bluuebunny/crossref_metadata_2025 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

The 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

A 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

Electron 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

A 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

When 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

The 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

The 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

The 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

The 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

The 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

The 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

When 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

A 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

Multiple 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 I

1. A method for the estimation of vitamin B1in milk by a modified Jansen test involving takaphosphatase treatment is described in detail.

Part II

2. 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 III

3. 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

Details 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

A 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

Proteinase 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

A 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.
A pilot plant for the removal of cationic fission products from milk: I. Design and construction
Authors: Glascock R. F. , Hall H. S. , Suffolk S. F. , Bryant D. T. W.
Published: June 2009

A pilot plant with a capacity of 2300 1./5 h day for the removal of cationic fission products from milk is described. The process involves the acidification of the milk with citric acid to pH 5.25 and its passage through an ion exchange resin charged with the ions of Ca, K, Na and Mg in the same proportions as those in which they occur in milk. The effluent milk is neutralized with potassium hydroxide. At the end of the day the plant and resin bed are washed and sterilized.

Two resin beds are provided and are used on alternate days, one being washed and regenerated while the other is in use. Regeneration is carried out with a solution which removes radioactive cations and restores the resin bed to its original ionic composition.

Bacteriological tests show that the method of cleaning both plant and resin bed is satisfactory.

Conclusions are drawn as to a suitable design for a larger scale plant.
Further studies on the effects of dietary cottonseed oil on milk-fat secretion in the cow
Authors: Steele W. , Moore J. H.
Published: June 2009

The effects of the isocaloric replacement of part of the dietary concentrate mixture by cottonseed oil on the yield and composition of the milk fat and on the pattern of rumen fermentation was investigated in 2 feeding experiments with a total of 8 cows in mid-lactation. The concentrate mixtures were given with high- or low-roughage diets that supplied 9·1 or 1·8 kg of hay/day.

In expt 1 the yield of milk fat was not altered by the addition of 10% cottonseed oil to the concentrate mixtures given either with the high- or with the low-levels of dietary roughage. On the low-roughage treatment, dietary cottonseed oil increased milk yield but reduced the fat content of the milk. The change from the high- to the low-roughage diets containing no cottonseed oil resulted in reductions in the yield and percentage of fat in the milk. In expt 2 the yields of milk and milk fat were similar irrespective of whether the concentrate mixture contained 5 or 10% cottonseed oil.

In expt 1 the inclusion of 10% cottonseed oil in the concentrate mixture reduced the yields and percentages of the medium-chain fatty acids (12:0, 14:0 and 16:0) and increased the yields and percentages of the C18 fatty acids in the milk fat. In expt 2, when the concentrate mixture contained 5% cottonseed oil, the yields and percentages of all the fatty acids in the milk fat were similar to the values obtained when the concentrates contained 10% cottonseed oil. For any given concentrate mixture, the change from the high- to the low-roughage treatments in both expts 1 and 2 resulted in increases in the percentage of oleic acid in the milk fat. The highest concentration of trans-octadecenoic acid was observed in the milk fat of the cows when they were given the high-roughage diet with the concentrate mixture containing 10% cottonseed oil.

In expt 2 the level of cottonseed oil in the concentrate mixture did not influence the pattern of rumen fermentation as measured by the concentrations of the various volatile fatty acids in the rumen liquor. However, the change from the high- to the low-roughage diets reduced the proportion of acetic and increased the proportions of propionic and n-valeric acids in the total volatile fatty acids in the rumen liquor.
The effect of ageing on heat-sterilized milk
Authors: Wheelock J. V. , Hindle E. J.
Published: June 2009

During 7 months' storage of heat-sterilized milk there were changes in the glycopeptides released by rennin (E.C. 3.4.4.3) action and soluble in 12% (w/v) trichloroacetic acid (TCA). The results showed a progressive decrease in the amount of carbohydrates attached to κ-casein. As these carbohydrates may contribute to the micelle-stabilizing power of κ-casein it was concluded that the loss of carbohydrates could be one factor in the development of gelation in heat-sterilized milks during storage.
The structure of a bitter peptide derived from casein by digestion with papain
Authors: Clegg K. Mary , Lim C. L. , Manson W.
Published: June 2009

