Varying Pump Speeds on the Physical Properties of Cultured Buttermilk Made from Dry Skim Milk The Effect of Different Cultures on the Flavor and Physical Properties of Cultured Buttermilk Made from Dry Skim Milk The Effect of Adding Dry Skim Milk or Reconstructed Skim Milk to Normal Skim Milk on the Properties of Cultured Buttermilk S u mm a r y ..................................................................................................................... 12 17 _ 6 20 26 28 30 33 36 38 39 Practical Recommendations and Suggestions for the Preparation of High Quality Cultured Buttermilk from Dry Skim Milk Ref er e n ces ------------------------------------------.-----------------------------------------------------------------........ The Use of Dry Skim Milk in the Manufacture of Cultured Buttermilk CONSUMER demand for a constant supply of high quality dairy products is the greatest asset of the dairy industry. Both producer and manufacturer, equally appreciative of this fact, are bending every effort to produce products of high quality. The manufacture of cultured buttermilk is no exception and the preparation of a uniform, high quality product is becoming increasingly important to the consuming public and to the entire dairy industry. The Standard Milk Code, United States Public Health Service, defines cultured buttermilk as "the product resulting from the souring or treatment, by a lactic acid culture, of milk or milk products. It contains not less than 8.5 % of milk solids not fat, and shall be pasteurized before adding the culture." Various dairy products have been used for the manufacture of cultured buttermilk. One of these products, dry skim milk, is gaining rapidly in favor because of its uniformity, ease of handling, splendid keeping qualities, and general suitability. Few attempts have been made to study the underlying factors responsible for the manufacture of a high quality buttermilk from dry skim milk. As a result wide variations have occurred in flavor, viscosity, body, texture, and stability of the finished buttermilk. One of the most outstanding experiments dealing with its preparation and processing is that of Reid and Welch (1) who found essentially "that increasing the pasteurization temperature above 1800 F. or exposing the milk for a period exceeding 30 minutes decreased the score of the aroma and flavor by causing a powder taste and odor to become apparent;" that cooling of the fermented milk prior to breaking the curd should be practiced; that the reconstructed buttermilk should be stored at temperatures lower than 420 F.; that the higher the percentage of starter used to inoculate the reconstructed buttermilk, the more desirable the flavor, aroma, body, and texture; and that the addition of normal skim milk in amounts exceeding ten per cent improved the reconstructed buttermilk in aroma, flavor, body, and texture. is expressed to: The American Dry Milk Institute, Acknowledgements-Appreciation Inc., Chicago, Ill., for the grant of a fellowship which made these studies possible; Prof. M. L. Nichols and Messrs. F. A. and T. H. Kummer of the Department of Agricultural Engineering for the construction of much equipment used in the work; CHR. Hansen's Laboratory, Milwaukee, Wis.; Elov. Ericsson Co., St. Paul, Minn.; National Canners Laboratory, Pittsburgh, Pa.; Dairy Laboratory, St. Louis, Mo.; Dairy Products Laboratories, Pittsburgh, Pa.; Lacteal Analytical Laboratories, Buffalo, N. Y., for furnishing cultures used in part of these studies; Viking Pump Co., Cedar Rapids, Iowa; Cherry Burrell Corp., Little Falls, N. Y.; and Specialty Brass Co., Inc., Kenosha, Wis., for the loan of pumps; Mr. John L. Whatley for extending facilities of the Opelika Creamery for commercial application of these studies. ~II " ~Li? " ~'rd ,/1 d81 I I(;( 1. IJF 1)1,%[r1 < P u: I (; ANT A1,1 1 ru I r rII ( (' r11: Seexal studies bearing indirectly on the preparation of dryW skim milk butteimil k hav e been performed by various wvorkers. Larsen and White (2) successful ly used dry skim milk for starter making in creameries and found it to be "a suitable substitute for nat ural skim milk in creameries where skim milk is not easily Burke (3) d1e fines gool buttermilk as being of "a mild, rather sw eet, acid flax or which should be viscous and1 creamy in appleailance, cour1ii ng from a bottle much the same as thick gravy. After curdling, it should 1bcak u p readily into a tine. flocculent, smooth, homogeneous mixture which contains no lumps and when held in storage at a lowr temlertaure do(s not wxhev-off The same worker has shown vigorous for twxo days or longer.'' agitation to be reslonsible for the dlefect of "wheying-off" in normal skim milk buttermilk. Klavsi (4), repo ting investigations on buttermilk made from normal skim milk, foun 11(n) ben e fit as a result of homogenizing eithei' prior to or after souring. 11am mer (5) reports a t emlerature range of 21 to 28 C. as being most suitable for the propagation of starters. OBJECT The object of these studies 'vas to letermine those factors and plant practices essential to the preparation of high duality cultured buttermilk through the use of drv skim milk. The effect of the followving tiactors on the flavor andl physical v rope rties wxas St udied : ( 1) (2) (:8) (1) Vaiation in total conltent. solidls 1 Breaking the curd at (lifferent tern pelat toes. Viscolizatioii. (5) InIcorp)orationl of air. Porniug undl~er dIifferenit (6) (7) cond(it ions. Use of (different lactic starters. Addition rnilk to milk. of drv natoral skirn skirn METHODS AND EQUIPMENT "Throughout the entire series tests a careful attemplt was nr 2. II iL iR m ade to control each factor. A TO SI MIA TEST \lN oSrr TH BEL ll~\NI) A HUlRh c lactic ferment, l iquid1( typ~e, wxas P1:. N I lwN)I F I R. usedl throughout the series and carried forward by daily translets. All culItulre tot inoculation was rneasured wxit h a sterilized D ry skirn mnilk of the highest grade was used neasure. ounce m The normal skim rnil k, used tor cornparison, was ini the tests. seplaratedl frorn rnilk ob~tained fromn the college herd of Jersey r: slK of cows. Except) as notedl in the text, cooling and breaking the curd for each series of tests was accornp)1ish ed by mf1eanis of a special dev ice which consisted of a glass churn jar held in place by t The jar was supwxooden frame set in a small metal container. p otted by t hec fra mc in a rnan ner that permitted ice water to comle in) cotactt with t he s ides and bottom, thus afforini g uniform cooling of the curd, either pior 01. subseqluenlt to breaking andl~ agitating (Fig. 1) V isco sit v detelminations were mace xxith ani instru ment (Fig. 2) similar to that of Bell aiic Burkey (6) by noting the bob101 travel to tite in seconds requtirecd for a mi niatuore 1)1um down watd thrtough a col urnn of buttermilk1 a (distance of 70 centi meters. Analysis fot total solids was made on a 1\I oionnier tester. Acidity wvas determined on wveighed 9-gram samles with N 10 sod iutm hydroxide, using ph enol phthalei n as indicator. P~lacinugs for flax or were made by plersons to whom the idlentity of the samples was Unknown. THE EFFECT OF DIFFERENT TOTAL SOLIDS CONTENT AND TEMPERATURES OF BREAKING THE. CURD ON THE PHYSICAL PROPERTIES OF CULTURED BUTTERMILK MADE FROM DRY SKIM MILK Procedure Test 1.-In a preliminary test the cultured buttermilk was prepared by dissolving in water various weighed quantities of dry skim milk to obtain samples of approximately 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, and 12.0 per cent of total solids, respectively. The buttermilk containing 8.0 to 9.0 per cent solids had a flat, watery flavor, low viscosity, and poor keeping qualities. Samples containing 12.0 per cent solids had an objectionable heated flavor and a gelatinous, somewhat slimy body and texture; hence, percentages above 11.0 and under 9.0, were disregarded in the succeeding experiments. Three series of tests were made on duplicate 6-pound portions of buttermilk prepared by dissolving dry skim milk in water. The buttermilk samples of each series contained a total solids content of approximately 9.0, 10.0, and 11.0 per cent, respectively. Buttermilk made from normal skim milk was used for comparison. All samples were made in glass jars of 1-gallon capacity. The dry skim milk water mixture and the normal skim milk samples were heated to 180 ° F. for 30 minutes. All samples were then cooled to 68 ° F. and cultured with 7 per cent culture. At the end of 15 to 16 hours the samples were treated as follows: Portion 1 was broken up at the temperature of incubation. The curd was then cooled to 50 ° F. and two half-pint samples taken from each of the 9.0, 10.0, and 11.0 per cent lots. One group of half-pint samples was held at room temperature; the other, at a temperature of 350 to 380 F. Portion 2 was treated the same as Portion 1 with the exception that samples of Portion 2 were cooled to 500 F. prior to breaking the curd. The curd in both portions was broken with an agitator operating at a speed of 323 R.P.M. for two minutes. Acidity and viscosity tests were made after breaking the curd of each portion. Wheying-off measurements were made at the end of 24, 48, 96, and 1.68 hours. Results are recorded in Table 1. Test 2.