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A view of the structure of the casein micelle is given. It is built of submicelles, roughly spherical aggregates of several casein molecules held together by hydrophobic bonds and salt bridges. Regions of amorphous calcium phosphate link the submicelles to each other, the ester phosphate groups form part of this colloidal phosphate. In this way, almost all regions of the casein molecules are severely restricted in mobility. The C terminal part of the κ-casein is however predominantly present as flexible "hairs" located at the outside of the micelles. There are essentially two types of submicelles, with and without (much) κ-casein. The casein micelles greatly change in properties upon lowering the pH, mostly due to dissolution of colloidal phosphate; at still lower pH, increased formation of salt bridges predominates. Temperature also has pronounced effects: upon lowering it, the micelles become more voluminous, presumably due to protruding hairs of (mainly) β-casein. Also at high temperature (>70°C), parts of the casein molecules become more flexible. Casein micelles are very stable, If conditions are changed they may disintegrate or aggregate. Aggregation mostly leads to formation of a gel. The application of the theory of fractal floc formation to gelation is briefly discussed: it serves to explain the very strong dependence of gelation times on volume fraction of aggregating particles. The stability against aggregation is primarily due to steric repulsion, caused by the hairs of κ-casein, and at low temperature presumably also pcasein. The hairs on different casein micelles may however touch, and this may lead to lasting contact of the micelles, i.e., aggregation. The bonds formed can be salt bridges or, at high temperature, covalent bonds (chemical crosslinks). Hydrophobic bonds are probably not involved. The probability that casein molecules in different micelles may touch each other for a sufficient time for bonds to be formed appears to depend on electrostatic as well as steric repulsion, which thereby affect aggregation rate.

The influence of three different concentrations, 0.05%, 0.10% and 0.15% of monobasic sodium phosphate on the heat stability (at 130°C) and pH of buffalo milk and its 2:1 concentrate was determined. It was observed that sodium phosphate caused a considerable increase in the heat stability, determined as heat coagulation time (HCT) of concentrated buffalo milk. The optimum concentration of sodium phosphate for imparting maximum stability to the concentrate was different for different samples. However, with the addition of an appropriate concentration of sodium phosphate it was possible to manufacture evaporated milk up to 36% total solids. Depending on the HCT/pH profile, some of the samples of fluid (unconcentrated) milk were stabilized while the others were destabilized due to the addition of sodium phosphate. Addition of monobasic sodium phosphate caused a decrease in the pH of fluid milk and its concentrate.

The influence of passing electric current in the acidic buffalo milk with a view to explore the possibility of retaining and utilizing such milk for the manufacture of dairy products was studied. Twelve trials were conducted on de-acidification of milk and the quality of milk was judged by the Heat Coagulation time and the concentration of major minerals, namely, calcium, magnesium, phosphate and citrate in normal buffalo milk, its rennet whey, acidic milk whey and the de-acidified milk whey. The average HCT for normal milk, acidic milk and de-acidic milk was 42.66 ± 1.40, 2.74 ± 0.03, 44.41 ± 1.78 min, respectively. The average pH of these milks were 6.72 ± 0.19, 6.21 ± 0.02 and 6.77 ± 0.03, respectively. The soluble calcium, in different types of whey obtained from whole milk, acidic milk and de-acidified milk were 24.03%, 33.11% and 21.37%, respectively. Similarly, magnesium contents were 56.78%, 66.58% and 56.61% and the phosphate contents were 43.87%, 60.74% and 42.24%; and citrate 67.93%, 81.48% and 62.16%.

The influence of homogenization (two stage) on heat stability (determined as heat coagulation time at 130°) as well as the salt balance of buffalo milk and its 1:2 concentrate was determined. Homogenization had no significant influence on the heat stability and salt balance (molar ratio of Ca + Mg to P + Cit. in the dissolved phase) of fluid milk. However, during concentration both the heat coagulation time and salt balance of homogenized milk were affected significantly. Homogenization caused a significant decrease in the dissolved phosphate but had no significant effect on calcium and magnesium and this resulted in a significant increase in the molar ratio of Ca + Mg/P + Cit. This disruption in the salt equilibrium caused the destabilization of homogenized concentrated milk.

