bluuebunny/crossref_metadata_2025_split huggingface dataset:
A modified form of lactoperoxidase isolated from milk cultures ofstreptococcus cremoris or Streptococcus lactis
Authors: Pickering A. , Oram J. D. , Reiter B. 
Published: June 2009

SummaryLactoperoxidase activity has been measured in whey form fresh milk and from milk cultured withStr. cremorisorStr. lactis. It was found that with benzidine as hydrogen donor, the optimum H2O2concentration in whey from fresh milk was 10–4M, whereas in whey from cultured milk it was greater than 10–2M. The lactic acid streptococci appeared to modify lactoperoxidase. The modified form of the enzyme resembled lactoperoxidase in its absorption spectrum, its inhibition by fluoride and cyanide, its chromatographic behaviour on IRC50 resin and its activation energy of heat denaturation, but differed in its heat and pH stability, and its optimum hydrogen peroxide concentration for reaction with benzidine oro-dianisidine.
The effect of fatty acids on the metabolism of lactic acid streptococci: I. Inhibition of bacterial growth and proteolysis
Authors: Anders R. F. , Jago G. R. 
Published: June 2009

SummaryThe early loss of viability ofStreptococcus cremorisstrain C 13 in Cheddar cheese was investigated. The growth of this strain was markedly inhibited by cheese extracts containing unesterified fatty acids of which oleic acid was the major inhibitory constituent active against the coccus. This acid was found to accumulate in cheese early in the ripening process and may be responsible for the early loss of viability of strain C 13 in cheese.Early loss of viability of a starter organism in cheese could result in a low peptidase activity by limiting the number of bacterial cells present. The subsequent accumulation of unhydrolysed bitter peptides would produce a bitter flavour.
The effect of ultra-high-temperature heat treatment on the content of thiamine, vitamin B6 and vitamin B12 of milk
Authors: Gregory Margaret E. , Burton H. 
Published: June 2009

SummaryResults are given for the effect of different ultra-high-temperature milk sterilizing processes on the thiamine, vitamin B6 and vitamin B12 contents of milk. For all the processes examined, the loss of thiamine is negligible, and the losses of vitamins B6 and B12 lie between zero and 35%. Indirect-heating processes appear to cause more loss of vitamin B12 than of vitamin B6, but the reverse is true of directheating processes.
An electron microscope study of the ultrastructure of bovine and human casein micelles in fresh and acidified milk
Authors: Calapaj G. G. 
Published: June 2009

SummaryWhen examined under the electron microscope, bovine casein micelles were seen as aggregates of spheroidal granules arranged in spherical symmetry. The granules were of 2 kinds—one transparent in the electron beam and the other relatively opaque. With increasing acidity of the milk the regular arrangements of granules tended to break down, and bridges composed of granules, formed between neighbouring micelles. The average diameter of the granules was about 8 mμ, from which a molecular weight of about 225000 was calculated. Evidence was adduced for the identity of these granules with the macromolecules of native casein in equilibrium with whey.Human casein micelles showed the same structural features. The average diameter of the granules was about 6 mμ, from which a molecular weight of about 100000 was calculated.
Rate of infection of milked and unmilked udders
Authors: Neave F. K. , Oliver J. , Dodd F. H. , Higgs T. M. 
Published: June 2009

SummaryThe teats of milked and unmilked quarters of 6 cows were deliberately contaminated twice daily by immersion in a suspension of streptococci and staphylococci. Only the unmilked quarters became infected, 7 with Staphylococcus aureus and 3 with Streptococcus uberis. Neither previous infection with the same strain or a different strain of pathogen nor existing infection with Corynebacterium bovis appeared to influence the results.
Biuret and urea in concentrates for milking cows
Authors: Waite R. , Castle M. E. , Watson J. N. , Drysdale A. D. 
Published: June 2009

