bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure of the casein micelle. The accessibility of the subunits to various reagents
Authors: Dumas B. Ribadeau , Garnier J. 
Published: June 2009

SummaryCarboxypeptidase A (CPA, mol. wt = 34600) and 1-dimethylaminonaphthalene-5-sulphonyl chloride (dansyl chloride, mol. wt = 270) were shown to react with the 3 casein subunits, αs1-, β- and κ-caseins, which constitute the micelle. Virtually all of the C-terminal amino acids were released by CPA from these subunits without disrupting the micellar structure.It was verified that the rate of dissociation of the micelle into low molecular weight complexes is considerably slower than the rates at which these reagents act on micellar components. It is concluded that dansyl chloride, CPA, and probably also rennin, whose molecular weight is similar to that of CPA, are able to penetrate to the interior of the micelles. This was confirmed in a quite independent way with a non-reacting agent, myoglobin (mol. wt = 17000).It is postulated that the casein micelle has a sponge-like structure in which the 3 different subunits are distributed fairly uniformly.Micellar fractions obtained by differential centrifugation from skim-milk and colostrum were examined for their content of αs1-, β-, κ- and para-κ-caseins by the use of CPA as described by Ribadeau Dumas (1968). The results confirm that there is a real difference in κ-casein content of the micelles, according to their rate of sedimentation.
The influence of various treatments on the drainage of continuously made curd
Authors: Berridge N. J. , Scurlock P. G. 
Published: June 2009

SummaryThe effect of layer thickness and orientation, and of pressure, temperature, and disturbance on the drainage rates of continuously made curd were determined. The effects of heat treatment of the milk and adjustments of its pH were briefly examined. An increase in temperature of the curd caused the expected increase in drainage rate as did also the application of pressure. Vertical layers of curd drained more quickly than almost horizontal layers, and keeping curd in whey retarded its drainage. The effects of pH change over the narrow range of interest (6·1–6·5) were relatively small. Pasteurization of the milk had no effect. Disturbance of the curd had the most pronounced effect in increasing its rate of drainage.
Local cooling of the mammary gland and milk production in the cow
Authors: Holmes C. W. 
Published: June 2009

SummaryAn experiment has been performed with 2 Jersey cows to determine the effect of a reduction in udder temperature on milk production. One half of the udder was covered while the other half was cooled by an increase in air movement at an air temperature of 6−10°C; for closely clipped udders it was estimated that the cooling conditions might be equivalent to an air temperature of −10°C with low air movement. Yields of milk, fat, protein and lactose were reduced significantly at the morning milking after 22 h cooling; the decreases which occurred at the afternoon milking after 9 h cooling, in all components except fat, were not significant. Wisconsin Mastitis Tests on the milk indicated that changes in udder health did not contribute to these effects.
The effect of ageing cooled milk on the composition of the fat globule membrane
Authors: Anderson M. , Cheeseman G. C. , Knight Dorothy J. , Shipe W. F. 
Published: June 2009

SummaryThe effect of ageing fresh milk for 24 h at 4°C on the composition of 4 fractions of milk fat globule membrane (FGM) – microsomal pellet membrane (MPM), deoxycholate soluble membrane (DOCM), high density membrane (HDM) and low density membrane (LDM) – prepared from washed cream treated with sodium deoxycholate (DOC), was studied for milk of individual cows. Total FGM and its fractions were solubilized by treatment with sodium dodecyl sulphate (SDS), EDTA and β-mercaptoethanol, and the dissociated FGM proteins were separated by polyacrylamide gel electrophoresis in the presence of SDS.Ageing resulted in a greater loss of phospholipid during cream preparation than was found with fresh milk, and also in a reduction in the total amount of FGM isolated. Loss of FGM material was confined to MPM, DOCM and LDM and was accompanied by compositional changes in DOCM and LDM, quantitatively the most significant fractions. Ageing also produced changes in the gel electrophoresis patterns of DOCM, where the band of greatest mobility (mol. wt about 16000) was partially lost, and of LDM, where there was an increase observed in the major protein band.The implication of the results on the proposed models of FGM structure is discussed.
The alkali-induced elimination of phosphate from β-casein
Authors: Manson W. , Carolan T. 
Published: June 2009

