bluuebunny/crossref_metadata_2025_split huggingface dataset:
The uptake of amino acids and peptides byStreptococcus lactis
Authors: Rice G. H. , Stewart F. H. C. , Hillier A. J. , Jago G. R. 
Published: June 2009

SummaryPeptide and amino acid transport inStreptococcus lactiswas both energy-and temperature-dependent. Separate systems were present for the transport of amino acids, dipeptides and oligopeptides as well as for individual amino acids. Both tri- and tetra-peptides were readily transported while an apparent size restriction at the point of uptake resulted in a relatively low rate of uptake of the pentapeptide. The effects of pH, temperature and salt concentration on the uptake of amino acids and peptides were studied. Exchange reactions played a significant role in the uptake of both peptides and amino acids.
Antibacterial effect of the lactoperoxidase system on psychrotrophic bacteria in milk
Authors: Björck L. 
Published: June 2009

SummaryActivation of the antibacterial lactoperoxidase system in milk, i.e. increasing the thiocyanate concentration to 0·25 mM and adding an equimolar amount of H2O2, results in a substantial reduction of the bacterial flora and prevents the multiplication of psychrotrophic bacteria for up to 5 d. This treatment has no effect on the physico-chemical properties of milk and does not lead to the accumulation of resistant bacteria. The practical application of the lactoperoxidase system in prolonging the storage period of raw milk at low temperatures is discussed.
Heat stability of milk: influence of denaturable proteins and detergents on pH sensitivity
Authors: Fox Patrick F. , Hearn Catherine M. 
Published: June 2009

Summaryα-Lactalbumin and SDS in addition to β-lactoglobulin introduced pH sensitivity to the heat stability–pH curve of serum protein free casein micelles particularly by increasing stability in the pH range 6·4–6·7. Bovine serum albumin, ovalbumin and lysozyme caused marked destabilization of milk and casein micelle suspensions throughout the pH range 6·4–7·4. Tetramethyl ammonium bromide caused destabilization of milk at pH values > 7·0, but had no effect in the region of maximum stability while the non-ionic detergents Triton X-100 and Tween 80 had no effect on heat stability.
Heat stability of milk: influence of κ-casein hydrolysis
Authors: Fox Patrick F. , Hearn Catherine M. 
Published: June 2009

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.
Effects of mechanical agitation of raw milk on the milk-fat globule in relation to the level of induced lipolysis
Authors: Deeth Hilton C. , Fitz-Gerald Carolyn H. 
Published: June 2009

SummaryThe amount of damage caused to the milk-fat globule by mechanical agitation of raw milk was assessed by several methods and related to the level of induced lipolysis resulting from the agitation. The results obtained by measuring the amount of ‘free’ fat formed, the percentage of fat in the skim-milk phase after separation, and the increase in the proportion of alkaline phosphatase associated with the skim-milk phase, showed little correlation with the level of lipolysis induced by agitation over a range of conditions. However, the level of induced lipolysis showed good correlation with the amount of lipolysis caused by addition of an exogenous lipase (from Candida cylindraceae) to the agitated milk. It is concluded that classical methods of assessing milk-fat globule damage are unsuitable for predicting the amount of fat available for lipase action and the lipolytic potential of raw milk subjected to mechanical agitation.
The metabolism of [14C]bicarbonate byStreptococcus lactis: the synthesis of succinic acid
Authors: Hillier Alan J. , Jago G. Richard 
Published: June 2009

SummaryWhole cells ofStreptococcus lactisC10, when incubated with an energy source, converted fumarate to succinate and malate to lactate. Cell-free extracts ofStr. lactisC10 contained fumarate reductase, but no aspartase, adenylosuccinate synthetase and lyase or argininosuccinate synthetase and lyase activity could be detected. Cells grown in the presence of [14C]bicarbonate produced labelled succinate during the synthesis of purine bases. However, the amount of succinate produced by this pathway only accounted for approximately one-sixth of the succinate produced by the cells.
Comparative aspects of milk proteins
Authors: Jenness Robert 
Published: June 2009

