bluuebunny/crossref_metadata_2025 huggingface dataset:
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

The 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

The 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

The 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

Published 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

From 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

The 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

The 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

A 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

Bovine, 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

Three 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

The 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

The 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

β-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

The 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

Possible 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

Milk 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

The 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

Whey 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

Casein 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

A 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 phosphoamidase action of rennin on casein
Authors: Aiyar K. R. , Wallace G. M.
Published: June 2009

It is proposed that —N—P—N— bonds exist in casein and that these bonds can be hydrolysed probably at different rates by the action of rennin. It is proposed that the phosphorus is linked with the guanido group of arginine.
The cysteine content of caseion micelles
Authors: Hill R. D.
Published: June 2009

Following 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

A 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

Similar, 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.
The composition of milk deposits in an ultra-high-temperature plant
Authors: Lyster R. L. J.
Published: June 2009

Milk deposits from an ultra-high-temperature (UHT) plant were analysed for protein, fat and minerals. The physical appearance and composition of the deposits was found to vary with modifications of the plant. For each particular arrangement of the plant, a characteristic pattern of deposits occurred. Possible mechanisms involved in the formation of the deposits are discussed.
A pilot plant for the removal of cationic fission products from milk: II. Efficiency of the process and composition of the product
Authors: Glascock R. F. , Bryant D. T. W.
Published: June 2009

AS previously described, the process consists essentially of the passage of milk at pH 5·2–5·25 through an ion exchange resin charged with a suitable mixture of the ions of Ca, K, Na and Mg.

When citric acid was used for reduction of the pH and 30 resin bed volumes (r.b.v.) were treated, the concentration of residual85Sr was reduced to 2–4% whether it had been introducedin vivo or in vitro. There was no evidence that repeated use of the resin bed resulted in diminished radiochemical efficiency.

About the same efficiency of removal of133Ba was obtained but this efficiency was achieved with137Cs only if not more than 15 r.b.v. were treated. If 30 r.b.v. were treated the concentration of residual137Cs was as much as 30%.

When hydrochloric acid was substituted for citric acid the residual concentration of85Sr was 11%. Analyses of milks processed after adjustment of pH with either citric or hydrochloric acid showed the products to be satisfactory. The only important constituent lost was thiamine. Concentrations of heavy metals remained well below maximum values. Although the flavour of milk was detectably changed by the treatment it was still acceptable.

The results are discussed in relation to the problem of achieving maximum decontamination and to the design of a large scale plant.
Detection of cow's milk in goat's milk by gel electrophoresis
Authors: Aschaffenburg R. , Dance Janet E.
Published: June 2009

Hypersensitivity to cow's milk is not uncommon in humans, particularly babies and infants. Those afflicted may be found to tolerate goat's milk which, in this country, commands a considerably higher price than cow's milk. For economic as well as ethical reasons it is therefore desirable to ascertain that goat's milk offered for sale is free from admixtures of cow's milk. Tests should be sensitive to relatively minor admixtures, since even small additions of cow's milk may undo the benefit which hypersensitive subjects expect to derive from the consumption of goat's milk.
A kinetic model of the clotting of casein by rennet
Authors: Tuszyński W. B.
Published: June 2009

A kinetic model of casein clotting caused in milk by rennet was defined by measuring changes in viscosity and in the complex modulus of rigidity. Three separate stages of the process were distinguished: the enzymic, the flocculation and the gelification. The kinetic equations and the main activation parameters were defined for each stage.
The chemical composition and physical properties of fractions of milk fat obtained by a commercial fractionation process
Authors: Norris R. , Gray I. K. , McDowell A. K. R. , Dolby R. M.
Published: June 2009

Samples of liquid and solid fractions obtained by a commercial process from anhydrous milk fat of softening point (S.P.) 33·5–34°C had S.P. values of 22–23°C and 36–38°C respectively.

Determinations of fatty acid composition by GLC showed that unsaturated and short chain fatty acids were present in increased concentration in the liquid fraction (average 37·8 and 12·4% as compared with 35·1 and 10·8% in the original milk fat) and long chain saturated acids in the solid fraction (average 57·8 as compared with 53·8%). There was some concentration of carotene and vitamin A, and to a lesser extent of cholesterol, in the liquid fraction.