SUMMARYPreheating milk at 140 °C for 1 min at pH 6·6, 6·8, 7·0 or 7·2 shifted the heat coagulation time (HCT)/pH profile to acidic values without significantly affecting the maximum stability. Whey proteins (both β-lactoglobulin and α-lactalbumin) co-sedimented with the casein micelles after heating milk at pH < 6·9 and the whey protein-coated micelles, dispersed in milk ultrafiltrate, showed characteristic maxima–minima in their HCT/pH profile. Heating milk at higher pH values (> 6·9) resulted in the dissociation of whey proteins and κ-casein-rich protein from the micelles and the residual micelles were unstable, without a maximum–minimum in the HCT/pH profile. Preformed whey protein–casein micelle complexes formed by preheating (140 °C for 1 min) milk at pH 6·7 dissociated from the micelles on reheating (140 °C for 1 min) at pH > 6·9. The dissociation of micellar-κ-casein, perhaps complexed with whey proteins, may reduce the micellar zeta potential at pH ≃ 6·9 sufficiently to cause a minimum in the HCT/pH profile of milk.

THREE well defined zones can be discerned in a typical thermal burn of the skin; these have been characterized by Sevitt (1949) and Jackson (1953). Contact of the skin with sources of heat frequently causes immediate coagulation of tissue protein (Moritz, 1947) and this zone of coagulation is surrounded by a region of capillary stasis and this, in turn, is bounded by an area of hyperaemia (Fig. 1); these zones which can often be discerned on the surface (Fig. 2) also occur in depth (Fig. 3). Heat coagulation of tissue protein due to burning can almost certainly be regarded as irreversible whereas hyperaemia, on the other hand, possibly represents minimum tissue damage and rarely presents any local problem other than pain, though pigmentation sometimes occurs and this may be permanent. There are also changes in capillary permeability within this region which may persist for 2 days or sometimes longer (Sevitt, 1957). Until recently the tissue damage associated with the capillary stasis that develops following a burn was considered irreversible (Jackson, 1969). The development of stasis and its subsequent pathology has been described by Sevitt (1949, 1957); the condition develops within a short time of burning and persists for some days. During this time the trapped blood ceils and the surrounding tissue become necrotic and eventually indistinguishable from coagulated tissue. Thus, if the zone of stasis penetrates below the plane of the deepest epithelial structures (hair follicles, sweat glands, etc.) the burn will be full skin thickness in depth (see also Fig. I). Many full skin thickness burns require surgical intervention to facilitate healing; surgery may either be performed early by excising all damaged tissue and applying skin grafts to the obviously viable bed thus exposed or grafting is delayed until necrotic tissue has formed a slough and granulation tissue has appeared below the burn eschar. Some years ago Janzekovic (1968) showed that some burns did not require as complete an excision as hitherto supposed in order to provide

SummarySkim milk was heated rapidly to 130 °C in stainless steel tubing, and was then held at this temperature for periods of up to 1 h in a stainless steel holding vessel. Samples taken at intervals during the holding period were analysed for cations, inorganic and organic phosphate and protein in the total sample and in the supernatant after centrifugation at 60 500g. The cation and total phosphate (organic+inorganic) contents of the sedimentable material remained constant throughout the heating, although the caseins became extensively dephosphorylated. Dephosphorylated protein dissociated from the casein micelles during the first 20 min of heating, after which its concentration in the serum began to decrease, perhaps indicating the onset of the heat coagulation reaction.

Egg albumen was modified with succinic anhydride and a water-soluble carbodiimide, 1-ethyl-3(3-dimethylaminopropyl) carbodiimide. The chemically modified proteins exhibited only minor conformational changes, but were altered in their responses to heat treatment. Heat-induced coagulation was retarded by both modifications suggesting that thermocoagulation requires a balanced electrostatic attraction between protein molecules. Hydrophobicity measurements and pH-titration data suggest the involvement of hydrophobic and ionic interactions in heat aggregation and gelation of egg white proteins. The soluble fraction of the heat-coagulated proteins contained mainly monomers, while under conditions where a gel or coagulum was not formed, the heat-treated egg albumen solutions contained high M.W. soluble aggregates. A scheme for the thermal coagulation of egg albumen is proposed.

