bluuebunny/crossref_metadata_2025_split huggingface dataset:
The precipitation of proteins by carboxymethyl cellulose
Authors: Zadow J. G. , Hill R. D. 
Published: June 2009

SummaryCarboxymethyl cellulose (CMC) formed insoluble complexes with β-lactoglobulin, bovine serum albumin and Na caseinate. Maximum precipitation of the β-lactoglobulin-CMC complex occurred at pH 3·2, whereas maximum precipitation of the bovine serum albumin-CMC complex and the Na caseinate-CMC complex occurred at pH 2·8. The ratio of CMC to protein for maximum precipitation depended on the protein, being greatest for Na caseinate and least for bovine serum albumin. The percentage of protein precipitated by CMC decreased with increasing ionic strength of the solution, the rate of decrease being least for bovine serum albumin. At a given ionic strength, more protein was precipitated by CMC of high degree of substitution than by CMC of low degree of substitution. The change in pH (ΔpH) occurring on mixing CMC and unbuffered protein solutions, each initially at the same pH, was measured. ΔpH was negative for β-lactoglobulin-CMC mixtures over the pH range 7–2 (minimum at pH 5·5). For bovine serum albumin-CMC and Na caseinate-CMC mixtures, ΔpH was positive between pH 7 and 3·2 (maximum at pH 4·5), zero at pH 3·2 and negative between pH 3·2 and 2·0 (minimum at pH 2·8).
Relationship between temperature and sterilizing efficiency of heat treatments of equal duration. Experimental testing with suspensions of spores in milk heated in an ultra-high-temperature sterilizer
Authors: Hermier J. , Begue P. , Cerf O. 
Published: June 2009

SummaryA relationship between temperature and sterilizing efficiency of heat treatment at constant time is described and checked experimentally using spores of Bacillus coagulans 604 in a pilot ultra-high-temperature plant. The relation is:whereN0andNare initial and final concentrations of spores,Tthe temperature (°C),zthe temperature coefficient (°C,z=10/logQ10) andAa dimensionless constant. A special effect of the injection of spores into live steam is observed. The sterilizing efficiency curve can be used in determining the heating temperature for a desired sterilizing efficiency and in predicting the influence of temperature fluctuation on sterilizing efficiency.
The quantitative measurement of whey proteins using polyacrylamide-gel electrophoresis
Authors: Hillier Robyn M. 
Published: June 2009

SummaryA method is described for the quantitative estimation of a mixture of whey proteins by spectrophotometric scanning of the stained protein bands following polyacrylamide-gel electrophoresis. The incorporation of β-lactoglobulin A as an internal standard improves the accuracy of the technique. The method has been used to measure residual native whey proteins in milk after heating. Results are presented for whey protein denaturation in skim-milk after heat treatment at 130 and 140 °C for various periods of time.
Compositional and electrophoretic changes in buffalo milk-fat globule membrane proteins during lactation
Authors: Singh Sukhminder , Ganguli N. C. 
Published: June 2009

SummaryChemical analyses, polyacrylamide-gel electrophoresis and isoelectric focusing of milk-fat globule membrane proteins (FGMP) obtained from the milk of 2 Murrah buffaloes were done to determine if any change in composition occurred during lactation. Changes in the levels of sialic acid, hexose, hexosamine, N and P were found in the FGMP obtained at different stages of lactation. On the day of parturition, 8 major proteins in FGMP were determined by sodium dodecyl sulphate polyacrylamide-gel electrophoresis whereas 6 major proteins were obtained in FGMP of middle and late lactation milks. Isoelectric focusing of FGMP showed 8–9, 9–13 and 13–16 proteins from colostrum, middle and late lactation milks, respectively and the isoelectric pH of the proteins varied from 5·25 to 7·80, 5·85 to 8·30 and 5·75 to 8·61 respectively.
A study of cow's milk containing high levels of linoleic acid: isolation and properties of the fat-globule membrane
Authors: Sleigh R. W. , Bain Joan M. , Burley R. W. 
Published: June 2009

