bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantification of milk-clotting enzymes in 40 commercial bovine rennets, comparing rocket immunoelectrophoresis with an activity ratio assay
Authors: Rothe G. A. L. , Harboe M. K. , Martiny S. C. 
Published: June 2009

SummaryThe enzymes chymosin, bovine pepsin A and bovine pepsin B in 40 commercial rennets were assayed by rocket immunoelectrophoresis, using monospecific antibody preparations against the 3 enzymes. Concentrations found were chymosin, 0–1208 mg/l; bovine pepsin A, 359–3818 mg/l; bovine pepsin B, 0–320 mg/l. Bovine pepsin B was found to be a minor enzymic component in bovine rennets, representing maximally 2·9 % of the milk-clotting activity or 9·7 % of the weight of the enzymes. The sensitivity for the quantification of the 3 enzymes was 0·5–1·0 mg/l. The coefficient of variation was 3·7 %. The sum of the immunochemical data converted into milk-clotting activities was in good agreement with the directly observed milk-clotting activity, indicating that there was no immunochemical overestimation due to the presence of non-enzymic active antigens. A high correlation was found between the enzymic composition determined immunochemically and by activity ratio assay.
An improved method for the quantitative fractionation of casein mixtures using ion-exchange chromatography
Authors: Davies D. T. , Law A. J. R. 
Published: June 2009

SummaryA method for the quantitative analysis of casein mixtures is described. The method uses ion-exchange chromatography at 4 °C on DEAE cellulose, Whatman DE52 in the presence of tris-chloride-urea buffer (pH 8·6), and a NaCl gradient to fractionate the alkylated casein mixtures and a micro-biuret technique to determine protein concentrations. Values for fractions representative of (1) γ-caseins, (2) κ-casein plus some unknown proteins, (3) β-casein, (4) minor αs-caseins and (5) αs1- plus αs0-caseins were obtained, and whole casein from herd bulk milk was found to consist on average of about 2, 13, 36, 11 and 38% respectively of these fractions. Agreement between duplicate fractionations was satisfactory and the recovery of material varied between 94 and 98%.
Milk-fat globule membranes: chemical composition and phosphoesterase activities during lactation
Authors: Diaz-Mauriño Teresa , Nieto M. 
Published: June 2009

SummaryThe morphology, protein and glycoprotein composition, amino-acid analysis, phospholipid and carbohydrate contents and 3 phosphoesterase activities of the milk-fat globule membranes were studied in 4 cows during their whole period of lactation. No differences were found in the morphology and the overall chemical composition. However, glycoprotein composition varied with the cow and, for each cow, with the stage of lactation. The differences were more marked for membranes obtained from colostrum. Acid phosphomonoesterase was practically unchanged during the whole period of lactation, while alkaline phosphomonoesterase and phosphodiesterase increased as lactation proceeded.
The oxidation of lipids by components of bovine milk-fat globule membrane
Authors: Allen J. C. , Humphries Catherine 
Published: June 2009

SummaryBovine milk-fat globule membrane was solubilized with a zwitterionic surfactant and subjected to chromatography on agarose, with the surfactant in the eluant. Fractions were tested for their effects on the oxidation of buffered linoleate. The maximum oxidative capability was greatly enhanced by the addition of Cu, and became associated with the phospholipids.Further chromatography of the retarded protein peak from agarose on Sephadex G-200, again in the presence of surfactant, gave 2 protein peaks. Oxidative effectiveness resided almost entirely in the first peak, which was devoid of phospholipid, but high in xanthine oxidase activity. This fraction was subjected to isoelectric focusing, and the xanthine oxidase from this was highly pro-oxidative. Furthermore, its oxidative capability was almost doubled on heat treatment.
A calorimetric study of the thermal denaturation of whey proteins in simulated milk ultrafiltrate
Authors: Rüegg M. , Moor Ursula , Blanc B. 
Published: June 2009