SummaryTwo experiments, one with 18 and one with 21 cows, were made to compare the feeding value for milk production of concentrates in which the nitrogen normally supplied by oil cake was completely replaced by either biuret or urea. In expt 1 the urea and biuret contributed 52% of the total nitrogen in the concentrate and in expt 2 they contributed 43%. Hay was fed as the sole roughage. The estimated energy intake in expt 1 was 102–104% of the Woodman standard and in expt 2 it was 108–109%.In both experiments milk production was about 10% less on the urea and biuret treatments than on the control treatment. There was no significant difference in milk yield between the biuret and the urea treatments. The percentages of fat and protein in the milk from the urea and biuret treatments were higher than from the control treatment, but the weights of these milk constituents were slightly lower than from the control treatment. Liveweight changes and water consumption were not affected by the experimental treatments. In expt 2 an intake of nitrogen about 20% lower than is often recommended in the United Kingdom did not appear to depress milk yields. Three cows that had received biuret concentrates in expt 2 continued to do so during a nitrogen balance trial lasting 3 weeks. Each cow was slightly in negative balance, the average value being −4gN per cow per day.
Milk fat globule membrane material in skim-milk
Authors: Wooding F. B. P. 
Published: June 2009

SummaryIt has been claimed by Stewart, Puppione & Patton (1972) that milk is a valuable source of cell membrane in a ‘relatively pure’ state originating from shed mammary secretory cell microvilli and golgi vesicles. The morphological basis for this has been re-examined in this paper. It is shown that the vesicular and elongated membranous structures found in skim-milk are identical to structures present as part of the initial milk fat globule membrane (MFGM) of alveolar and expressed milk, and that both structures survive extraction with chloroform–methanol. It is therefore suggested that a major part of the skim-milk membrane is material shed from the freshly secreted milk fat globule and consists of a specialised derivative of the secretory cell plasmalemma, the initial MFGM.
Studies on milk yield and composition of the West African dwarf goat in Nigeria
Authors: Akinsoyinu A. O. , Mba A. U. , Olubajo F. O. 
Published: June 2009

SummarySix adult West African dwarf does, about 2½ years old and weighing from 24 to 29 kg, were kept for 18 weeks/lactation, and for 2 lactation periods in all. During these periods the does were hand-milked twice daily and the daily samples were bulked for each animal for subsequent analysis. Milk yields for the period were low. Colostrum was characterized by a high content of total solids of 19·2%, fat 8·3%, total protein 5·1% and a gross energy of 517 kJ/100 g milk, but a low lactose content of 4·9%. The composition tended to approach that of mature goat milk between the second and third d after parturition. The mature goat's milk contained higher mean percentages of fat (6·9) and lactose (6·3) than any temperate breeds of goats and indigenous dairy cattle, but their protein (3·9%) and total ash (0·8%) contents were comparable with any temperate breeds of goats. The percentage protein, lactose, fat and total solids declined slightly with advance in lactation and there was a steady fall in milk yield which was statistically significant (P< 0·01).
Estimation of the prevalence of udder infection in dairy herds based on a single-quarter sample from each cow in the dairy herd
Authors: Clarke G. P. Y. , Oliver J. 
Published: June 2009

SummaryIndividual quarter milk samples were taken from 719 cows in 7 dairy herds and examined for mastitis-causing pathogens. Analyses were made to ascertain the prevalence of mastitis infection when the results from a single quarter were compared with those from all 4 quarters. There was a very close similarity between the 2 methods of assessment. When the number of samples is limited, sampling of a single quarter instead of all 4 quarters permits more cows to be examined.
Chemical changes in ultra-heat-treated milk during storage: I. Hydrolysis of casein by incubation with pronase and a peptidase mixture
Authors: Möller A. B. , Andrews A. T. , Cheeseman G. C. 
Published: June 2009

SummaryCasein samples from untreated milk and stored ultra-heat-treated (UHT) milk were hydrolysed with pronase (protease exStreptomyces griseus K-1) and subsequently with a mixture of peptidases prepared from the microsomal fraction of hog kidneys. Incubation of casein from unheated milk with pronase alone hydrolysed 70–80% of peptide bonds involving Ile, Leu, Tyr, Phe and His residues; other amino acids were released less well and proline hardly at all. The pronase/peptidase treatment resulted in 90–100% hydrolysis of peptide bonds involving all amino acids, including proline.Caseins from stored UHT milks were more resistant to proteolysis than casein from unheated milk. Reduced release of all amino acids was observed from samples taken after storage at 37 °C for 12 months or longer and for Lys, Arg and Asn residues from samples taken after storage at 30 °C for 14 months. Resistance to proteolysis was attributed to the Maillard reaction between milk proteins and lactose during storage of UHT milk.
Metabolic pathways of cytoplasmic droplets from freshly secreted goat's milk
Authors: Vernon R. G. , Christie W. W. 
Published: June 2009