-Results of the preceding test indicated that a total solids content in the dry skim milk buttermilk of somewhere near ten per cent was desirable from the standpoint of producing a palatable flavor and satisfactory body. Accordingly, a test was made wherein three series of 6-pound samples of buttermilk were prepared to contain approximately 9.5, 10.0, and 10.5 per cent total solids. These were compared with one sample of TABLE 1.--Effect of 9.0, 10.0, and 11.0 Per Cent Total Solids Content and Cooling Prior to Breaking Curd on the Viscosity, Appearance, and Separation of Whey of Cultured Buttermilk Made from Dry Skim Milk Compared With Normal Skim Milk Buttermilk. (Average of Three Tests) sos Total I Treatment Acidity per cent Desired 9 Actual 9.18 Viscosity seconds 9.6 Appear Whey after standing; measured in eighths of inches per cent Uncooled ance after breaking curd* Si. foamysmooth Smooth Si. f oamysmooth Smooth 51. f oamysmooth Smooth Si. lumpy Si. lumpy I At room temperature 24 hours hours hours hours 1 168 At 35 ° to 38 ° F. hours 4.3 1.3 6.6 1.3 3.3 hours 7.6 2.0 hours 9.3 2.6 6.3 2.0 2.0 0.3 0 0.6 .82 .85 8.6 7.3 5.6 3.3 13.0 14.6 12.0 11.6 16.0 14.0 13.3 Cooled 10 10.08 12.3 20.3 9.3 7.3 6.6 4.6 Uncooled Cooled .87 .92 .95 .98 .89 .86 1.6 0.3 0 0 0 0 4.6 1.0 0 0 0 0 37.6 99.3 167.6 1444.0 Too high for test 9.6 8.6 7.6 9.0 11.0 10.6 1.0 0 0 0 0 11 11.06 Uncooled Cooled 2.0 1.3 2.5 2.6 3.3 6.5 4.3 ___ 9.6 10.5 10.0 Normal skim, milk * _ 9.50 Uncooled Cooled _ I 8.3 "Si." in column is abbreviation for "slightly". TABLE 2.-Effect of 9.5, 10.0, and 10.5 Per Cent Total Solids Content on Viscosity, Appearance, and Separation of Whey of Cultured Buttermilk Cooled Prior to Breaking Curd Compared With Normal Skim Milk Buttermilk. (Average of Three Total solids per cent Desired 9.5 10.0 10.5 Normal skim milk * Tests) Acidity per cent .94 .98 1.02 1.00 _____ Viscosity seconds 14.3 26.3 49.0 Too high for test for "slightly". Actual 9.43 9.88 10.38 9.75 _____ Appearance after breaking curd* Smooth Smooth Smooth Whey after standing; measured in eighths of inches At 35° to 380 F. At room temperature 24 48 96 168 24 48 96 168 hours hours hours hours hours hours hours hours 11.6 11.0 9.3 6.6 13.3 13.0 11.6 8.3 14.3 14.0 12.0 9.6 15.0 14.0 13.0 10.3 6.3 5.3 2.0 0.3 7.6 6.6 3.6 1.3 8.6 7.0 4.6 1.6 9.0 8.6 5.3 2.6 lumpy S1. ______________________________________ "Si." in column is abbreviation buttermilk made from normal skim milk. All samples were treated in a manner identical with those in Test 1, with the exception that 5 per cent culture was used for inoculation in order to better control the development of acid. All samples were cooled prior to breaking the curd. Results are recorded in Table 2. Discussion of Results The method of handling the buttermilk prior to breaking the curd is important in preventing the separation of whey. In each case it proved highly desirable to cool the curd prior to breaking. Samples cooled after breaking the curd, regardless of the rapidity with which the temperature was lowered, gave evidence of much more whey separation than the uncooled samples. In the majority of cases, even where samples were held at room temperature, it was found desirable to cool the curd prior to breaking; whereas, those samples cooled before the curd was broken and held at a temperature of 350 to 38 ° F. showed very little whey separation, thus confirming the findings of Reid and Welch. There was a gradual decrease in the tendency to wheyoff as the percentage of solids increased in the cultured buttermilk. Typical examples of the effect of cooling and of the percentage of total solids on wheying-off are shown in Figure 3. The acidity increased as the percentage of solids increased. However, the increased acidity was desirable as it tended to mask the slightly heated flavor of dry skim milk buttermilk, thus improving the palatability. As might be expected, the cooled samples showed a slightly higher acidity because of the extra time required to cool the curd prior to breaking. The body and texture of the dry skim milk buttermilk was noticeably smoother and creamier than that of the control samples of cultured buttermilk prepared from normal skim milk and improved as the percentage of total solids was increased. The curd was more easily broken and entirely free from lumps; whereas, that of the normal skim milk buttermilk was very firm and somewhat lumpy when broken under the same conditions. Viscosity increased as the total solids increased. Flavor was improved as the percentage of total solids increased up to and including a concentration of about ten per cent. Immediately after breaking and cooling the curd a heated flavor was apparent which was quite pronounced in samples containing over 10.0 per cent total solids. However, after aging at 350 to 38 ° F. for 24 hours the heated flavor was greatly reduced and in most cases practically eliminated. Samples containing 11 per cent total solids had a distinctly heated flavor while those containing 9 per cent were somewhat thin and flat. In all cases the viscosity of the buttermilk increased as the concentration of solids increased. The flavor of those samples containing 10.0 per cent solids compared favorably with that of the buttermilk Fh li IIm j El (URD N l WVHEY 0 I l I SEP'ARAXTION ', N I i o (I r IN CU'I'LUREDI 1,1-I 'FI I n rNi *i nii. urI~NG at r(oomN temVperattlre. A fter fiP honR Stailding U1pper roxv F. At.\fter 96 hour standiing at :85 to :8 Lower row Samaples I and 2 contain approximately Ji per R~eading front left to right and 4, 10) per cent; Samples 5 and 6, 11 per cent. cent solids; Sam~ples Card in Samp~les 1, :i, 5, and 7wa Slallples 7and 8 were( normal skimI nilk. Curd in Samples 2, 4, 6f, and 8 Nwas cooled prior to I)Ioko1 prior to) Cooling. brieaki ng;. madle from~ normal shim milk and ini many instances was rated as being stuperbor. Conclusions (1) (Ctlturied buttternilik made from drx skim milk shotild be cooled prior to brea king the curid. (2) As t he total solids content is increased the amount of whey sepiaration dlecreases. An increase in acidlity tends to mask the slightly heated (:8) flaxvor oft cutlturied buttermilk madle from dry skim milk. (4) Body and textur e wvere im proxved anid v iscosity was increase'd wvith eac h increase in the~ p Pro ntago It f total solids up lroxi mately 11.0 per cent. to andl intclItoding app (5) A total soli(ds content of 1 0.0 per cent was considlered Samplles containmio(st (desiriabl)e from the stand1poinut of flavor. ing 11.0 per~ cent solids had a (distinctly h eated flavor while those containling 9.0 1pcr cent wxere thin and wxatery in taste. 