bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of dietary palmitic and stearic acids on milk fat composition in the cow
Authors: Noble R. C. , Steele W. , Moore J. H. 
Published: June 2009

SummaryThe effects of the isocaloric replacement of starch in a low-fat concentrate mixture by either 5 or 10% ‘stearic acid’ (85% pure) or 10% ‘palmitic acid’ (85% pure) on the yield and composition of milk fat were investigated in a feeding experiment with 12 cows in mid-lactation. The concentrate mixtures were given with a highroughage diet that supplied daily 4·4kg of hay and 2·7kg of sugar-beet pulp.The inclusion of 5 or 10% ‘stearic acid’ in the concentrate mixture decreased the concentrations and yields of 10:0, 12:0, 14:0, 14:1, 16:0 and 16:1 in the milk fat but increased the concentrations and yields of 18:0 and 18:1. When the concentrate mixture contained 10% ‘stearic acid’ the decreases in the yields of the shorter chain acids and the increases in the yields of 18:0 and 18:1 in the milk fat were more pronounced than when the concentrate mixture contained 5% ‘stearic acid’. The inclusion of 10% ‘stearic acid’ in the concentrate mixture also decreased the concentrations of 6:0 and 18:2 in the milk fat. The inclusion of 10% ‘palmitic acid’ in the concentrate mixture decreased the concentrations of 6:0, 8:0, 10:0, 12:0, 14:0, 14:1, 18:0 and 18:2 in the milk fat but increased the concentrations of 16:0 and 16:1. This dietary treatment also reduced the yields of 6:0, 10:0, 12:0, 14:0 and 18:2 but increased the yields of 4:0, 16:0 and 16:1 in the milk fat. The inclusion of 5% ‘stearic acid’ or 10% ‘palmitic acid’ in the concentrate mixture increased the yield of total milk fat.The inclusion of 10% ‘palmitic acid’ or 10% ‘stearic acid’ in the concentrate mixture increased the relative proportions of propionic and iso-butyric acids in the rumen liquor but decreased the proportions of η-butyric and valeric acids. The inclusion of ‘stearic acid’ at the level of 5% in the concentrate mixture increased the relative proportions of iso-butyric and iso-valeric acids but decreased the proportion of butyric acid in the rumen liquor.
Utilization of milk citrate by lactic acid bacteria and ‘blowing’ of film-wrapped cheese
Authors: Fryer T. F. , Sharpe M. Elisabeth , Reiter B. 
Published: June 2009

SummaryA study was made of the utilization of citrate in milk by some lactic acid bacteria. WhenStreptococcus diacetilactis1007 was grown alone or with eitherStreptococcus cremoris924 orLactobacillus caseiB 142/C or with both these latter organisms, > 99% of the milk citrate was utilized within 5 days.L. caseiB 142/C andL. casei/Str. cremorisutilized 57 and 14% of the citrate, respectively. WhenL. caseiC 2 andL. caseiC 5 were grown in milk in whichStr. cremoris924 had been previously grown, 94 and 64%, respectively, of the citrate was utilized after 7 days at 30°C.Cheeses were made using a citrate-fermenting and a non-citrate-fermenting starter and citrate concentrations of the milks, wheys and curds were determined during cheese-making. WithStr. cremoris924, citrate was preferentially retained in the curd at pressing, the concentration in the curd moisture being 2·9 times that in the whey. With the mixed starterStr. cremoris924/Str. diacetilactis1007, the curd at pressing and from the press contained only 27 and 5%, respectively, of the citrate present in theStr. cremoriscurd at these times.Cheeses were made usingStr. cremoris924, combinations ofStr. cremoris/Str. diacetilactis1007, or with δ-gluconic acid lactone instead of starter, with and without the addition ofL. caseiC 5, in order to examine the ability of the latter organism to produce ‘blowing’ in the sense of distension of the Cryovac wrapping of film-wrapped cheeses.L. caseiC 5 neither accelerated the decrease in cheese citrate nor produced blowing of the film-wrapping. Possible reasons for this behaviour are discussed.
Structural changes in whole milk during the production of sterile concentrates: an electron microscope study
Authors: Board P. W. , Bain Joan M. , Gove D. W. , Mullett J. T. 
Published: June 2009