SummaryProperties of whole milk and milk fractions from cows fed a diet that gave a greatly increased proportion of unsaturated fatty acid residues (especially of linoleic acid) in the milk lipids were studied, and this milk (high-linoleic milk) was compared with milk from cows on a control diet (control milk). The milk fractions were isolated by high-speed centrifugation of whole milk or cream and were examined by chemical analysis and electron microscopy. During centrifugation the globules of milk fat were disrupted and the membranes (fat-globule ‘ghosts’) floated as a layer beneath the free lipid. Membrane proteins from the 2 sorts of milk gave the same electrophoretic pattern and the amino acid compositions were the same. Lipid analysis of the membrane fraction from high-linoleic milk showed the expected increase in the proportion of unsaturated fatty acid residues in the neutral lipids, but there was an unexpected decrease in the proportion of unsaturated residues in the membrane phospholipids. No differences were found between high-linoleic and control milk in the ultrastructure of the milk-fat globules or the isolated membranes.
Volatile compounds in butter oil: IV. Quantitative estimation of free fatty acids and free δ-lactones in butter oil by cold-finger molecular distillation
Authors: Stark W. , Urbach Gerda , Hamilton Janet S. 
Published: June 2009

SummaryFree fatty acids (FFA) and free δ-lactones in butter oil were quantitatively estimated by cold-finger molecular distillation at 35 °C followed by silicic-acid column chromatography of the cold-finger distillate and gas chromatography of the fatty acid and lactone fraction. Typical values for FFA and free δ-lactones in butter oil prepared from export standard sweet-cream salted Australian butter were in the range 0·07–0·24, 0·75–2·4, 4·5–8·6, 34–40 and 44–89 ppm for the C4,6,8,10,12 fatty acids and 0·09–0·18, 1·2–4·9 and 3·0–5·8 ppm for the C8,10,12 δ-lactones. These values are in the range of organoleptically desirable levels.
Volatile compounds in butter oil: V. The quantitative estimation of phenol,o-methoxyphenol,m- andp-cresol, indole and skatole by cold-finger molecular distillation
Authors: Stark W. , Urbach Gerda , Hamilton Janet S. 
Published: June 2009

SummaryPhenol,o-methoxyphenol,m- andp-cresol, indole and skatole have been isolated from good quality butter oil by cold-finger molecular distillation, and separated into phenolic and indolic fractions by solvent extraction and silicic-acid column chromatography. The individual compounds were quantitatively estimated by gas chromatography. When phenol,o-methoxyphenol,m- and;p-cresol, indole and skatole were added to volatile-free butter oil, their recoveries were 94, 47, 90, 75, 71 and 61% respectively. The technique, when applied to fresh butter oil, gave the following ranges of values for the natural levels of these compounds: phenol 0·005–0·022,o-methoxyphenol 0·002–0·10,m-cresol 0·002–0·010,p-cresol 0·002–0·004, indole 0·07–0·13, skatole 0·16–0·22 ppm of butter oil. The results, when compared with flavour threshold studies, showed that indole and skatole are important contributors to the natural flavour of butter oil, but that phenolic compounds are of only borderline significance.
The use of short-term secretion rate measurements for estimating the milk production of suckler cows
Authors: Le Du Y. L. P. , Baker R. D. , Barker J. M. 
Published: June 2009

SummaryTwo experiments with dairy cows and one with suckler cows and their calves were conducted to examine the use of secretion rate measurements for estimating total milk production. In the first experiment both 4- and 6- h intervals between measurements gave similar estimates of total 7-d milk yield. The second experiment compared estimated and measured milk composition as well as yield. Milk and solids-not-fat yields were underestimated with dairy cows as a result of an extended milking interval before measurement. However, fat yield was overestimated, indicating that all residual milk was not removed at the first oxytocinaided milking. It was concluded that for the beef cow, previous interval effects would be eliminated by the frequency of calf suckling, but that residual milk effects might cause a 3–6% and a 16% overestimation of milk and fat yields respectively.In the third experiment, the milk yield of suckler cows was estimated from measurements of secretion rate and from changes in calf weight; good agreement was obtained provided there were at least 3 consecutive controlled sucklings.
The cell count of milk in relation to milk yield
Authors: Meijering A. , Jaartsveld F. H. J. , Verstegen M. W. A. , Tielen M. J. M. 
Published: June 2009