11 THE EFFECT OF DIFFERENT TOTAL SOLIDS CONTENT ON THE FLAVOR OF CULTURED BUTTERMILK MADE FROM DRY SKIM MILK Procedure Flavor tests of samples in Tests 1 and 2 showed a total solids content of approximately 10.0 per cent to be most desirable. As a further test, two lots of cultured buttermilk were prepaed Lot 1, consisting of normal skim milk, was divided into three 10-gallon samples, each of which was heated to 180 ° F. for 30 minutes and cooled to 70 ° F. At different time intervals culture was added to one of the three samples in order to vary the acidity. Lot 2, also consisting of three samples, was made of dry skim milk and each sample contained approximately 9.0, 10.0, and 11.0 per cent total solids, respectively. Both lots were tested for flavor by 100 different persons, each of whom placed Twenty-four hours later the samples according to preference. a second comparison was made of the best sample in each lot. Results are recorded in Table 3. Discussion of Results Data obtained in the test of both lots indicated very little preference of persons for any one of the three samples in either lot. The samples of dry skim milk buttermilk containing 9.0, 10.0, and 11.0 per cent solids (A, B, C) placed first in 33, 32, and 35 per cent of the trials, respectively; samples of normal skim milk buttermilk each of the same percentage of solids but of .86, .89, and .95 percentage of acidity (D, E, F), placed first However, in 36, 32, and 32 per cent of the trials, respectively. when first and second placings were combined the ratings for dry skim milk buttermilk were 81, 61, and 58 per cent for 10.0, TABLE 3.-Flavor Comparisons of Dry "Skim Milk Buttermilk Samples Containing Different Percentages of Solids and Normal Skim Milk Buttermilk Samples With Different Percentages of Acidity. Acidity Appearance Placings of 100 persons Second Third Total solids per cent per cent acdt f ter breaking curd* First Dry skim milk buttermilk 9.08 10.15 11.13 .96 1.01 1.04 Smooth Smooth Smooth 33 32 35 25 49 26 42 19 39 Normal skim milk buttermilk 9.56 9.56 9.56 * "Si." .86 .89 .95 is abbreviation Smooth Smooth S1. lumpy for "slightly". 36 32 32 41 30 29 23 38 39 12 11.0, and 9.0 per cent solids respectively; for normal skim milk buttermilk the ratings for combined first and second placings were 77, 62, and 61 per cent for acidities of .86, .89, and .95 per cent, respectively. A second test was made in which 100 persons compared Sample B of dry skim milk buttermilk containing 10.0 per cent solids with Sample D of normal skim milk buttermilk containing .86 per cent acidity. Results showed five ties for first place with 63 firsts for Sample D and 32 for Sample B. Many persons expressed the opinion that both samples were about equal in palatability but that Sample D was placed first because "it seemed to be a little less acid." For commercial purposes either sample would have rated as "excellent". The body and texture of dry skim milk buttermilk (Sample B) was smoother than that of normal skim milk buttermilk (Sample D). Conclusions (1) Buttermilk which has a flavor comparable with that of normal skim milk can be made from dry skim milk. (2) The body and texture of buttermilk made from dry skim milk is smoother and more creamy than that of buttermilk made from normal skim milk. THE EFFECT OF VISCOLIZING RECONSTRUCTED SKIM MILK PRIOR TO CULTURING ON THE FLAVOR AND PHYSICAL PROPERTIES OF CULTURED BUTTERMILK Procedure Test 1.-Seven series of tests were made on buttermilk, six of which were from dry skim milk and the other from normal skim milk for comparison. Each of the six dry skim milk series was divided into two lots. Lot 1 was viscolized; Lot 2, which served as a control, was unviscolized. Lot 1 of each Series 1, 2, and 3 was divided into two portions. Portion 1 was viscolized at a temperature of 1800 F. and one 6-pound sample collected at pressures of 1500, 2000, and 2500 pounds, respectively. Portion 2 of Series 1, 2, and 3 was cooled to 145 ° F. and samples collected at the same pressure as for Portion 1. Lot 1 of each Series 4, 5, and 6 was treated in an identical manner except that pressures of 3,000, 4,000, and 5,000 pounds were used. Buttermilk of Series 1, 2, 3, 4, 5, and 6 contained total solids percentages of 9.72, 9.72, 9.00, 10.85, 10.68, and 9.75, respectively. The results are recorded in Table 4. These percentages were used in order to determine whether or not viscolization had any relationship to quality in cultured buttermilk of different total solids content. The equipment used for viscolizing is shown in Figure 4. " J Ii I The milk was cooled to 68 F. and cultured with 5 per cent of starter. The acidity of the v arious lots, prior to cooling and breaking the to apicurd,, was regulatedl " the same percentSproximately age. This was accomplished a small samlple taken from each lot with a thin-walled glass tube, inch in diameter. Any lots falling below the desired acidity were held for a longer leriodl. When the acidity reached by making an acidity test on .93 per cent or above the samples were cooled to 50° F. and the curd broken for the time noted in the table. Two half-pint bottles were filled with buttermilk from each sample. One bottle was held at room temperature; the other, at a temperature of 835" to 38 F. MIeasurements were made periodically of the amount of whey aplpearing in the bottles. Viscosity studies were nade in the usual manner. All results ale recorded in Table 4. 1,IZING TESTS. Test 2.-As a further check on the effect of viscolization, a second test of two series was made. The reconstructed skim milk for each seiies was lrepared to contain, as nearly as possible, 1().0 per cent total solids. It was then heated to 180° F. for 8,0 minutes, coolel to 115 F., and divided into two lots. Lot 1 was passed through the viscolizer under 4,000 pounds pressure and caught diiectly in 6-pound quantities in foui separate glass jars. Lot 2 was unviscolized but like Portion I was taken in tour 6-pouind luantities. All eight of the 6-pound samples wvere then cooled to 70" F., In this test the and processed in the same manner. cultuiel, 1erccltage of total solids, viscolizing plressu ic, acidity, time and ternlecrature of breaking cuid and period of agitation were all conir lled to as nearly the same degree as possi)le for all ot the sam ples of both series. Studies of p~hysical tests weie made, as noted in the first test, recorded in Table 5. aniiid the axveraged rests Discussion of Results So far as could be observed. x iscolizirg the reconstructed skim milk had no beneficial effect in preventing wheying-off in cultured buttermilk. This is in agreement with the work of Knaysi (4) whose stutlies on fermented milk prepared from normal skim milk revealed no beneficial results from homogenizing TABLE 4.-Effect of Viscolizing Milk at Different Pressures and Temperatures Before Culturing on Viscosity, Appearance, and Separation of Whey of Cultured Buttermilk Made from Dry Skim Milk Compared With Normal Skim Milk Buttermilk. (Average of Three Tests) Viscolizer pressure pounds 1500 to 2500 1500 to 2500 3000 to 5000 3000 to 5000 Temperature OF. Total solids per cent 9.72 9.72 9.00 9.72 9.72 9.00 10.85 10.68 9.75 10.85 10.68 9.75 9.72 9.72 9.00 10.85 10.68 9.75 9.74 9.93 9.75 9.83 9.85 9.62 Time of breaking curd mains. 2 Acidity per cent 1.02 1.00 .93 1.01 .96 .92 .97 .91 .94 .97 .92 .94 1.02 1.03 .95 .97 .92 .93 1.04 1.03 1.01 1.01 .98 1.00 v cosity seconds 122 28 12 111 29 13 21 14 26 25 18 27 105 Appearance after breaking curd* i 1 Flavor after _____________At Whey after standing; measured in eighths of inches room temperature At .35°-38 °F. Breaking curd Si. lumpy Smooth Smooth Acid 81. acid Heated 145 5 5 2 5 168 24, 48, 168 96 24 24 48 and 96 hours hours hours hours hours hours hours 1-1-1-1 0.3 4.3 8.0 0 0 6.0 Acid 0.6 7.3 0 3.0 0.6 6.3 Acid 0 6.0 0 2.0 5.0 Good 0.0 Acid Good Good Good Good Good Good Good Good Acid Acid Good Good Good Good Acid Acid Acid Good Good Good 0.6 2.0 0.3 0 0.3 0 0 1.0 0 3 0 0 0 0 0 6 3 3 0 2 1 4.0 4.0 2.0 0 2.0 0 0.3 2.6 0.6 6 3 3 0 1 0 9 5 6 1 4 2 5.3 6.6 5.0 0 4.6 0.6 1.0 4.6 1.6 ,y3 Sl. lumpy 180 5 5 5 Smooth Smooth Smooth Smooth Smooth Smooth Smooth Smooth Lumpy 81. foamy 81. foamy Smooth Smooth Smooth 81. 81. 81. 81. 81. 81. .v . Sl. Acid heated 7.3 7.0 6.6 Heated 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2.0 0 "0 0 0 3.0 0 0 0 0 0 145 5 5 Heated Heated 81. heated Heated Heated 81. heated 0.6 6.0 2.6 3.0 6.0 4.3 7 7 180 5 5 2 5 5 5 Reconstructed milk not viscolized 5 5 5 29 9 15 10 25 185 450 240 110 95 155 ... ... Sl. Sl. Acid acid Heated Heated Heated heated 6 6 5 0 3 0 7 8 0 5 3 12 8 8 4 7 5 lumpy lumpy lumpy lumpy lumpy lumpy C1 1 Normal skim milk not viscolized rr\r\r\ I I * "S." in 10 10 10 10 10 v V Acid Acid Acid Good Good Good 10 8 2 5 column is abbreviation for "slightly". TABLE 5.