bluuebunny/crossref_metadata_2025 huggingface dataset:
Titrimetric studies on milk and milk products
Authors: Kirchmeier Otto
Published: June 2009

Potentiometric acid-base titration is a simple method that can be used successfully in the investigation of the protein system of milk and other protein-containing products. Its applications include the examination of conventional heating procedures, cheese ripening, the investigation of processed cheese and the effect of melting salts. The principle depends on the performance of pH-dependent phase transitions which are recorded by a single titration cycle and evaluated quantitatively by means of hysteresis loops.
Major elements in milk of the West African dwarf goats as affected by stage of lactation
Authors: Akinsoyinu Akintunde O. , Akinyele Isaac O.
Published: June 2009

Twelve adult West African dwarf (Fouta djallon) does, about 2 years old and weighing from 25 to 28 kg were kept for lactation studies lasting two 19-week periods. During these periods the does were hand-milked twice daily and the daily samples were bulked for each animal for subsequent analysis.

The results showed that the colostrum was much richer in its content (g/kg) of Na 1·44 ± 0·17, Κ 3·38 ± 0·22 and Cl 4·83 ± 0·29 than the mature milk which contained (g/kg) Na 0·65 ± 0·09, Κ 1·57 ± 0·19 and Cl 2·46 ± 0·58. The corresponding values obtained for Ca (0·65 ± 0·02) and P (0·36 ± 0·10) in the colostrum were, however, lower than 2·01 ± 0·98 and 1·18± 0·28 g/kg obtained for Ca and P respectively in the mature milk. The composition of these elements in the colostrum approached that of the normal goat's milk on the sixth d after parturition. The results showed a rise in Ca, P, Na and Cl levels with stage of lactation and a fall in Κ content of the milk with advancing lactation with the trends being highly significant (P < 0·01).
Effect of membrane perturbing treatments on the membrane-bound peptidases ofStreptococcus cremorisHP
Authors: Exterkate Fred A.
Published: June 2009

The effects of solubilization, treatment with organic solvents and storage under alkaline conditions on membrane-associated peptidases of intact cells ofStreptococcus cremorisHP were studied. Differences in the response of the peptidase activities towards these membrane perturbing treatments were observed. Pyrrolidonecarboxylylpeptidase (PCP) and an endopeptidase (P50) showed 50% irreversible inhibition at the same concentration of each solvent tested. An amino- and proline iminopeptidase activity and the endopeptidase P37were in this respect much more sensitive to the action of the solvents. Within a homologous series of n-alkanols irreversible inhibition of PCP showed a dependence on the hydrophobicity of the solvent molecules. Only P37activity was increased considerably upon solubilization of the enzyme. Similar levels of activation were found upon treatment of cells with 3% (v/v) n-butanol at 25 °C or storage at 30 °C at an alkaline pH. Optimal activity of P50during n-butanol treatment was at 25 °C using a concentration of 5% (v/v), but no activation was observed upon solubilization. The results are discussed in terms of enzyme–lipid interaction and accessibility of the enzymes in situ. It is concluded that the enzymes apparently occupy different positions within the membrane although they may together constitute a functional peptide-hydrolysing unit.
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

Lactoperoxidase 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

The 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

Results 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

When 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

The 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

Two 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

It 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

Six 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

Individual 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

Casein 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

A 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

Bovine 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

Hydrophobic 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

A 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

The 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

Dialysing 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

The 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

The 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

The 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

The 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

Proteolytic 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

The 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.
Ion exchange processing of skim-milk for food use
Authors: Burgess K. J.
Published: June 2009

Ion exchange is a unit operation which has several applications in the processing of skim-milk and whey. For example, in the field of whey processing, ion exchange is used in demineralization, lactose hydrolysis and in the pre-treatment of whey prior to protein recovery. In the case of skim-milk, applications include the manufacture of low Na milk and pre-acidification of skim-milk in casein manufacture. However, the ion exchange treatment of skim-milk to replace Ca ions with Na ions leads to far more fundamental changes with regard to the native protein conformation.

The effect of Ca removal from skim-milk is essentially to disrupt the native casein micelle structure into unassociated molecules of Na caseinate. Skim-milk modified in this way shows increased stability to alcohol and heat and increased functionality of the skim-milk protein in terms of water binding, emulsification and foaming capacity. The viscosity of Ca-reduced skim-milk is also substantially increased.