Treatment of unfractionated bovine casein with papain produced a digest which was bitter in taste. The bitterness was shown to be a property of a peptide originating only in β-casein and having an amino-acid composition consistent with its derivation from residues 53–79 inclusive of β-casein. The relationship existing between flavour and primary structure in this peptide is discussed briefly.
Measurements in vivo of the rate of production of protozoa in the rumen
Authors: Singh U. B. , Varma A. , Verma D. N. , Ranjhan S. K.
Published: June 2009

The rates of production of protozoa in the rumen of buffalo calves have been estimated using a single-injection isotope dilution technique. The calves were fed at 2 levels of crude protein, namely, 13% lower and 19% higher than that recommended by the National Research Council. The animals were given their rations at 2-h intervals for 3 weeks. Thereafter 14C-labelled rumen protozoa were injected into the rumen of each calf in a single injection. Samples of the rumen liquor were drawn at various time-intervals for 10 h and were analysed for the concentration of protozoa and radioactivity. The decline in the specific radioactivity of protozoa cells in the rumen as a function of time was used for calculating half life (t½). A mathematical equation was used to calculate the rate of production of protozoa. The average t½ was 1077 min for both groups and the rates of production of protozoa were 73·9 and 92·1mg/min in groups fed on low and high planes of crude protein respectively, showing that the production of protozoa is significantly (P < 0·01) higher in animals consuming a ration high in crude protein.
The nature of casein aggregates in heated and stored milk
Authors: Cheeseman G. C. , Knight Dorothy
Published: June 2009

Gel filtration on Sepharose 6-B was used to study the size distribution of sub-micellar casein aggregates in colloidal phosphate-free milk, and comparisons were made between the elution profiles obtained for fresh, heated, ultra-hightemperature (UHT) treated and stored UHT milks. Increase in length of storage of UHT milk gave rise to an increase in proportion of casein aggregates excluded from Sepharose 6-B, but no corresponding increase in size of included casein aggregates was observed.
Effect of urea on the heat coagulation of the caseinate complex in skim-milk
Authors: Muir D. D. , Sweetsur A. W. M.
Published: June 2009

Additions 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.
The role of various milk fractions and the importance of somatic cells in the formation of germinant(s) for Bacillus cereus when milk is pasteurized
Authors: Davies F. L.
Published: June 2009

Confirmation was obtained for the occurrence of an interaction between high and low molecular weight fractions of milk during its pasteurization, resulting in the formation of germinant(s) for Bacillus cereus. Various milk fractions were added to supernatants or dialysates of raw skim-milk, pasteurized and assayed for germinant. Micellar casein obtained by high speed centrifugation of raw milk stimulated germinant formation, but whole casein obtained by acid precipitation was less stimulatory and individual casein fractions showed no stimulation. A membrane rich ‘fluff’ layer obtained by high speed centrifugation of raw milk was highly stimulatory and suggested the possibility that the somatic cell count of milk may be related to germinant production.

Using milk from endotoxin infused and infected quarters of individual cows, a correlation between cell count and germinant formation was clearly demonstrated. Adjustment of the cell counts of individual milk samples was generally accompanied by corresponding changes in germinant formation, though removal of cells by filtration did not have this effect, possibly since germinant precursor had leached from the cells and remained in the milk. Pasteurization was necessary, not simply to express germinant from cells but to effect an interaction of germinant precursors. It is not clear whether the cell associated germinant precursor is derived from the cells themselves or from a related component. Addition of blood serum proteins was without stimulatory effect.

Since low cell count milks sometimes supported appreciable germination after pasteurization, but showed still higher levels when the cell count was raised, germinant may be formed via 2 pasteurization dependent processes, one between milk constituents alone and the other involving both milk constituents and somatic cells.
Effect of vacuum fluctuation during milking on the development of intramammary infection from teat duct colonization by Staphylococcus aureus
Authors: King Joseph S. , Neave Frank K. , Williams Raymond L.
Published: June 2009

Twelve of twenty-one udder quarters with colonized teat ducts became infected within 13 d when milked with a machine producing large cyclic and irregular vacuum fluctuations in the teatcup; of 23 quarters milked under the same conditions, but with metal shields fitted inside the liners to protect the teat apex (Thiel, 1974), only 2 quarters became infected in the same period. The introduction of a post-milking teat disinfectant teat dip resulted in the elimination of orifice colonization from 15 teats dipped in Na hypochlorite solution (40 g/l available chlorine) and from all but 2 of 15 teats dipped in an iodophor solution (5 g/l available iodine).
Relationship between trisaturated glyceride composition and the softening point of milk fat
Authors: Parodi Peter W.
Published: June 2009