SUMMARYThe current status of knowlege of the major proteins of milks of various species is evaluated. Most of the non-bovine milk proteins are homologous with the recognized families of those ofBos taurus, αs1-caseins, αs2-caseins, β-caseins, K-caseins, β-lactoglobulins, and α-lactalbumins, each family representing a separate genetic locus specific to the mammary gland. No prominent milk protein not homologous to one of these families has yet been discovered in milk of any species. Genetic polymorphism resulting from substitutions in the polypeptide chains and various degrees of post-translational phosphorylation, glycosylation, and proteolysis have been identified in milk proteins of several species. Total protein production ranges among species from about 0.5 to 10 g/d per kg0.75maternal weight. Proportions of the several proteins vary greatly among species, but few accurate analytical data are available except for total casein and total whey protein contents.
The association of bovine SH-κ-casein at pH 7·0
Authors: Vreeman Henk J. 
Published: June 2009

SUMMARYThe self-association of SH-κ-casein at pH 7·0 in 0·01 m-EDTA, 0·001 m-dithiothreitol buffer, containing 0·1, 0·2, 0·5 or 1·0 m-NaCl is of a monomer–polymer type. The polymer is a spherical particle, diam. 23 nm and mol. wt 570000 (30 monomers). These parameters are not greatly influenced by variations in ionic strength above 0·1. The critical micelle concentration, which is a property of a monomer–polymer equilibrium, decreases with increasing ionic strength. The standard free energy of association is about – 36 kJ/mol. monomer at 20 °C.
The synergic effect of urea and aldehydes on the heat stability of concentrated skim-milk
Authors: Muir D. Donald , Sweetsur A. W. Maurice , Holt Carl 
Published: June 2009

SUMMARYWhen urea is added to concentrated skim-milk (22·5% total solids) no increase in heat stability is observed. However, a similar addition of urea to concentrate stabilized with aldehyde brought about a significant further increase in heat stability. Urea can further stabilize concentrated skim-milk only when aldehyde addition has brought about a change in coagulation mechanism from the normal 2-stage process to a single-stage coagulation. These results can be related to the 2 coagulation mechanisms observed in unconcentrated milks.
Milk yield and fertility of high-yielding dairy cows in a sub-tropical climate during summer and winter
Authors: Folman Yeshayahu , Berman Amiel , Herz Zeev , Kaim Moshe , Rosenberg Miriam , Mamen Meir , Gordin Sali 
Published: June 2009

SUMMARYThe effect of season on milk yield, milk composition, oestrus manifestation, oestrus cycle characteristics and conception rate was studied in high-yielding Israeli-Friesian cows. ‘Summer’ cows were allotted to control (SC) and forced ventilation (SV) groups. ‘Winter’ cows (W) were kept in one group. During July-September mean rectal temperatures at 16.00 h in primiparous and multiparous cows were 39·6 and 39·8°C, respectively in cows of the SC group, and 39·4 and 39·3°C, respectively in cows of the SV group. Mean rectal temperatures at 16.00 h of the animals in the W group during December-March were 38·9°C in both primiparous and multiparous cows. The mean 122-d milk yields in primiparous cows were 3508, 3251 and 3571 kg/cow in the SC, SV and W groups respectively (not significant (NS)). In the multiparous cows the respective yields were 4183, 4416 and 4538 kg/cow (P < 0·05). Differences in milk composition were small and statistically NS.Observations on oestrus manifestation, performed 4 times daily, indicated that standing oestrus lasted 9·2 and 10·6 h in primiparous and multiparous cows respectively (P < 0·05); differences between groups were statistically not significant. Oestrous cycle lengths of primiparous and multiparous cows were 21·1 and 22·5 d respectively (P < 0·05) between ovulations and 23·0 and 28·05 d respectively (P < 0·01) between standing heats. Cows were inseminated following standing heat only. Conception rates (on all services within experimental periods) in primiparous cows were 50, 35 and 72% in the SC, SV and W groups respectively (NS). In the multiparous cows, the respective rates were 22, 52 and 80% (P < 0·05).It is concluded that in the present experiment hyperthermy decreased milk production to a very small extent, in spite of very high milk yields, but fertility was severely affected. It is also suggested that primiparous cows are less affected by heat stress than multiparous cows.
Neutral volatiles in cheddar cheese made aseptically with and without starter culture
Authors: McGugan W. A. , Howsam Shirlie G. , Elliott J. A. , Emmons D. B. , Reiter B. , Sharpe M. Elisabeth 
Published: June 2009