SummaryA new procedure is described for the preparation of cytoplasmic droplets from goat's milk and the metabolic potential of these droplets has been surveyed. Acetate was incorporated into fatty acids of varying chain lengths and acetate and glucose were oxidized to CO2by these cytoplasmic droplets in vitro. There was a low rate of protein synthesis but no detectable DNA or lactose synthesis. It is concluded that the cytoplasmic droplets can provide an alternative to biopsy material for studying certain aspects of goat mammary lipid metabolism in vitro.
Levels and location of adenosine 5′-triphosphate in bovine milk
Authors: Richardson Thomas , McGann Thomas C. A. , Kearney Robert D. 
Published: June 2009

SummaryBovine milk systems were analysed for adenosine 5′-triphosphate (ATP) using the luciferase-ATP reaction in a liquid scintillation counter. Approximately 0·2 µmol ATP/1 milk serum were evident both in whole milks and the corresponding skim-milks. ATP was not detectable in skim-milk ultrafiltrates. These findings indicated that ATP was present in a non-dialysable portion of skim-milk. Centri-fugation of whole milks from individual cows at 5500 g for 15 min at 10°C yielded skim-milks essentially devoid of somatic cells and bacteria. However, the ATP in the skim-milks decreased by less than 20% compared with the whole milks indicating that the calcium phosphate-citrate (CPC)–caseinate micelles were the source of the ATP. ATP was not detectable in colloidal phosphate-free milk, from which CPC had been removed, confirming that the ATP was sequestered in the constituent CPC. Likewise, the occurrence of significant amounts of Mg, another potent stabilizer of amorphous calcium phosphate (ACP) in other biological systems, was confirmed in the colloidal phosphate of milk. From 0·13 to 0·31 µmole ATP/1 (mean, 0·23) was found in the 9 milk samples studied. The discovery of small but appreciable levels of ATP in the CPC of milk provides further evidence for the analogy previously shown to exist between the CPC complex of milk and the ACP which accumulates in mitochondria. The latter has been postulated to provide an essential precursor for crystalline bone salts to form in ordered calcification processes. The implications of these findings in the biosynthesis of milk are briefly discussed.
Hydrophobic surface areas and net charges of αs1-, κ-casein and αs1-casein: κ-casein complex
Authors: Dosako Shun'ichi , Kaminogawa Shuichi , Taneya Shin'ichi , Yamauchi Kunio 
Published: June 2009

SummaryHydrophobic surface areas of αs1- and κ-casein polymers and αs1-casein: κ-casein complex were estimated by the salting-out technique using various salts according to the theory of Melander & Horvath (1977). Calculated hydrophobic surface areas of αs1, κ-casein polymers and αs1-casein: κ-casein complex were 1976, 3571 and 2989 Å2 respectively. Assuming that κ-casein polymer dissociated into 4 particles in complex formation and that 1 mole of αs1-casein: κ-casein complex was produced from 2 mole of αs1-casein polymer and one of these dissociated κ-casein particles, the hydrophobic surface area of αs1-casein: κ-casein complex was less than those of 2 mole of αs1-casein polymer plus a quarter κ-casein polymer. On the other hand, the net charge of αs1-casein: κ-casein complex was nearly equal to that of 2 mole of αs1-casein polymer plus a quarter of κ-casein polymer. From these results, it was concluded that the complex formation of αs1- and κ-casein polymers was hydrophobic and that electrostatic interaction did not participate in complex formation.
Effect of a disinfectant udder wash and a post-milking teat dip on the bacterial population of the teat end and on the rate of new intramammary infection
Authors: Sheldrake Richard F. , Hoare Roderic J. T. 
Published: June 2009

SUMMARYA pre-milking wash disinfectant procedure employing a 2% (w/v) chlorhexidine solution in a detergent base did not reduce the rate of new intramammary infection in a lactating herd challenged with Staphylococcus aureus. Teat-end swabs showed no significant difference in the number of Staph aureus isolated from the teat-ends pre-washed with either water, or water and chlorhexidine. In contrast, disinfecting teats after milking with a solution containing 5000 mg available iodine/1 significantly reduced the staphylococcal population of the teat-ends and the rate of new intramammary infection, compared with teats not disinfected.
Influence of elevated somatic cell count on casein distribution and cheese-making
Authors: Ali Ali E. , Andrews Anthony T. , Cheeseman Gordon C. 
Published: June 2009