Crystallization and melting curves determined by a differential scanning calorimeter (DSC) showed that while the liquid fraction was completely melted at 25°C, the solid fraction contained an increased proportion of fat melting between 30 and 40°C. In addition to these high melting triglycerides the solid fraction also contained some 65% of fat in the liquid phase at the original crystallization temperature of 25°C.
Factors affecting the concentration of vitamins in milk: III. Effect of season and solar radiation on the vitamin D potency of butter
Authors: Henry Kathleen M. , Hosking Zena D. , Thompson S. Y. , Toothill Joyce , Edwards-Webb J. D. , Smith L. P.
Published: June 2009

Between August and May-the butter-making season in New Zealand-the average vitamin Dcontent of the butterfat varied between 10 and 64 i.u./100g and during the corresponding months in Great Britain (February-November) the values were between 15 and 39 i.u./100g. At the beginning and end of the season the values in both countries were similarly low but in mid-season New Zealand values were up to twice those for Great Britain. Within each country the vitamin D values were highly correlated with hours of sunshine and, for both countries, with total radiation, which includes the diffuse radiation in ‘skyshine’ and also allows for variation in sunshine intensity. The higher content of vitamin D in New Zealand butter in mid-season was attributed to a higher level of total radiation.
A double-bed process for the removal of cationic fission products from milk
Authors: Glascock R. F. , Bryant D. T. W.
Published: June 2009

A process for the removal of cationic fission products from milk is described in which no prior acidification is necessary. The milk is treated at 40°C by 2 beds of suitably charged cation exchange resins, one of which is of the carboxylic acid type and the other of the sulphonic acid type. On the first bed all the metallic cations of the milk are replaced by K+and H+, and on the second the ioniccomposition is restored. During processing the pH is reduced from 6·8 to approximately 6·2 and is restored to 6·8 by the addition of alkali metal carbonates to the milk after treatment.

On a pilot plant of capacity 1600 1 (30 resin bed volumes) per 5-h day it was found that the radiochemical efficiency was approximately 80% for85Sr and 97% for137Cs.

The process caused some losses of vitamins, especially of thiamine, and an increase in the lead, copper and iron contents all of which, however, were at an acceptable level. Other changes in chemical composition were negligible and enzymic clotting time remained unchanged. Flavour and appearance of the product were satisfactory and it was satisfactorily both roller- and spray-dried. The process is discussed with reference to an earlier method in which prior acidification is necessary. It is concluded that the double-bed process is somewhat more efficient for the removal of fission products and that a full-scale plant would be little or no more expensive to erect and only slightly more expensive to operate.
The determination of acetic, propionic and butyric acids in cheese
Authors: Keen A. R. , Walker N. J.
Published: June 2009

A method has been developed for the routine determination of acetic, propionic and butyric acids in cheese. The cheese sample is homogenized with water (1:2) at 40°C for 15 min and the slurry centrifuged at −5°C and 12000 g for 10 min. The free fatty acids in a portion of the aqueous centrifugate are adsorbed on to a column of anion-exchange resin in the hydroxide form. After washing the column with water to remove extraneous material the acids are eluted from the resin with aqueous formic acid. Amino acids in the acidic eluate which interfere with subsequent analyses are removed by a cation-exchange resin column in the hydrogen ion form. The concentrations of acetic, propionic and butyric acids in the cation-exchange resin eluate are determined by isothermal gas chromatography using a glass column (1·8m×2mm i.d.) packed with Chromosorb 101 (100/120mesh). Cheese oil-water partition coefficients are then used to calculate the concentrations of acetic, propionic and butyric acids in the cheese sample.
Denaturation of porcine pepsin during Cheddar cheese manufacture
Authors: O'Keeffe A. M. , Fox P. F. , Daly C.
Published: June 2009

Porcine pepsin was rapidly denatured in phosphate buffers, pH 6·4–6·7, in the temperature range 31–39 °C and was only slightly more stable in milk under similar conditions. However, the enzyme was considerably more stable in Cheddar cheese curd in which the extent of denaturation was very markedly influenced by the pH of the milk at setting. Under normal cheese-making conditions, porcine pepsin was about equally stable with chymosin. Two modifications of the cheesemanufacturing procedure were developed which permit the manufacture of cheese almost free of coagulant and suitable for the assessment of the contribution of starter proteinases to proteolysis during cheese ripening.
The caseins of buffalo milk
Authors: Addeo F. , Mercier J.-C. , Ribadeau-Dumas B.
Published: June 2009