SummaryElectron microscopy was used to study the effect of addition of NaOH, forewarming, homogenization, concentration, and heat sterilization on the structure of whole milk during the production of 4 heat-sterilized concentrates that showed different degrees of physical stability. The samples were prepared for electron microscopy by adding fixative either to liquid or freeze-dried material, and then embedding for sectioning.Noticeable structural changes occurred during forewarming of samples containing added NaOH, during homogenization, and during heat sterilization. Addition of NaOH and forewarming decreased the closeness of packing of the subunits in the casein micelles. Homogenization reduced the average size of the fat globules, and protein became attached to their surfaces. Heat sterilization caused coalescence of protein. In non-homogenized sterilized concentrate with added NaOH, protein bodies of about 100 times the volume of the original casein micelles were formed; these were free-floating and the concentrate was stable. In non-homogenized sterilized concentrate with no added NaOH the protein bodies were about 15 times the size of the casein micelles and bridged to each other, thereby forming a sediment consisting of large irregular particles. Very large protein bodies containing fat globules formed during heat sterilization of the homogenized samples, both in the presence and in the absence of NaOH, and were responsible for the formation of sediment in these 2 products.Needle crystals observed in most samples were identifed as CaCO3. H2O by selected area diffraction; KC1 crystals were also detected.
Growth studies on the lactic streptococci: I. A laboratory apparatus suitable for fermentation studies using skim-milk medium
Authors: Keen A. R. 
Published: June 2009

SummaryA versatile continuously-stirred fermentation apparatus, suitable for batch and continuous culture studies, has been constructed from glassware normally available in the laboratory. With the aid of normal workshop facilities an effective stainless steel stirrer gland was constructed. This apparatus has been used successfully for batch and continuous culture studies on the growth of lactic streptococci in skim-milk medium.
Comparison of milks processed by the direct and indirect methods of ultra-high-temperature sterilization: VI. Effects on sediment formation and clotting with enzymes
Authors: Perkin A. G. , Henschel M. J. , Burton H. 
Published: June 2009

SummaryWhen heat treatments of the same sporicidal effectiveness were given, directly heated ultra-high-temperature sterilized milk gave twice as much sediment as indirectly heated milk after storage at room temperature for 100 days. Both types of process reduced the rate of clotting of the milk with pepsin and rennin, but the effect of the indirect process was markedly greater than that of the direct process.
Comparison of the specificity and kinetic properties of 3 milk-clotting enzymes
Authors: Kovács-Proszt Gizella , Sanner T. 
Published: June 2009

SummaryThe biochemical properties of rennin purified from calf stomach,Mucor pusillusandEndothia parasiticahave been compared.The specificities of the enzymes have been studied by separating by disk-gel electrophoresis the macropeptides released on incubation with acid casein and κ-casein. The products formed on incubation with rennin from calf stomach andM. pusillusshowed some similarity although several bands were found which did not correspond to one another. The products formed with rennin fromE. parasiticadiffered considerably from those with the 2 other enzymes.The kinetic properties of the enzymes have been investigated in stopped-flow experiments on the enzyme-induced aggregation of κ-casein. The aggregation has been characterized by 2 parameters—the lag time prior to the increase in extinction and the maximum rate of change in extinction during aggregation.The specific activity measured from the inverse value of the lag time was under optimal conditions nearly 2·5 times higher for rennin from calf stomach than for rennin from the 2 micro-organisms. The fact that with increasing enzyme concentration the maximum rate of change of extinction during aggregation was identical for all 3 enzymes indicates that the same product is responsible for the formation of the aggregates. The data suggest that theKmvalue for the aggregation of κ-casein by the enzymes is about 100 times smaller thanKmfor the proteolytic activity of calfstomach rennin on κ-casein. The possibility is suggested that the high specificity of the enzymes in milk clotting is due to the very lowKmvalues for the peptide bond modifications involved in the formation of para-κ-casein, the first enzymic step in the clotting of milk.
Lipases in bovine milk and the relationship between the lipoprotein lipase and tributyrate hydrolysing activities in cream and skim-milk
Authors: Castberg H. B. , Egelrud T. , Solberg P. , Olivecrona T. 
Published: June 2009