SummaryThe effects of increased somatic cell count, whether caused by infection or by experimental infusion of bacterial endotoxin, on the distribution in milk of caseins between the micellar and soluble forms were investigated. The relationship of somatic cell count to some cheese-making parameters was also studied. With quite modestly elevated cell counts (2–3 × 106/ml) increases of up to 37% in total casein in the soluble phase were observed, most of which was contributed by β-casein, while κ- and αs1-caseins increased only slightly. With storage at 4°C, the concentrations of all the caseins, Ca and phosphate in the soluble phase increased substantially during the first 48 h, but this was followed by a slight decline on further storage. Rennet clotting time, losses of fat in whey, curd moisture, and losses in curd yield and rigidity were all greater the higher the somatic count. Clear differences were detectable in these parameters between milks of very low cell count (e.g. 5 × 104 cells/ml) and milks with counts more typical of those found in bulk supplies (e.g. about 5 × 105 cells/ml). If these findings can be reproduced in commercial practice even a modest reduction in bulk milk somatic cell counts might be expected to bring definite benefits.
Factors affecting the ethanol stability of bovine milk: II. The origin of the pH transition
Authors: Horne David S. , Parker Thomas G. 
Published: June 2009

SummaryDialysing milk against phosphate-free sera showed that the transition in the ethanol (EtOH) stability/pH profile was associated with the soluble phosphate component of the milk serum. Sigmoidal behaviour similar to that of milk was reproduced when the EtOH stability of artificial mixtures of casein, Ca and phosphate was measured as a function of pH. A mechanism for the s coagulation of skim-milk is discussed.
Citric acid concentration in subclinical mastitic milk
Authors: Oshima Masaharu , Fuse Hiroshi 
Published: June 2009

SummaryThe effect of subclinical mastitis on the citric acid concentration of cow's milk was studied by comparing milk from the mastitic quarter with that from a healthy quarter of the same udder. Forty-two pairs of fore-milk from the morning milking of 17 cows were examined and the citric acid content was measured by an automated carboxylic acid analyzer. The citric acid concentration decreased in subclinical mastitic milk and the extent of decrease was proportional to the degree of mastitis as expressed by the quarter difference value in concentration of Na+Cl in mm/1, i.e. the increase in the Na and Cl concentrations in the abnormal milk over that found in normal milk from the same udder. The correlation coefficient between the quarter difference value of Na+Cl and the value for citric acid was –0·77, (d.f. = 46, P <0·001) and a linear regression equation was obtained. The result showed clearly that subclinical mastitis is one of the causes of variation in the citric acid content of cow's milk. The quantitative change in citric acid concentration in subclinical mastitic milk is discussed with reference to the admixture theory for the formation of abnormal milk.
Effect on the composition and properties of casein micelles of interaction with ionic materials
Authors: Green Margaret L. 
Published: June 2009

SummaryThe effect on the composition and properties of casein micelles of the binding of ionic materials which accelerate the coagulation of milk on rennet treatment, was investigated. When considered in terms of their relative charge concentration, all the materials tested caused similar effects. The casein, inorganic phosphate and Ca contents of the micelles increased slightly. Micelle hydration decreased as additive binding increased. Casein and Ca dissociation on cooling increased at low concentrations of bound material, then progressively decreased at higher concentrations. The mean size of micelles and their electrophoretic mobility was little affected by bound ionic materials. The aggregation of the casein complexes in colloidal calcium phosphate-free milk was markedly increased by adding ionic materials, the efficiencies of these additives paralleling their efficiencies in accelerating the coagulation of milk by rennet. The results suggested that the ionic materials were bound in the interior of the casein micelles and promoted aggregation after rennet treatment by shielding charged groups, thus increasing the micellar hydrophobicity.
Mode of binding of ionic materials to casein micelles
Authors: Green Margaret L 
Published: June 2009

SUMMARYThe proportion of materials which adsorb to casein micelles and accelerate milk coagulation, and remain bound on dilution of the micelle suspension with milk dialysate was determined. This was higher than expected from the postulate that equilibration took place between the solution and many equivalent binding sites on the micelle. This suggests that binding involved either or both hydrophobic interactions and multipoint attachment to charged groups. The location of the additive binding sites in the micelle was investigated using models Na caseinate and hydroxyapatite at pH 6·6. Materials which accelerated coagulation bound to either or both models. Those with the greatest effect on milk coagulation probably bound primarily to the casein rather than to the colloidal calcium phosphate moiety of casein micelles.
Acid-soluble nucleotides of human milk at different stages of lactation
Authors: Gil Angel , Sanchez-Medina Fermin 
Published: June 2009