-Effect of Viscolizing Milk Before Culturing on the Viscosity, Appearance, and Separation of Whey of Cultured Buttermilk Made From Dry Skim Milk. (Average of Eight Tests) Treatment Total solids per cent Time of breaking curd Flavor after Acidity per cent 1.00 1.01 Viscosity Appear-oAtm35u ance afterA38 breaking24 - _ _ Whey after standing; measured in eighths of inches F. curd Breaking 24 244 and 8 96 168 96, and curd* seconds 137 138 Smooth Smooth hours Good Good hours 0 0 hours 1 1 hours ____ minutes 5 5 168 hours 0 0 Viscolized at 4000 lbs. pressure, 145° F. Unviscolized *"Si.,' 10.02 10.02 Sl. heated Sl. heated 1.7 1.1 in column is abbreviation for "slightly". u~pper row: After 96) hours stand~ing; at room temp~erature. Lower rI ow: After 96hours >taliihg at 35 to 38 F. Reading from left to light: Sample 1 was viscolized at 1500 pounds pressure at ISO) I.; Sample 2 at 2,000) poands at 180) F.; Sample 3i a t 2,500 ponnf> at 151) I.; Sample 9 at 1,5001 poands at 1,15 F'.; Samaple 5 at 2,0001 pounds at 1.15 F.; Sample Gi at 2,500) pounds at 145 F'.; Sample 7 waS tlllXiscIliZedl andl Sample S nlUrlmal -lkim miI l niscolized. Samples in illustration conltainle 9 per cent total Soilidls. (ithe(r prior to or Sn bseq uent to souring. The only observed adv\antage in these stud~ies wxas that the process aided ini remioving or breaking til any small lumps ot unidissolved dr1y skim milk (Fig. 5). The (dat in lfales 4 and 5 indicate, as has already been a obseirved, that high ac idlit ies tend to submrnege the heated flaxvor inl ctilttiiei butttermilk plrelpared from driy skim milk. Between the acidlitit's of .90) and .9 ; per cent the heated flavor was readily distinguished, but above the limit of' .95 1pcr rent it gr'adltilly blecame submerged (me to the prIep~onderailce of' arid and a c haraciteristic lactir flaVor'. Conclusions 1 ) Visrolizing the reconstructed dry skim milk prior to culturing is (ot no significant valute or benetit in the proeparation of culttured buttermilk. (2) hIigh acidities, .95 per cent and abov e, tend to m ask the slightly heated flavor and thus l)1odtire a moire plalatable prodntc t. THE EFFECT OF AIR INCORPORATION ON THE FLAVOR AND PHYSICAL PROPERTIES OF CULTURED BUTTERMILK MADE FROM DRY SKIM MILK Procedure It (eleie was piepared. F'i this work a Special \'acuuml conlsisted1 of ia 1-gallon glass churn fitted1 with a specially degauge A vacuumr signed top xxhich could be made air tight. wxas co)nstructedl by fastenFing at glass tuble to at yardl stick and A small sublimerging the louver e iii of the tu be in merc ury. rubber hose, connected fiom at nipple on the special churn-] top tthe glass tuibe, served to pull the mecrc ury into the tuiibe and nd icate the n iimber of inches of xVac uumn when suction w\as apA high vac uum not only c aused1 collapse ot the pliedo (Fig. 6). bvlouttermnilk into) the suction line; hence, 20 inches a Is, but (lie wxas the stand(1ard( vac Ium mainitained. 'Tbhree series of tests xwere perf orm ed . Samples ofI reconst riitedl skim milk, preparedl to contain as nealrly as possib~le 10.0 heatedl to 180 F. for :10 minutes. ee lper cent totall solids,. wx Buttermilk so p~repoaredl cooledl to 68 to 70 F.. and cultured. was ico('01ed to 50 F. andl sepI aratedl into three lots of twxoort11ions The caird frorn Portion I of each lot xxas broken under each. vacuutim xwith agitator speeds as shoxxn ill Tfable 6; wh ereas, that fr'oom Port ion 2 xwas bro)keni xxithout xac uurn under the same Saml Ies of normal skim milk xxere used a moout ot agitation. for coomplarison. Studies ot flax or, xviscos)ity, aind other prop~erties xxere mnade Resulis are recorded in Table 6. in the usual manner. Discussion of Results by jiioloogoo (t shoxx that excessix e air incorporation, causedl I a~ta ini Tfable 6> afltatioii, is respoonsible for the de1m viL,-elm feto heying-off in cultutred nuterilk. This is clearly esahihd, particularly in that the table which ., prtionof sosthe amount of xxhey eprton on samplles held at a 'toae temperat uri of 835 :8 F. XChen agitation is rto l~s a U Ad".... Iufiet eoily to ; Iwhch Figure to break t he curd to a s~mooth consistency xxit hout excessivec foa miproduci1ng ep~aration of xwhey cithtrss si~ erdoes not occu 0d Ievelop~s o1r at negligible s ow.m extent. c 1, tF~ov)I ; Am izo Irrzt TABLE 6.-Effect of Air Incorporation on the Viscosity, Appearance, and Separation of Whey of Cultured Buttermilk Made from Dry Skim Milk. _______ ____ ______ ____________ (Average of Three Tests) Whey after standing; measured in eighths I I I Speed of agitator R.P.M. 181 252 323 i Total solids per cent Air 10.07 Vacuum 10.07 i Curd broken in -Ii Acidity per cent .97 .97 .96 .98 .95 Viscosity seconds 107 73 32 45 10 17 233 222 Appearance after breaking curd* Smooth Smooth Foamy Smooth Foamy Smooth Si. lumpy Si. lumpy Flavor after Breaking curd* 51. heated Si. heated of inches At room temperature, At 35°-380 F. 24 48 96 168 168 24 .48 24 hours hours hours hours hours hours hours hours hours Good 0.3 3.0 7.0 8.0 0 0 0 0 0 0, 9.3 0 0 1.0 4.3 Good 96 10.6 Air Vacuum Air Vacuum 10.07 10.07 10.07 10.07 9.57 9.57 .98 .94 .95 Si. Si. Si. Sl. heated heated heated heated Good Good Good Good Good Good Good Good 8.6 0 12.3 0 10.3 2.3 13.0 3.3 12.3 8.0 14.0 9.0 13.3 9.3 14.0 0 0 4.6 0 0 1.6 0 6.3 0 0 0 2.6 0 8.0 0 0 0 3.3 0 9.0 0 0 0 10.3 6.3 252 Air Normal skim Vacuum milk ,,, * "Si." 1.0 1.3 3.0 3.0 5.0. 5.0 6.3 0 in column is abbreviation for "slightly". A\it ANi I'NER VACUU xi5I CUiLT iaoU Bu'iqiii ll~: Upper row: After 24 hours standinog at room templerature. Lower row: After 24 hours staning at 35' to :8 F. Reading from left to right: Curid ini Samples I and 2 was broken up) at an agitator speed of 181 R.P.M.; Samples 3 anil 4 at 252 R.P.M.; Samples 5 and 0 at 323 R.P.M.; Samples 7 and 8 at 252 R.P.M. Samples 1, 3, 5, and 7 were agitatedl in air. Samples 2, 4, 6, and 8 were agitated under a 20 inch vacuum. Samples 7 alnd 8 were buttermilk madle from normal skim milk. in sampe agitated in a vacluum than in those agitated excessively uinder normal conditions in air. It was further observed that the curd from those samp~les subjected to excessive or vigorouts agitation became vecry porous, floated to the top of the container, and had the appearance of being badly contam invated with gas-prou ing organisms. At room ternpertc atture, mold andl bacterial growth appeared to be more rapid on samp~les vigorously agitated in air than on similar samples which had been agitatedi under vacuum. As a further check on the deleterious effect olf air incorporation, two samp~les were agitated at a high rate of sp)eed and allowed to stand at room temp~erature. A rapid separation of whey took place with the cutr d floating to the topl. Thie samltpes were then placed under vat uumn and sl owly~ agitated until btubbles ceased to rise and( free air app1earedl to be entirely elim inated. H1all-pint b~ottles were tilled with the agitated avid vacuum treatedl product and held at room templerature for observ ationi. The results are clearly shown in Figure 8. less~ whey separ'ati101 I . N, II i~ii 1'1F I oI i lI oN A SAM-1Ni Iii' 01 iiiIF NI' LK )u.I )Inh FRO I N -\ \A( II Itty DRY~ SkIM ?i I. Il. Ii AI I NI! ' Bottles I and sanme as in jar with Bittles .) and 5 are milik frm a jar allowxed to statnd 21 hour, andi was aid wh Iey. Bottle 5 had air renioxed Age of mtili: In bottles w hen phitt wasi tak~en: First boitties, 48~ hunt' Last 2 bottles, 21 boatr. Reaing (I ) (2) (:8) (4) fonm left to right: .Jar algitaltedi (ecessiel Mottle 2 is sFimple from1 andi jar. allowedi to set 48 houns. air extracted under v acuum. similar to jar in phto, which was thett agitated enough to maix cUrd unlder vacuum. Conclusions (1 ) Thbe i ncorp~orationt of eXc(55i \Q air ini hu ttermlilk is a mtajor faictor in ca usinig the separation of whey. (2) Excessive air incorlporation is responsible for the broken, un1ev-en, a itt "gassy" aplpearanc'e (If the c urd in bntteirnilk. (:) E'Xtessix e air i ncttrpttratittn seriotisly ijurties the flavor -illti impl arts a th in, flat, watery taste. THE EFFECT OF PUMPING WITH DIFFERENT TYPES OF PUMPS AT DIFFERENT TEMPERATURES ON THE PHYSICAL PROPERTIES OF CULTURED BUTTERMILK MADE FROM DRY SKIM MILK Ini may pait nts the ariianigemnt of equti pmenit mtake(s it necessa ry to piump ibuttermil k from the vat is proc essed into a sttiag(e vat or bottli ng machine. In order to determine the effect of pumping on and physical ptroperties of buttermilk, the following made. somnetimes( inl which it the quality tests were 21 Procedure Test 1.