During the last twenty years heat coagulation has become a more important technical procedure for the isolation of milk proteins because of its very efficient utilization of raw material. Experiments are reported to get approximation equations for the mass transfer in the production of milk protein coprecipitates from skim milk and mixtures of skim milk with rennet and acid whey by means of statistical planning and interpreting of experiments. Good exactness was reached. The coagula consist of casein fractions, whey protein fractions, calcium, and phosphates. The products are thermically rather stable, sensorically indifferent and contain water insoluble protein. They are suitable to improve the fat: protein ration of sausages, but also for the protein enrichment of other foods and for dietetic purposes.

SUMMARYThe increase produced by formaldehyde (HCHO) in the heat stability of milk did not occur when milk was treated with HCHO at temperatures up to 60°C followed by dialysis at 5°C. However, the minimum in the heat coagulation time (HCT)–pH curve was irreversibly removed if the milk was preheated at 80–C for 10 min in the presence of 5 mM-HCHO. Although this treatment blocked the ε-amino groups of lysyl residues, the stabilizing mechanism is considered to be due to the cross linking action of HCHO which reduced the level of non-sedimentable, κ-casein-rich protein dissociated from the micelles on heating. The specific crosslinking agent, dimethyl suberimidate, modified the HCT-pH profile of milk in a manner similar to preheating at 80°C for 10 min with 5 mM-HCHO, supporting the crosslinking hypothesis. The results of this study appear to lend some support to the proposal of Kudo (1980) that the minimum in the HCT-pH curve of milk is due to the dissociation of κ-casein from the micelles on heating at high temperatures at pH values greater than 6η7.

The homogeneity of arachin prepared by different methods was determined by the techniques of polyacrylamide gel electrophoresis, DEAE-cellulose chromatography, and ultracentrifugation. Arachin obtained by the method of Tombs ( Biochem. J. 96 , 119, 1965) or Dawson ( Anal. Biochem. 41 , 305, 1971) appeared to be homogeneous by these techniques. Total groundnut proteins, extracted in 1 m NaBr solution and subjected to double precipitation with 23% (NH 4 ) 2 SO 4 , also gave a homogeneous arachin preparation. These three homogeneous arachin preparations differed in their rate of hydrolysis by alpha-chymotrypsin, heat coagulation, and dissociation into subunits. However, SDS 1 and GuHCl denatured them to the same extent, as could be judged by the difference spectra. The phosphorus and carbohydrate content of the three preparations did not differ significantly.

SummaryThe release of 12% (w/v) TCA-solubleN-acetylneuraminic acid from casein at 5 temperatures between 110 and 150°C was determined and showed aQ10°C about 3; coagulation occurred when about 20% of the κ-casein was hydrolysed. Renneting of milk or colloidal calcium phosphate-free milk rendered the caseinate very heat-labile at its normal pH when more than about 20% of the κ-casein had been hydrolysed. Heat stability at the pH of maximum stability was not significantly decreased until after very prolonged renneting, but stability at pH values alkaline to the minimum was very sensitive to such hydrolysis suggesting that κ-casein is the principal factor responsible for heat stability in that region. Systems which do not have a maximum or minimum in the heat coagulation time–pH profile, i.e. serum protein-free casein micelles in milk diffusate, or milk which had been dialysed against water, were destabilized by renneting throughout the pH range 6·4–7·4.

The heat coagulation of water soluble proteins from walleye pollack, rat-tail, morid fish, eel-pout, halibut, and mackerel was examined to compare the difference in thermostabillty among fish species. From the thermodynamic parameters accompanying the heat coagulation process, it was shown that van't Hoff plots gave two lines with different slope in the temperature range of between 50° to 60°C. The ΔG° of walleye pollack, rat-tail, and morid fish showed the negative values at both 50° and 80°C. The results suggested that the thermostability of these fish proteins was lower, compared to that of the other fishes examined. The thermal reaction at 50°C resulted in a large value of the ΔS°.

