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In the sterilizing process in the manufacture of evaporated milk, it is desirable to produce an incipient coagulation, in the nature of a tender jell or "fiver" as it is called by the practical men. Such a product will have a heavy creamy body after the "fiver" has been broken up by the shaking process. This is desirable because the product presents a richer appegrance to the consumer, and on account of the greater viscosity, there is little danger of fat separation from such a product. However, evaporated milk differs widely in the readiness with which it coagulates. At times the milk coagulates so readily that it would be unmarketable, on account of its curdy appearance, if it were heated long enough to preserve it. This constitutes the problem with which we are concerned in this paper. There is probably no condensery that is entirely free from this trouble throughout the year. I t is undoubtedly one of the biggest problems that confronts the industry.

Summary This work shows that the addition of citric acid or sodium citrate to either cream or the starter or both tends to produce a butter of more desirable flavor and aroma than the untreated butter made from the same cream. The findings of previous investigators concerning the effect of high acidity on the keeping quality has been confirmed in some of the samples of butter scored, while in other instances there is very little difference in the scores of the fresh butter and the score after storage. In numerous samples the score after six weeks’ storage was higher than that given the fresh butter. It was noticed that the use of citric acid tended to lower the fat losses in the buttermilk. In flavor and aroma the buttermilk from the treated cream compared very favorably with the starters. The addition of citric acid or its equivalent in sodium citrate in amounts not to exceed 0.2 per cent of the weight of the cream is sufficient to produce an increase in the score of the butter made from the cream. Their addition in the starter only, is noticeable in the score of the butter. In conclusion the authors wish to express their thanks to Charles Pfizer and Company, Inc., for the fellowship that has made this work possible, and to those gentlemen who gave their time and services in the scoring of the samples of butter.

Summary The end of the induction period during the oxidation of butterfat in the absence of light is well marked by a rapid bleaching of the color and a rapid increase in peroxides, followed by an increase in volatile acids. The development of peroxides ordinarily precedes the appearance of a tallowy flavor but the tallowy flavor is not always apparent at the same peroxide number. Light, especially ultra-violet light, exerts a marked catalytic effect on the oxidation of butterfat. Aluminum foil wrappers, which excluded the light entirely, prevented the oxidation of the butterfat. Of the colored transparent wrappers dark green and dark red were the most effective. To protect butter from the catalytic effect of light a transparent wrapper should exclude at least the ultra-violet light and decrease the transmission of the longer rays as much as possible. The authors wish to express their thanks to Professor L. C. Thomsen for the help given in judging the flavor of the butter samples.

There is considerable variation in the stability of the butter fat toward oxidation where it is obtained from different cows and from an individual cow at different periods.

Summary From the preference shown there is a decided eye appeal in processed cheese containing pimientos in which the pieces of pimiento are of a bright red color and of such size as to be readily seen. The use of fire-roasted peppers will eliminate the possibility of off flavors that are due to oil roasting, either because of the use of old or rancid oil or the incomplete removal of the oil after roasting. The authors wish to thank all of those who so kindly examined the samples submitted to them and offered their comments. This work was conducted under the fellowship sponsored by Chas. Pfizer and Company, Inc., to whom the authors also wish to express their appreciation.

Summary A concentration of 10 −4 . moles per liter of added MnSO 4 was found to prevent development of an oxidized flavor in spontaneous milk and in susceptible milk containing 10 −5 moles per liter of added CuSO 4 Addition of the Mn salt either before or after pasteurization was equally effective. Such addition, however, had no effect on the rate of oxidation of ascorbic acid. The addition of ascorbic acid (100mg. per liter) to washed cream induced development of an oxidized flavor during 48-hr, storage at 40° F. The presence of added CuSO 4 (10 −5 moles per liter) showed no tendency to catalyze development of the flavor in washed cream. MnSO 4 , when added to washed cream containing ascorbic acid, did not prevent oxidized flavor development. The action of pure trypsin retarded or prevented development of an oxidized flavor in spontaneous and susceptible milk. The suggestion is made that the protective action obtained by treating milk with the pancreatic enzyme preparations presently being marketed is due to the trypsin contained therein. A possible mechanism by which milk proteins may function as reducing agents, through their "fixed" or reactive –SH groups, is discussed. The suggestion is made that these –SH groups in milk proteins may have a pronounced influence on the susceptibility of milk toward oxidized flavor development.

