bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of homogenization of concentrated milks on the structure and properties of rennet curds
Authors: Green Margaret L. , Marshall Richard J. , Glover Frank A. 
Published: June 2009

SummaryWhole milk was concentrated by ultrafiltration in a plant causing some homogenization of the fat. Comparisons were made with milk concentrated in a plant causing little homogenization and with milk homogenized conventionally. None of the processes appreciably affected the casein micelle size distribution. On rennet treatment of homogenized milk, casein micelle aggregation occurred more slowly, the protein network in the curd was less coarse and the rate of whey loss was reduced, compared with non-homogenized milk at the same concentration. In using concentrated milks for cheesemaking homogenization improved the composition of Cheddar cheese, because of increased fat and moisture retention, but curd fusion was poorer. Some aspects of the texture of the mature cheeses were improved, but the free fatty acid levels were higher. Values for the firmness of curds, formed from milks processed in different ways, did not relate to the extent of aggregation of the casein micelles. It is suggested that the complete cheesemaking process is driven by the tendency of the casein to aggregate.
Suitability of some microbial coagulants for Feta cheese manufacture
Authors: Alichanidis Efstathios , Anifantakis Emmanuel M. , Polychroniadou Anna , Nanou Marinela 
Published: June 2009

SummaryThree microbial rennets, Noury rennet (Mucor pusillus, Lindt), Rennilase (M. miehei) and Suparen (Endothia parasitica), were assessed as calf rennet substitutes for Feta cheesemaking, in comparison with calf rennet. Cheeses prepared were all of good quality with similar organoleptic properties. Yield (referred to 55% moisture), moisture content, NaCl and protein content did not differ significantly. Different rates of proteolysis were observed in the cheeses, the highest of which was exhibited by calf rennet followed by Rennilase, Noury rennet and Suparen preparations. These calf rennet substitutes are well suited for Feta cheese manufacture.
Effect of prazosin on the function of the teat sphincter in lactating cows
Authors: Messom Georgette Vandeputte-Van , Bernabé Jacques , Burvenich Christian , Peeters Georges 
Published: June 2009

SummaryOxytocin was infused for 60 min into the jugular vein of 8 lactating cows with full udders before milking. Under these circumstances milk loss occurred spontaneously in 3 cows and was evoked in 5 cows by reducing pressure around one teat (–30 cm water) using a plethysmographic chamber. Milk loss was measured continuously. The postsynaptic α-blocking agent prazosin (PRZS) injected either into the udder artery (2 or 5 mg) or into the jugular vein (200 mg) consistently induced a significant increase in milk leakage. It is suggested that PRZS effectively inhibits α-adrenoceptors in the teat sphincter muscles and thus promotes the action of β-adrenoceptors, in this way inducing relaxation of the teat sphincter.
Isolation and composition of milk fat globule membrane material
Authors: McPherson Avis V. , Dash Mary C. , Kitchen Barry J. 
Published: June 2009

SummaryMilk fat globule membrane (MFGM) material was isolated from commercial pasteurized milks and pasteurized creams using a procedure specifically adapted for these products (McPhersonet al.1984a). Pasteurized cream membranes contained higher lipid levels while pasteurized milk membrane material had lower lipid contents than fresh raw MFGM. Electrophoretic analysis showed that membrane material from both commercial products contained, in addition to native MFGM polypeptides, significant amounts of β-lactoglobulin with lower levels of caseins and other skim-milk components. The incorporation of β-lactoglobulin was more pronounced in pasteurized cream membranes. Examination of the lipoprotein complexes present in these membrane preparations by linear sucrose density gradient centrifugation showed that pasteurized milk membrane material had a similar profile to fresh raw MFGM except that preferential binding of skim-milk components was found in some of the lipoprotein fractions. Pasteurized cream membranes showed considerably different density gradient patterns with only 2 lipoprotein fractions present, of which the major one was a low density complex.
Measurement of electrophoretic mobilities and zeta-potentials of particles from milk using laser Doppler electrophoresis
Authors: Dalgleish Douglas G. 
Published: June 2009