No relationship was found between the trisaturated glyceride content and the softening point (SP) of milk fat. Inter-esterification of milk fat increased its SP, but did not change the trisaturated glyceride content or the fatty acid composition of the trisaturated glyceride fraction. Inter-esterification increased the amount of both low and high and decreased the amount of medium molecular weight triglyceride species in the trisaturated glyceride fraction. The increase in the amount of high molecular weight triglyceride species was up to 3 times greater than the increase in the amount of low molecular weight triglycerides.

The triglyceride species composition of the trisaturated glyceride fraction of milk fat was found to vary seasonally. Excellent correlation was found between SP and groups of low molecular weight triglycerides, groups of high molecular weight triglycerides and some individual triglyceride species. Correlation coefficients were higher than those previously reported between groups of fatty acids and SP.
Susceptibility of the bovine udder to bacterial infection in the dry period
Authors: Cousins Carol L. , Higgs Trevor M. , Jackson Eric R. , Neave Frank K. , Dodd Frank H.
Published: June 2009

The teats of 18 cows were externally exposed to infection with mastitis organisms by dipping them daily for 1 or 2 weeks in a mixed suspension of Streptococcus dysgalactiae and Str. uberis at the start, the middle or the end of the dry period. The teat sinuses of quarters which remained uninfected after external exposure at the beginning or the middle of the dry period were then infused with the same strains of streptococci. Of the 9 quarters infected following external exposure 8 occurred in animals exposed at the start and one in the middle of the dry period. Thirty-six new infections occurred after infusion of bacteria into the teat sinuses of 38 quarters. In a further trial with 10 cows, Staphylococcus aureus and Str. zooepidemicus were inoculated into the distal 3 mm of the streak canals of 5 cows immediately after drying-off and into those of 5 cows which had been dry for 28 weeks. Animals were slaughtered 48 h later and infection determined by teat puncture. Five infections occurred in cows which were at the start of the dry period and only one in the cows dry for 28 weeks. It is suggested that these differences in the rates of new infection between the early dry period and a very extended dry period are due to differences in the ease with which bacteria can penetrate the teat canal. At the later stage bacterial growth through the teat canal appeared to be inhibited.
Post-milking iodine teat skin disinfectants: 3. Residues
Authors: Sheldrake Richard F. , Hoare Roderic J. T. , Chen Stanley C. , McPhillips John
Published: June 2009

Teat dipping of lactating cows with either 1000 or 5000 mg available iodine/; (mg avI/;) solution and thoroughly washing and drying of the teats before sampling resulted in levels of 70 and 99 µg avI per quarter per milking respectively. Without any pre-milking udder preparation prior to sampling the levels of iodine recorded were 143 and 291 µg avI per quarter per milking respectively. Some systemic transfer of iodine from the teat skin to the milk was observed, but the bulk of iodine residue in milk was of direct teat skin origin.
Casein compositional studies: 1. The composition of casein from Friesian herd milks
Authors: Barry J. Gerard , Donnelly William J.
Published: June 2009

Casein composition in Friesian herd milks was examined by quantitative column chromatography on hydroxyapatite. Whole casein was resolved into 5 fractions: (1) γ-casein + para-κ-casein; (2) κ-casein + unidentified chymosin-resistant components; (3) unidentified minor protein; (4) β-casein; (5) αs1,0- + minor αs-caseins. Protein in fractions 1, 2, 4, 5 was measured by ultraviolet spectrometry, using appropriate specific absorption coefficients. The quantitative contribution of chymosin-resistant components to the κ-casein fraction was measured by a method involving hydroxyapatite chromatography of chymosin-treated whole casein. Compositional analysis was carried out throughout a lactation cycle on a total of 24 casein samples from the milks of a winter/spring calving and autumn-calving herd. Average composition (expressed as % total casein), which was similar for both herds, was 48·7% αs-, 33·8% β-, 4·9% γ-, 9·5% κ- and 3·2% unidentified components. Lactational effects on composition were also similar for both herds and were most pronounced in late lactation where increases were recorded in γ-casein and unidentified components, and decreases in β- and αs-caseins. Fluctuations in κ-casein proportions were small and slightly higher values were obtained in early and late lactation. Casein composition also appeared to be affected to some extent by season, as shown by differences in the proportions of αs-caseins and unidentified components between mid-lactation milks from the 2 herds. Compositional variations resulted partly from the action of milk proteinase on β-casein and also, apparently, from differences in relative rates of protein biosynthesis.
Effect of concentration by ultrafiltration on the heat stability of skim-milk
Authors: Sweetsur A. W. Maurice , Muir D. Donald
Published: June 2009