SummaryQuarter-milk cell counts and milk yields from 1000 cows in the province of Noord-Brabant were obtained over a 12-month period. The data from 933 animals, mainly heifers, were used to examine statistically the relationship between cell counts, as a criterion for sub-clinical forms of mastitis, and milk yield. Losses in milk were assessed by quarter, by pairs of quarters and by cow. The conclusions were that the losses in milk due to sub-clinical forms of mastitis, as indicated by cell count, can be substantial. The existence of a compensating increase in milk yield from a healthy gland, in response to the loss of milk from a neighbouring quarter with raised cell count, could not be demonstrated.
Bovine milkN-acetyl-β-D-glucosaminidase and its significance in the detection of abnormal udder secretions
Authors: Kitchen B. J. , Middleton G. , Salmon M. 
Published: June 2009

SummaryA new spectrofluorimetric assay procedure for bovine milkN-acetyl-β-D-glucosaminidase (NAGase) is described for use as a routine screening test for the detection of abnormal uddersecretions. This procedure uses 4-methylumbel-liferyl-N-acetyl-β-D-glucosaminide as substrate. On the basis of the greater sample throughput, increased product sensitivity detection of NAGase and the absence of turbidity problems, it is considered to be superior to a previously reported spectrophotometric procedure (Kitchen, 1976). The correlation coefficient between the somatic cell count and the fluorimetric procedure using 243 quarter fore-milk samples was 0·86. Distribution studies on bovine milk and mammary gland homogenates indicated that this enzyme activity was located predominantly in the soluble whey protein fraction and the post-microsomal supernatant. Mammary gland secretory cells contained high levels of NAGase and appeared to be the major source of the enzyme in milk whilst NAGase from other sources (white blood cells, blood serum) contributed only a minor proportion (5–15%) of the total activity in milk. The implications of these findings on the value of the NAGase test as a means of mastitis diagnosis are discussed.
Seasonal changes in the heat stability of milk from creamery silos in south-west Scotland
Authors: Holt Carl , Muir D. Donald , Sweetsur A. W. Maurice 
Published: June 2009

SummaryThe heat stability of the milk supply to manufacturing creameries in south-west Scotland was examined over 15 months from Nov. 1975 to Jan. 1977. For all but 2 months of this period the heat stability of the milk was very highly significantly correlated with the naturally occurring level of urea. Between 72 and 90% of the variation of coagulation time (CT), measured at the natural milk pH, was accounted for by changes in milk urea alone. For a short period, in May and June, the CT of the milk at natural pH fell within the minimum of the CT–pH profile, but insufficient data were available to allow the occurrence of this phenomenon to be related to changes in milk composition.
Preparation and fractionation of goat κ-casein: analysis of the glycan and peptide components
Authors: Addeo Francesco , Soulier Solange , Pelissier Jean-Pierre , Chobert Jean-Marc , Mercier Jean-Claude , Ribadeau-Dumas Bruno 
Published: June 2009

SummaryWhole goat κ-casein was prepared by chromatography of whole casein on hydroxyapatite. Chromatography of whole κ-casein on DEAE-cellulose separated 5 fractions. All of them were sensitive to chymosin. Their amino acid and carbohydrate composition, phosphate content and molecular weight were determined. Galactose,N-acetylgalactosamine,N-acetyl andN-glycolyl neuraminic acids were identified in whole κ-casein. It appears that goat κ-casein, like cow, buffalo and ewe κ-caseins, is composed of several fractions having identical peptide chains and differing in their carbohydrate contents. The main fraction, devoid of carbohydrate, was treated with chymosin. The para-κ-casein and caseinomacropeptide were isolated. Their amino acid composition and phosphate content were determined.
Calorimetric identification of several strains of lactic acid bacteria
Authors: Fujita Teruyuki , Monk Paul R. , Wadsö Ingemar 
Published: June 2009

SummaryA microcalorimetric method has been developed for the identification of 9 representative strains of lactic acid bacteria used in the dairy industry. A chemically defined medium containing several carbohydrates gave reproducible and characteristic growth patterns. The technique is proposed as a rapid alternative method for the identification of bacteria selected for commercial use.
Dynamic responses of the dairy cow's teat to step changes in pressure
Authors: Reitsma Sybren Y. , Scott Norman R. 
Published: June 2009