SummaryDifferential scanning calorimetry (DSC) was used to study thermal transitions of the following whey proteins and enzymes in milk ultrafiltrate solution: β-lactoglobulin, α-lactalbumin, serum albumin, γ-globulin, apo- and Fe-lactoferrin, lysozyme, ribonuclease, α-chymotrypsin and xanthine oxidase. Denaturation enthalpies (ΔHD), denaturation temperatures (TD) and the half width of the denaturation peaks in DSC thermograms (ΔT½D) were determined and the degree of renaturation was estimated by rescanning previously denatured samples. A fair correlation between the results obtained by DSC and other more classical methods was found in general. However, for some proteins (α-lactalbumin, lysozyme, ribonuclease and xanthine oxidase), which have so far been considered relatively thermostable, calorimetry reveals conformational changes starting at temperatures as low as about 45 °C. In these cases thermostability observed after heat treatment of milk should be interpreted in terms of renaturation and not of high temperatures of denaturation.
The acceleration by cationic materials of the coagulation of casein micelles by rennet
Authors: Green Margaret L. , Marshall R. J. 
Published: June 2009

SummaryThree cationic materials markedly reduced the rennet clotting time of casein micelle suspensions, the efficacy of each being primarily dependent on the charge and the amount absorbed by the micelles. The reduction in coagulation time was unaffected by components of the milk serum other than salts. No enzymic action by lysozyme on casein micelles was detected. All materials acted by the same mechanism, increasing the affinity of rennet for the micelles and accelerating the aggregation phase. Coagulation did not occur until a minimum amount of κ-casein had been hydrolysed to para-κ-casein. All additives increased the proportion of added rennet retained by the casein in the coagulum. The results indicated that coagulation occurs by specific interactions between micelles modified by rennet.
Relative importance of pre-partum and post-partum factors in the control of milk yield in the guinea-pig
Authors: Davis Stephen R. , Mepham T. Ben , Lock Kathryn J. 
Published: June 2009

SummaryExamination of data pertaining to milk yield and litter growth rate of guinea-pigs at peak lactation showed that milk yield increased with increasing number of pups carried by the dam during pregnancy and also with increasing maternal weight. There was a significant linear correlation (P < 0.05) of mammary gland weight (expressed per unit of maternal body weight) with litter size. Increasing litter size, within 18 h of parturition, from 1 pup to 5 pups did not elicit a response in milk yield. Decreasing litter size from 5 pups to 1 pup reduced milk yield to the level expected of a monotocous dam. Data are presented showing the ability of the guinea-pig pup to survive from birth without access to milk and the inadequacy of milk supply to meet litter requirements when the litter size is more than 2 pups. The mechanisms controlling lactation in the guinea-pig are discussed in relation to data obtained in other species.
Application of reverse osmosis to the manufacture of dried whole milk and skim-milk
Authors: Abbot James , Glover Frank A. , Muir Donald D. , Skudder Paul J. 
Published: June 2009

SummaryPowders were prepared from whole and skim-milk using reverse osmosis (RO) as a first stage followed by either evaporation and spray drying or spray drying alone. They were compared with powders made by the conventional method of evaporation and spray drying. Measurements were made of powder solubility, free fat content, whey protein denaturation, vitamin content, powder morphology and bacterial count. The free fat contents of powders prepared from whole milk concentrated by RO were high; otherwise, there were no significant differences in the properties of powders made from milks concentrated initially by RO and those prepared by conventional evaporation. The results indicate that it is feasible to use RO for the manufacture of skim-milk powder and for dried whole milk production where higher free fat levels are not detrimental.
Post-milking iodine teat skin disinfectants: 1. Bactericidal efficacy
Authors: Sheldrake Richard F. , Hoare Roderic J. T. , Hutchinson Jo-Anne E. 
Published: June 2009

SummaryAn iodine teat skin disinfectant tested in lactating cows over a range of concentrations, 100 to 10 000 mg available iodine/1 (mg avI/l) was found bactericidally effective against Staphylococcus aureus when containing 1000 mg avI/l or greater. Against Streptococcus dysgalactiae 5000 mg avI/l or greater was bactericidally effective.The addition of glycerine to a disinfectant containing 5000 or 1000 mg avI/l at levels of 225 ml/1 and 105 ml/1, respectively, resulted in a reduction in bactericidal efficacy of the disinfectant. Emulsified paraffin added at concentrations of between 50 and 500 ml/1 had no effect on the efficacy of the 5000 mg avI/l disinfectant, but the addition of 200 ml/1 emulsified paraffin to a 1000 mg avI/l disinfectant significantly reduced its efficiency. Iodine disinfectants containing emulsified paraffin phase separated rapidly during storage, and the bactericidal efficacy of the phases differed significantly and diminished with time.
Post-milking iodine teat skin disinfectants: 2. New intramammary infection rates
Authors: Sheldrake Richard F. , Hoare Roderic J. T. 
Published: June 2009