SummaryThe use of a commercial laser Doppler electrophoresis apparatus to measure electrophoretic mobilities of milk constituents is demonstrated, and calculations of apparent ζ-potentials from these mobilities are given. Systems studied were: native and renneted casein micelles suspended in milk ultrafiltrate and different buffers containing Ca2+, particles from homogenized milk before and after renneting, fat globules, and homogenized fat/caseinate systems. The results confirmed previous estimates of the ζ-potentials of these materials, but also extended to cover the effect of changing the concentrations of Ca2+ and other salts on the electrokinetic properties of the particles. Increasing concentration of Ca2+ caused considerable decrease in the ζ-potentials of native and renneted casein micelles, and temperature increase caused the apparent ζ-potential to increase in both cases. Particles from homogenized milk showed ζ-potentials very similar to those of native casein micelles, and renneting of the homogenized milk gave behaviour similar to renneted casein micelles. The ζ-potential of the homogenized materials could be distinguished clearly from those of native fat globules. Likewise, milk fat which had been homogenized using whey protein showed distinct differences in its surface properties from particles based on caseinate or casein micelles.
Catabolism of L-phenylalanine by some microorganisms of cheese origin
Authors: Lee Chang-Won , Richard Jean 
Published: June 2009

SummaryThe ability of 42 microorganisms isolated from cheese, including strains of yeasts,Geotrichum candidum, Arthrobacter, Moraxellaspp.,Brevibacterium linensandStaphylococcus saprophyticusspp. to produce phenethyl alcohol (PEA) from L-phenylalanine was studied. All the yeast strains produced labelled PEA from L-[U-14C]phenylalanine. Phenylpyruvic acid was detected as an intermediate of PEA production and CO2was produced by decarboxylation of this acid. For five strains tested, the level of PEA which had accumulated in the culture at the end of exponential growth phase represented 39–52% of the L-Phe added. None ofG. candidumstrains nor bacterial isolates produced PEA from L-Phe. Strains ofMoraxellaspp. and four strains of theS. saprophyticusgroup produced phenylacetaldehyde. For three strains ofArthrobacterspp., five ofB. linensand all theMoraxella,14CO2produced from uniformly labelled L-Phe represented more than one carbon atom of the L-Phe molecule, suggesting that Phe was catabolized beyond the stage of phenylacetic acid. Production and disappearance of PEA during Camembert cheese ripening is probably related to the metabolic activity of microorganisms present at the cheese surface.
Yield and composition of milk from Friesian cows grazing either perennial ryegrass or white clover in early lactation
Authors: Thomson David J. , Beever David E. , Haines Michael J. , Cammell Stephen B. , Evans Roger T. , Dhanoa Mewa S. , Austin Anthony R. 
Published: June 2009

SUMMARYThe yield and composition of milk from Friesian cows grazing either perennial ryegrass (Lolium perenne) (G, ten cows) or white clover (Trifolium repens) (C, nine cows) were evaluated between d 21 and 129 post partum. The two forages, of similar digestible energy content, were the sole source of nutrients and were offeredad lib. (exp. 1). Digestion and flow at the duodenum were measured on 13 occasions in early lactation with comparable cows fitted with rumen and duodenal cannulae and grazing similar forages (exp. 2). The gross milk yield (22·2, G; 25·0, C, kg/dP< 0·05) and the yield of protein (0·66, G; 0·77, C, kg/d,P< 0·01) were higher, but the protein content was similar and the fat content lower for cows fed C compared with G. Cows fed G were heavier at the beginning of the experiment and lost weight more rapidly than cows fed C. Milk energy output, adjusted for tissue energy gain or loss, was 83·9 for cows fed C compared with 71·8 MJ/d for cows fed G (P< 0·001), during the period of tissue energy repletion (weeks 11–18). From week 18 to the end of lactation all cows from exp. 1 were fed silagead lib. and 502 kg dry matter of concentrates. The total (305 d) difference in lactation response to grazing C compared with G was 931 1 (5657 1, C; 4726 1, G); this was a direct response during the experiment of 301 1 and a residual response of 630 1. In exp. 2, more organic matter (6·47, G; 8·01, C, kg/ d,P< 0·001), and more non-ammonia N (433, G; 575, C, g/d,P< 0·001) entered the duodenum of cows grazing C compared with G.
Lipolysis and the distribution of lipase activity in bovine milk in relation to stage of lactation and time of milking
Authors: Ahrné Lennart , Björck Lennart 
Published: June 2009