SummaryAnalyses of the neutral volatile components from 3 Cheddar cheese are presented. Two were made aseptically in an aseptic vat, with and without starter culture; the third was made with starter culture in an open vat. Gas–liquid chromatography and mass spectrometry detected the same volatiles in starterless cheese having little or no Cheddar flavour as in cheese made with starter and having a characteristic Cheddar flavour. Methyl disulphide and dimethyl sulphide were the only compounds consistently detected in higher concentrations in the cheese made with starter than in the cheese made without starter. However, using a total trapping technique, it was found that the combination of components recovered from the effluents of the chromatographic columns did not have the cheese-like aroma of the distillate vapours that were injected. Reasons for this are discussed.
The digestibility coefficients of myristic, palmitic and stearic acids in the diet of sheep
Authors: Steele W. , Moore J. H. 
Published: June 2009

SummaryThe apparent digestibility coefficients of the various constituents of diets containing myristic, palmitic or stearic acids have been determined in an experiment with 8 sheep.The inclusion of myristic acid in the diet had no effect on the digestibility coefficient of total dry matter or crude protein, but it decreased the digestibility coefficients of crude fibre and nitrogen-free-extractives and increased the digestibility coefficients of fat and minerals. When palmitic acid was included in the diet there were decreases in the digestibility coefficients of total dry matter, crude fibre and nitrogen-free-extractives. The inclusion of stearic acid in the diet resulted in decreases in the digestibility coefficients of dry matter and nitrogen-free-extractives. There was an inverse relationship between the melting points and the digestibility coefficients of the added fatty acids.The findings of this investigation are discussed in relation to the results of a previous study on the effects of these dietary fatty acids on the yield and composition of cow's milk.
Density-gradient electrophoresis of native and of rennet-treated casein micelles
Authors: Green Margaret L. , Crutchfield G. 
Published: June 2009

SummaryAnalytical electrophoresis of native and of rennet-treated casein micelles was carried out at 26 and at 5°C in a sucrose density gradient in a medium of the same ionic composition as milk. Under normal circumstances, the micelles were negatively charged and showed little heterogeneity in the electric field, the fastestmoving ones having at 26°C a mobility not more than 30% greater than that of the slowest. Native micelles were more highly charged at 5 than at 26°C; at each temperature, the mobility was approximately halved by rennet treatment. The results suggest that the effects of rennet treatment and of alterations in temperature on the tendency of the micelles to clot can be entirely explained as being caused by changes in charge.
The formation of 2-butanone and 2-butanol in Cheddar cheese
Authors: Keen A. R. , Walker N. J. , Peberdy M. F. 
Published: June 2009

SummaryThe bacteriological formation of 2-butanone and 2-butanol was investigated. The data suggest that 2-butanol is formed in cheese via 2-butanone in 3 steps, each step being carried out specifically by a different microbial species. Suitable species have been isolated from a single cheese. The first step could be carried out (in the present investigation) either by certain starter organisms or by a strain ofPediococcus cerevisiae. This strain formed substantial amounts of 2,3-butylene glycol in milk, presumably from citrate, but could not metabolize this compound further. A second micro-organism, a strain ofLactobacillus plantarum, was isolated which, in Cheddar cheese, could convert 2,3-butylene glycol into 2-butanone. The final reduction of 2-butanone to 2-butanol could be readily carried out in MRS medium by a strain ofL. brevis. Results from cheese made aseptically indicate that 2-butanone is formed in Cheddar cheese only when non-starter organisms are present.
Molassed sugar-beet pulp nuts supplemented with urea and phosphate used as a milk production concentrate for dairy cows
Authors: Parkins J. J. , Hemingway R. G. , Ritchie N. S. 
Published: June 2009

SummaryA cubed molassed sugar-beet product with added urea, dicalcium phosphate, trace elements and vitamins was prepared containing 17% crude protein and up to 0·53% P. The product was evaluated in 3 changeover trials with lactating cows and the treatments involved comparisons with a low protein (10%) concentrate and one supplemented with groundnut plus cottonseed meals. When the product was included at 35–62% in milk production diets the mean daily yield of about 15 kg was about 0·5kg less than when full supplementation was as vegetable protein. This was considered more likely to be associated with inefficient utilization of urea rather than because of an energy difference between molassed sugar-beet pulp and barley.
Some operating characteristics of a simple homogenizing poppet valve; pressure profiles and separation: zone of fat globule dispersion
Authors: Phipps L. W. 
Published: June 2009