SummaryThe dephosphorylation of β-casein, type A1, by dilute aqueous solutions of sodium hydroxide has been studied. It has been found that the mechanism whereby inorganic phosphate is liberated by the action of alkali is one of β-elimination from O-phosphoserine residues which are themselves converted initially to dehydroalanyl residues.
Application of differential scanning calorimetry to butter
Authors: Sherbon J. W. , Dolby R. M. 
Published: June 2009

SummaryThe effects of varying salt contents and cream-cooling treatments on thermograms of the resultant butters were determined by differential scanning calorimetry (DSC). A procedure is described for loading the calorimeter without erasing the thermal history of the sample. Unsalted butter had only one melting transition associated with the aqueous phase, at −0·5 °C. Salted butters had two such transitions. One occurred at a constant −22 °C and corresponded to melting of a NaCl–water eutectic mixture. The other varied with the salt content and probably corresponds to melting of the ice in a NaCl solution. Slow-cooling treatment of cream resulted in butter thermograms similar at 10 and 25 °C to those from the Alnarp treatment, but differed between 22 and 25 °C. Shock-cooling resulted in higher amounts of crystallization than the other 2 treatments. The DSC was shown to be useful in following the effects of cream treatment upon the melting characteristics of the resulting butter.
Milk triglycerides: the degree of non-random associations of fatty acids
Authors: Breach R. A. , Dils R. , Watts R. 
Published: June 2009

SummaryPublished data are available for the fatty-acid compositions and molecular-weight distributions of triglycerides in milk and adipose tissue from the guinea-pig, rat, mouse and rabbit, and in milk from the human, cow, mink and hamster. These data have been used to calculate the extent of non-random associations of fatty acids of different chain lengths in these triglycerides.The results support, in general, the concept of non-correlative acylation, i.e. that during the biosynthesis of these triglycerides, fatty acids already present on the glycerol backbone do not influence the selective acylation of subsequent fatty acids. However, milk triglycerides from these animals show varying degrees of intermolecular specificity which can be explained in terms of positional specificity of fatty acids on the glycerol backbone.
Further short-term studies of the influence of the milking machine on the rate of new mastitis infections
Authors: Cousins Carol L. , Thiel C. C. , Westgarth D. R. , Higgs T. M. 
Published: June 2009

SummaryFrom a series of short-term experiments under accentuated milking machine conditions predisposing to new mastitis infections, it appears that the cow is at increased risk near the end of a milking. The observations recorded are consistent with the view that bacteria implanted in the teat during milking as a result of the action of the machine are the less likely to be washed out the nearer implantation occurs to the end of milk flow.
The effects of increasing amounts of dietary tallow on milk-fat secretion in the cow
Authors: Storry J. E. , Hall A. J. , Johnson V. W. 
Published: June 2009

SummaryThe effects of 2, 4, 7 and 10% supplements of tallow to a basal diet low in fat on the composition of volatile fatty acids (VFA) in the rumen and on the secretion in milk of fat and its component fatty acids are reported. There were no significant effects of the tallow on rumen VFA or on the secretion of total milk fat. The yields in milk of stearic (18:0) and oleic (18:1) acids were positively correlated and those of palmitic (16:0) and myristic (14:0) acids negatively correlated with their respective dietary intakes. Apart from butyric acid which increased, the yields of other short-chain acids synthesized within the mammary gland decreased with increased intake of tallow. Possible factors influencing the output of total milk fat through a balance between increased transfer to milk of dietary fatty acids and decreased intramammary synthesis of fatty acids are discussed.
The effects of pregnancy, lactation and involution on the metabolism of glucose and acetate by rat liver tissue
Authors: Smith R. W. 
Published: June 2009

SummaryThe incorporation of14C from [1-14C] and [6-14C]glucose and [2-14C]acetate into CO2and fatty acids by rat liver slices was measured at intervals during pregnancy, lactation and involution.During late pregnancy, the rates of oxidation of the C-1 and C-6 atoms of glucose were respectively 65 and 40 % higher than those for unmated animals. These increases were maintained during lactation, but the highest values were observed 3 days after weaning. Pregnancy and lactation had little effect on the oxidation of [2-14C]acetate.The incorporation of14C from all 3 labelled substrates into fatty acids was increased by a factor of 3–4 during late pregnancy. There were further increases during lactation, and 3 days after weaning the values were as much as 10 times as high as those for unmated animals.The incorporation of both [14C]glucose and [14C]acetate into cholesterol was increased by a factor of 6–7 during lactation.The activities of the enzymes glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, ATP citrate lyase and acetyl-CoA carboxylase were also increased during lactation and involution.The similarity between the changes summarized above and those brought about by changes in the pattern of food intake is discussed, and the idea that fatty acids synthesized from non-lipid precursors in the liver may make some contribution to the formation of milk fat is also considered.
The relationship between head-space volume and dissolved O2 content of water and UHT milk in sealed containers
Authors: Zadow J. G. 
Published: June 2009