SUMMARYThe increase in levels of free fatty acids (FFA) in morning and afternoon milk after 48 h cold storage at 5 °C was determined at two stages of lactation in milk from 96 cows. Lipolysis was positively correlated to day of lactation (r= 0·6,P< 0·001), while the correlations between lipolysis and milk yield and fat content respectively were due to these factors being related to day of lactation. In afternoon milk the level of FFA increased almost three times above that in morning milk. Lipolysis was closely related to the lipoprotein lipase (LPL) activity associated with the cream fraction (r= 0·8,P< 0·001). Afternoon milk had higher LPL activity in the cream fraction than morning milk. Lipase activity in the cream increased with increasing stage of lactation. Cooling of milk increased LPL activity associated with the fat phase. This effect was greater in afternoon milk from late lactation than in morning milk from early lactation. When heparin was added to milk the LPL activity associated with the fat increased substantially; again, this effect was greater in afternoon milk from late lactation than in morning milk from early lactation. Lipolysis was higher in heparinized milk than in normal milk, and there was a close correlation between lipolysis and LPL activity associated with the fat (r= 0·82,P< 0·001). Characteristics of the milk fat globule influencing the attraction of LPL were found to be fundamentally important to lipolysis.
Role of oxygen radicals in the bacteriostatic effect of whey and production of bacterial growth by free radical scavengers
Authors: Mattila Tiina 
Published: June 2009

SUMMARYThe involvement of toxic oxygen intermediates in the bacteriostatic effect of milk was determined by producing bacterial growth curves using turbidimetry in the presence and absence of oxygen radical-scavenging substances. Using whey as substrate, catalase, haemoglobin combined with ascorbic acid and xanthine oxidase inhibitors all provided protection against oxygen toxicity for a strain ofStaphylococcus aureusand ofStreptococcus agalactiae. Superoxide dismutase and mannitol were less effective. This was evident in whey alone and in the presence of oxygen radicals produced exogenously by the t-butylhydroperoxide, H2O2and xanthine/xanthine oxidase systems.
Comparison of the structure of micellar calcium phosphate in milk from six species by extended X-ray absorption fine structure spectroscopy
Authors: Irlam James C. , Holt Carl , Hasnainj S. Samar , Hukins David W. L. 
Published: June 2009

SUMMARYExtended X-ray absorption fine structure spectra, above the Ca K absorption edge, were recorded from lyophilized casein micelles obtained from the milk of cow, pig, goat, rabbit and rat. A spectrum was also obtained from the calcium phosphate prepared from the casein micelles of human milk. Comparison of these spectra showed that the short-range environment of calcium in the micellar calcium phosphate was the same in all six species. Furthermore, these spectra closely resembled that of brushite (CaHP04. 2H20). However, X-ray diffraction showed no evidence for an extensive crystal lattice in micellar calcium phosphate.
Products of the heat-promoted reaction between urea and the protein fraction of bovine milk
Authors: Manson William , Carolan Thomas , Annan W. Douglas 
Published: June 2009

SUMMARYEnzymic digests of samples of heated skimmed milk were found to contain small amounts of S-carbamyl-L-cysteine. This material was concluded to have arisen from reaction of a cysteinyl residue in βlactoglobulin (β-lg) with cyanate derived from the native urea of bovine milk. After heating at 75 or 90 °C for 20 min skimmed milk contained 0·009 and 0·029 μmol/ml respectively of protein-bound S-carbamyl-cysteine. Evaporated milk contained 0·058 μmol/ml. The S-carbamylcysteine contents of samples of β-lg heated under similar conditions in equimolar 0·17 mM-KCNO at pH 6·6 were 0·016 and 0·062 μmol/ml respectively. At 60 °C no formation of S-carbamyl-cysteine was detected. Samples of evaporated milk and skimmed milk which had been heated for 20 min at 60, 75 or 90 °C were examined, after acid hydrolysis, for the presence of homocitrulline. None was found. Similarly αs1- and β-caseins heated at 60 and 75 °C in 4 mM-urea at pH 6·6 yielded no homocitrulline, but after treatment at 90 °C for 20 min αs1-casein contained 68 μg/g and β-casein contained 73 μg/g protein-bound homocitrulline. This was concluded to have been the product of reaction of cyanate and ε-amino groupings of lysyl residues of the caseins. The relative importance of carbamylation involving ε-amino groups or sulphydryl groups in milk is discussed.
Centrifugal fractionation of homogenized milks
Authors: Dalgleish Douglas G. , Robson Elizabeth W. 
Published: June 2009