The improved functionality of Ca-reduced skim-milk makes the latter a potentially useful food ingredient in products where the above mentioned properties are important.
Fermentation of goat's milk by two DL-type mixed strain starters
Authors: Rysstad Gunnar , Abrahamsen Roger K.
Published: June 2009

Variations in the biochemical performance of 2 DL-type mixed strain starters CH 01 and FDn grown in a sample of skimmed goat's milk I (obtained 2–3 weeks after parturition) and of goat's milk II (8 months after parturition) were studied, and results compared with those of the cultures grown in skimmed cow's milk. The initial levels of citrate differed in the 3 milks, with goat's milk II containing 0·7 mg/ml, goat's milk I 1·4 mg/ml and cow's milk 1·8 mg/ml. The production of diacetyl, α-acetolactic acid and acetoin was very low in goat's milk II. In goat's milk I the production of these compounds was higher, but still considerably lower than in cow's milk. Production of ethanol (EtOH) was similar in the 3 milks incubated with starter CH 01, but with FDn the production of EtOH was distinctly higher in goat's milk II. The total amount of CO2produced corresponded with the initial level of citrate; consequently the highest production was found in cow's milk and the lowest in goat's milk II. The use of different starters for fermented products made from goat's milk in early and late lactation is suggested.
Threonine aldolase and alcohol dehydrogenase activities inLactobacillus bulgaricusandLactobacillus acidophilusand their contribution to flavour production in fermented milks
Authors: Marshall Valerie M. , Cole Wendy M.
Published: June 2009

Cell-free extracts of bothLactobacillus bulgaricusandL. acidophilusdemonstrated threonine aldolase activity, the end product of which was acetaldehyde, the major flavour compound of yoghurt.L. acidophilusalso possessed an alcohol dehydrogenase activity capable of reducing acetaldehyde so that little yoghurt flavour was present in milks fermentation with this organism. Addition of threonine to fortified milk before fermentation withL. acidophilusincreased acetaldehyde production and resulted in a well flavoured product similar to that of yoghurt made withL. bulgaricus. The contribution of these 2 enzymes to flavour production is discussed.
Isolation andin vitrotranslation of mRNA from the calf abomasal mucosa and identification of an mRNA coding for a precursor of prochymosin
Authors: Nicholson Bruce H. , Jones Peter
Published: June 2009

The mRNA coding for prochymosin (prorennin) has been partly purified from calf abomasum. Thein vitrotranslation products of the total polyadenylated RNA show a major band on gel electrophoresis which reacts with antibody raised against purified chymosin. The mol. wt of 43000 is higher than expected from the reported amino acid sequence and would correspond to prochymosin with an unprocessed signal sequence of ∼ 17 amino acids. The synthesis of chymosin mRNA is age-related, and ceases by 3 months even in milk-fed calves.
Distribution, location, and ultrastructure of plasma cells in the uninfected, lactating bovine mammary gland
Authors: Nickerson Stephen C. , Pankey J. Woodrow , Boddie Nancy T.
Published: June 2009

Quantitative cytological analysis demonstrated a marked and progressive increase in concentration of subepithelial plasma cells from milk-secreting parenchyma to the distal teat end mucosa in the normal, lactating bovine mammary gland. Parenchymal plasma cells exhibited typical ultrastructure with abundant, flattened stacks of rough endoplasmic reticulum, and hypertrophied Golgi components, while many cells in the teat end mucosa displayed an ergastoplasm distended with fine, flocculent material. Intraepithelial plasma cells were also observed in teat end mucosa. Results suggest that teat end tissues function by recruiting plasma cells to serve as protection against invading mastitis-causing organisms.
Chemical characterization of milk concentrated by ultrafiltration
Authors: Green Margaret L. , Scott K. John , Anderson Malcolm , Griffin Mary C. A. , Griffin Frank A.
Published: June 2009