Summary 1. A slight increase in the magnesium or calcium content will cause a positive alcohol test; an increase of potassium, sodium, chloride, citrate, and phosphate, will not cause a positive alcohol test. 2. The effect of the calcium and magnesium on the alcohol test is counteracted by the citrates and phosphates in the milk. A positive test with fresh milk depends mainly upon the relative amounts of these four salts present in it. 3. A high calcium content in a ration fed to cows can cause coagulation of milk in the alcohol test. 4. The effect of milk salts is of such importance that it can easily account for any lack of correlation between the alcohol test, acidity, and bacterial counts. The effect of acidity and the milk salts are additive. 5. Prepared rennet will cause a positive reaction in the alcohol test. The degree to which a sample of milk becomes positive will depend on the amount of rennet and the time it is allowed to act. 6. The coagulating enzymes produced by rennet forming organisms, numbering 856,000 per cubic centimeter are sufficient to cause a positive alcohol test. However, rennet forming organisms must be regarded as a minor factor in the alcohol test for their prevalence in milk rarely approaches this figure.

Summary Influence of pasteurization on the nitrogen distribution was studied by pasteurizing milk at 143°F. for 30min. in a laboratory pasteurizer. No appreciable change occurred on pasteurization, except in the case of albumin and globulin. About 9 per cent coagulation was observed in the case of albumin and 5 per cent coagulation for globulin. Pasteurization at 155°F. for 30min. and homogenization at 2,000lb. pressure per in. 2 produced no significant changes in the nitrogen distribution, except that globulin nitrogen decreased, whereas the non-protein nitrogen and α-amino nitrogen increased. On storage of evaporated milk at 100°F., the non-protein nitrogen increased with a decrease in viscosity.

The stability of milk under various conditions has been studied from both a theoretical and practical standpoint. The milk has been subjected to temperatures ranging from room temperature to 150 ° C., and to the influence of salts and acids that are foreign as well as those normal to milk. Although valuable information has been added to our knowledge of milk, yet many theoretical and practical questions have not been answered which are significantly related to the stability of milk during pasteurization, boiling, preparation of various food-stuffs involving milk, and the manufacture of condensed and evaporated milks. The purpose of the work presented herein is to show the relationship between the pH and the coagulation temperature of milk ranging from about room temperature to the coagulation temperature of stable milk, and to show the effect of added salts, evaporation and previous heat treatment in displacing the '~coagulation curve."

Summary From the foregoing discussion it is evident that there are a number of factors which play a part in the darkening of the tin foil. The use of phosphate emulsifying salts appears to accelerate the discoloration, especially when the reaction of the cheese-quinhydrone paste is more alkaline than pH 5.8. The results presented in this paper were obtained from investigations on Cheddar cheese, and it is probable that other types of cheese might show different reaction values which are connected with the darkening of the tin foil. It is also probable that there may be some other factors involved, which may be studied at a later date. It is also evident that the metal foils are still superior to any other type of foils as a wrapper for processed cheese. For general use with all types of cheese tin foil is probably more satisfactory than aluminum foil, but when relative costs are considered there may be types of cheese with which aluminum foil, properly coated to prevent corrosion, may offer distinct advantages. In conclusion the authors wish to express their thanks to Chas. Pfizer & Co., Inc., for the fellowship under which this investigation has been conducted and also to those who supplied samples of wrappers for this experiment.

In a sensitive colloidal system such as milk small changes in the .various ionic concentrations are likely to exert a great influence on the stability of the system. Since the electrical conductivity of milk depends upon the various ions present and the hindering effect of the non-electrolytes, it is reasonable to expect that any changes occurring in the ionic equilibrium and the concentration of the non-electrolytes during the manufacture and aging of sweetened condensed milk would be reflected in a change in the electrical conductivity. I t is a matter of common experience that an increase in .acidity almost invariably decreases the heat stability of milk. With these facts in mind, electrical condaetivity and hydrogen-ion concentration measurements were made during the preparation and aging of several batches of sweetened condensed milk. The different batches varied in their stability toward age thickening.

Summary Methods have been described for determination of total nitrogen casein, albumin, globulin, proteoses-peptones, non-protein nitrogen, ammonia, urea, creatinine, creatine, uric acid and alpha -ammo nitrogen in milk. Bulk milk samples were analyzed fresh and after holding at 0 to 5° C. for 10 days (toluene preserved). No significant change was observed in the nitrogen distribution during this aging.