-Three series of twelve samples each were prepared to contain approximately 10.0 per cent total solids. The product was made in 10-gallon milk cans, heated to 1800 F. for 30 minutes, cooled to 700 F., and cultured with 5 per cent starter. At this point the milk was thoroughly mixed by being carefully poured back and forth into a third can, due precaution being taken to avoid contamination or loss. Two full cans were then incubated until the acidity reached .95 to 1.04 per cent. The curd was then broken with an agitator identical with that used in previous tests, but made especially to fit a 10-gallon milk can and operated at a speed of 108 R.P.M. for five minutes, this being the slowest speed that could be maintained for breaking the curd to a smooth consistency with a minimum of air incorporation. A portion of buttermilk from can No. 1 was pumped at incubation temperature (700 F.) through one of a series of five different types of pumps designated as follows: (1) Rotary pump. (2) Centrifugal pump A; disc type with removable one piece three blade impeller. (3) Centrifugal pump B; disc type with fixed impeller of four curved blades. (4) Centrifugal pump C; disc type with removable impeller of four straight blades. (5) Steam piston pump. The buttermilk in can No. 2 was first cooled to 550 F., separated into different portions, and passed through the pumps. Prior to pumping, a control sample was removed from each can. All buttermilk was pumped for a vertical distance of 5 feet 3 inches, then 2 feet 6 inches horizontally, and 5 feet 3 inches downward, a total of 13 feet, into a glass jar. About one gallon of milk was allowed to pass through the pump and pipe line prior to taking the sample in order to eliminate possible contamination with a portion of the previous sample remaining in the pump or pipe and also to prevent incorporation of air from an unfilled line. Two half-pint bottles were filled with a portion of the buttermilk from each pump; one was held at room temperature and the other at 350 to 380 F. for observation. Because of the slight variations in wheying-off observed in preliminary tests, 100 cc. graduated cylinders were also filled and held for examination at a temperature of 350 to 380 F. Viscosity studies were made of each sample immediately after pumping. Variations in flavor as well as the effects of different types of pumps were noted also. Results are recorded in Table 7. TABLE 7.-Effect of Pumping With Different Types of Pumps on the Viscosity, Appearance, and Separation of Whey of Cooled and Uncooled Samples of Cultured Buttermilk Made from Dry Skim Milk. _______ _______ ______ ___________(Average of Three Appearance Tests) Pump Treatment i i Total solids i Acidity Viscosity I per cent per cent I seconds 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 .97 .97 .97 11.6 24 5.3 5 5 5 4 4 5 5 Whey after standing; measured in eighths cc. whey of inches At 350 -381 At 35°-38° F. At room temperature after .24 24 48 168 48 24 48 96 168 96 pumping hours hours hours hours hours hours hours hours hours hours 1 L 1I 11 _I L 1'_ Control not pumped Rotary Cen. A Cen. B Uncooled Cooled Uncooled Cooled Uncooled Cooled Uncooled Cooled Unco oled Cooled Uncooled Cooled Smooth Smooth Foamy Foamy Foamy Foamy Foamy Foamy Foamy Foamy 7.3 9.0 11.0 11.6 6.3 10.0 8.0 9.6 9.0 9.0 11.6 11.6 11.3 11.3 10.6 12.6 12.6 13.0 12.6 12.0 13.6 13.3 14.0 13.6 0 0 0 0 2.0 2.0 0.6 1.3 2.6 2.3 0 0 3.3 2.0 2.0 2.6 0 0 4.6 0 0 6.0 7.3 4.3 0 0 10.6 11.0 9.0 16.3 11.3 13.3 12.3 0.6 1.0 0.3 1.0 1.0 1.0 .97 .97 .97 .97 .97 .97 .97 4.0 4.3 5.3 5.6 4.6 4.3 3.3 4.0 11.0 7.0 10.0 9.0 9.0 9.0 8.6 11.3 10.6 10.6 10.3 11.6 11.0 12.3 12.0 11.6 11.6 13.0 12.6 13.0 13.0 12.3 12.3 14.0 13.3 3.6 4.0 Cen. C 0.6 1.3 2.0 1.3 2.3 3.3 2.6 3.3 3.0 8.0 7.3 7.3 11.0 11.3 14.6 Steam piston 1 .97 5 .97 UI 1111 5.6 1 11 10.0 Foamy Foamy rr 9.3 0.6 I On c l.. lIl 1.0 1.3 c 4.6 10.0 .. a } AT I ASIA 1' 'Irno ii s Tvrs o1 Pu-mis. after 21 heor-, sanding at room temrperature. Lower row: After 24 hours tand ing at 835 to :15 F. Reairig from left to right: Samles I and 7 were controls unpuraped SampIes 2, :3, -1, 5, aid 6 were paim ped at 70 F. while Samples 8, 9, 10, 11, and 12 Were cooledi to 55° F. and piump~edl thietigh rotary, centrifugal, A, B, and C, arid teani piston pumps, respectively. Upper row: Test 2. A second series of three tests was made on six samples to (determine more closely the relative effect of different types of pumps. All samples were prelared as in the previous test andl p~umledl at a temnperatur'e of 70 F. Tests of physical plroperties were made in the usual manner and samples set aside in half-pint bottles and 100o cc. graduated cylinders for observation as in Test 1. Results are recorded in Table 8. Discussion of Results The tylpe of pumlp had little effect on the separation of whey. The variations that occurred were very slight and were about equal. All Iumpss caused the incorporation of air in the buttermilk and, although a number of samples held at ice-box temperature failed to develop a definite separation of whey, examination showed the curd to contain small mechanical openings and to be somewhat broken (Figs. 9 and 10). It lacked the desired The incorposmooth aplpearance of the best quality buttermilk ration of air was detrimental to flavor. Pumping greatly reduced the viscosity of buttermilk as compared with that of the controls. While all p~umped1 samlples as well as the controls increased in TABLE 8.-Effect of Pumping With Different Types of Pumps on the Viscosity, Appearance, and Separation of Whey of Uncooled Samples of Cultured Butermilk Made from Dry Skim Milk. (Average of Three Tests) Pump ______per Totall ids AppearWhey after standing; measured inAt 350 - 38° inches eighths of F. ance At room temperature afe 4 48 96 168 24 48 96 168 cent per cent seconds pumping hours hours hours hours hours hours hours hours 1.01 1.01 1.01 1.01 1.01 1.01 Acidiy Viscos Atcc. whey F. 35°-38° 24 48 hours hours 0 10.0 6.6 10.0 6.3 10.0 Control Rotary Cen. A Cen. B Cen. C SteamI 10.11 10.11 10.11 10.11 10.11 10.11 14.0 5.0 5.3 4.3 5.6 4.6 Smooth Foamy Foamy Foamy Foamy Foamy 7.3 9.6 9.3 10.0 9.0 10.0- 8.3 11.6 11.3 11.6 11.0 12.0 9.6 12.0 12.0 12.6 11.6 10.3 12.6 13.0 13.6 12.6 14.0 0 1.3 1.0 1.3 0.6 1.3 0 2.6 1.6 3.3 1.6 3.3 0.6 4.6 3.6 4.6 3.0 4.6 0.6 5.0 4.6 5.3 3.3 4.6 0 12.3 9.6 12.6 7.6 13.0 piston 12.6 viscosity upon staUnding", the pup~ried samnples failecl to <0 tain the maimumnin visciosity at- tainied Iby the controls. It oservXedl as a reslt wee .o p)umpinig the butttermilk and 55 temp leratures of 70 F. ( Fig. 9). This appeals con-I to0 results of experitraitory ments on the desjiraility Oft The exl lal iitiuii utdlhbitehl}' lies iln the ip-motis agitation and torce I a> iih w\hich (lie hiiltelflilk XX jeteto ill its pass5iat II Ii) the pumps.~l Conclusions (1) TVhere N)vas nI) \('I' markedl \ aviation in the e~l'ect of diferent ty'pes of p~umps> o onl culturiedl buitteirmilk. (2) All pumpn~s causedl the incorp~orailoll of air in the hreaking. rrmii Hill I w-ww-.od W-i rFXI (ii Pt! \ING ( .rrt~ ttPs. I)IIOt- '1'rrKa or Pt U pper row: After 2 hours istand)inig. (:)) When held at 8,5 to at 37 ' t10 38 F.U Lowe (iix row: After 24 hou, S>tanid in g 38 F. manyi of the pumrnped F. at 35 to :2S samp1)1es, regaridtless ofI the tylpe of pomph) tlevex (lle(l Readint from left to, ight: Sample 1 open ings~ coniftril, unputi niwi smnal Imnec haical Samples~ 2, 2I -I 5, ad aii spol itt inlg of cu11(. I ) The inlc~oortioni of dueo to pum~inolg dlecreased~ palatability. (5) Pumnping greatly redutcedl the v iscosityv of cultuired but-1 teirmilk made frorn div skim milk. (6) lthere was 1no \ (IV mar1)kedl diffeieince in the effect of tumirng att 70) andI 55 1,. 