SummaryUse of an iodine teat dip containing 5000 mg available iodine/l (mg avI/l) resulted in a significant reduction in the number of new Staphylococcus aureus infections in a lactating herd, while no significant reduction was found with a disinfectant containing only 1000 mg avI/l. When Streptococcus dysgalactiae was used as the challenge organism, the rate of new infection was extremely low, and no reduction in levels of new infection were found with either disinfectant. The pathogenicity of the Str. dysgalactiae strain was high, as 60 % of the quarters becoming infected produced clinical symptoms.
Identification, properties, and differential counts of cell populations using electron microscopy of dry cows secretions, colostrum and milk from normal cows
Authors: Lee Chee-Seong , Wooding F. B. Peter , Kemp Patrick 
Published: June 2009

SummaryDifferential counts of electron microscope sections of cell pellets isolated from bovine udder secretions showed that no secretory epithelial cells and very few ductal epithelial cells were present at any stage. The predominant cell type was the macrophage in dry and lactating cows or the polymorphonuclear leucocyte (PMNL) in colostrum. Lymphocytes were also present but no plasma cells were found. The macrophages took up polystyrene latex particles (as did the PMNL) and adhered toglass in culture. Neither macrophage-nor PMNL-rich cell suspensions produced any increase in free fatty acid levels when incubated with fresh milk.
Isolation and characterization of the principal caseins in rat milk
Authors: Pelissier Jean-Pierre , Yahia Ahmed , Chobert Jean-Marc , Dumas Bruno Ribadeau 
Published: June 2009

SummaryThe 4 major caseins, A1, A2, B1, B2, from rat milk have been isolated and analysed. From molecular weight determination, amino acid and phosphorus analyses and N-terminal sequence determination, A1 and A2 are concluded to possess similar peptide chains as do B1 and B2, with the individual fractions within each of these 2 groups differing only in their sialic acid content.Mol. wts of approximately 22000 and 38000 were found for A1–A2 and B1–B2 respectively. The amino acid sequence of the first 13 residues of A1–A2 has been partly established. Components A1 and A2 appeared to be homologous with bovine β-casein, whereas B1 and B2 were different from any known casein, especially in their molecular weight.
Binding of calcium ions to bovine αsl-casein and precipitability of the protein–calcium ion complexes
Authors: Dalgleish Douglas G. , Parker Thomas G. 
Published: June 2009

SummaryBinding isotherms for the calcium ion–αsl-casein system have been measured, as functions of ionic strength, temperature, and pH, and the isotherms have been analysed in terms of binding constants modified by substitution effects. The results demonstrate that the strength of binding is increased with increasing temperature and decreased by increasing ionic strength or decreasing pH, all of which may be explained semi-quantitatively. Parallel studies on the precipitability of the αsl-casein–Ca2+complexes showed that there is considerable variation in the extent of calcium binding required to initiate precipitation of the protein, and in the calcium concentration necessary to achieve the required extent of ligand binding.
Determination of the proportion of κ-casein hydrolysed by rennet on coagulation of skim-milk
Authors: Chaplin Brian , Green Margaret L. 
Published: June 2009

SummaryA method has been developed for quantitative determination of para-κ-casein, involving spectrophotometric scanning of stained protein bands following polyacrylamide gel electrophoresis. The rate of hydrolysis of κ-casein in skim-milk at pH 6·6 and 30 °C was compared with that in EDTA-treated skim-milk under the same conditions. This showed that at the visually observed clotting time, at least 90% of the total κ-casein in milk had been hydrolysed. The time course of the reaction was consistent with all the κ-casein molecules being hydrolysed with the same efficiency. The results strongly suggest that essentially all of the κ-casein in milk is equally accessible to rennet action. This is consistent with the casein micelle being porous, or having all the κ-casein on the surface.
Calculation by computer of individual concentrations in a simulated milk salt solution. I
Authors: Wood Geoffrey B. , Reid David S. , Elvin Roger 
Published: June 2009

SummaryA modegl is proposed for the equilibria between the components of the salts in milk. The model includes complex formation between calcium ions and the various ionized forms of citric, lactic and phosphoric acids, and makes allowance for the effect of ionic strength. A computer program has been written to calculate the pH of the milk salt solutions and the concentration of each of the complexes formed. Calculated pH values agree with observed values for solutions of known composition.
Effect of the addition of extracts of thermophilic lactobacilli on acid production byStreptococcus thermophilusin milk
Authors: Hemme Denis H. , Schmal Véronique , Auclair Jean E. 
Published: June 2009