Summary The data in Tables 2, 3, and 4 reveal that the white particles selected from a number of different samples of Cheddar cheese are definitely heterogeneous in composition. The compounds found most commonly were tyrosine and calcium lactate. Quantitative analyses for tyrosine show that its concentration varied from 3 per cent to 50 per cent in the samples studied. Cystine was found in the white particles from three of the six samples of cheese. The white particles from one cheese sample contained only a small amount of tyrosine and yielded no X-ray diffraction evidence of calcium lactate. This sample did contain appreciable quantities of leucine, and isoleucine was probably present. The study included four raw milk and three pasteurized milk cheeses; there is no indication that this factor influenced the composition of the white particles. No significance could be attached to the location of the white particles in the cheese in regard to their composition. The method of ripening appears to have a definite influence on the composition of the white particles.

Summary 1. Formaldehyde addition to sugar-saturated-cream inoculated with raw cream greatly limited lipolysis. Tributyrin greatly increased lipolysis as here measured. 2. Gravity separated cream was found to show appreciably greater lipolytic activity than separator cream of the same fat content. 3. Shaking increased lipolysis in the case of milk samples held as such, but decreased lipolysis in the case of sugar-saturated-cream inoculated with the same milk samples. The latter effect was also observed where cream was used as the inoculum. 4. In a comparison of 3–4° C, 27° C. and 37° C, lipolysis was most extensive at 37° C, slightly less at 27° C. and decidedly less at 3–4° C. 5. The optimum pH for lipolysis in cream samples at 3–4° C. was found to be pH 8.4 to 8.6. 6. The indications are that lipolysis varies considerably in the milk from the same cow, and differs widely from cow to cow. A study of milks from 18 cows at known stages of lactation failed to indicate a relationship between lipolysis and stage of lactation. 7. Cream separated at 110° F. showed less lipolysis than cream separated at 75° F. both as observed by holding the samples at 3–° C. and by using the cream to inoculate sugar-saturated cream and incubating at 37° C. Similarly the 110° F. skim milk caused less lipolysis than the 75° F. skim milk in sugar-saturated-cream.

Summary The limited oxidation of milk phospholipids yielded material which reproduced the typical oxidized flavor in milk. Isolation and characterization of the major oxidized flavor compounds showed that they are predominantly carbonyl compounds. Five different carbonyl compounds were evidenced by chromatography. The empirical formulae calculated for three compounds were C 15 H 26 O 3 , C 11 H 22 O, C 22 H 38 N 5 O 2 (as bis-hydrazone) and C 10 H 18 N 2 O (as monohydrazone). There is indication that the C15 was a di-unsaturated ketone without conjugation. The C 11 was presumably undecanal.

Summary It was shown that in the creaming of milk the greater portion of the fat rises during the first hour. A slow, gradual rise of residual fat continues indefinitely. There is some indication in the data that during the creaming process the fat content of the skimmilk at one level may be slightly less than the fat content of the skimmilk at a lower level. Indications were obtained that such differences may occur at several points in a skimmilk column suggesting a wave-like progression of the fat. This suggestion should be further verified before it is accepted as a definite conclusion. There appears to be no difference in the manner in which the cream layer forms on raw milk as compared with pasteurized milk.

Summary The problem of fat separation in evaporated milk can be divided into at least three factors. The extent of fat separation is inversely related to the viscosity, directly related to the square of the radii of the fat particles and directly related to the density difference between the fat particles and the suspending phase. A suggested procedure is given for determining the effectiveness of homogenization. This method is based on the total effect, or the result of the rate of travel, of the fat particles. Extending the same logic, a method is given for determining the extent of gravity fat separation during storage. In addition, the procedure and description are given for a modified Gardner Mobilometer as a means of measuring viscosity. These methods were applied to samples of commercially prepared evaporated milk, and the correlation between the tests was highly significant.