SUMMARYDynamic responses of the teat end, measured as changes in external diameter and milk flow-rate, due to step changes in pressure, uniformly applied to the whole teat, are presented. The experiment involved a front and a rear teat of each of 6 Holstein–Friesian cows. The measured variables were: (1) step change in pressure, (2) milk flow-rate, (3) step change in external teat end diameter, (4) rise times of pressure and teat end diameter changes, (5) fall times of pressure and teat end diameter changes, and (6) delay times between pressure and teat end diameter changes both at start of rise and of fall times. A statistical analysis showed that front teats expanded more than rear teats (P < 0·05). Several other findings of importance to any system of milk removal through the streak canal of the teat are discussed.
Changes in the activity of lactose synthetase in the goat udder during pregnancy
Authors: Jones Edward A. 
Published: June 2009

SUMMARYThe lactose synthetase activity of homogenates and particulate fractions prepared from the udders of goats killed at various stages of pregnancy were determined. Both components of the enzyme, galactosyltransferase and α-lactalbumin, became detectable about half way through the gestation period, at the time when rapid proliferation of mammary epithelial tissue commences. Throughout the second half of pregnancy the udder possessed a high level of lactose synthetase activity though the lactose content of the tissue did not increase. These findings are discussed in relation to the endocrine control of lactogenesis in the goat and possible mechanisms for the induction of milk production at parturition.
Effects of restriction of amino acid supply to the isolated perfused guinea-pig mammary gland
Authors: Mepham T. Ben , Peters Andrew R. , Alexandrov Stephen 
Published: June 2009

SUMMARYWhen individual essential amino acids were omitted for periods of 40–100 min from the infusate substrate solution in isolated perfused guinea-pig mammary gland experiments, uptake of methionine, tyrosine, phenylalanine, histidine and tryptophan (group 1) was significantly depressed by a mean of 49·8%, whereas the remaining essential amino acids (group 2) showed no significant decrease in uptake. During depletion periods oxidation of [14C\amino acids was increased. The possible significance of the differences in absorption between the 2 groups of amino acids is discussed.
Biosynthesis and secretion of milk proteins: a review
Authors: Larson Bruce L. 
Published: June 2009

SUMMARYRecent years have seen a great increase in the knowledge and understanding of milk proteins. Arising from several origins including the blood stream and various cellular sources, many of the proteins found in milk are products of the secretory cells directly involved in the synthesis and secretion processes of various milk components. The lactation-specific proteins present in major amounts are synthesized in the rough endoplasmic reticulum (RER) under genetic control and undergo further post-translational modifications in their secretory route from the RER through the Golgi apparatus and secretory vesicles before ejection into the lumen with other milk components. Various molecular aspects of these mechanisms and their control are now understood, but many remain to be described.
A phosphate-induced sub-micelle-micelle equilibrium in reconstituted casein micelle systems
Authors: Slattery Charles W. 
Published: June 2009

SUMMARYIn reconstituted casein systems, complete sub-micelles were previously observed only under extreme conditions of ionic strength, namely a NaCl concentration of 2 M or greater. However, studies with the analytical ultracentrifuge on phosphate-containing casein systems revealed that under certain conditions, a stable sub-micelle-micelle equilibrium was established. Conditions which were standard throughout were 7.5 mg/ml protein, 0.04 M-NaCl, pH 6.6 and 37 °C. The concentrations of added CaCl2 (Ca2+) and inorganic phosphate (P1) were variable. With no P1 present, Ca-sensitive caseins precipitated or formed micelles when k-casein was present, between 6 and 7 mM-Ca2+. With 10–20 mM-P1 precipitation or micelle formation began at about 4 mM-Ca2+ and was complete at about 5 mM-Ca2+. Over this interval, during micelle formation, a sub-micelle peak with s20, w of about 13 S was observed in equilibrium with the broad micelle peak. In a system containing a 2:2:1 weight ratio of ±sI-:²-:k-casein, this sub-micelle was isolated at 4 mM-Ca2+ and 2.5 mM-P1. The mol. wt was 760000 and it thus contained approximately 33 monomer caseins. The reconstituted micelle system formed in the absence of P1 was quite temperature sensitive, forming at 37 °C but disappearing upon cooling. In the presence of P1 the micelles formed at 37 °C but were stable to cooling as are natural micelles. Evidently, a combination of hydrophobic and electrostatic interactions are involved in natural micelle formation, probably with the production of salt bridges of Ca and phosphate ions between sub-micelles.
CPG-chromatography studies on the stability of casein micelles
Authors: Larsson-Raźnikiewicz Märtha , Almlöf Elisabeth , Ekstrand Bo 
Published: June 2009