The components of whole casein from water buffalo (Bubalis L.) have been re-investigated in the light of recent studies elucidating the primary structure of all the bovine caseins (αs1, αs2, β & κ). Whole casein samples obtained from individual Italian buffaloes all contained 2 αs1- and 2αs2-casein fractions. These 4 components were isolated and identified by their amino acid compositions and terminal amino acid sequences. The 2 αs1-casein fractions seem to have identical peptide chains as do the 2 αs2fractions, with the individual fractions within each group differing only in their phosphate content. Buffalo β-casein was also isolated and characterized by its amino acid composition and terminal sequences. The isolation of different buffalo κ-casein fractions was reported earlier (Addeo, Chobert & Ribadeau-Dumas, 1977). These fractions were purified and analysed. They were found to have the same amino acid compositions and C-terminal sequences, but to differ in their carbohydrate content. The prominent component, κ1, was treated with chymosin; the caseinomacropeptide and para κ-casein were separated from the digest and analysed. Starchgel electrophoresis at alkaline pH showed no polymorphism of αs1-, β- and κ-caseins in 170 individual buffalo whole casein samples. On 5 occasions the electrophoretic pattern of αs2-casein suggested genetic polymorphism. The behaviour of buffalo αs1−and αs2-caseins in the presence of Ca2+was also studied.
Effect of deflector shields fitted in the milking machine teatcup liner on bovine udder disease
Authors: Griffin Tony K. , Mein Graeme A. , Westgrath David R. , Neave Frank K. , Thompson William H. , Maguire Peter D.
Published: June 2009

Deflector shields were inserted in the teatcup to prevent ‘impacts’ against the teat end, and their effect on the rate of new udder infections was studied on 15 commercial dairy farms in Britain and 16 in Australia. Small metal shields were fitted between the liner barrel and short milk tube of 2 teatcups in each cluster in a milking installation so that all cows in a herd always had the same 2 quarters shielded. Half-udder comparisons were made using 1039 cows in the British herds and 1268 in the Australian herds. Herds were quarter-sampled for cytological and bacteriological examination when shields were fitted at the start of the experiment and again after 6 months. The shield effects were similar in the 2 experiments. The combined results from the 31 farms showed that 10·5% fewer quarters became infected when protected by shields (P < 0·05). In the 1287 cows that had no infected quarters at the start of the trial, 15% fewer quarters became infected when protected by shields (P < 0·01). The shield effect was mainly confined to hind quarters in which 23% fewer shielded quarters became infected (P < 0·001). The small reduction of 2% in forequarters was not significant. In the 16 herds in which post-milking disinfection of teats was practised, shielded quarters had 23·5% fewer new infections than unshielded quarters (P < 0·01). In 6 British herds milked in installations classed as non-standard, shielded quarters had almost 50% fewer new infections than the unshielded quarters (0·05 < P < 0·10). The results provide evidence of a milking machine effect, at varying levels of intensity, to increase new infection rates on all or most farms. Control of this machine effect could lead to substantial reduction in new infections in some herds and a modest reduction in most.
Effect of oil-enriched diets on the milk yield and composition, and on the composition and physical properties of the milk fat, of dairy cows receiving a basal ration of grass silage
Authors: Banks William , Clapperton John L. , Kelly Morag E.
Published: June 2009

The effects of supplementing a basal diet of grass silage with various oil-enriched mixtures on milk yield and composition, fatty acid composition and the melting characteristics of the milk fats are reported. In the first experiment, various dietary fats (soya oil, tallow and a palm oil/palmitic acid mixture) were fed at a fixed level (10% by weight of the concentrate ration). Soya oil had no effect on the proportion or yield of milk fat, and increased the proportion of low melting material in the milk fat; tallow increased the proportion of milk fat, and had little effect on the melting characteristics of the milk fat; the palm oil/palmitic acid mixture increased both the content and the yield of milk fat, and increased the proportion of high-melting material in the milk fat. In the second experiment, soya oil was fed at 3 levels (10, 15 and 20% by weight of the concentrate ration). No statistically significant effect on the yield of milk or of its constituents was observed; the proportion of low-melting material in the milk fat increased progressively with increasing intake of soya oil.
Effect on milk lipolysis of restricted feeding with and without supplementation with protected rape seed oil
Authors: Astrup Harald N. , Bævre Lars , Vik-Mo Lars , Ekern Asmund
Published: June 2009