The effect of adjusted pH on the heat coagulation time (HCT) of milk from Zebu cattle and their crosses with animals of exotic breeds was determined. It was observed that the majority of individual milks and all the bulk milks from these animals were of Type-A. Further, most of the Type A milks from individual animals and all the samples of bulk milk were most stable at acidic pH or at the natural pH, indicating the unsuitability of common stabilizers during processing. Through selective cross breeding it is possible to produce milk with a desired HCT/pH profile and better stability.

SummaryAdditions of urea progressively increased the heat stability of milk outside of its coagulation time (CT)–pH minimum. In the region of the CT–pH minimum larger amounts of urea were required before an increase in heat stability occurred. The effect of urea was observed over the temperature range 125–140 °Cfornaturalmilk, milk which had been dialysed against synthetic sera, and milk to which a sulphydrylblocking agent had been added. Urea additions did not affect the activation energy of the heat coagulation reaction or the stability of milk to rennet or ethanol.

SummaryAddition of reducing agents such as 2-mercaptoethanol (2-ME), dithio-threitol and Na sulphite to milk markedly reduced its heat stability at pH values below 7·1. 2-ME reversibly destabilized milk or serum protein-free casein micelle dispersions and promoted the release of κ-casein-rich protein from the micelles. Reduction of either casein micelles or β-lactoglobulin (β-lg) with 2-ME and subsequent blocking of the newly formed –SH groups with N-ethylmaleimide irreversibly reduced the maximum to minimum ratio in the heat stability profile. 2-ME disrupted κ-casein/β-lg complexes and stripped κ-casein from the micelles on heating. The milk or caseinate systems were thus destabilized. Addition of KBrO4or iodosobenzoate to milk at 5 HIM eliminated the minimum but destabilized milk in the region of the maximum. However, KIO3at 5 mm had a strong stabilizing effect throughout the pH range 6·5–7·3.

The An Bord Bainne method, the Australian Standard method and an automatic electromagnetic method for determining the heat-coagulation time of 20% skimmed milk powder solutions have been examined for accuracy and comparability of the results, based on 50 samples. Nine representative samples were chosen from the classes ‘non-heat-stable’, ‘moderately heat-stable’, and ‘highly heat-stable’ and used for evaluating the standard deviation and the coefficient of variation of the respective procedures. The statistic correlation between the measured values was carried out by means of Spearman's coefficient of rank correlation (rs), whereby the calculation was done not only for all the 50 milk powder samples but additionally also for 14 samples classified as ‘highly heat-stable’. In both cases the correlation was significant at the 5% level (α= 0.05).

Addition of high protein fractions derived from whey to pasta to bring the protein content to 20% increases the PER of the pasta (macaroni) to that of casein. The flavor or texture quality of cooked enriched pasta is acceptable, and cheese or tomato sauce flavored enriched pastas are indistinguishable from controls. To avoid problems that would force major modifications in pasta processing and control equipment, it is recommended that the high protein fraction be insolubilized (denatured). The amino acids from these proteins are not changed by heat coagulation, pasta production, or cooking to a palatable table dish.

Processes are described for obtaining a low moisture, free-flowing protein powder of high nutritional value through the high temperature (120°C) heat coagulation of cottage cheese whey protein in a constant stirred reaction vessel using steam injection heating. Dried protein concentrates produced by the suggested alternative processes contain 65%, 85% and 95% protein, respectively. Essentially all the coagulable protein can be removed in 8 min of holding time in a pH range of 5.5–6.5. Increasing coagulation temperature to above that of conventional methods (85–100°C) significantly decreases processing time without adversely affecting product quality. The highly nutritious protein fraction produced has potentially wide application in the protein fortification of foods not requiring the normal functional properties of whey protein.