SUMMARYCasein micelles fractionated on controlled pore glass (CPG-10/3000) were shown to be stable by recycling experiments. Only minor effects on the size distribution of the casein micelles were found after heating skim-milk to 100 °C for 10 min, or freeze-drying skim-milk at – 70 °C followed by resuspension in the synthetic milk serum of Jenness & Koops (1962). The heating caused some whey proteins (β-lactoglobulin) to enter the micelle fractions while the freeze-drying caused some of the largest micelles to disrupt. In colloidal calcium phosphate-free skim-milk prepared according to Pyne & McGann (1960) all the micelles appeared to dissociate into monomeric caseins.
The equilibria of calcium and phosphate ions with the micellar calcium phosphate in cow's milk
Authors: Lyster Richard L. J. 
Published: June 2009

SUMMARYCalorimetric measurements of the heat of solution of micellar Ca phosphate suggest that this material more closely resembles OH-apatite than amorphous Ca phosphate or any other crystalline form. Preliminary computer calculations of the ionic equilibria of milk salt solutions indicate that, over a wide range of pH and temperature, such solutions are supersaturated with respect to OH-apatite and to various other Ca salts under certain conditions.
Heat stability in concentrated and non-concentrated milks - the effect of urea and β-lactoglobulin levels and the influence of preheating
Authors: Pearce R. John 
Published: June 2009

SUMMARYHeat stability as a function of pH has been studied in concentrated and non-concentrated milk systems. The influence of preheating has also been examined. The concentration of β-lactoglobulin has been shown to affect markedly the heat stability behaviour in both systems but with different characteristics. Increasing the level of urea resulted in increased heat stability in non-concentrated milks, but corresponding concentrated milks showed a small decrease in maximum heat stability. It has not been possible to extrapolate heat stability data from nonconcentrated to concentrated milks.
Electrophoretic mobility of casein micelles
Authors: Darling Donald F. , Dickson John 
Published: June 2009

SummaryA simplified moving boundary electrophoresis technique has been developed for the measurement of the electrophoretic mobility of casein micelles. The zeta potentials of casein micelles from different skim-milk samples were calculated using Henry's equation and shown to decrease with decrease in pH between pH 6.9 and 5.3 and to increase with increase in temperature between 10 and 45 °C. Neither severe heat treatment (up to 135 °C for 51 min) nor centrifugal fractionation of micelles into different micelle size ranges had any significant effect on zeta potential. The ionic composition of the serum phase has been shown to be extremely important in determining the electrophoretic mobility. Casein micelles electrophoresed through milk ultrafiltrate consistently gave a lower mobilities than the same micelles centrifuged through milk centrifugate. The results are discussed in relation to present theories of casein micelle structure; these theories do not accommodate all of the observations.
Thermograms ofStreptococcus thermophilusandLactobacillus bulgaricusin single and mixed culture in milk medium
Authors: Monk Paul R. 
Published: June 2009

SummaryMicrobial thermograms have been used to investigate the growth ofStreptococcus thermophilusandLactobacillus bulgaricusin single and mixed culture in milk medium. Growth has been observed with different ratios of the strains in the inoculum and, at one ratio, the effect of the amount of inoculum. The effect of serial sub-culture both with and without pH control has been observed, and stimulation ofStr. thermophilusby cell-free fitrates ofL. bulgaricushas been examined. The development of the technique is discussed in terms of the application of microbial thermograms in selecting cultures for incorporation into mixtures and evaluating their performance.