SummaryA relationship between the level of dissolved O2 in a product and the head-space volume of a sealed container after filling was derived. The validity of the relationship was confirmed by studies using both water and milk which had been subjected to ultra heat treatment (UHT), and stored in glass bottles. The relation held well for water, but some deviation was noted using milk. The relationship allowed selection of the processing conditions necessary for the manufacture of products with a desired dissolved O2 level.As part of this study a device was developed which permits continuous monitoring of dissolved O2 in sterile liquids being pumped between a container and an O2 sensor. Only very minor problems were encountered with the device through biological contamination or entry of atmospheric O2.
A procedure for the isolation of gastric enzymes
Authors: O'Leary P. A. , Fox P. F. 
Published: June 2009

SummaryBovine, ovine and caprine pepsin and lamb, piglet and kid chymosins (rennins) were isolated by basically the same procedure of selective pH precipitation, DEAE-cellulose chromatography in phosphate buffer, pH 6·5 and Sephadex G-100 chromatography. The homogeneity of the preparations was assessed by (a) re-cycling on Sephadex G-100, (b) chromatography on DEAE-cellulose using piperazine buffer, pH 5·3 and (c) ability to inactivate ribonuclease.
Microstructure of Cheddar cheese: sample preparation and scanning electron microscopy
Authors: Eino M. F. , Biggs D. A. , Irvine D. M. , Stanley D. W. 
Published: June 2009

SummaryThree techniques were used for preparing Cheddar cheese specimens for examination by scanning electron microscopy. Resulting micrographs prepared from fresh cheese made with calf rennet revealed that while all the techniques were satisfactory, different structural features were observed depending upon the method used. A modified critical point drying technique and a freeze-drying method displayed surface features whereas trypsin hydrolysis showed internal microstructure. The surface microstructure of the cheese was found to be formed of protein aggregated and fused into structural units of 1·5 μm. The internal microstructure appeared to be formed of thin compact walls. Cross sections prepared by freeze-drying displayed arrays in the protein matrix and locations where fat globules had been embedded.
Autolysis ofStreptococcus cremoris
Authors: Mou Lynette , Sullivan J. J. , Jago G. R. 
Published: June 2009

SummaryThe autolysin ofStreptococcus cremorishad the specificity of an endo-N-acetylmuramidase as it hydrolysed the linkage betweenN-acetylmuramic acid andN-acetylglucosamine. The enzyme had no amidase or endopeptidase action. It reached highest activity in the exponential phase of growth and in the electron microscope seemed to fragment the coccal wall at the equatorial ring.
The contribution of starter streptococci to flavour development in Cheddar cheese
Authors: Law B. A. , Castañón Marisi J. , Sharpe M. Elisabeth 
Published: June 2009

SummaryThe number of starter bacteria in Cheddar cheese was increased approximately 2 or 8 times by supplementing the normal starter inoculum with starter-cell suspensions which had been incubated with lysozyme in the absence of salt. Lysozyme-treated cells were also introduced into chemically acidified cheese in an attempt to achieve ripening in the absence of a normal starter culture. The added starters did not interfere with normal cheese-making by producing acid. The lysozyme-treated starter cells were lysed when the curd was salted and lysis was detected by the release of cell-free DNA and an intracellular marker enzyme (dipeptidase) into the cheese matrix. Free amino acid concentrations in maturing cheeses were increased up to 3 times compared with control cheeses. The intensity of Cheddar flavour was not increased in starter cheeses by the presence of additional lysozyme-treated starter and no Cheddar flavour developed in chemically acidified cheese containing the lysozyme-treated cells. It is concluded that intracellular starter enzymes play no direct part in flavour formation, but produce breakdown products from which Cheddar flavour compounds may be formed by other unknown mechanisms.
Action of milk-clotting enzymes on β-caseins from buffalo's and cow's milk
Authors: El-Shibiny Safinaz , El-Salam M. H. Abd 
Published: June 2009