Whole milks concentrated 1·5–4-fold and acidified and citrated milks concentrated 2·8-fold by ultrafiltration at 50 °C were analysed for chemical changes relevant to further processing, storage or nutrition. Fat and protein were entirely retained in the concentrate. The retention of water-soluble vitamins, Ca, Mg, phosphate and trace minerals depended on the proportion bound to the protein. Ascorbic acid was rapidly destroyed during concentration. Because of the differential retention of nitrogenous components, protein comprised a progressively higher proportion of the total N as the milk became more concentrated. No denaturation of whey protein or disruption of casein micelles was detected during concentration of whole milk, but some solubilization of the casein occurred after citration. Reduction of fat globule size occurred early in the concentration process, damage to the fat globule membrane was indicated and the milk became more susceptible to lipolysis. Apart from a tendency for preacidified or precitrated concentrates to gel, no change in the susceptibility of the milks to heat damage was detected.
Physical and chemical properties of zabadi manufactured from skim milk powder reconstituted with sweet whey
Authors: El-Safty Mohamed S. , El-Zayat Ali I.
Published: June 2009

Zabadi was manufactured using reconstituted skim milk powder prepared with different ratios of water and sweet whey and the organoleptic properties and chemical composition of the milks were measured. Sweet whey could be used successfully to replace up to 50% of the water added for reconstitution, whilst with 75 or 100% whey a sweet off flavour appeared. However, these higher levels could be used for fruit flavoured zabadi, and about 40–60% less sucrose could be used because of the additional glucose + galactose contributed by the whey.
The 31P nuclear magnetic resonance spectrum of cows' milk
Authors: Belton Peter S. , Lyster Richard L. J. , Richards Colin P.
Published: June 2009

The 31P nuclear magnetic resonance spectrum of liquid milk was examined. Of the three peaks observed, the two larger were assigned to inorganic phosphate (Pi) and the seryl phosphate (SerP) residues of casein; the third peak was assigned to a phosphodiester, which is probably glycerophosphoryl choline. The pH-dependences of the chemical shifts of the Pi and SerP were measured with and without added EDTA, and the results confirm the assignments. The width of the Pi peak in milk is significantly greater than in similar solutions lacking casein, probably because of binding to, or chemical exchange with, the casein micelle. Most of the SerP residues in milk are not sufficiently mobile to have been detected in these experiments but a significant fraction of SerP residues is able to move freely and can be titrated.
Use of liposomes for proteinase addition to Cheddar cheese
Authors: Law Barry A. , King Joseph S.
Published: June 2009

A commercial neutral proteinase was encapsulated in liposomes (multilamellar) and incorporated into cheese curd via the cheese milk. The milk proteins were protected from proteinase attack during curd manufacture. A significant proportion of the liposome-entrapped enzyme was retained in the curd and its subsequent release into the cheese matrix was inferred from an increased rate of β-casein breakdown.
Nutritional value of yogurt
Authors: Hewitt David , Bancroft Helen J.
Published: June 2009

Yogurt, made from fortified skim milk by conventional methods using Streptococcus thermophilus and Lactobacillus bulgaricus, was used in studies of the effect of fermentation on nutritional value of milk. In all experiments, the product was compared with the uninoculated base milk. The concentration of most vitamins was less in yogurt than in milk and was most noticeably so for biotin which was 60% less. The effect on folic acid content was inconsistent. In nutritional experiments with rats, high values for true digestibility, biological value and net protein utilization were obtained for both yogurt and its base milk, only minor differences being apparent between the two materials. In growth tests with rats, yogurt was not found to be consistently superior to the base milk when the milk was subjected to a double heat treatment to reduce bacterial contamination. Yogurt did not confer a nutritional advantage on fresh milk in this respect.
Quantification of β-casein in human milk
Authors: Chtourou Abdessatar , Brignon Ghislaine , Ribadeau-Dumas Bruno
Published: June 2009

A method is described for preparing immunologically homogeneous human milk β-casein, against which monospecific rabbit antiserum was prepared. The antiserum was used to quantify β-casein, the major human casein, by rocket Immunoelectrophoresis in individual milk samples. However, it was found that in most samples β-casein occurred together with degradation products originating from its proteolysis by plasmin. Immunological quantification of human β-casein, treated with plasmin for various time periods, showed that rocket height was not affected by proteolysis up to degradation states clearly more advanced than those observed in all samples of fresh human milk tested. Assays of 150 individual milk samples from 80 women, covering a lactation period of up to 730 d, gave an average concentration of β-casein (native+degraded) of 4·67±0·89 standard deviation (g/1); extremes at 2·1 and 7·3 g/1 did not vary significantly during the period under study. Comparison of this average value with an accepted casein content of 4·4 g/1 (Macy & Kelly, 1961) showed that the casein content of human milk is underestimated when obtained by N determinations on milk and on its supernatants at pH 4·6 (whey). Caseins other than β-casein occurred only in minute amounts, if at all.
Does β-lactoglobulin occur in human milk?
Authors: Brignon Ghislaine , Chtourou Abdessatar , Ribadeau-Dumas Bruno
Published: June 2009