SUMMARYThe acid-soluble ribonucleotides of human milk were measured by enzymic and ion-exchange chromatographic procedures at different stages of lactation. Human colostrum and milk contained CMP, AMP, GMP, UMP, GDP-mannose, UDP-N-acetyl-glucosamine, UDP-N-acetyl-galactosamine, UDP-glucose, UDP-galactose, UDP and other minor nucleotides. Cytidine and adenosine derivatives were present in relatively higher amounts than in milk from ruminant species. The nucleotide concentration decreased with advancing lactation. Human milk at 3 months of lactation contained about 10 µmol/100 ml nucleotides, which represented about 75% of the amount of nucleotides present in human colostrum. Human milk did not contain orotic acid. The UDP-glucose/UDP-galactose ratio was constant during lactation and was similar to that of milks from ruminant species.
Qualitative and quantitative determination of proteolysis in mastitic milks
Authors: de Rham Olivier , Andrews Anthony T. 
Published: June 2009

SUMMARYProteolytic activity in mastitic skim-milk was often 5–10 fold higher than in normal milk, its level being related to somatic cell count but not precisely correlated with it. In milks with the highest levels of activity plasmin accounted for about one third of the total proteinase. A further third was sedimented with the micellar fraction together with the plasmin, but unlike plasmin, was not inhibited by addition of soyabean trypsin inhibitor (SBTI). The final third remained in the serum phase.Polyacrylamide gel electrophoresis (PAGE) showed that αsl- and β-caseins were degraded at about the same overall rate. The plasmin produced the usual readily identified fragments from β-casein, but incubation of mastitic milk also produced changes in patterns in the γ-casein region differing from plasmin-induced changes which were also apparent when the micellar fraction was incubated. As they were inhibited by SBTI, a second trypsin-like enzyme in addition to plasmin may also have been present. Other proteinase(s) not inhibited by SBTI was also associated with casein micelles and produced at least 3 characteristic protein fragments seen on PAGE. The serum phase proteinase(s) was likewise not inhibited by SBTI, and did not produce any well-defined electrophoretic bands, suggesting a rather non-specific breakdown of caseins. After separation of mastitic whole milk, a considerable proportion of the proteolytic activity was found in the cream phase. The proportion was enhanced by freezing and thawing, and the enzyme appeared to be identical to the SBTI-resistant micellar proteinase.Because of the considerable proteolysis likely to occur under the time and temperature conditions involved, our results may provide some explanation for the problems encountered in cheesemaking with mastitic milks (e.g. yield losses, poor curd strength and off-flavour development).
Probing the location of casein fractions in the casein micelle using enzymes and enzyme–dextran conjugates
Authors: Chaplin Brian , Green Margaret L. 
Published: June 2009

SUMMARYThe rates of milk clotting and of formation of para-κ-casein in milk, colloidal phosphate-free milk and isolated κ-casein by pepsin and by its soluble size-fractionated conjugates with dextran were determined. Milk clotting with all the enzyme derivatives was dependent on the rate of the enzymic phase and required essentially complete κ-casein hydrolysis at 30 °C and throughout the range of pH 5·6–6·7. κ-Casein hydrolysis by pepsin at pH 6·6 was fastest in milk and slowest in isolated κ-casein, but the rate decreased as the enzyme size increased, especially with milk. When corrected for the changes in pepsin activity, the rates of κ-casein hydrolysis in all substrates were identical at 30 and 5 °C, but increased with decrease in pH, especially with the larger enzyme conjugates. Hydrolysis of the C-terminal bonds of β-and κ-casein in native and disrupted casein micelles by carboxypeptidase A and soluble conjugates of it were also investigated. κ-Casein was hydrolysed much faster, and β-casein slightly faster, in native than in disrupted micelles by the native enzyme. Increase in the size of carboxypeptidase A increased the rate of hydrolysis of κ-casein in disrupted micelles and also induced lag periods before hydrolysis commenced, especially with disrupted micelles. The results are compatible with a model for the casein micelle in which the κcasein is on the outside and the casein components are in a more ordered arrangement than in the casein complexes formed on micelle disruption. They also indicate that immobilized coagulants would be unable to clot milk.