SummarySoluble extracts of 20 strains of thermophilic lactobacilli (Lactobacillus helveticus, L.lactisand L.bulgaricus) were prepared and added to milk for the culture of 10 strains ofStreptococcus thermophilus. Acid production was stimulated in 64·5% of cases for 9 of these 10 strains. The L.helveticusextracts were the most stimulatory, but the same extracts did not always strongly stimulate each strain ofStr. thermophilus. The stimulatory effects observed varied with the volume of extract and the strain ofStr. thermophilus. The exception wasStr. thermophilus385, which was never stimulated. The stimulatory effects observed were due to aminopeptidases present in the lactobacillus extracts and were not related to a general caseinolytic activity. The possible addition of such extracts to milk for cooked hard cheese is discussed.
Effects of feeding level in late pregnancy and dietary protein concentration during early lactation on food intake, milk yield, liveweight change and nitrogen balance of cows
Authors: Cowan Robert T. , Reid George W. , Greenhalgh James F. D. , Tait Charles A. G. 
Published: June 2009

SummaryThirty-nine British Friesian cows and 17 British Friesian heifers were used to measure the effects on milk yield, food intake and digestion, and N balance of increasing the protein concentration in the diet from 111 to 147 g crude protein/kg dry matter during the first 16 weeks of lactation. The comparison was made for animals given food either ad lib. or at a level which allowed them to gain 0·5 kg/d during the 8 weeks before parturition, and for animals given ad lib. diets of either 60:40 or 40:60 hay: concentrate ratio during early lactation. Milk yield was increased by a higher protein concentration in the diet (P < 0·01) and the increase was evident from the first week of lactation. Mean increases over the first 8 weeks of lactation were 3 kg/d for animals on the diet of high roughage content and 7 kg/d for animals on the diet of low roughage content. A higher crude protein content in the diet also increased food intake (P < 0·05) and digestion (P < 0·05), and the increases were greater for animals given the diet of low compared with high roughage content. Level of feeding before parturition did not influence food intake or milk yield and there were no differences between cows and heifers in their response to treatments. N balance over the first 10 weeks of lactation averaged –13 g/d for cows and 6 g/d for heifers (P < 0·025). and was not significantly altered by treatments. Mean N balance of all animals was estimated to increase from –37 g/d immediately after parturition to zero at 8 weeks of lactation. The results demonstrate that an increased protein concentration in the diet during early lactation is associated with increased food intake and digestibility of food, which are in turn largely responsible for higher levels of milk production.
Inhibition of lipolysis in bovine milk by proteose peptone
Authors: Anderson Malcolm 
Published: June 2009

SummaryThe ability of total milk proteose peptone and individual proteose peptone components to inhibit lipolysis in milk was examined. Proteose peptone (1·5 mg/ml) when added to milk inhibited lipolysis, and component 3 was a more effective inhibitor than component 5 or component 8-fast. Inhibition by proteose peptone also occurred when the milk was treated with between 2 and 20% v/v bovine blood serum or with 5 μg/ml heparin. In vitro activity of milk lipoprotein lipase and its stability were not affected by proteose peptone. It was concluded that proteose peptone does not interact with lipase or its activator and that the mechanism of inhibition involves the substrate.
Milk coagulation by cationic polyelectrolytes
Authors: Gregorio Francesco Di , Sisto Raffaello 
Published: June 2009

SummaryPositively charged materials, polyethyleneimine, poly-L-lysine and partly estcrified proteins (i.e. methyl bovine serum albumin, methyl casein and ethyl casein), in aqueous solution at the natural pH of milk, caused milk coagulation. This occurred at pH 6–6·7 at ≤ 30 °C using a defined amount of coagulant, which was quantitatively recovered in the curd. The protein and fat recovery yields were higher than with acid and rennet coagulation; the (Ca + Mg) partition between whey and curd was very similar to rennet milk clotting: the curd obtained showed high syneresis rate.
In vivo studies on the digestion of bovine caseins in the rat stomach
Authors: Miranda Guy , Pelissier Jean-Pierre 
Published: June 2009