Although β-lactoglobulin (β-lg) has been considered to be absent from human milk, recent results of other workers, based on immunological reactions between human milk and rabbit antiserum to bovine β-lg, suggest that this protein may be present. Although our results show similar immunological reactions, we consider that lactoferrin is responsible for these, as it was the only reactive protein species which could be prepared to homogeneity. Indeed two types of antibodies were found by ELISA test in the antisera to bovine β-lg. One of them would be able to bind loosely to human lactoferrin, but its binding sites would not be antigenic in the rabbit.
Effect of serotonin on the motility of smooth muscles in teats of lactating cows
Authors: Messom Georgette Vandeputte-Van , Burvenich Christian , Peeters Georges
Published: June 2009

The effects of serotonin, injected into one udder artery, on teat smooth muscle function were investigated in four lactating cows. Motility of longitudinal smooth muscles was recorded by a plethysmographic technique, and sphincter function by measuring milk leakage from the full udder. Serotonin (40, 120 and 360 μg) activated teat muscle tonicity and reduced the volume of milk leakage. The effects on longitudinal smooth muscles were reduced by mianserin and ketanserin (0·375, 1·5 and 6 mg) and by methysergide (1·5 mg). These blocking substances were also effective (0·2, 0·6 and 1·8 mg respectively) in antagonizing the inhibiting action of serotonin on milk leakage. It is suggested that serotonin effects are mediated by receptors of the S2-type.
Increasing cheese yields by high heat treatment of milk
Authors: Marshall Richard J.
Published: June 2009

Milk was heated at 97 °C/15 s to denature ∼ 30% of the whey protein and then used to make Cheshire cheese. Measurements of para-κ-casein production indicated that heating milk did not inhibit the enzymic action of rennet, but additional Ca and an initial pH of 6·4 were required for normal coagulation and curd-firming. In the experimental cheeses, about 4·5% more dry matter was recovered compared with controls made with pasteurized milk owing to a 6·7 and 0·7% increase in protein and fat recovery respectively. Experimental cheeses tended to be too moist and the curds did not fuse as well but these problems could be overcome by raising the scald temperature and cheddaring the curds. When the moisture in non-fat solids of control and experimental cheeses was similar (61%), the flavours and textures were not significantly different. The procedure requires little modification to existing commercial plant and should be suitable for varieties of cheese with higher moisture content and more crumbly texture than Cheddar.
Use of Platelet Aggregometer to monitor the chymosin-initiated coagulation of casein micelles
Authors: Bringe Neal A. , Kinsella John E.
Published: June 2009

The chymosin-initiated coagulation of casein micelles was followed by monitoring light transmission using a Platelet Aggregometer. The release of macropeptide by chymosin was monitored using fluorescamine. The lag period in the clotting reaction was proportional to clotting time and the reciprocal of enzyme concentration. The average rate of coagulation, which was approximately equal to the reciprocal of clotting time (Tc), increased in proportion to enzyme concentration at low enzyme concentrations and reached a limiting value at high enzyme concentrations. The percentage hydrolysis at the Tc was 47 ± 5% in the presence of 20 mM-CaCl2 and it was calculated that a 5-fold decrease in the speed of the enzyme-catalysed reaction would decrease this value at the Tc to 43 ± 5%. The possible uses and limitations of the Platelet Aggregometer for determining the influence of the chemical environment on the velocity of the chymosin-catalysed reaction and para-casein micelle aggregatability are discussed.
Purification and characterization of the extracellular proteinase ofPseudomonas fluorescensNCDO 2085
Authors: Fairbairn David J. , Law Barry A.
Published: June 2009