SUMMARYThe manufacture of skim-milk powder with heat stable characteristics was investigated commercially during the course of 8 trials carried out over a 12-month period. Skim-milk was preheated to temperatures ranging from 110 to 130 °C with a 2-min holding time prior to evaporation and drying. The effect of added urea was also examined during each trial run. Heat coagulation times at 120 °C were determined upon reconstitution of the powders to 20% total solids. From February to April the heat stability of the skim-milk powders increased, with the more heat stable samples being obtained at the higher preheating temperatures. Addition of urea increased the heat stability, particularly so in those milks which had been preheated to 130 °C. The presence of added urea during preheating was not found to be necessary as an equal effect on heat stability was observed when urea was introduced at the concentrate stage before drying. Later in the season optimum heat coagulation times were obtained by maintaining preheating temperatures at 118–120 °C.

The biological value (BV) and true digestibility of lucerne and barley juice protein mixed with ground barley grain were estimated using the Thomas-Mitchell balance method with rats. The BV with forage barley juice protein was similar to that of barley grain protein alone and was not improved by any of the applied treatments. The BV with lucerne juice protein was lower and was improved by separating the ‘brown juice’ after heat coagulation. Better results were obtained in a group fed diets with lowered levels of potassium and calcium which suggested an imbalance in the mineral content of lucerne juice; there was no difference in water consumption. The haemoglobin content of the blood of rats fed lucerne or barley juice alone was lower than that of animals fed plant juice/barley grain mixtures. No pathological lesions were observed in the guts, kidneys and livers of the rats.

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.

Durch statistisch angelegte Untersuchungen wird die Hitzekoagulation der Lactalbumine in Milch in Abhangigkeit von der Temperatur und deren Einwirkungsdauer untersucht. Die Ergebnisse werden biophysikalisch ausgewertet. Biophysical Investigations of the Heat Coagulation of Lactalbumine The heat coagulation of lactalbumine in milk with respect to its dependence on temperature and period of its action have been statistically investigated and the results are biophysically evaluated.

Summary The variations in the time of coagulation with variations in the temperatures used have been shown to be of a logarithmic nature. However, these variations in the time of coagulation are less with milk of 9 per cent solids-not-fat than they are when milk of 18 per cent solids-not-fat is used. The results indicate also that the use of temperatures of from 110° to 120° C. yield results of greatest practical value. Higher temperatures are apt to give results wherein the errors are large. 2. The data presented upon forewarming also indicate that the concentration of solids-not-fat is an important factor in varying the relative effects of this procedure. The results show that forewarming at high temperatures lowers the stability of those of higher solids-not-fat concentration. Hence, in any comparison of results obtained with milks of different solids-not-fat concentration similar treatment with respect to forewarming must be assured. These results indicate also that the relationships established by forewarming are not altered by the addition of electrolytes except in degree of stability. It appears, therefore, that forewarming does not affect stability merely through changes in the equilibria of the soluble salts, as the stability cannot be restored by the addition of electrolytes in those cases wherein it has been reduced. 3. The results show conclusively that the heat stability of a milk of 18 per cent solids-not-fat concentration cannot be predicted from the heat stability of the original milk. They show further why the use of phosphates as a "neutralizer" has not led to serious trouble. In those cases wherein its use has not materially improved stability its use has not greatly reduced it. 4. The existence of two types of milk, one stabilized by the addition of positively charged electrolytes and the other stabilized by the addition of negatively charged electrolytes, has been confirmed. The effect of the addition of various electrolytes to these types of milk has been studied over a wide range of concentration and it has been shown that in the lower concentrations they are most sensitive to the effect of di- tri- and quadrivalent ions and the monovalent H-ion while in the higher concentrations the monovalent K-ion is also very effective. The relationships of these effects are similar to those found for As 2 S 3 sols. Hence it again seems to have been shown that the calcium caseinate suspension in milk is analogous to hydrophobic sols in its reactions with electrolytes at higher temperatures. Increased stability has been shown to result from the addition of citrates and phosphates to a milk stabilized by negatively charged electrolytes. Finally, complete data have been presented upon the effect of various electrolytes upon the two types of milk at 9 and 18 per cent solids-not-fat concentrations. In general, a study of the data presented shows clearly that in studies on coagulation careful consideration must be given to phase concentrations and that conclusions drawn from work on milk of one concentration are not applicable to other milks of widely different concentrations. Furthermore, at the lower concentrations of solids-not-fat various electrolytes exhibit critical.concentrations or ranges wherein their effect is great. Hence, any work which does not include results over a range of concentration of electrolyte as well as range of concentration of the sol used is apt to lead to erroneous conclusions.