SummaryThe action of gastric proteinases on bovine caseins was studied in vivo on rats fed skim-milk, or whole casein in water or whole casein in mineral solution, by analysing the gastric content after 30 min digestion. Clotting of the diet in the stomach greatly reduced the rate of gastric emptying. The proteolysis of caseins observed by gel electrophoresis appeared to follow a different pathway for the 3 different diets. The amino acid compositions of the trichloracetic acid sediments of the stomach contents did not differ between the 3 diets. The presence of free amino acids in the stomachs at significant levels (0·8–5 % of the total amino acid content) was observed.
Induction of some enzymes of citrate metabolism inLeuconostoc lactisand other heterofermentative lactic acid bacteria
Authors: Mellerick Dervla , Cogan Timothy M. 
Published: June 2009

SummaryCitrate stimulated growth, totally induced citrate lyase, partly induced acetolactate synthase activity and partly repressed both diacetyl and acetoin reductases inLeuconostoc lactisNCW1. Similar results were obtained with 2 other leuconostocs and a heterofermentative lactobacillus. In 2 of the 3 leuconostocs tested, diacetyl reductase and acetoin reductase were NADPH specific, while in the 2 heterofermentative lactobacilli, they were NADH specific.
Positional distribution of fatty acids in the triglyceride classes of milk fat
Authors: Parodi Peter W. 
Published: June 2009

SUMMARYA sample of milk fat was fractionated into high, medium and low molecular weight triglycerides by silicic acid column chromatography. Each fraction was further separated by silver ion adsorption thin-layer chromatography into triglyceride classes which were subjected to stereospecific analysis.Trans-monoene fatty acids were incorporated into triglycerides in the same manner as their cis-isomer. The specific positional distribution for fatty acids in intact milk fat triglycerides was not always maintained in the molecular weight fractions or in the various classes of unsaturation. The significance of these findings is discussed in relation to biosynthetic mechanisms for milk fat synthesis.
Influence of milk proteins on lipid oxidation in aqueous emulsion: I. Casein, whey protein and α-lactalbumin
Authors: Allen John C. , Wrieden Wendy L. 
Published: June 2009

SUMMARYA milk-related model system, 2 mM-trilinolein in 0·1 M-piperazine-N, N′-bis-2-ethanesulphonic acid buffer, pH 6·8, stabilized by lysophosphatidylcholine was used to assess the effect of milk proteins on lipid oxidation in emulsion, catalysed by Cu2+ions. In some experiments the trilinolein was replaced by sunflower oil (2 g 1-1). Oxidation at 25°C was assessed by measurement of the rate of O2-utilization and by the thiobarbituric acid assay. The features, relevance and reliability of the model are described in terms of the observed effects in the absence and presence of added protein. Casein was antioxidative at concentrations relevant to those in bovine milk, human milk, infant milk formulations and ‘high linoleic acid’ milk. Whole whey protein was a less effective inhibitor of lipid oxidation at similar concentrations. Purified α-lactalbumin was also marginally antioxidative, and its effect was independent of the molar Cu2+: protein ratio between 1:1 and 3:1.
Studies on salivary and pancreatic lipases of the pre-ruminant calf
Authors: Toothill Joyce 
Published: June 2009

SUMMARYSalivary and pancreatic lipases of the pre-ruminant calf have been studied using ion-exchange chromatography and gel filtration. In addition, pancreatic lipase has been fractionated using concanavalin A-affinity chromatography. The effects of 5,5′-dithiobis(2-nitrobenzoic acid), organic solvents and trypsin on pancreatic lipase have also been investigated. The effect of taurodeoxycholate on the lipolytic activity of the 2 lipases has been compared. Salivary lipase behaved as a single enzyme on ion-exchange chromatography, and gel filtration gave a mol. wt value of 52000 for the enzyme. Although pancreatic lipase appeared to be a single enzyme on gel filtration, with a mol. wt of almost 80000, the lipase was shown by ion-exchange and affinity chromatography to consist of at least 2 enzymes of mol. wts 72000 and 60000, and did not require colipase for maximum activity in the presence of high concentrations of bile salts. Colipase-dependent lipase, mol. wt about 45000, and probably amounting to not more than 10% of the total activity, was also present. This was the predominant form only after large losses in total lipolytic activity had occurred, as after treatment with a mixture of ether, ethanol and deoxycholate, or prolonged action of trypsin. When the concentration of taurodeoxycholate was increased from zero to 1 mM in a tributyrin substrate, the lipolytic activites of calf salivary and pancreatic lipases, and pig pancreatic lipase, increased. At a concentration of 4 mM-taurodeoxycholate, calf salivary lipase activity was higher, that of calf pancreatic lipase slightly lower and pig pancreatic lipase activity markedly lower.