SUMMAEY

Pseudomonas fluorescensNCDO 2085 produced a single heat-stable extracellular proteinase in Na caseinate medium at 20 °C and pH 7·0. The proteinase was purified to electrophoretic homogeneity using chromatofocusing, gel filtration and ion-exchange chromatography. The purification procedure resulted in a 158-fold increase in the specific activity and a yield of 3·5% of the original activity. The enzyme is a metalloproteinase containing Zn and Ca, with an isoelectric point at 5·40±0·05 and a mol. wt of 40200±2100. It is heat-stable having D-values at 74 and 140 °C of 1·6 and 1·0 min respectively; 40 and 70% of the original activity remained after HTST (74 °C/17 s) and ultra high temperature (140°C/4 s) treatments respectively. The amino acid composition of the proteinase was determined and compared with those from otherPseudomonasspp.
Pre partum milk fat secretion and concentrations of progestins, prostaglandin and oestrone sulphate in mammary fluid of the goat
Authors: Thompson Gordon E. , Goode Jane A.
Published: June 2009

As much secretion as possible was removed manually twice daily, from both mammary glands of 6 late-pregnant goats beginning on d 137 of gestation. Removing mammary fluid before parturition stimulated fluid secretion by different amounts in individual goats. The mean volume of fluid secreted pre partum by the goats correlated directly with their secretion of triglyceride and the percentage composition of C18 fatty acids in the triglyceride fatty acids; the volume also correlated with the concentration of progestins, but not prostaglandin F2α or oestrone sulphate, in the fluid.
Use of monoclonal antibodies for radioimmunoassay of water buffalo milk progesterone
Authors: Capparelli Rosanna , Iannelli Domenico , Bordi Aldo
Published: June 2009

In order to standardize a radioimmunoassay of milk progesterone as a routine method for confirmation of oestrus and diagnosis of pregnancy in water buffalo, monoclonal antibodies against progesterone were produced. Hybridomas were prepared by fusing spleen cells from a Balb/c mouse immunized with progesterone 11α-hemisuccinate–bovine serum albumin conjugate with the mouse myeloma cell line NS-1. Thirty wells out of 94 secreted anti-progesterone antibodies. Of the ten independent hybridomas derived, one (AF65) was suitable for the quantification of milk progesterone by radioimmunoassay. The tracer used in the assay was progesterone-11α-hemisuccinate ([2-125I]iodohistamine). The sensitivity of the assay was 50 pg/tube. The mean progesterone concentration at oestrus was 0·8±0·2 ng/ml increasing to 8·5±0·8 ng/ml 24 d later in pregnant animals.
An automated enzymic micromethod for the measurement of fat in human milk
Authors: Lucas Alan , Hudson Geoffrey J. , Simpson Peter , Cole Timothy J. , Baker Brian A.
Published: June 2009

Most (98%) of the fat in human milk is present as triglycerides. This paper describes the use of a clarification procedure that enables the level of human milk fat to be determined by measurement of glycerol released by enzymic hydrolysis of triglycerides. The method requires only 10–50 μl milk, thus presenting a possible technique for work with small mammals, and is suitable for use with autoanalysers, permitting rapid sample throughput.
Effects of parity and stage of lactation on adenosine triphosphate, somatic cell count and antitrypsin content in cows' milk
Authors: Emanuelson Ulf , Olsson Thomas , Mattila Tiina , Åström Göran , Holmberg Olof
Published: June 2009

Significant effects of parity and stage of lactation were found on ATP content, somatic cell count and antitrypsin content when using morning milk samples from 39 cows over a period of 18 months. A close similarity was evident between variation in ATP and somatic cell count, except during the first 10 d after parturition when the variation in ATP was more pronounced. The same result was obtained in the whole material as well as in a healthy subset. This study shows clearly that parity and stage of lactation must be taken into account when establishing normal values for ATP as an indicator of mastitis.
Proteolysis of Cabrales cheese and other European blue vein cheese varieties
Authors: Fernandez-Salguero Jose , Marcos Andres , Alcala Manuel , Esteban Maria Asuncion
Published: June 2009

The extent and level of proteolysis were evaluated in Cabrales and five other European blue vein cheese varieties, Bleu de Bresse, Danablu, Edelpilzkäse, Gorgonzola and Roquefort, by analysing their different N-containing constituents and determining the degree of casein hydrolysis. The electrophoretic patterns of the caseins in the cheeses confirmed their strong proteolysis, components featuring the lowest electrophoretic mobility offering the greatest resistance to subsequent hydrolysis. Component αs1 — I was detected in all varieties studied with the exception of Roquefort cheese.