SummaryThe lipoprotein lipase and tributyrate hydrolysing activities were found to be similarly distributed in the fractions obtained when whole milk was separated into skim-milk and cream, and when the cream was washed and freed from lipid. These enzyme activities in skim-milks and in extracts of lipid-free cream could not be separated by affinity chromatography on heparin-Sepharose. The enzymes were inactivated to the same degree when incubated at 37°C in the presence of 1·5 M-NaCl, pH 8·5, and both showed the same marked decrease in stability at 4°C in 1·5 M-NaCl, when the pH was changed from 8·3 to 9·0. Irradiation of skim-milk with UV-light caused the same decrease in both lipoprotein lipase and tributyrate hydrolysing activities. An antiserum against a highly purified skim-milk lipoprotein lipase caused total inhibition of the lipoprotein lipase and tributyrate hydrolysing activities in skim-milk and in extracts of lipid-free cream. It is suggested that in bovine milk there is only one major lipase and that it is identical to lipoprotein lipase.
Milk-fat globule membrane in homogenized cream
Authors: Darling Donald F. , Butcher David W. 
Published: June 2009

SummaryThe proteins of the milk-fat globule membrane in homogenized cream have been studied using polyacrylamide-gel electrophoresis and electron microscopy. The effects of pasteurization and subsequent storage of the homogenized cream on the strength and composition of the membrane have also been investigated. Caseins and undenatured whey proteins are adsorbed to the fat–serum interface during homogenization; the caseins are the more dominant group, but with no apparent preference for any individual protein. After homogenization, but before pasteurization, whey proteins are more easily removed by washing than are the casein components. After subsequent pasteurization, and on storage, whey proteins become more tightly bound and are no longer readily removed by washing. Electron micrographs showed that the interfacial membrane between fat droplets and the serum phase consists of a protein composite material containing casein micelles, casein micellar sub-units and molecular, or non-micellar protein.
Chemical analysis of flavour volatiles in heat-treated milks
Authors: Jaddou Haytham A. , Pavey John A. , Manning Donald J. 
Published: June 2009

SummaryThe effect of heat treatment of milk on low molecular weight, volatile compounds was studied in order to relate changes in the flavour of milks to changes in chemical composition. Milks were heat treated in a UHT plant for 3 or 90 s at 140 °C and stored at ambient temperature for periods up to 112 d. Volatile compounds in raw milk and in heated milks were isolated by a low temperature spray distillation technique and identified using gas chromatography and mass spectrometry. Cabbagey defects in heated milks are correlated with total volatile sulphur and it is concluded that the compounds H2S, COS, CH3SH, CS2 and (CH3)2S could be responsible for this defect.
Effects of increased supply of essential amino acids on the metabolism of the isolated perfused guinea-pig mammary gland
Authors: Peters Andrew R. , Alexandrov Stephen , Mepham T. Ben 
Published: June 2009

SUMMARYThe effects of high rates of infusion of essential amino acids on amino acid uptake by the isolated perfused guinea-pig mammary gland were studied. Infusion of methionine, tyrosine, phenylalanine, histidine and tryptophan (designated group 1) resulted in significant increases in the uptakes of tyrosine, phenylalanine and histidine. Methionine, tryptophan and other essential amino acids were not significantly affected. Infusion of threonine, valine, isoleucine, leucine, lysine and arginine (designated group 2) resulted in significant increases in uptake of all these amino acids. Group 1 amino acid uptake was not significantly affected. Infusion of all the essential amino acids (i.e. groups 1 and 2 together) resulted in significant increases in all their uptakes. Using as index ‘the predicted rate of protein synthesis’, infusion of group 1 and 2 together led to an apparent 27% increase in protein synthesis. The above results are discussed in relation to the control of milk protein synthesis by limiting essential amino acids.
Model proteolysis of β-casein by immobilized trypsin
Authors: Reimerdes Ernst H. 
Published: June 2009