Feeding lactating cows at a reduced level for a 6-d-period caused blood serum and milk free fatty acids (FFA) to rise. Milk lipolysis developed more slowly and lasted longer than elevation of the level of FFA in blood. In a second experiment protected rape seed oil was given to underfed animals and inhibited the development of rancidity in the milk. Since unsaturated fat reduced lipoprotein lipase activity in the underfed cow, this supplement appears to reduce the effect of underfeeding if it is accepted that a normal response to underfeeding is to improve the efficiency of fat metabolism through increased lipoprotein lipase activity.
Factors influencing the stability of milk dialysate
Authors: Parker Thomas G. , Horne David S.
Published: June 2009

The turbidity increase on storage of milk dialysate was shown to be due to Ca phosphate precipitation. The rate of precipitation at 40 °C could be decreased by shortening the duration of dialysis or by the addition of small amounts of EDTA. The dialysate was stabilized against Ca phosphate precipitation by the addition of the whey protein fraction of milk. Individual whey proteins varied in their stabilizing ability: α-lactalbumin was found to be more effective than β-lactoglobulin which gave approximately the same effect as an immunoglobulin fraction. BSA and lysozyme had a destabilizing effect and ovalbumin possessed a slight stabilizing ability.
Effect of ripening cream with selected lactic acid bacteria on the quality of ghee
Authors: Joseph Abraham M. , Appachar Srinivasan R.
Published: June 2009

The effect of ripening cow'milk cream (40% fat) with 4 strains of lactic acid bacteria on the quality of ghee, an Indian product resembling clarified butterfat, was studied by measuring changes in titratable acidity, pH, volatile acids and diacetyl content due toStreptococcus lactis, Str. lactissubsp.diacetylactis (Str. diacetylactis), Str. thermophilusandLactobacillus bulgaricusin cream prior to conversion into ghee.L. bulgaricusproduced the maximum titratable acidity (1·25% lactic acid) followed byStr. diacetylactis(0·80 % lactic acid) after 72 h.Str. diacetylactisproduced the highest level of diacetyl (28 ppm), after 48 h.L. bulgaricusproduced no detectable diacetyl. Both of these strains produced the maximum amount of volatile acids (2·2–3·5 ml), after 72 h. The flavour and keeping quality of ghee were improved byStr. diacetylactisandStr. lactiswhilstStr. thermophilusandL. bulgaricushad no effect.
Effect of use of milk concentrated by ultrafiltration on the manufacture and ripening of Cheddar cheese
Authors: Green Margaret L. , Glover Frank A. , Scurlock Elizabeth M. W. , Marshall Richard J. , Hatfield David S.
Published: June 2009

Milks were prepared at 1·7- to 4-fold the initial concentration by combining skim-milk concentrated by ultrafiltration with cream, and used for Cheddar cheese-making. Starter growth was unaffected, but the increased buffering capacity in the more concentrated milks resulted in a slower decline in pH and a higher pH value in the cheese. Curd formation was faster despite the use of reduced amounts of rennet. With milk concentrated more than 2-fold, large amounts of fat were lost in the whey, so that the cheeses had less fat than normally. Fat losses may be partly related to the lower degree of aggregation of the casein micelles when the curd was cut. As the concentration factor of the milk increased, the rate of casein breakdown, the intensity of Cheddar flavour, and the levels of H2S and methanethiol in the cheese decreased. These factors may relate to the reduced concentration of active rennet retained in the curd at pressing.
Immunological identification of milk-clotting enzymes
Authors: Collin Jean-Claude , de Retta Graciela Muset , Martin Patrice
Published: June 2009