The usefulness of 14 common organic solvents in lowering the temperature necessary for the heat coagulation of serum proteins is evaluated. Six of the compounds, when added to serum in final concentrations varying from 14.3 to 28.6% (v/v), result in the formation of a firm clot at 60°. Ethylene glycol monomethyl ether is effective at 50° at 22.8% (v/v). Lower concentrations are effective at higher temperatures. The boiling points of the six range from 65° (methanol) to 153° (N,N-dimethyl formamide).

The need for further studies on heat coagulation became apparent during attempts to measure the influence of various electrolytes upon the coagulation temperature of various milks. The data available proved rather limited, and attempts to check certain published results were only partially successful. A lack of uniform methods, it is felt, largely accounts for the differences obtained by various workers. In the present study, the method adopted was carefully standardized, in an attempt to minimize the error in judgment regarding the point at which coagulation first occurs. Goat's milk as well as cow's milk was used.

The sterilization processes used in the manufacture of evaporated milk are designed not only for sterility but for those physical characteristics which improve the quality of the milk. As a rule, most manufacturers of evaporated milk grade the sterilized milk in terms of viscosity, grain and color; the relative importance assigned to these properties varies, depending on the point of view of the manufacturer. In the quest for improved sterilization processes, the lack of organization of processing data has been an impediment to a comprehensive understanding of the :;terilization process. A knowledge of the relationship existing between the color. viscosity, grain formation and surface tension for processes in general would assist greatly in predicting the effects of contemplated changes in processing. Considerableattention has been given to the problems arising in the steriliza'don of milk. Bell et al. (1) found that high temperature-short time sterilized evaporated milk thickened on storage, but if the milk was filled into cans after the high temperature-short time sterilization process and the color increased by further heating, the gelation tendency was reduced greatly, if not eliminated. Holm et al. (3) determined the relationship between the cooking time and the temperature necessary for coagulation. Later, the logarithmic nature of the heat coagulation was noted by Webb and Holm (5) in test tube experiments. While many of the phenomena associated with the processing of evaporated milk are recorded in the literature, little if any attention has been given to the character of the heat coagulation or its relationship to color, viscosity and surface tension. The purpose of this paper is to examine the results obtained in various sterilization processes with reference to grain formation, surface tension, viscosity and color and to show the relationship of these measurements to one another.

Vosburg and Richards1 first noted that blood coagulated more rapidly in animals after administering adrenalin, and Cannon and his coworkers reasoned from their experiments with adrenalin and from other evidence that the liver furnished some factor to increase the clotting process of the blood. In a study to determine just what this factor was, Grabfield2 concluded that adrenalin decreases the coagulation time by increasing the amount of prothrombin in the circulating blood.Grabfield could find no change in the anti-thrombin or in the fibrin content of the blood following the administration of adrenalin, but he says: “The fibrin determinations were made by the heat coagulation method of Whipple and Hurwitz, an unsatisfactory and unreliable method for this work because, chiefly, the amounts of blood required for accurate results are too large to obtain from cats without introducing the factor of hemorrhage.”In reviewing the problem it seemed that fibrin instead of prothrombin may have been an active factor ...

When myosin solutions were coagulated at 53°, pH 6.2, 8–18% of the protein remained in solution. This material could be divided by dialysis into two parts: (a) a myosin-like fraction, P, comprising 4–13% of the myosin and containing a well defined major component P1 together with some heavy disperse material; (b) A low-molecular-weight, water-soluble fraction, D, containing three components D1, D2, D3 in the approximate proportions 4:5:1. The adenylic deaminase activity of P was 3–4 times greater than that of myosin while that of D was low. D2 contained C-terminal isoleucine to the extent of one end-group in a particle weight of 20–30,000. The effect on the coagulation products of variables such as myosin concentration, temperature, pH, etc., has been studied.