SUMMARYThe enzymic degradation of β-casein by immobilized trypsin is described and its use as a model system to study proteolytic reactions which occur in milk during processing is examined. Quantitative determination of proteolysis can be obtained by densitometric transmission measurement of patterns obtained by polyacrylamide-gel electrophoresis. Staining properties of some of the individual components in the electrophoretic patterns were determined by calibration with pure protein and peptide preparations. The isolation of pure β- and γ-caseins and the preparation of several forms of immobilized trypsin are outlined.
Studies on the induction of heat stability in evaporated milk by preheating: effects of milk concentration, homogenization and whey proteins
Authors: Newstead David F. , Conaghan Errol F. , Baldwin Alan J. 
Published: June 2009

SUMMARYWhen milk was preheat-treated after either evaporation or homogenization with fat present the degree of heat stability induced in the resulting evaporated milk (EM) was considerably less than with the normal process in which the preheat treatment was carried out first. When the preheat treatment was carried out after both evaporation and homogenization, no heat stability was induced by the preheat treatment. Removal of the whey protein fraction from the milk increased the heat stability of both the EM homogenized before preheat treatment and the EM made by the normal process.
Inorganic constituents of milk: I. Correlation of soluble calcium with citrate in bovine milk
Authors: Holt Carl , Muir D. Donald 
Published: June 2009

SUMMARYA high correlation was found between soluble calcium and citrate concentrations during a study of seasonal changes in the composition of the commercial milk supply to South-west Scotland. A simple physicochemical model of the ion equilibria in the aqueous phase of milk suggests that the observed correlation is causal. This hypothesis was corroborated by an analysis of data on individual cow milks and by experiments involving the addition of citrate to milk at constant pH.
Cheddar cheese flavour studies: II. Relative flavour contributions of individual volatile component
Authors: Manning Donald J. 
Published: June 2009

SummaryMultiple regression analysis has been used to relate contributions of individual flavour components to the flavour of Cheddar cheese. Equations have been derived that relate Cheddar flavour to the headspace concentrations of 2-pentanone, methanethiol and methanol. The concentrations of ethanol and H2S found in cheese headspace have been related to the flavour defects ‘fruity’ and ‘sulphide’ respectively
256. The protein requirements for milk production
Authors: Bartlett S. , Foot A. S. , Huthnance S. L. , Mackintosh J. 
Published: June 2009

1. In a large-scale experiment, using about 500 cows, half the cows were fed a production ration consisting of decorticated ground-nut cake, maize meal, wheat offals and molasses supplying about 0.6 lb. protein equivalent per 10 lb. milk produced, and the remaining half were fed a production ration containing the same constituent foods in different proportions supplying a similar starch equivalent, but only two-thirds the amount of protein. No measurable difference was observed in the fatness, handling properties of the skin, hair on the body and percentage of fat and solids-not-fat in the milk.The milk yields showed no difference during the winter feeding period of about 20 weeks, but during the succeeding period when all the cows were allowed ample grass the milk yield response of the cows previously given the low-protein ration was significantly greater than that of the corresponding cows previously given the high-protein ration.The experiment was repeated the following winter, using about 600 cows, and confirmatory results were obtained.2. Another experiment similarly planned, using 300 cows, compared highwith low-protein production rations consisting of the constituents noted above together with soya-bean meal and rice bran. No significant differences were observed between the effect of the two rations on milk yield or composition, fatness of the cows, etc. There was, however, an indication (not statistically significant) that the low-protein ration which contained a relatively high proportion of rice bran depressed the milkfat percentage.3. A small but more completely controlled experiment confirmed the findings of the large-scale experiments.
258. The Vitamin B1and Riboflavin of Milk
Authors: Houston J , Kon S. K. , Thompson S.Y. 
Published: June 2009

Part I1. A method for the estimation of vitamin B1in milk by a modified Jansen test involving takaphosphatase treatment is described in detail.Part II2. It is shown by ultra-filtration experiments, by treatment with pepsin and takaphosphatase, with trichloroacetic acid and with fuller's earth that vitamin Bx is present in milk unesterified and phosphorylated and that both forms may be freely diffusible or combined with protein either loosely or by firmer bonds.Part III3. The effect of the stage of lactation on the amounts and partition of vitamin B1in milk has been studied. Samples of colostrum and early milk were found to contain large amounts of cocarboxylase (up to 80 % of the total). Hardly any cocarboxylase was present in mid or late lactation milks. The total vitamin B1content was 60–100μg./100 ml. for colostrum, up to 60μg./100 ml. for early milk and 30–40μg./100 ml. for mid and late lactation.4. A marked negative correlation exists between the cocarboxylase content of cow's and goat's milk and their alkaline phosphomonoesterase titre. As this enzyme cannot dephosphorylate cocarboxylase it is probably accompanied in milk by other enzymes more suited to this process.5. The suggestion is put forward that the vitamin B1of milk is mostly derived not directly from the blood but from the secretory cells of the mammary gland.
A method of preparation of x-casein and some observations on its nature
Authors: Cheeseman G. C. 
Published: June 2009