2 oi THE EFFECT OF FINENESS OF THE CURD PRIOR TO PUMPING THROUGH DIFFERENT TYPES OF PUMPS ON THE PHYSICAL PROPERTIES OF CULTURED BUTTERMILK MADE FROM DRY SKIM MILK Procedure As a result of previous tests w hich showed pumnping to be detrimental to buttermilk, it was assumed that the usual agitation to break the Curd pr'ior to pumping might be partly responsible. Accordingly, this factor~ was eliminatedI by the following procedure in which two series of tests were made. The buttermilk was prepared in two cans as described in previous experiments. When piroperly termentetd the curd in can No. 1 was b~roken with the special agitator operatinug at a speed of 108 R.P.M. for 5 minutes. After saving a sample for comlparison the remaining portion was (Iivxidled into fire sampl)1es; each sample was passed through one of the fixve p urnps, respec~itivelyv. The turd in can No. 2 was not agitatedl but was broken only enough to permit easy passage of a p~ortion through one of the respective pumps, thus e fIectingl cornpl1etc breaking of the curd and1 pump)ing all in one operatio x re Nvep placed in half' lint botlIes and grad uated cylinders andl set away at room andI ice-b~ox ternpera- ture for obserxvation. Resul I Discussion of Results Passage of the unagita~tedI samnples th rough the v arious t ypIes 0of pumps resulltedl ino neither a signiticant implroxement in xviscosity nor a marked( dIecriease in the sep~arat ion of' whey (Fig. 11) . Whey sep)arationl was greater ini -I . ,it RE IW I. IIL. z'l 0 II li t[I F ,-L those samples of low xviscosity; the flaxo wvas also less VCTo! (OF' FIN ENESS OE ('ian PRIOR '10 PUMP'ING; ON' THE PHIYSICAL PRPRIES paantable. Conclusions So far as these studies are concernedl no significant advantage is to be gained1 by passing the unbroken curd through ai pump; neither is the amount of whey separation materially reduced nor the viscosity materially increased. OFl CULTUIRED B~ TI Exiln.. 1' pper row: A fter 24 hours stanin g at room temperature. Lower row: Af(ter 24 hiours standinig at 35° to 8" F". Reading from left to right: Sample 1 contrvol. Samples 2, 4, 6, 8, and 10, card was agitatedl prior to pumping. Samples 3, 5, 7, fl, anad 11, curd was passed dlirec(tly through pump. Samples 2 and 8 pass~ed through rotary puump; 4 and 5 through centrifugal pump A; 6 andl 7 through centrifugal pump B; 8 and 9 through centrifugal pump C; 10 and 11 through steam piston pump. TABLE 9.-Effect of Fineness of the Curd Prior to Pumping Through Different Types of Pumps on the Viscosity, Appearance, and Separation of Whey in Cultured Buttermilk Made from Dry Skim Milk. (Average of Two Tests) Appearance after pumping Whey after standing; measured in eighths of inches ~ 1 cc. whey Lri 11 Pump Treatment Total solids per cent Acidity Viscosity per cent seconds F. 48 168 24 24 24 48 48 96 168 96 hours hours hours, hours hours hours hours hours hours hours i i At room temperature At 35 -38°F. At 35-~38° Control not pumped Rotary Cen. A Cen. B Cen. C Steam piston Normal Normal Unagitated Normal Unagitated Normal Unagitated Normal Unagitated 10.01 10.01 10.01 10.01 10.01 10.01 10.01 10.01 10.01 1.01 1.01 1.01 1.01 1.01 1.01 1.01 1.01 1.01 1.01 I 1.01 - VI 22.5 6.5 9.5 6.0 10.5 4.0 4.5 6.0 7.5 5.0 7.5V V Smooth Foamy Foamy Foamy Foamy Foamy Foamy Foamy Foamy Foamy 5.0 9.0 9.0 7.5 8.0 8.5 8.0 7.5 8.0 8.0 7.5 11.0 11.5 9.5 10.5 10.5 10.5 10.0 10.0 10.0 10.0 12.0 12.0 12.0 12.0 12.0 12.0 11.0 11.5 11.5 11.5 13.0 13.5 13.0 13.0 13.0 13.0 12.5 13.0 13.0 13.5 0 1.0 1.0 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0 1.0 2.0 1.0 1.0 1.5 1.5 1.0 1.0 1.0 1.0 0.5 2.5 3.0 2.0 2.0 3.0 3.0 2.0 2.0 2.0 2.0 1.0 3.5 3.5 2.0 2.5 4.0 4.0 2.5 2.5 3.0 3.0 1.0 8.0 10.0 7.0 6.5 3.0 4.0 5.0 5.0 1.5 5.0 2.0 11.0 13.5 9.0 9.0 10.0 10.0 8.5 7.5 6.5 8.5 Normal 10.01 Unagitated I 10.01 VLLW~-LVCVVVU IV VI I Foamy I 9.0V I 11.0 I 12.5 ~-V~YIIII V -- 'V -- ry LLIZ) 28 THE EFFECT OF VARYING PUMP SPEEDS ON THE PHYSICAL PROPERTIES OF CULTURED BUTTERMILK MADE FROM DRY SKIM MILK Procedure Since the Steam piston pump was the onlyv pump that could be opleratedl at v.aiale speeds, other p~umpt were el iminlatedl skim The butt ermil1k w\as priepariedl from ry tiom these tests. milk accordinig to the method alieadlv described andl div ided into f oui ipoitions, one of. which w as usedl as a control. ( )ve (8kb of the remaining thiee portions wXas passed through the steamn piston pumipl op~eratedl at diff ereiit tpe'( (lesitviated as high, medium, avid low, ieSlpect i\( t . l'h si al tt tl %\ t ImLtt in the ui'ial manner avid Samples held fti oltserVatioii at room tempfltraturi( avid at :)5 il1 :u'l rlcndhd to :18 F. ICI in Table 10. Discussion of Results of the x aiiatioln in steam p~ressurie and comItaiati\ e stiffness of the view steam Iputmpi it was, dilicuIt to arc ii lately control the Slpeedl bet ween medium avid fast. h ow ev~er, an examination of the talble indlicates results to be somewhat favorable to slow sp~eedl in so far aLS \he'V sepl anton and irlpio\c ((ViSCOSitV ale (oniceiled. The inipio~emuvit \Vas toot small to be of an}' comunri cial significance t(Fig. 12). Recause [D Conclusions The steam Ittmpl olperatng t l~ed i les detrsow ing tpee isles sow deri-at mentalI ttt the Ithv'sical ptrtop,it ies of Ituvtterm ilk than wh en ttperatedl at high speed ;howN- riii r PlteiYta iF I1ilkADE~t FROtM SKIiM ILK. Kcrlai I 11v hee, ifs e ffect is ttt slight to be of a nd conise u envce. Iutper tow: afIter 24 hour is tantding rootm temperata re. 1ttxx p vow: Aftter 24 htturs standinog at 8:5 to S5 F. Reatditg frttm left ttt right: Sample 1 conrI; Samples 2, :8, and 4 punipetd p at i'at oediujm and slttw speeds, risptetix cl. TABLE 10.-Effect of Varying Pump Speeds on the Viscosity, Appearance, and Separation of Whey of Cultured Buttermilk Made from Dry Skim Milk. (Average of Three Tests) Whey after standing; measured in eighths Viscosity of inches cc. whey 350-380 F. Speed of pump Total solids Acidity seconds Immedi- After 6 ately hours 9 4 4 4 21 13 12 14 Appearance after pumping At room temperature At 35 oAt - 380 F. per cent per cent Control Fast Medium Slow 10.00 10.00 10.00 10.00 .96 .96 .96 .96 24 48 96 168 24 48 96 168 24 48 hours hours hours hours hours hours hours hours hours hours Smooth Foamy Foamy Foamy 8.6 10.6 10.3 11.0 10.6 12.3 12.0 12.3 12.3 13.6 13.0 13.0 12.3 13.6 13.0 13.6 0 1.6 1.3 0.6 0 3.3 2.6 1.6 0 5.3 5.3 4.6 0 6.0 6.0 5.6 0 11.3 9.6 7.3 0 16.0 13.0 10.6 30 THE EFFECT OF DIFFERENT CULTURES ON THE FLAVOR AND PHYSICAL PROPERTIES OF CULTURED BUTTERMILK MADE FROM DRY SKIM MILK Procedure Three series of tests were made using twelve different lactic cultures, obtained from 6 different firms and designated by letter. The reconstructed milk was prepared as usual and divided into twelve 6-pound samples, each sample being placed in a glass churn jar. Five per cent culture was added as in previous tests and samples incubated until the proper curd had formed. The curd of each sample was broken with an agitator speed of 181 R.P.M. and the customary physical tests made. Results are recorded in Tables 11 and 12. TABLE 11.-Flavor Comparison of Samples in Table 12. I I I I.() I.W C-'V~-~ ~--II( III 11(1 Sil. I rI Il I PS I First Second Fourth Third Fifth Sixth Culture No. % No. % No. No. % % No. No. % % A 1 14.3 1 14.3 . 1 14.3 B 1 14.3 1 14.3 C 1 14.3 1 14.3 1 14.3 1 14.3 D Th- 28.6 1 14.3 E 2 1 14.3 F 2 28.6 3 42.8 1 14.3 1 14.3 G 3 42.8 H 1 14.3 2 28.6 I 1 14.3 J 1 14.3 4 K 57.1 2 28.6 1 14.3 1 14.3 1 14.3 L 2 28.6 /1 1 14.3 2 28.6 TABLE 11.-(continued) Flavor Comparison of Samples in Table 12. Culture A B C D E F G H I J K L -No. 1 1 1 2 2 Seventh -- - - Eighth No. % Ninth No. 1 2 1 1 1 % 14.3 28.6 14.3 14.3 14.3 14.3 I Tenth No. %o 14Eleventh No. 2 % I Twelfth No. % % 14.3 14.3 14.3 28.6 28.6 1 1 1 2 14.3 14.3 14.3 28.6 2 1 28.6 28.6 14.3 14.3 1 1 1 14.3 14.3 1 2 1 14.3 28.6 14.3 1 1 14.3 14.3 1 2 2 28.6 28.6 3 1 1 42.8 14.3 14.3 Discussion of Results There was a variation in both flavor and viscosity as produced by the various cultures. Some cultures (F, K, L) produced a flavor similar to ordinary churned buttermilk; others (B, C, E, G) gave clean, lactic flavors. Two cultures (H, I) TABLE 12.-Effect of Different Cultures on the Viscosity, Appearance, and Separation of Whey in Cultured Buttermilk Made from Dry Skim Milk. (Average of Three Tests) I I I I I Whey after standing; measured in eighths of inches Viscosity seconds i cc. whey At 3538 Culture Total solids per cent Acidity per cent 1.04 .94 .98 .92 1.03 1.05 1.02 1.03 1.02 1.02 1.03 1.04V I L Appearance after breaking curd* At room temperature 24 hours i At 35-38° F. ________ F. 48 hours 96 hours 1.0 5.0 1.0 168 hours 1.6 24, 48, 96 hrs. 168 hours 0 0 0 24 and 48 hours 0 0 0 0 0 0 0 0 0 0 0 0 A B C D E F G H I J K L * 10.01 10.01 10.01 10.01 10.01 10.01 10.01 10.01 10.01 10.01 10.01 10.01 28 35 26 8 35 32 23 32 23 41 35 58 for Smooth 0 Gelatinous 0 Sl. lumpy 0 Sl. lumpy 1.0 Smooth 0.3 Lumpy 0 Smooth 0 Smooth 0 Si. lumpy 0 Sl. lumpy 0 Smooth Gelatinous 0 Smooth Sl. lumpy vv I N' 0'~L'^'~JI 0 2.3 0.3 3.3 2.3 0.6 0.3 1.0 1.3 0.3 6.6 2.3 9.0 6.6 4.3 2.0 1.6 2.6 3.0 2.3 1.3 2.0 5.7 3.7 3.3 3.7 4.5 4.5 2.3 3.0 0 0 0 0 0 0 0 0 0 0 0 0 0.6 0 0 0 0 0 0 0 0 0.3 0.6 ---- "Si." in column is abbreviation "slightly". 