SUMMARYA set of 12 fractions was isolated from homogenized cows' milk by a method of successive centrifugation steps. The fractions were analysed in terms of fat and protein contents and the diameters of the particles in them were also measured. Detailed comparisons of the turbidities of the samples and their light scattering properties allows comparison between them. It is concluded that the separation is less effective than a similar technique applied to casein micelles, but nonetheless that the different fractions do contain particles with different properties.
Complementary action of dipeptidyl peptidase IV and aminopeptidase M in the digestion of β-casein
Authors: Heymann Eberhard , Mentlein Rolf 
Published: June 2009

SUMMARYPurified bovine β-casein was digested in vitro with varying mixtures of purified proteinases and peptidases including trypsin, chymotrypsin, dipeptidyl peptidase IV (DP IV), aminopeptidase M and prolidase. In digestion mixtures without DP IV the yield of free amino acids was considerably lower than in the corresponding assays with this peptidase. Especially, the release of proline increases drastically from almost zero to the theoretical amount in the presence of DP IV. Quantitative results indicated that the specificities of the two microvillar peptidases (aminopeptidase M and DP IV) optimally complemented each other. This effect elucidates the hitherto obscure physiological role of intestinal DP IV. A similar effect may also apply to other caseins and nutritional proteins.
Keeping quality of milk in relation to the copper content and temperature of pasteurization
Authors: Ford John E. , Schröder Monika J. A. , Bland Michael A. , Blease Kim S. , Scott K. John 
Published: June 2009

SUMMARYFor milk from four herds of cows, maintained under different conditions of feeding and management, the natural Cu content and the stability of the ascorbate were highly correlated. Low Cu levels in milk from cows at pasture at farms A and B during the summer were associated with low storage losses of ascorbate. During this period, the milk of cows at farms C and D (on forage and Cu-supplemented concentrate) was richer in Cu, and losses of ascorbate were high. Heat treatment of the milk stabilized the ascorbate. Thus, in ‘high Cu’ milk (60 µg Cu/l), loss of ascorbate in the raw milk was 58% at 2 d, as against 17% after pasteurization at 72 °C and no loss after treatment at 82 °C. Storage of milk in light caused rapid destruction of ascorbate, equally with 72 and 82 °C heat treatments. The effects were examined of milk pasteurization temperature (72–82 °C) on flavour stability, bacteriological quality and vitamins of the B-complex. Heat treatment at 82 °C increased the susceptibility of vitamin B12to destruction by light, but otherwise caused no greater losses of B-complex vitamins than did treatment at 72 °C. Taste panel ratings showed an initial preference for milk heated at 72 °C, but on storage of this milk in darkness the flavour score fell progressively and at 5 d it was judged ‘stale’. Treatment at 82 °C gave a faint ‘cooked’ flavour although, unlike that of the 72 °C-treated milk, the flavour remained stable throughout 14-d storage and after d 8 was increasingly preferred. On exposure to light after treatment at 72 °C milks rapidly acquired an unpleasant‘oxidized’ flavour, but after treatment at 82 °C, exposure to light had no such adverse effect on flavour during the early days of storage. Pasteurization at ∼ 80 °C offers a potential for improvement in the oxidative stability of milk and its contribution of vitamin C to the diet.
Effects of milk protein genetic variants and composition on heat stability of milk
Authors: McLean Douglas M. , Graham E. R. Bruce , Ponzoni Raul W. , Mckenzie Hugh A. 
Published: June 2009