The 6 most widely used milk-clotting enzymes, i.e. chymosin, bovine and porcine pepsins and proteinases from Mucor miehei, M. pusillus and Endothia parasitica, have been purified and used to prepare rabbit antisera against each of them. The antisera were adsorbed with appropriate cross-linked antigens to remove non-specific antibodies. Monospecific antisera thus obtained were used to identify enzymes eventually added to calf or bovine rennets, using the double radial immunodiffusion technique. The threshold of sensitivity was c. 1%, expressed as clotting activity. This qualitative method complements the quantitative procedure recently proposed for determining chymosin and bovine pepsin A in commercial extracts of bovine veils.
Sources of Streptococcus uberis in the dairy herd: II. Evidence of colonization of the bovine intestine by Str. uberis
Authors: Kruze Juan , Bramley A. John
Published: June 2009

Swabs taken from the rectum and vulva of 14 dairy cows on 7 occasions at approximately weekly intervals revealed a pattern of isolations of Streptococcus uberis which were not random. Two of the 14 cows were responsible for 80 and 40% respectively of the swabs of the rectum and vulva which were found to be positive. It is suggested that these patterns are consistent with these 2 cows being intestinally colonized with Str. uberis. The implications of this work are discussed with reference to the sources of Str. uberis in the dairy herd.
Some aspects of the ethanol stability of caprine milk
Authors: Horne David S. , Parker Thomas G.
Published: June 2009

Caprine skim-milk exhibits markedly lower ethanol (EtOH) stability than bovine skim-milk but can still be characterized by a sigmoidal pH profile. As with bovine milk, the position of this profile along the pH-axis was found to be sensitive to available Ca levels. Manipulation of salt levels, either by serum interchange, addition or diminution did not result in any significant increase in the EtOH stability high pH asymptote, Smax, and reduction of the colloidal calcium phosphate of caprine milk also had no significant effect. EtOH stability/pH profiles similar to those of bovine milk were achieved only by chemical modification of the caprine milk protein by reaction with aldehydes and anhydrides. It is concluded that the low EtOH stability of caprine milk as compared with bovine milk is due to the different proportions of the individual caseins present, in particular the lack of an αsl-casein homologue in caprine milk.
A study of proteolysis during Camembert cheese ripening using isoelectric focusing and two-dimensional electrophoresis
Authors: Trieu-Cuot Patrick , Gripon Jean-Claude
Published: June 2009

SUMMABY

Isoelectric focusing and 2-dimensional electrophoresis were used to study the development of the pH 4·6-insoluble fraction during Camembert cheese ripening. Modifications of this fraction were due mainly to the action of 5 proteinases: rennet (chymosin + bovine pepsin), plasmin and Penicillium caseicolum aspartyl-and metalloproteinases. Rennet was inactive on β-casein, but acted very early on αs1-casein. However, rennet and P. caseicolum aspartyl-proteinase had a very similar action on the latter substrate, which prevented clear definition of the respective actions of these proteinases on αs1-casein after 7 d of ripening. Plasmin action on β-casein was important from 21 and 35 d of ripening at the surface and in the centre of the cheese respectively, suggesting an important influence of pH changes during maturation. The respective activities of the metallo-and aspartyl-proteinases of P. caseicolum were characterized and followed using β-casein degradation products as markers. The metallo-proteinase activity was detectable immediately after the development of the Penicillium (7 d), while that of the aspartyl-proteinase was observed 3 d later. Thereafter, the amount of β-casein degradation peptides resulting from the metalloproteinase decreased while that resulting from the aspartyl-proteinase increased, suggesting a more important role of the latter enzyme.
Investigations into falsely elevated somatic cell counts of bulked herd milk
Authors: Hoare Roderic J. T. , Nicholls Paul J. , Sheldrake Richard F.
Published: June 2009

Bulk milk cell counts obtained by a Coulter Milk Cell Counter were shown to be falsely elevated because of the formation of non-cellular particles (NCP). The NCP, which were detected by the use of a particle size analyser, were removed if the milk samples were heated to 55 °C for 15 min before the addition of formalin. A survey of bulk milk supplies in New South Wales showed that NCP occurred in milk from 2 % of farms, the counts being falsely elevated by about 200000 cells/ml. Surveys of milking equipment of farms where the bulk milk had shown this phenomenon demonstrated a relationship between the use of centrifugal milk pumps and the presence of NCP with a much lower prevalence in herds where spit chamber releasers were used. These particles were not air bubbles since air was removed from the milk by heating to 60 °C for 5 min, vacuum at 65 mmHg for 15 minor 0·5% v/voctan-2-ol; only the heat treatment removed the NCP.
A yoghurt-like product made by fermenting ultrafiltered milk containing elevated whey proteins withLactobacillus acidophilus
Authors: Marshall Valerie M. , Cole Wendy M. , Vega J. Roberto
Published: June 2009