Summary A pure salt solution was prepared to simulate the composition of salts in milk serum, in order to study the mineral balance in milk. The salts were distributed into soluble and colloidal phases and a sediment was separated from the solution by centrifugation. Storage resulted in formations that resembled “lime grains.” Analysis showed that 35.9, 72.9, 51.8, and 80.9% of Ca, Mg, P, and citric acid, respectively, were soluble. The Ca :P ratio in the sediment was 1.46, indicating predominance of tricalcium phosphate. Heating decreased soluble Ca and pH, whereas cool-aging had the reverse effect. Variations in soluble Mg and citric acid were insignificant, but soluble P decreased on heating and on cool-aging in the pasteurized lot. The Ca :P ratio in the sediment from the untreated aliquot decreased to 1.26 on cool-aging, but pasteurization increased it to 1.63, which decreased again to 1.08 on cool-aging. Adding Ca increased Ca :P ratio, whereas adding P decreased it. The pH decreased with added Ca and increased with added P. Undissolved Ca, Mg, and citric acid in the sediment, when accounted for as tribasic salts, left 0.5 mg. of P and 0.4 mg. of Mg unaccounted for per 100 ml. of solution.

Summary 1.A method is described, based on the theory of streaming potentials, that may be used in measuring the magnitude of the electric charge at the fat-serum interface. 2.The stability of colloidal systems is discussed and a mathematical development of the streaming potential formula is given. 3.Data are presented to show that an interface quite comparable to that of the fat globule as it exists in milk is being considered. 4.The electrokinetic potentials observed using various samples of milk from individual cows are shown to vary over a comparatively wide range. 5.The iso-electric point of the interface was found to be at about pH 4.3. 6.Potassium chloride, added in increasing amounts, caused an increase that was later followed by a decrease in potential. Chlorides of calcium, iron and thorium decreased the electrokinetic potential. Thorium was found to be the most effective and at certain concentrations reversed the sign of the charge. 7.Di-sodium phosphate and sodium citrate caused the potential to become more strongly negative. The latter salt was found to be the most effective. 8.Increasing temperatures produced a very pronounced increase in the observed electrokinetic potential.

Summary The reaction of normal sweet cream is probably the most satisfactory for the production of a good whipping cream. If the cream has developed a slight acidity, but not enough to affect the taste it is better to pasteurize it at once rather than neutralize and then pasteurize. The addition of small amounts of acid (less than 0.03 per cent) does not have an appreciable effect upon the cream. If the titrable acidity calculated as lactic acid is above 0.27 per cent the cream will whip rapidly, but such a cream is eliminated from practical consideration because of its sour taste and the low overrun and soggy appearance of the whipped product. Fat losses in the cream decrease with increasing acidity. Cream separated at temperatures of 60 to 72° F. (15.5 to 22.2° C.) and 150° F. (65.6° C.) whipped better than creams separated at intermediate temperatures. The lower separating temperatures gave better results as regards the amount of serum lost and its fat content. The temperature of pasteurization is not an important factor as far as whipping quality is concerned. The usual temperatures are very satisfactory. Cream intended for whipping must be thoroughly cooled before it is bottled and placed in storage for aging. Poorly cooled cream showed a marked increase in whippability after storage for more than 70 hours at 44° F. (5.6° C). Cream should not be used for whipping until it has aged for 24 hours. If it is necessary to use the cream after a shorter period of aging, the temperature of storage should be as close to 0° C. as possible. Homogenization of the cream does not have a beneficial effect. If the cream is homogenized it should be done at a low temperature and the pressure should not exceed 100 pounds. It is essential that the gauges be watched continually to avoid changes in pressure. The addition of sodium citrate to the cream before pasteurization decreases the whipping time; the same effect was noted when sodium citrate was added immediately after homogenization. Fat losses in the drainage increase markedly with increasing homogenization pressures. In conclusion the authors wish to express their thanks to Chas. Pfizer and Co., Inc., who have sponsored the fellowship that has made this study possible.

Whipping cream occupies a very strategic place in the list of products sold by the average commercial dairyman. I t is known that consumers often draw their conclusions concerning the quality of an entire line of dairy products from the quality of the whipping cream. While the actual volume of business is relatively small the prestige that seems to accompany the production of a high quality of whipping cream is more than sufficient to repay the dairyman for his extra labor. Of the many variable factors that may be concerned in the production of a high quality whipping cream, the following will be discussed in this paper