SummaryDetails are given of the method used in this laboratory for the preparation of k-casein. The recovery is about 25% and the material has a purity, estimated from electrophoretic patterns, of about 90% with β-casein as the main contaminant. Higher temperatures and lower ion concentration caused precipitation of k-casein in the presence of calcium ions, 0·1m-acetate buffer at pH 6·5 being sufficient to stabilize a 0·5% solution in the presence of 0·01–0·2m-CaCl2 at 20 and 30°C but not at all calcium concentrations at 40°C. It was also found that solutions of para-k-casein did not aggregate in the presence of concentrations of electrolytes above about 0·25m.The rate of release of non-protein nitrogen and decline in viscosity during the enzymic stage of gel formation in solutions of k-casein and rennin had similar apparent first order constants (0·087 ± 0·03 min—1 and 0·086 ± 0·021 min—1, respectively, at 25°C). A gel could be formed by rennin action in a solution containing as little as 6·25mg of the protein per litre. In the non-enzymic stage of gelling of k-casein solutions the calculated activation energy over the range of 20–40°C was much lower than that obtained from the non-enzymic stage of milk coagulation.
Quelques facteurs de variation de la teneur en calcium des laits de vaches
Authors: Auriol Par P. , Mocquot G. 
Published: June 2009

SummaryA study was made of the effect of various factors which may influence the calcium content of milk. The basic data consisted of the calcium content of 20840 samples of individual milks, taken once a month, during the course of 2300 lactations of Montbeliarde cows. For each lactation, a weighted average figure for the calcium concentration was calculated, taking into account the milk quantities recorded on each sampling day. The calcium content has been expressed in g/kg of milk.The stage of lactation caused significant variations in calcium content mainly during the first month and the last three months. Expressed as percentages of the arithmetic mean for the whole lactation period, these variations were always within the limits —4 to +8% (Fig. 1).The season of calving did not greatly affect the weighted lactational average content of calcium but caused some important changes in the average value with advancing lactation (Fig. 2). The minimum values were always observed in July, whatever the month of calving (Fig. 3).The age of the cow, as well as the age at first calving (Table 1), had very small effects on the calcium content.
Characteristics of proteinases of 3 strains ofStaphylococcus lactisisolated from Cheddar cheese
Authors: McDonald I. J. 
Published: June 2009

SummaryProteinase systems of 3 strains ofStaphylococcus lactisfrom Cheddar cheese have been studied. Proteinase of one organism was found in the culture supernatant, those of the other two were obtained in significant amounts only by disruption of the cells of the organisms. All 3 proteinases possessed maximum activity at alkaline pH (about 9·0–10·0). They were most active at relatively high temperatures (45–55 °C) and possessed temperature characteristics (μ) of 7000–8000 cals. Casein, ²-lactoglobulin and haemoglobin were hydrolysed by the proteinases; casein most readily and β-lactoglobulin more readily than haemoglobin. Because of their characteristics, such proteinases are considered potentially capable of contributing to the ripening of Cheddar cheese.
The separation of milk protein on dextran gel
Authors: Hill R. D. , Hansen Raione R. 
Published: June 2009

SummaryA method was devised for separating proteins of skim-milk on Sephadex G 100 dextran gel. Four fractions were obtained, the first 3 corresponding to casein micelle, lactoglobulin, and lactalbumin fractions while the last contained no protein. The fractions were examined using starch gel electrophoresis, and results are also given for the average composition of the fractions. Differences between the composition of the casein micelle fraction and that of sodium caseinate made from the same milks are reported.