An examination has been made of the heat stability characteristics of skim-milk concentrate prepared by ultrafiltration (UF). Concentrate prepared by UF was found to be more stable than that prepared by conventional evaporation. In contrast to conventional concentrate, the heat stability of UF concentrate was not appreciably affected by forewarming or addition of permitted stabilizers, but the effect of addition of urea was generally the same for both UF and conventional concentrates; an increase in heat stability was obtained if the milk total solids level was less than 14%. As with conventional concentrate, addition of simple aldehydes induced large increases in the heat stability of UF concentrate. It is suggested that a novel range of sterile milk products could be prepared from UF concentrates. Because of the high protein and low lactose contents of these concentrates, the products might be nutritionally more attractive than those prepared from conventional concentrates.
Occurrence of γ-caseins in buffalo milk
Authors: Trieu-Cuot Patrick , Addeo Francesco
Published: June 2009

Using polyacrylamide gel electrophoresis, 2-dimensional gel electrophoresis and electrofocusing, it has been shown that 4 basic fragments were produced by action of plasmin on buffalo β-casein. These fragments were present in whole buffalo casein prepared from bulk milk. Their mol. wts, 20000, 16000 and 11000 (2 components) were determined by SDS-gradient polyacrylamide gel electrophoresis. It is suggested that 3 of them are homologous to bovine γ1-, γ2- and γ3-caseins respectively, while the last one (mol. wt 16000), which has no counterpart in plasmin digest of bovine β-casein, could arise from a cleavage at bond 68–69.
Constitutive nature of the enzymes of citrate metabolism inStreptococcus lactissubsp.diacetylactis
Authors: Cogan Timothy M.
Published: June 2009

Four enzymes of citrate metabolism (viz. citrate lyase, acetolactate synthase, diacetyl reductase and acetoin reductase) were constitutively present in cells of several strains ofStreptococcus lactissubsp.diacetylactis. In strain DRC1, which was studied in detail, diacetyl reductase and acetoin reductase were partly repressed and acetolactate synthase partly induced by growth on citrate. The stage of growth also affected the formation of each enzyme. The buffer species affected the activity of acetolactate synthase, diacetyl reductase and acetoin reductase.
A new method for the detection of microbial proteolytic enzymes in milk
Authors: Cliffe Allan J. , Law Barry A.
Published: June 2009

Optimum conditions have been determined for the use of Hide Powder Azure (HPA) to estimate extracellular proteinases produced by psychrotrophic Gram-negative bacteria. This assay is quicker, more precise and 3·2 times more sensitive than assays of soluble N released from casein. It provides a simple alternative method for monitoring proteinase purification schemes. With the modification described it is now possible to determine proteinase activities directly in milk. In its simplest form the HPA assay is sufficiently sensitive to detect proteinases produced by as few as 1·5 x 106c.f.u. ml-1psychrobtrophs without the necessity for any sample processing.
Effects of thermal industrial processing on acid-soluble nucleotides of milk
Authors: Gil Angel , Sanchez-Medina Fermin
Published: June 2009

Commercial bulk milk contained, in its acid-soluble nucleotide fraction, small quantities of CMP and AMP as well as a high proportion of orotate (503±16 μg/g of total solids). These components were altered by thermal treatment during processing. Standard sterilization and spray drying of milk lowered significantly the CMP, AMP, and orotate concentrations. HTST pasteurization caused a slight decrease in CMP and AMP concentrations, but the orotate content remained unchanged. The UHT sterilization seemed to be the thermal treatment in which the acid-soluble nucleotides of milk underwent least change. It is therefore concluded that the decrease in concentration of the nucleotides of milk is more directly related to the time for which the milk remains at the processing temperature than to the temperature itself.
Determination of oxidative deterioration of milk powder and reconstitute milk by measurement of chemiluminescence
Authors: Timms Ralph E. , Roupas Peter , Rogers William P.
Published: June 2009