Summary Whey powder tends to give a weaker body to cheese spreads than skimmilk powder, but it also gives a rather distinctive sweet taste that may be very agreeable to some consumers. When used in the proper proportions skimmilk powder gives a product that seems to meet with quite general approval. The cheese food compound can be spread easily, or, if occasion demands, may be sliced in a satisfactory manner. The use of sodium citrate gave a very satisfactory product as there was no fat leakage except with very old cheese and the body of the samples containing this salt was more uniform than that produced with either Rochelle salt or di-sodium phosphate. With the latter salt there was a greater tendency to fat leakage than with either of the other emulsifiers. In order to obtain a satisfactory product it is advisable to blend cheese using some old cheese for the flavor. The use of very old cheese alone is apt to give a product that is grainy and shows fat leakage, while with young cheese alone the finished product is too rubbery to spread easily. The choice made by the different examiners indicates that preference varies with the individual taste. It is therefore impossible to give any composition formula that would meet with universal approval. In conclusion the authors wish to thank all those men who examined the samples of cheese food compounds and offered their comments. This work was carried on under a fellowship sponsored by Chas. Pfizer and Company, Inc., to whom the authors also express their appreciation.

The effect of salts on the stability of simple colloidal sols is quite well understood. However, due to the complicated nature of the colloidal system of milk, their effect on the stability of the milk colloids is not so well understood, but has been investigated by a number of workers. Sommer (1) found that there is an optimum balance between the magnesium and calcium on one hand and the citrates and phosphates on the other hand in order to obtain the maximum heat stability of milk. Sommer and Binney (2) have shown that magnesium or calcium ions will change alcohol negative milk to alcohol positive milk, while citrate or phosphate ions will change an alcohol positive milk to alcohol negative. Sommer and Young (3) showed that with certain ice cream mixes the addition of sodium citrate or disodium phosphate before homogenization greatly increases the whipping ability and that additions of calcium lactate decrease the whipping ability. Henning and Dahlberg (4) found that the addition of sodium citrate and disodium phosphate to ice cream mixes before homogenization decreases the tendency of the fat globules to clump, decreases the viscosity of the mix and increases the whipping ability, while the addition of calcium salts has an opposite effect. They also showed that by the addition of potassium oxalate the calcium salts are precipitated and clumping is prevented entirely. North and Sommer (5) have shown that the electrical charge on the fat globules is involved in fat clu~nping and that the addition of positively charged ions decrease the charge on the globules and favors clumping while negatively charged ions have an opposite effect. Templeton and Sommer (6) reported that the whipping ability of whipping cream is increased by the addition of sodium citrate while calcium salts have an opposite effect. Traey and Ruehe (7) have demonstrated that calcium salts affect the feathering of cream in coffee and that feathering can be prevented by the addition of sodium citrate or disodium phosphate. The destabilizing effect of calcium on milk proteins has also been shown by the work of Van Slyke and Bosworth (8). They found that in neutralizing the excess of lime in a casein-lime-water solution with hydrochloric acid, Received for publication August 2, 1935. Published with the permission of the Director of the Wisconsin Agricultural Experiment Station.

Oxidized flavor in milk and milk products is generally accepted to be the result of oxidation of one or more of the lipids present in milk. The oxidation of the unsaturated fat ty acids present in butterfat was originally thought to be the source of oxidized flavor, but the evidence presented by certain workers shows that the phospholipids present in milk may play an important rSle. The work reported herein was undertaken to determine which of the lipid constituents in milk had undergone a change on the development of oxidized flavor. The oxidized flavored milk used in these experiments was obtained by the addition of copper in the form of copper sulfate solution. Unfortunately there was no milk available which would develop the off flavor spontaneously.

Summary The effects of pasteurization and cool-aging on the distribution of calcium, magnesium, phosphorus, and citric acid in milk into curd and whey were studied by analyzing these constituents in rennet whey from milk after the appropriate treatments. Statistical analysis of the data from ten bulk-milk samples revealed that the differences were not significant, except with respect to magnesium in curd from cool-aged milk. These variations, however, did not reflect any significant change in the Ca:P ratios in the curd. The results were not in harmony with the observations on pure salt solution under similar conditions, and the variations in the behavior of milk are considered partly due to the colloidal systems present in milk. The importance of considering magnesium and citric acid simultaneously is pointed out in any attempt to explain the ionic equilibria regarding calcium phosphate in milk.