SummaryThe influences of different operating parameters upon the distribution of pressure across a simple homogenizing poppet valve have been investigated. Regions of contracted and separated flow were defined by detailed probing of static pressures and found to correlate well with the results from previous visual and photographic observations.Direct confirmation was obtained of the conclusion, first reported by Loo & Carleton (1953), that fat globules in milk are disrupted chiefly in a zone between the valve and seating surfaces which is close to the seating inlet boundary. Progressive coarsening of the globule suspension was detectable in the flow downstream from this zone.
The concentration of lactate in relation to other components of bovine mammary secretion during premature regression and after resumption of milking
Authors: Mackie R. I. , Giesecke W. H. , Lück H. , de Villiers P. A. 
Published: June 2009

SummaryAn experiment lasting 42 d was performed in 4 consecutive stages on 6 healthy Friesian cows during mid-lactation. Mean values for the different components of mammary secretion during normal lactation were established. Milking was then suspended on all quarters from d 1–14. The mean values for lactate increased 20- to 30-fold over the mean value for normal lactation. Over the same period the leucocyte count (polymorphonuclear leucocytes and lymphocytes) also increased, whereas the mean values for glucose and the estimated redox potential decreased. From d 15–28 milking was resumed on one half of the udder and from d 29–42 milking was also resumed on the other udder-half. When milking was resumed the above-mentioned changes were reversed, taking 5–7 d to reach values obtained during normal lactation in the udder-half which had not been milked for 14 d, but at least 14 d in the udderhalf which had not been milked for 28 d. The changes in the levels of lactate, glucose, leucocyte count and estimated redox potential are discussed in relation to changes in the secretory activity of the mammary gland (lactose, β-lactoglobulin and epithelial cell count), permeability changes of the mammary epithelium (Na+, K+and serum albumin) and the immune defence mechanism in the udder (immunoglobulins). The results indicate that lactate is formed during anaerobic glycolysis by the leucocytes in the mammary secretion, most probably due to reduced blood flow to the udder and the accumulation of secretion in the gland and teat cisterns on cessation of milking.
Chemical changes in ultra-heat-treated milk during storage: III. Methods for the estimation of lysine and sugar-lysine derivatives formed by the maillard reaction
Authors: Möller A. B. , Andrews A. T. , Cheeseman G. C. 
Published: June 2009

SummaryFour chemical methods were used in a comparison of the measurement of the extent of modification of lysine residues in casein during storage of ultra-heat-treated (UHT) milk. Determination of homoarginine after reaction with o-methylisourea appeared to be the best measure of total lysine modification. Reduction with borohydride before acid hydrolysis prevented recovery of lysine from lactuloselysine (ε-N-deoxylactulosyl-L-lysine) and fructoselysine (ε-N-deoxyfructosyl-L-lysine). This procedure gave values for these derivatives which were in good agreement with those obtained from the determination of furosine (ε-N-(2-furoylmethyl)-L-lysine) in acid hydrolysates. Determination of lysine after acid hydrolysis showed that lysine loss was accounted for by lactuloselysine and fructoselysine formation in most of the samples.Browning was most apparent in UHT milk stored at 37 °C for 3 years and in this sample only part of the lysine residues was accounted for as lactuloselysine and fructoselysine, thus indicating that lysine had become involved further in sugar degradation products.
An examination of the factors affecting the reverse osmosis of milk with special reference to deposit formation
Authors: Skudder P. J. , Glover F. A. , Green Margaret L. 
Published: June 2009

SummaryChanges in the dependent variables flow velocity, inlet pressure and temperature affected the rate of concentration of separated milk by reverse osmosis; their values were measured for minimum fouling at the membrane, resulting in maximum rates of concentration. Most of the deposit formed at an early stage of concentration and its extent depended on the operational variables.Electron micrographs showed that the major component of the deposit was casein micelles linked by bridges to form a lattice. Chemical analysis of the deposit confirmed a high casein content and showed that Ca phosphate was precipitated in the deposit throughout concentration. When fat globules and fat globule membrane were present in the feed, they appeared to be caught up in the deposit, but did not affect its initial formation.
The composition of whole casein from the milk of Ayrshire cows
Authors: Davies D. T. , Law A. J. R. 
Published: June 2009