SummarySkim milk samples from 126 Friesian and 147 Jersey cows in eight commercial herds were preheated at 85 °C for 30 min and concentrated to 200 g l−1 total solids. A heat coagulation time–pH curve was determined at 120 °C for each treated sample. Heat coagulation times ranged from 1 to 50 min at the non-adjusted pH and 1 to 60 min at the pH of maximum stability. The following statistically significant effects were found. Maximum heat stability was affected by genetic variants of κ-casein (B > AB > A; P < 0·001) and β-lactoglobulin (B, AB>A; P < 0·05) whereas natural heat stability was affected only by κ-casein genetic variants (B > AB > A; P < 0·001). Maximum and natural heat stability were corre-lated positively with β-casein and κ-casein concentrations and were negatively correlated with αs1-casein and β-lactoglobulin concentrations. Milk from Jersey cows had greater maximum and natural heat stability than milk from Friesian cows. Differences were found between herds within breed for natural heat stability, but not for maximum heat stability. Maximum heat stability declined with age of the cow. The heat stability of skim milk samples taken from 40 Jersey cows in one of the herds was determined at 140 °C. A considerable variation was found in the coagulation time–pH curves. There was a difference in natural heat stability between κ-casein variants (B > AB; P < 0°05). Natural and maximum heat stability were correlated positively with urea concentration. No relationship was found between the heat stability of preheated concentrated skim milk and the heat stability of the original skim milk. The pH of skim milk samples was associated with αs1-casein genetic variant, age of cow, stage of lactation and concentration of γ-casein.
Peptidases from two strains ofPseudomonas fluorescens: partial purification, properties and action on milk
Authors: Shamsuzzaman Kazi , McKellar Robin C. 
Published: June 2009

SummaryPseudomonas fluorescensstrains 240 and 32A expressed cell-associated peptidase activity which was shown by subcellular fractionation to be primarily intracellular. Two peptidases were partly purified from strain 32A. One specifically hydrolysedN-α-benzoyl-DL-arginine-4-nitroanilide and was termed endopeptidase and the other hydrolysed L-lysine- and L-leucine-4-nitroanilide and was termed aminopeptidase. The endopeptidase had very low activity on bovine serum albumin compared with that of trypsin and probably was not a proteinase. The endopeptidase had a mol. wt of 33000 and a pH optimum of 8·0. The enzyme was stimulated by Ca2+and Mg2+and inhibited by Co2+, Mn2+, Hg2+, Zn2+and leupeptin. Soya bean trypsin inhibitor and phenylmethane sulphonyl fluoride (PMSF) had no effect on its activity. The aminopeptidase had a mol. wt of 44000 and a pH optimum of 8·0. It was inhibited by all the metal ions mentioned above and by PMSF. Little proteolysis was found when ultra high temperature (UHT) sterilized milk was treated with cell-free extract from strain 32A. It was concluded that the cell-associated peptidases fromPseudomonasstrains normally present in raw milk may not contribute significantly to the deterioration of UHT sterilized milk.
Influence of pH, type of enzyme and ultrafiltration on the retention of milk clotting enzymes in Camembert cheese
Authors: Garnot Pascaline , Molle Daniel , Piot Michel 
Published: June 2009

SummaryCamembert cheeses were made with pasteurized skim milk or with ultrafiltered milk concentrated 2-fold, using either rennet or Mucor miehei proteinase as coagulant. Using rennet, the rapid acidification during cheesemaking increased enzyme retention and 55% was retained after 24 h. With the M. miehei proteinase, acidification had no effect and only 17% of it was retained after 24 h. The use of ultrafiltered milk resulted in less rennet being retained in the curd.
Compressive load applied by the teatcup liner to the bovine teat
Authors: Mein Graeme A. , Williams David M. , Thiel Cliff C. 
Published: June 2009

SummaryThe magnitude of the cyclic load applied to the teat apex by the collapsed liner during milking was estimated by measuring the pressure required to cause retrograde flow of milk into the teat canal from a manometer attached to the external teat orifice. The study was extended by observation of the milk flow cycle within a transparent teatcup assembly and by pressure recordings within the teat canal using a catheter-tip transducer. The source of the force compressing the teat is the small airspace, within the collapsed liner, directly below the teat apex. The total force generated is determined mainly by the size of this airspace and the pressure difference (PD) acting across the opposing liner walls. When the PD reached 80–90% of the liner vacuum, the load was just sufficient to occlude the teat canal. Further increase in PD provided the compressive load capable of offsetting vascular congestion of the teat apex. Increasing liner tension increased the load applied. The narrow range of compressive loads applied by conventional liners (5–12 kPa above atmospheric pressure) may be sufficient to offset congestion and oedema in the teat. Loads greater than the mean arterial pressure within the teat apex might serve only to expose the tissues to non-productive compression.