Summary From the results obtained in this experimental work, there are a number of conclusions that may be drawn: 1.The use of the so-called emulsifiers is beneficial and the results obtained with sodium citrate indicate that it is superior to di-sodium phosphate. The use of more than 3 per cent of these salts should be avoided not only to remain within the legal limits but also for the effect on the finished product. 2.Temperature regulation is essential in order to insure the proper pasteurization of the cheese and also to prevent the color from changing to "salmon pink." If the cheese is to be held in the kettle for any length of time, it should be at the lower pasteurization temperature and water should be added to make up for the losses due to evaporation. 3.Close observance of the standards set for the moisture content of processed cheese are essential not only for economic reasons, but also to insure having cheese of as uniform body as possible. 4.Good results were obtained with cheese ranging in reaction from pH 5.8 to 6.2. This would indicate that this factor can be adequately controlled by exercising discrimination in blending. 5.Very young cheese showed excessive fat separation in processing, and a rubbery texture in the finished product. Very old cheese also processed unsatisfactorily producing a product with a weak body and grainy texture. Good results were obtained when the blending was such that the average age of the cheese was from 4 to 7 months. 6.A comparison of the reaction in terms of pH and the titratable acidity furnishes a means of getting some ideas as to the kind of cheese that was processed and the treatment that it received. 7.Cheese that can be cut in slices 0.02 inch thick and requires 800 to 1200 grams with a mechanical advantage of 5 to crush an inch cube to one-half of its original thickness may be considered as having a very desirable body. 8.The keeping quality of processed cheese is dependent upon the heat treatment, the reaction and to some extent upon the temperature of the store-room. 9.Discoloration of the tin foil may be due to the use of phosphate as the emulsifier or to the use of alkali giving a reaction above pH. 6.3. 10.Frozen cheese can be processed satisfactorily. 11.Processing increases the water soluble form of nitrogen in the cheese. In conclusion the authors wish to express their thanks to the Chas. Pfizer and Company, Inc., who have sponsored the fellowship under which this work has been done. The analytical work on the nitrogen distribution was done with the assistance of Glenwood Mutten.

Summary Data are presented to characterize further the phenomenon of age-thinning of evaporated milk. The loss of viscosity is inversely related to the logarithm of the storage time, and the slope of the curve for age-thinning is directly related to the storage temperature. These relationships can be expressed in mathematical terms. A method is presented for the utilization of the above relationships in the calculation of the average viscosity during the early stage of quiescent storage. In addition, a method is described whereby it is possible to dissipate quickly the temporary viscosity formed during sterilization.

Summary A detailed study of the protein and non-protein nitrogen fractions in individual, single-milking and mixed-milk samples has been made. Great variations were observed among individual fractions.

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Summary 1. Under ordinary conditions the citric acid content of milk disappears in two to four days. 2. If milk is allowed to remain after the disappearance of the citric acid and then analyzed by the method used, another substance appears which behaves similarly to the compound formed by the mercury and citric acid. The nature of this material is unknown. 3. The addition of either citric acid or an equivalent amount of sodium citrate to milk increases the volatile acidity produced by approximately 50 percent and does not increase the total acidity more than 10 percent. 4. In most cases and with different men, cultures to which citric acid or sodium citrate was added were preferred to the untreated ones from the same original culture. 5. From this work and that to be presented later it would seem that as satisfactory results are obtained when citric acid or its equivalent of sodium citrate was added to the milk only at the time of inoculation as when the culture is carried in milk having these reagents added at each transfer. In conclusion the authors wish to express their thanks to the Charles Pfizer and Company, Inc. for giving the fellowship under which this work was done. The commercial cultures used were supplied by the Ohio Dairy and Food Laboratory, the Elov Ericsson Laboratory, the Dairy Laboratories of Philadelphia, and the Chr. Hansen Laboratories. The cultures were placed in order of their preference by Messrs. L. C. Thomsen, H. T. Sondergaard, H. C. Larson, A. T. Bruhn, C. W. Vilbrandt, L. Germain, L. L. Bishop, and W. B. Sarles.

Summary The cream plugs contain a high percentage of fat and microscopic examination shows that the fat has coalesced into irregular masses. The fundamental cause of cream plug formation is the presence in the cream of large fat globules which will rise rapidly into a dense layer and coalesce. This rising and coalescing of these fat globules is most rapid at higher storage temperatures because of the fact that the serum through which the globules must rise is less viscous. The prevention of cream plug formation, therefore, resolves itself into handling the milk and cream in such a manner that partial churning is avoided, or if this is impossible, reducing the size of the fat globules by either emulsifying or homogenizing at low pressures. Storing the cream at proper storage temperatures is helpful in preventing the formation of the cream plugs, but this is beyond the control of the milk dealer after it leaves his plant and, therefore, should not be relied upon to any great extent.