SummaryThe composition of whole casein of 5 herd-bulk and 42 individual-cow milks from a single herd of Ayrshire cows has been determined. The percentage composition of the herd-bulk samples varied relatively little over a period of more than a year with the whole casein consisting on average of 38·4 % αs1,0-casein, 36·5 % β-casein, 12·5 % κ-casein, 10·5 % minor αs-caseins and 2·1 % γ-casein. For the individual-cow samples from mid-lactation, casein composition also was relatively constant, but in early and late lactation composition varied more with the relative amount of β-casein often being lower and those of κ- and γ-caseins often higher than in mid-lactation, these differences tending to be more marked in samples from older cows. Stage of lactation appeared to have little effect on the relative amounts of αs1,0-and minor αs-caseins.The concentrations of all casein fractions were significantly positively correlated (P < 0·001) with the concentration of whole casein in the milk. Also, there were significant negative correlations (P < 0·001) between the percentages of whole casein present as β- and κ-caseins, β- and γ-caseins and minor αs- and γ-caseins, and a significant positive correlation (P < 0·001) between the relative amounts of κ- and γ-caseins. The relative amount of the major αs1,0-casein fraction, however, was not closely related to those of any of the other fractions.Generally, milks with high lactose and low Na values yielded casein which was comparatively rich in β-casein and comparatively poor in κ- and γ-caseins.
Fractionation and characterization of the membranes from bovine milk fat globules
Authors: Kitchen B. J. 
Published: June 2009

SummaryBovine milk-fat globule membrane (MFGM) has been fractionated in to 3 membrane components by isopycnic sucrose density gradient centrifugation. The 3 components, designated as heavy, medium and light material, were characterized by particular polypeptide, lipid, carbohydrate and enzyme compositions.The heavy material (density > 1·145 g/ml) was red-brown in appearance and consisted of 63% protein, 32% lipid and 5% carbohydrate. The lipid moiety contained 40% triglyceride and 60% phospholipid, while the protein consisted of 3 major polypeptides (apparent mol. wt 135000, 70000 and 53000) in the ratio of 3:6:1. This membrane class was also characterized by the presence of both xanthine oxidase and acid phosphatase. The medium density material (density 1·055–1·145 g/ml) was light red to pink in colour and consisted of 35% protein, 58% lipid and 6% carbohydrate. The lipid contained 45% triglyceride and 55% phospholipid, with nearly 70% of the original MFGM phospholipid being found in this material. The ratio of the 3 major polypeptide bands was 2:4:4 and high levels of both alkaline phosphatase and 5'-nucleotidase were present. The light material (density < 1·055 g/ml) was white to pale pink in colour and was composed of 88% lipid of which 94% was triglyceride, together with 8% protein and 4% carbohydrate. There were virtually no enzymes present and 70% of the protein consisted of a polypeptide with apparent mol. wt of 53000. The 3 membrane classes also differed in carbohydrate content and in the fatty acid composition of their triglycerides.
Lipoprotein lipase of goat mammary tissue: comparison of extraction methods
Authors: Chilliard Yves 
Published: June 2009

SummaryMammary lipoprotein lipase of lactating goats was extracted by 3 methods: homogenization of tissue acetone-ether powders; aqueous homogenization of crude tissue using an Ultra-Turrax apparatus; aqueous homogenization of crude tissue using a Sorvall Omni-mixer microhomogenizer. Although there were differences between absolute values obtained by the 3 methods, each type of homogenate had a lipolytic activity with lipoprotein lipase characteristics (i.e. more than 90% inhibition by serum omission or NaCl addition). Furthermore, the 3 methods were highly correlated and presented similar variations with the stage of lactation, in parallel with long-chain fatty acid secretion into milk. Repeatability of the measure of homogenate lipolytic activities was about 8%, whereas day-to-day repeatability of enzyme extraction and assay was about 20% for each method.