A fermented milk with typical yoghurt flavour and aroma was prepared using a human strain ofLactobacillus acidophilus. Growth of the lactobacillus was stimulated when the whey proteins of the ultrafiltered skim-milk substrate were increased by addition of ultrafiltered Cheddar cheese whey. Fermentation, which was carried out at 37 °C, was accelerated by addition of lactase. The resulting product had a smooth consistency, a pH of 4⋅2, acetaldehyde levels up to 15 p.p.m. and no off-flavours.L. acidophilusremained viable at a level of approx. 108colony forming units/ml, with no impairment of quality, for up to 14 d at 4 °C.
Nitrogen content of human milk: limitations of spectrophotometry for the determination of protein in milk
Authors: Hudson Geofrey J. , Lucas Alan
Published: June 2009

Nakai & Chi Le (1970) have described a rapid method for the determination of the N content of bovine milk based on the close correlation of absorbance at 280 nm with values for total N as determined by the Kjeldahl procedure. The applicability of the method to human milk samples has been investigated. The procedure is limited by: (1) the dependence of the relation between absorbance value and N content on both the mode of collection and the postnatal age of the donor, and (2) variable interference by non-protein components of the milk. In spite of these shortcomings, the method may be of value as a screening test for certain human milk banks.
Growth of an extracellular proteinase-deficient strain of Pseudomonas fluorescens on milk and milk proteins
Authors: Torrie Joan P. , Cholette Hilaire , Froehlich Debbi A. , McKellar Robin C.
Published: June 2009

An extracellular proteinase-and lipase-deficient mutant of a psychrotroph, Pseudomonas fluorescens strain 32A, has been isolated and the absence of the proteinase enzyme confirmed by growth on differential media, enzyme assay and polyacrylamide gel electrophoresis. Competition between the parent and the mutant was observed when equal numbers of the 2 strains were inoculated together into raw skim-milk at 6 °C. Bitterness was detected at 6 °C in pasteurized skim-milk inoculated with the parent cells concurrent with the detection of proteolytic activity. In the case of the mutant, slight bitterness which did not increase with increasing cell numbers was detected in the absence of proteolysis. Mutant cells failed to grow on Na caseinate as the sole source of carbon. It was concluded that the extracellular proteinase, while not essential for growth in milk, does provide a selective advantage to the producer organism. This enzyme is, however, essential for growth on milk proteins and contributes to the development of bitterness in pasteurized milk.
Purification and characterization of porcine κ-casein
Authors: Cerning-Beroard Jutta , Zevaco Claude
Published: June 2009

κ-casein from porcine milk was isolated and purified by affinity chromatography on thiopropyl Sepharose followed by hydroxyapatite chromatography. The amino acid composition of this protein is similar to that of bovine κ-casein. The sugar composition was established and sow κ-casein was found to be highly glycosylated. It contains 12 N-acetylneuraminic acid, 10 N-acetylgalactosamine, 2 N-acetylglucosamine and 22 galactose residues.
An automatic method for measuring the heat coagulation time of milk powder solutions
Authors: Foissy Helmut , Kneifel Wolfgang
Published: June 2009

An apparatus for the objective determination of the heat coagulation time of milk powder solutions is described. In the apparatus a chromium plated iron piston is moved by means of a ring magnet, driven by a control mechanism, through a heated cylinder containing a small sample of milk. When the milk coagulates, the increased impedance between the inner wall of the cylinder and the metal piston overcomes the magnetic strength of the ring magnet and the magnetic coil moves away from the piston core, resulting in a momentary change in coil current, which after amplification is used to stop a digital clock. The method was tested with 10 and 20 % milk powder solutions at various pH values, at temperatures of 120 and 140 °C. The results are comparable with those obtained using a traditional method involving visual determination of coagulation (Davies & White, 1966).