Summary 1.Information concerning metal solution in milk is of great interest to the dairy manufacturer because of the effect of dissolved metals on the color, odor, flavor, healthfulness and keeping quality of dairy products; further, such information is needed by the dairy engineer for the proper construction of equipment. 2.The data in the literature on the solution of metals in milk have quite generally been obtained by procedures that did not give sufficient control over important factors, viz., velocity of the liquid to the metal, composition of the milk (especially gaseous content), temperature, and the surface condition of the metal. 3.Data are presented for various metals to show the effect of variations in the acidity, oxygen content and temperature, and of steam sterilization on the corrosion losses. 4.The solution of Allegheny steel, stainless steel, aluminum, and tinned copper is very slight in acid milk at room temperature, and in fresh milk at various temperatures and oxygen contents. 5.On the basis of the data presented the relative corrosion resistance of the various metals is discussed.

Summary From the experimental work described in this paper, a number of conclusions may be drawn: 1.The body and texture of processed cheese are improved by the addition of the salts used as emulsifiers. 2.Sodium citrate gave the most desirable body and texture, Rochelle salt and di-sodium phosphate following in the order named. Defects noted with Rochelle salt were mealiness tending toward graininess and poor fusion of the warm cheese in the molds. Di-sodium phosphate gave a very soft, soapy product that also showed poor fusion. 3.Graininess is associated with lack of air cells in the cheese and is often accompanied by fat separation. 4.The use of one-half of one per cent of sodium chloride is sufficient. More than one per cent is noticeable to the taste and weakens the body of the cheese. The use of the emulsifying agents lessens the body defects caused by the use of sodium chloride. 5.Temperature control is necessary. 6.The reaction of the cheese is important, commercially it is modified by blending. The addition of one per cent of acid or its equivalent of alkali weakens the body of the cheese and produces decided changes in the texture. 7.Between reactions of pH 5.7 and 6.3 the differences in the body and texture are very slight. On either side of this range of reaction defects are noted that become more serious as the difference between the reaction of the sample and the limits set above increases. 8.When all other factors are kept constant the body of processed cheese varies in an inverse ratio with the amount of water that is incorporated in it. 9.The body of the cheese becomes weaker as the age of the cheese used increases. An average age of five to seven months in blending mixtures should give satisfactory results. 10.The casein-to-fat ratio in the milk used for the original cheese has a marked effect upon the body of the processed cheese, the greater the pro portion of fat the weaker the body. In conclusion the authors wish to express their thanks to Chas. Pfizer and Co., Inc., who have sponsored the fellowship under which this work has been done.

This brief article is to record the occurrence of "sandiness" in processed cheese. Two samples of sandy processed cheese were examined independently by the writer and by the Wisconsin Dairy and Food Commission chemists, respectively. In the former case, the sample was submitted by the manufacturer for identification of the gritty particles and diagnosis of the defect; in the latter case, the sample was obtained from a retailer after a consumer had complained that the cheese contained broken glass. I t is not definitely known, but it is likely that both samples originated from the same source. The gritty particles were easily visible to the naked eye and were obviously crysts.lline. The appearance and sensation on chewing was as though quartz sand had been incorporated into the cheese. Figure 1 is a photomicrograph, magnification 24 times, of the gritty particles removed from the cheese. Some of the gritty particles were removed with the aid of a scalpel, mad cleaned by removing adhering cheese and washing successively with water, alcohol and ether. The crystals were soluble in hYdrochloric and nitric acids, and disintegrated in sulphuric acid, leaving a fine precipitate (calcium sulphate). Calcium was demonstrated to be present by the oxalate test applied either to a solution obtained by dissolving the residue after ashing some of the particles, or to a solution obtained by dissolving some of the particles in nitric acid, evaporating to dryness and taking up the residue with water. The acid in combination with calcium was found to be an organic acid. The crystal structure of the gritty particles suggested that they consisted of calcium tartrate. Tartaric acid was demonstrated by the re

The oxidation of fats for soap making greatly decreases the time required for saponification, but does not influence the cleaning properties of the soap. However, the color of the soap is impaired and the yield decreased.