Summaryβ-Caseins isolated from buffalo's and cow's milk were hydrolysed either with rennet or with microbial proteases fromMucor miehei, M. pusillusLindt orEndothia parasitica. The degradation products were separated by polyacrylamide-gel electrophoresis and the residual β-casein was determined quantitatively after various times. The electrophoretic patterns of the degradation products of buffalo and bovine β-casein produced by the different enzymes were not identical. β-Casein of buffalo's milk was hydrolysed by rennet andM. mieheiprotease at a slower rate than that of cow's milk. The reverse was found withE. parasiticaandM. pusillusLindt proteases. Carbamylation of buffalo β-casein was found to retard its proteolysis by all the enzymes but particularly by rennet andM. mieheiprotease.
Recovery of whey proteins from precipitated complexes of carboxymethyl cellulose and protein
Authors: Hill R. D. , Zadow J. G. 
Published: June 2009

SummaryThe recovery of proteins from whey by complex formation with carboxymethyl cellulose (CMC) has been studied. After precipitation of the CMC–whey protein complex at pH 3·2, the complex was separated, washed and redissolved at pH 7. The CMC was separated from the protein by precipitation as its Ca salt. By this method protein concentrations in the supernatant liquor of up to 6 times that of the original whey were achieved. Between 10 and 70% of the protein was precipitated with the Ca CMC, depending on the pH and the excess of Ca present. The effective protein binding capacity of the recovered CMC decreased on re-use because of firm binding of both protein and Ca to the CMC.
Interrelationships between acetylation and the disposal of acetyl groups in the livers of dairy cows
Authors: Snoswell Alan M. , Costa Nicholas D. , Mclean Jock G. , Baird G.david , Lomax Michael A. , Symonds Herbert W. 
Published: June 2009

SummaryPossible mechanisms by which the degree of acetylation of hepatic CoA might be regulated were examined in lactating and in non-lactating dairy cows. This involved the measurement of the hepatic steady-state concentrations of free CoA, acetyl-CoA, free carnitine, acetylcarnitine and total acid-soluble carnitine in freezeclamped biopsy samples, the measurement of the hepatic release of acetate from acetylcarnitine in vitro, and the measurement of the rate of hepatic output of acetate and ketone bodies in vivo.The hepatic ratio of [free CoA]/[acetyl-CoA] was 0·11 in lactating cows and 0·59 in non-lactating cows. There was a significant rise in the hepatic concentration of acetyl-CoA and a significant fall in that of total acid-soluble carnitine in the lactating cows as compared with the non-lactating cows.There was a net in vivo output of acetate and of ketone bodies from the livers of both lactating and non-lactating cows. The rates of output amounted to 7·77 and 2·00 mmole/min for acetate and ketone bodies respectively in the lactating cows, and 4·95 and 2·14 mmole/min in the non-lactating cows.The rate of enzymic release of acetate from acetylcarnitine in vitro amounted to 0·93 and 0·34 μmole min−1(g wet wt)−1at 37 °C for liver homogenates derived from lactating and non-lactating cows respectively. The activity observed in the case of the lactating cows was sufficient to account for the rate of hepatic acetate output observed in vivo.
Natural variations in the average size of bovine casein micelles: I. Milks from individual Ayrshire cows
Authors: Holt Carl , Baird Linda 
Published: June 2009

SummaryMilk samples from 3 groups of cows were taken at regular intervals throughout lactations following 2 spring and 1 autumn calving. The average radius of casein micelles in milk was determined either from the wavelength dependence of turbidity or from the diffusion coefficient as measured by a quasi-elastic light scattering method. A 2-fold variation in naturally occurring average radii was found both in milks from the same cow at different times and between milks from different cows at the same time.
Development of volatile fatty acids in Ras cheese
Authors: El-Shibiny Safinaz , Soliman Mervat A. , El-Bagoury Ekram , Gad Ahmed , Abd El-Salam Mohamed H. 
Published: June 2009