32 produced a less palatable flavor somewhat resembling that of mild Bulgarian buttermilk. The flavor imparted by two cultures (A, J) was very desirable but the body of the buttermilk was "slick" and somewhat gelatinous. One culture (D) appeared to be somewhat weak and failed to produce sufficient acid to mask the slightly heated flavor otherwise apparent in buttermilk made from dry skim milk. Placings for flavor were made by members of the dairy department and others. Results are recorded in Table 11 which shows the number of times and respective percentage each sample was rated as first, second, third, etc. Examination of Table 12 shows that all cultures, with the exception of D, produced buttermilk of a satisfactory viscosity which did not whey-off when held for a period of one week at a temperature of 35° to 38° F. Even at variable room temperature the separation of whey was remarkably low. Five cultures (B, E, J, K, L) produced buttermilk of high viscosity, culture L being particularly outstanding in this respect. Throughout all of these tests wide variations in viscosity have occurred even when the same culture was used and, so far as could be determined, under identical conditions. A careful study of results of all tests reported in this bulletin appears to A very throw considerable light on a solution of the problem. close relationship exists between acidity and viscosity; viscosity and lumpiness; and lumpiness and whey separation. Each couplet of factors is in turn related to the other. For example, a buttermilk of low acidity can normally be expected to have low viscosity and be easily broken to a smooth consistency. However, much separation of whey occurs. On the other hand, a buttermilk of high acidity and of comparatively high viscosity may or may not develop whey. The evidence presented points to the fact that if buttermilk is held at a high acidity for a considerable period prior to breaking, the curd becomes very firm and is broken with difficulty, many small lumps occurring. Under such conditions wheying-off is very likely to occur. However, if the curd is broken soon after the acidity reaches the desired percentage, a smooth buttermilk results with very little or no whey formation. If a firm curd is agitated to the point where smoothness is attained with freedom from lumps, wheying-off is not likely to occur unless excessive air is incorporated. There is, thus, a certain adjustment that must be maintained between the percentage of acidity developed, the time held prior to breaking the curd, the amount and speed of agitation, and the degree of fineness to which the curd is broken if wheying-off is to be prevented and a smooth buttermilk produced (Fig. 13). Conclusions (1) There is cOHil4181 1 )IQ variation in the flavor and viscosity prloducedI by different FELT OF I)1FFIlRFl'. CULUE ~. Oi N I pper row: Ii) 100111 telp 0 Af ter 2L1 itu1it. houris standing. For the preparation high dtality btittermilh Promi (liy skim milk a v igorous, active culture is essential. Stuch a culture should larat ively high prioducle a comp viscosity without "slic kness' 01 gelatinous c haracteristics. The turd of the ter(83) merited milk should be brloken soon after the dlesi red p~ertenhtage o f at idity h as d evel(2) ofI ope~td. Lo~wer row: A fter 24 hours standing. at ;5 to :H F'. headIing 8tiolef ht to right: Sample, 1, 2,8.1, 5, (i, 7, 9,S,10, 11, an 2 are culture; A, 13, C, 1), E, F, Regardless of the cutl ofI apprloximately .95 to 1.00 per i15 oU t d to he most tent wa dlesirabile in the finished buttermtilk. (4) ttlie used, an aciit i THE EFFECT OF ADDING DRY SKIM MILK OR RECONSTRUCTED SKIM MILK TO NORMAL SKIM MILK ON THE PROPERTIES OF CULTURED BUTTERMILK As a result of eXitelirnental studies Reid and «Welcek (1) found that "the addition of normal skim milk to reconstrutted mnilk increased the dlesira bi lity of the fermented milk at the time of breaking the turd."''They ftirth er report that "the stoles ot aroma, flavor, body, anrd texture wxere constantly higher in those lots to which normal skim mnil k hacd been addcedl betore fermentation." Resul ts oft sttudies re ported in this bulletin suggestedl a posbilIity that the converse might like wise be true and that the addition of small quanitities of dry skim milk to normal skim) milk, prior to heating arid fermentation, would povXe benefitial. Procedure 't'hree series o f tests were matde to theeck the abov e possiiliies. Five 6-pound sampl~les of t ultured buttermilk were p~reparedl from the following milks: Samp1l1e 1 Normal skim milk obtai ned dirtect tiom separ~ ator. Sample 2-Normal skim milk to cent. wxhitch had been add(ed suffitient dry skim milk to intrease the solids by one-half' p~er 34 Sample 3-Normal skim milk to which had been added sufficient dry skim milk to increase the solids by 1 per cent. Sample 4-Reconstructed skim milk of approximately 10.0 per cent total solids. Sample 5-Equal parts of normal skim milk and reconstructed skim milk of 10.0 per cent total solids. All samples for each series were prepared in glass jars and treated in the usual manner. When fermentation had reached the desired point, the curd was cooled and broken with an agitator speed of 181 R.P.M. for five minutes. Physical tests are recorded in Table 13; flavor studies are recorded in Table 14. Discussion of Results An examination of Table 13 shows that for every increase in the increment of added dry skim milk there was a corresponding increase in viscosity and in the degree of smoothness. Sample 4, prepared entirely from dry skim milk, was lowest in viscosity, being followed in turn by Samples 5, 1, 2, and 3. The degree of smoothness and ease of breaking the curd was also closely related to the percentage of added dry skim milk. Sample 4, made entirely from dry skim milk, was most desirable in this respect, being followed in order by Samples 5, 3, 2, and 1. In these studies the curd of normal skim milk buttermilk, when compared with that prepared from dry skim milk, was more difficult to break and produced buttermilk of the highest viscosity, but lacking somewhat in smoothness when handled under the same conditions. From the standpoint of acidity, Samples 1, 4, and 5 were practically identical; Sample 2 was a little higher; Sample 3, containing 1 per cent of added solids, was the highest of all. This is to be expected on account of the increase in solids. With the exception of the normal skim milk buttermilk, whey formation was comparatively low even after a week's standing at room temperature. None of the samples wheyed off at temperatures of 350 to 38 ° F. (Fig. 14). As in previous tests, there was a close relationship between ease of breaking the curd, lumpiness, and the separation of whey. Studies of flavor show the interesting fact that the samples of normal skim milk containing 1 per cent of added dry skim milk solids were placed first in 31.3 per cent of the trials; whereas, samples made entirely from dry skim milk were placed first in 26.3 per cent of the trials. In addition to being highly palatable both buttermilks were of a smooth, creamy consistency. In all flavor studies it was found that buttermilk made entirely of dry skim milk, or of normal skim milk to which dry skim milk had been added, was less harsh and coarse in flavor than buttermilk made of normal skim milk even though acidities were the same or slightly higher. TABLE 13.-Effect of Adding Dry Skim Milk or Reconstructed Skim Milk to Normal Skim Milk on the Viscosity, Appearance, and Separation of Whey in Cultured Buttermilk. _________ (Average of Three Tests) Whey after standing; measured in eighths of inches ____ cc. whey ____ Preparation of milk Total solids per cent Acidity Viscosity seconds 177 267 301 41 79 Appearance after breaking curde hours Lumpy 51. lumpy Si. lumpy Smooth Smooth 2.7 1.3 1.3 0 0 At room temperature hours 4.7 3.0 3.0 0 0 hours 6.7 5.3 4.7 0 0.3 hours 7.3 6.0 5.7 1.0 per cent 1.01 1.04 1.06 .99 1.01 At 35°- At 35°F. 38 ° F. 38~ 24, 48, 24 and 96 and 168 hrs. 48 hrs. 0 0 0 0 0 0 0 0 0 0 N.S control '/2% 9.68 10.17 10.63 10.01 9.85 N.S. ± D.S.M.S.