A scintillation counter was used to measure chemiluminescence (CL) from milk powder and reconstituted milk. Only a small amount of CL, just above the background level, was observed from powders, but reconstituted milks emitted easily measurable CL. CL from milk was stimulated by exposure to light and found to decline gradually but non-exponentially after the exposure ceased. CL was at a maximum immediately after the milk was reconstituted from milk powder. Without light exposure, CL then declined gradually but non-exponentially over several hours to reach a constant value related to the level of oxidation of the powder. When determined under standard conditions 60 min after reconstitution, CL of milk reconstituted from stored milk powders correlated well with peroxide values and oxidized flavour as assessed by a taste panel.
Chemical composition and coagulating properties of renneted milks from different breeds and species of ruminant
Authors: Storry John E. , Grandison Alistair S. , Millard David , Owen A. Jane , Ford Graeme D.
Published: June 2009

The detailed chemical composition of 25 milks from different breeds of cow, sheep and goat were related to their properties of rennet clotting, coagulum development and syneresis at pH 6·4. Experiments in which concentrations of fat and whey proteins in milk were manipulated, and in which milks were homogenized at different pressures, were also carried out and the effects observed were related to the above processes.

The composition of milks varied widely and many relations between concentrations of components could be related to their known modes of secretion from the alveolus or to their structural functions in the colloidal phase of milk. Rennet clotting was related to total Ca concentration and also to the proportions of αs- and β-caseins present. Coagulum strength was strongly related to total casein concentration in milk but was unaffected by total fat content or by casein/fat ratios. Syneresis was inversely related to fat content of milk and little affected by coagulum strength. Homogenization retarded syneresis, probably by altering coagulum structure and modifying entrapment of fat globules within the coagulum.
Domiati cheese made with ultrafiltered reconstituted milk and lipolysed recombined cream
Authors: Abd El-Salam Mohamed E. , El-Shibiny Safinaz , El-Koussey Laila A. , Haggag Hamdy F.
Published: June 2009

A new method was developed for making Domiati cheese, based on blending ultrafiltered reconstituted milk and lipolysed recombined cream. The chemical composition of the new product was similar to the traditional cheese. The flavour intensity increased with the amount of lipase used in the cream hydrolysis. During storage the acidity and tyrosine content of cheese from different treatments increased at nearly similar rates. The level of total volatile fatty acids was affected by the level of lipase used. Organoleptic scoring showed that cheese made with cream treated with the intermediate levels of lipase (2 or 5 g/500 g cream) ranked the highest, after 1 and 4 months of storage respectively.
Influence of sulphydryl group interactions on the heat stability of homogenized concentrated milk
Authors: Sweetsur A. W. Maurice , Muir D. Donald
Published: June 2009

SUMMABY

The heat stability of homogenized concentrated milk was found to be more susceptible than that of unhomogenized concentrated milk to changes in the ratio of β-lactoglobulin to κ-casein which were deliberately designed to alter the extent of disulphide-linked complex formation during heating. When sulphydryl group interactions were prevented by the addition to the milk before homogenization of blocking or oxidizing agents, homogenization did not change the heat stability of subsequently concentrated milk.
Milk composition and yield of the black Bedouin goat during dehydration and rehydration
Authors: Maltz Ephraim , Shkolnik Amiram
Published: June 2009

Milk composition and yield were measured in the black Bedouin goat during 4 d of dehydration followed by 2 d of rehydration. During this time the goats were exposed to strong solar radiation with no access to shade; all of these conditions occur commonly in the desert. Milk yield, initially similar to that found in the desert, was maintained during the first 2 d of dehydration, fell to 35% of the initial value over the third and fourth days and recovered fully during 2 d of rehydration. As yield fell, milk osmolality, and milk fat and protein concentrations rose. During rehydration all 3 fell once more, but whereas osmolality finished below initial values the concentrations of fat and protein remained higher than before dehydration. The milk remained isosmolar with plasma throughout. Total yields of milk solids and milk water during the whole experimental period were 70 and 67% of normal respectively and normal growth of the young was not disturbed.