Summary The relationship between the heat stability and the composition and other properties of the milks of four cows during the course of a lactation period was investigated. No marked correlation was found between the heat stability and the various tests and analyses conducted upon the milks. The "rapid" tests sometimes used to classify milks to be used for condensing, such as the acid test, the alcohol test, and the phosphate test, did not satisfactorily indicate the relative heat stability of the milks. The salt balance as determined by analyses of the milks showed no direct correlation with the heat stability of the samples. The buffer intensity was not related to the stability of the milks toward heat. No clear relationship was noted between the heat stabilities of the fresh milks and of their evaporated products. Each of the individual milks for the most part retained fairly constant values in many of the tests, these values being characteristic of the milk from each cow. The results of this investigation of the individual milks of four cows conclusively demonstrated the inadequacy of our present knowledge of the heat stability of milk.

ConclusionsCertain colloidal dyes, namely, congo red, vital red, trypan red, mercurochrome, rose bengal and sodium fluorescein, strikingly prevent the heat-coagulation and mercuric-precipitation of horse serum and egg albumin, and also the alkaloidal precipitation by Mayer's reagent. These powerful protective actions in vitro appear to be associated with the physical (colloidal) properties of these dyes, in agreement with a similar mechanism of protection exerted by some of these dyes on the actions of potent toxins and drugs in vitro. The possible significance of the mechanism of these common protective phenomena, for chemotherapy in general, is briefly discussed.

Summary Laboratory experiments in which high temperature-short time sterilization of concentrated milk was carried out under static conditions showed that heat and storage stability were at times adversely affected by the presence of a lipid phase. Three types of milk were encountered. The predominant type (if forewarming was employed) consisted of milks in which the fat phase behaved as an inert phase, that is, the processed whole and the corresponding processed skimmilks were heat-stable and resisted gelation during storage to approximately the same degree. On occasions, a type of milk was encountered in which the processed whole but not the corresponding processed skimmilk coagulated during sterilization. On other occasions, a type of milk was met in which the processed whole milk had a slightly greater shelf-life than the corresponding processed skimmilk. Exchanging the fat globules belonging to a heat-stable for those in a heat-labile milk tended to reverse the order of stability. Substitution of fat for an equal weight of protein showed that both heat stability and storage stability were significantly decreased by the substitution. Milks prone to coagulate because of an unstable lipid phase were stabilized to some extent by forewarming against both heat coagulation and gelation during storage. Mixing of forewarmed and unforewarmed milks resulted in composite milks with heat and storage stabilities intermediate between those of the unmixed milks. Milks reconstituted from butter oil and skimmilk were stabilized by the addition of fat-soluble interfacially active mixtures to the butter oil. Sterilization under static conditions yields results which, supplementing the results of sterilization under turbulent canditions, allows one to isolate the effect of heat from the combined effect of heat and turbulent flow.

5′-Adenylic acid deaminase activity associated with preparations of rat-muscle actomyosin has been dissociated in high yield and with a 15-fold increase in specific activity by precipitation of actomyosin sols at low ionic strength in the presence of inorganic phosphate. Comparative studies made on various protein preparations from both rat and rabbit muscle show that this phenomenon does not occur with myosin or actomyosin from the rabbit. This dissociative procedure is much more efficient than separations by heat coagulation previously employed by other workers. A short method of producing highly purified deaminase in high yield has therefore been developed, which is suitably convenient and practicable to be of value to workers concerned with studies of the pure enzyme. The product has a K m of 1.41 ± 0.15·10 −3 M , a sedimentation constant of 12.61, and a ratio of absorbancy values (280 mμ/260 mμ) equal to 1.86. The work is discussed in relation to the studies of previous investigators.

SummaryAn anionic detergent such as Na dodecyl sulfate or Na dodecylbenzene sulfonate, a strong inhibitor against protein denaturation, showed also a strong inhibitory effect on the inflammatory edema by caolin or formalin. Phenylbutazone and salicylate inhibited the heat coagulation of serum or egg albumin at a low concentration. However, other antipyretic or analgetic agents showed very weak or no inhibitory action against the heat coagulation of albumin.From these data and the data from our previous experiment it is considered that antirheumatic action of phenylbutazone and salicylate might be due to their inhibitory effects against aggregation or denaturation of proteins.