SummaryThe development of free volatile fatty acids (FVFA) in Ras cheese treated with lipases was investigated. Ras cheese was made with the addition of Italase, Capalase K and Capalase KL and then analysed periodically for the FVFA by quantitative gas-liquid chromatography. Lipase treatment markedly increased the total FVFA content of the cheese during storage, particularly when Capalase K was used. The FVFA of Ras cheese were found to consist of propionic, butyric, caproic, caprylic and traces of acetic acid. The relative concentration of FVFA varied with storage and lipase treatment.
Effect of proteose-peptone on the heat gelation of whey protein isolates
Authors: Hillier Robyn M. , Cheeseman Gordon C. 
Published: June 2009

SUMMARYWhey proteins have been isolated from cheese whey by complex formation with carboxymethylcellulose. The protein preparations form stable gels and foams when reconstituted in water. A study has been made of the effect of concentration, pH and temperature on the gelling behaviour of the whey protein isolates, and the conditions necessary for a standard gelling test have been defined. Proteose-peptones (p-p) have been prepared from a whey protein isolate which showed a strong tendency to gel, and also from heated and unheated milk. The gelling behaviour of whey protein isolates, which showed either no tendency or a strong tendency to gel, has been studied in the presence and absence of added p-p. The quantities added varied from 0·05 mg isolated from unheated milk to 15 mg from heated milk. No change in gelling time was observed, and it was concluded that p-p were not responsible for the gelling behaviour exhibited by whey protein isolates.
Role of mammary casein kinase in the phosphorylation of milk proteins
Authors: Bingham Elizabeth W. 
Published: June 2009

SUMMARYCasein kinase from lactating bovine mammary gland catalyses the transfer of the terminal phosphoryl group of ATP to specific serine residues in dephosphorylated caseins. Best substrates for casein kinase are the dephosphorylated proteins (bovine αs1- and β-caseins and pepsin), unphosphorylated human β-casein and the dephosphorylated peptide (residues 1–25) from bovine β-casein. Results obtained with bovine and human β-caseins indicate that the two serines underlined in the cluster Ser-Leu-Ser-Ser-Serare particularly susceptible to the action of casein kinase. Since a similar sequence is found in dephosphorylated αs1-casein, it is probable that serines in this region of αs1-casein are also phosphorylated. The results support the concept that certain serines in casein are particularly susceptible to phosphorylation by casein kinase.
Buffalo αs0-casein: isolation and characterization
Authors: Petrilli Pasquale , Chinese Lina , Addeo Francesco 
Published: June 2009

SUMMARYA method for the preparation of αs0-casein, and for the preparation of αs0-casein fractions 1 and 2 from buffalo casein are described. The amino acid composition and phosphorus content of αs0-casein are given and compared with those of other αs0-caseins.
The cysteine content of caseion micelles
Authors: Hill R. D. 
Published: June 2009

SummaryFollowing enzymic digestion with pronase, masked SH groups in micellar casein became available for titration in disaggregating media with mercurial reagents. The content of cystine and cysteine was also estimated after reduction with (a) sulphite, and (b) borohydride, and also by reaction in alkaline conditions with Cd(OH)2. The results show that the micelles contain mainly cysteine, and that it is likely that cystine is not present.
Identification of a C20 multibranched fatty acid from butterfat as 3,7,11,15-tetramethylhexadecanoic acid
Authors: Hansen R. P. , Shorland F. B. , Morrison James D. 
Published: June 2009

SummaryA C20 multibranched fatty acid earlier isolated from butterfat in trace amounts has been conclusively identified by means of mass and infra-red spectrometry and gas-liquid chromatography as 3,7,11,15-tetramethylhexadecanoic acid.
The relationship in the cow between the osmotic pressure of milk and of blood
Authors: Wheelock J. V. , Rook J. A. F. , Dodd F. H. 
Published: June 2009

SummarySimilar, marked variations in the freezing-point depressions of jugularvenous blood and of milk throughout a day were observed in cows when drinkingwater was offered for a single, short period each day. Values for milk were found to agree more closely, however, with those for mammary-venous blood than with those for jugular-venous blood. It appears that milk is in osmotic equilibrium with the blood flowing through the udder continuously throughout the period the milk remains within the udder and not only during its formation, and that milk secretion causes a slight alteration in the osmotic pressure of fluids within the immediate locality of the mammary gland. Changes in the milk composition that occurred in association with the observed changes in freezing-point depression were consistent with a movement of water into or out of the udder in response to any change in the osmotic pressure of blood.