** N.S. ± 101cD.S.M.S. R.S.M.* control Equal parts N.S. and R.S.M. * 1.0 N.S. is abbreviation for normal skim milk. ** D.S.M.S. is abbreviation for dry skim milk solids. *** R.S.M. is abbreviation for reconstructed skim milk. * "Si." is abbreviation for "slightly". 36 TABLE 14.-Flavor Comparisons of Samples in Table 13. Sample 1 2 3 4 5 No. 3 3 6 5 2 First % 15.8 15.8 31.6 26.3 10.5 Second No. % 3 3 2 6 5 15.8 15.8 10.5 31.6 26.3 Third No. % 7 3 5 1 3 36.8 15.8 26.3 5.3 15.8 Fourth No. % 1 7 3 2 6 5.3 36.8 15.8 10.5 31.6 dry skim skim Fifth No. 5 3 3 5 3 milk milk to to % 26.3 15.8 15.8 26.3 15.8 increase increase Sample 1-Buttermilk made from Sample 2-Buttermilk made from solids 1/2 per cent. Sample 3-Buttermilk made from solids 1 per cent. Sample 4 -Buttermilk made from Sample 5-Buttermilk made from skim milk. normal skim milk. normal skim milk plus normal skim milk plus dry dry skim milk. equal parts of normal skim milk and reconstructed Conclusions (1) The addition of dry skim milk to normal skim milk in quantities sufficient to raise the total solids 1 per cent prior to heating and fermentation, improves the body, texture, and flavor of the resulting buttermilk. (2) The addition of dry skim milk to normal skim milk prior to heating and fermentation increases the viscosity of normal skim milk buttermilk and produces a product the curd of which is easier to break and smoother than that prepared solely from normal skim milk. (3) The addition of dry skim milk to normal skim milk is beneficial in helping to prevent the separation of whey. SUMMARY (1) A total solids content in the reconstructed skim milk of 10.0 per cent with a variation allowance of 9.8 to 10.2 per cent was found most desirable from the standpoint of producing a desirable flavor, body, and texture. (2) Whenever possible, the curd of buttermilk should be cooled to 50° F. or lower prior to breaking. (3) In these studies 5 per cent of added starter was found to be satisfactory in the development of the proper acidity, flavor, body, texture, and viscosity. (4) An acidity of .95 to 1.00 per cent in the finished buttermilk was most satisfactory from the standpoint of flavor. Flavor improves after 24 hours of holding in cold storage and the slightly heated taste noticeable in the freshly made product practically disappears. (5) The curd of cultured buttermilk prepared from dry skim milk was easier to break than that produced from normal skim milk and the body and texture of the finished buttermilk was invariably smoother and more creamy. d6) rce Viscolization of the nst-ructe1 skim milk p)1i0r l)f apparent benetit. (7) Vigorous agitation of tculturing was found to be the Curd, particularly to the poiint of slight foaminess, is responsible for many major dlefects of cultured biuttermilk. esp~ecially the (defect of whley ing-off. 8) It Was found poissible restore a vigorously agitatedl andl badly wrheyed sample toi buttermilk to its original xx1e-free state by' r'enmoval of. niri under vac uurn. 9) The incorporation of exc essix e air in buttermilk is responsible tor a porotis, brok(f en, andi~ KD) SKIM gassy app~eiaance of Mulsh To NouMtux. SKIM thie curd. (10) The presence of excessive air' is (detrimental to flavor in that it produces a Uppeir row: at room1 At er iii) I. te1(perature hours standing thin, flat. watery taste. Such Lowe row: at 35' to) 88 Reing samile After 1(6i houris standing F'. ) buttermilk (deteriorates rapidl y. (11) The pumping of but- d to from letrnl rigmht, 1 -Buttermilk made from nor- ter milk w,,as found to be objectionable in th at air incor- nilk OIhiik. Sample 82-Butlterm0ilk made(1 from) nor1 per' cent dryv skimi mal11skim mill: porationl OCCiiried regardless of the temperature of pumping. type andl speed1 of pump. andl condition of the curdl. The pumped buttermilk had a porous, mal im mui lk 1prcetdysi oIpen, br1oke pai Sample 5 -Butterilk1I made fronm equal skimnil1k andt reconpar~ts of normal1 and lacked the pearance smooth consistency- desired. (12) A variation 'w a s cidlity p)r01duc ed by different cultures. ( 1:;) Tbhe addition (of small quantities of dryT skim nmil k to normal skiml milk prior to feimentation. increases the v iscosity and i mlrox ('5 the flavor and consistency of' the resultinlg culandl ttiied buttermilk. (141) Tbhe flavor, aroma, a nd desired physical proplerties of the fi nished buttermilk can be satisfactorilyv mainltained1 for sev- eral (laxs at a storage temperattire (if 85 to 38 F. 38 (15) Cultured buttermilk of a quality practically equal to and in some respects superior to that prepared from normal skim milk can be made through the use of dry skim milk. PRACTICAL RECOMMENDATIONS AND SUGGESTIONS FOR THE PREPARATION OF HIGH QUALITY CULTURED BUTTERMILK FROM DRY SKIM MILK (1) Fresh dry skim milk of the highest quality should be used. In these experiments the dry skim milk remained in good condition over a period as long as four months when held under proper storage conditions, and was found satisfactory for the production of good buttermilk. (2) A lactic starter, maintained in a vigorous active state Off-flavored by daily transfer and propagation, is essential. starters, or those which fail to produce an acidity of .95 to 1.00 per cent, may be responsible for a poor quality product. (3) The reconstructed skim milk should be prepared to contain as nearly as possible 10.0 per cent total solids. A variation allowance of 9.8 to 10.2 per cent will not materially affect the results. In practical work it has been found desirable to weigh both water and dry skim milk and to consider dry skim milk as containing 96 per cent total solids. An example will illustrate. It is desired to make about 60 gallons or approximately 500 pounds of cultured buttermilk. Solution: (a) The buttermilk must contain 10 per cent of total solids. (b) Therefore 500 pounds of buttermilk must contain 500 X .10 = 50 pounds of total solids. (c) Since dry skim milk contains approximately 96 per cent .96 = 52.08 pounds total solids it will be necessary to use 50 of dry skim milk and 447.92 pounds of water in the preparation of 500 pounds of cultured buttermilk. (4) Place water at about 700 F. in vat and add dry skim milk in two or three installments, mixing thoroughly to avoid lumping and to secure complete solution. (5) Heat to 1800 F. for 30 minutes, cool to 680 to 700 F., and culture with 5 per cent starter. (6) Allow the cultured buttermilk to stand until an acidity of .95 to 1.00 per cent has developed. (7) Where possible, cool the curd to 500 F. prior to breaking. When this is impractical, satisfactory results can be secured by cooling the curd with slow, intermittent agitation in the vat. Satisfactory results have also been secured by breaking the curd in the vat, drawing it off into cans, and placing the cans 39 in ice water or in a cold room with frequent agitation to reduce it to the desired temperature of 500 F. or lower. (8) In every case the curd of fermented reconstructed milk should be broken to a smooth consistency with an agitator operating at a speed which results in a minimum amount of air incorporation. (9) In so far as possible, avoid pumping. REFERENCES (1) Reid, Winm. H. E., and Welch, F. F., Factors Influencing the Properties of Fermented Reconstructed Milk. Jour. Dairy Science, Vol. XIII, No. 2, 1930, pp 124-139. Larsen, C., and White, W., Milk Powder Starters in Creameries, S. Dakota Agr. Exp. Sta. Bul. No. 123, 1910. Burke, A. D., Commercial Buttermilk, Okla. Agr. Exp. Sta. Bul. No. 156, 1926. Knaysi, Georges, Some Factors Other than Bacteria that Influence the Body of Artificial Buttermilk, Jour. Agr. Res. XXXIV-771-84-1927. Hammer, B. W., Volatile Acid Production of S. lacticus and the Organisms Associated with It in Starters, Iowa Agr. Exp. Sta. Res. Bul. No. 63, 1920. Bell, R. W., and Burkey, L. A., Effect of Heat Treatment of Skim Milk on the Stability and Viscosity of Cultured Buttermilk. Proceedings of the Twenty-Second Annual Convention of the International Assoc. of Milk Dealers. Laboratory Section, Oct. 1929. (2) (3) (4) (5) (6)