bluuebunny/crossref_metadata_2025_split huggingface dataset:
Irreversible heat denaturation of bovine α-lactalbumin
Authors: Chaplin Lesley C. , Lyster Richard L. J. 
Published: June 2009

SUMMARYThe irreversible heat denaturation of α-lactalbumin (α-la) in 0·1 M-phosphate, pH 7·0, at 100 °C was studied using polyacrylamide-gel electrophoresis (PAGE). PAGE revealed two groups of bands, one moving faster than native α-la and one slower, in addition to some denatured protein which remained at the origin and some residual native α-la. The faster group had unchanged molecular weight, but an increase in charge, partly due to hydrolysis of glutamine and asparagine residues. The slower group was shown by two-dimensional sodium dodecyl sulphate-PAGE to be oligomers of denatured α-la; formation of the smaller oligomers preceded the larger ones. The oligomers reverted to monomers in the presence of dithiothreitol, showing that they were disulphide-linked aggregates of denatured α-la. Immuno-blots of the gels showed that both fast and slow groups of bands had irreversibly lost most of the antigenicity of the native protein.
Determination of tensile strength of gels prepared from fractionated whey proteins
Authors: Langley Keith R. , Millard David , Evans E. William 
Published: June 2009

SUMMARYA novel method for measuring tensile strength of heat-setting gels is described and is applied to whey protein gels. Contributions made by β-lactoglobulin and α-lactalbumin individually to the tensile strength of the gel are calculated. The tensile strength can be found from power law equations related to concentration of α-lactalbumin and β-lactoglobulin in whey protein mixtures.
Phage typing of Staphylococcus aureus associated with subclinical bovine mastitis
Authors: Mackie Dermot P. , Pollock David A. , Rodgers Sean P. , Logan Ernest F. 
Published: June 2009

SummarySix hundred and seventeen isolates of Staphylococcus aureus from sub-clinical mastitis cases in 63 dairy herds in Northern Ireland were typed using a set of 25 phages. Ninety-four per cent of the isolates were typable, with nine phages, predominantly from groups I and III, being responsible for almost all of the lysis. Although 68 phage patterns were found, six of them typed 47·2 % of the isolates. One strain accounted for 14·7% of the isolates, but the largest number of strains (44) was restricted to individual farms. The epidemiological significance of these findings for on-farm mastitis control is discussed.
Metabolism of the lactating cow: I. Animal elements of a mechanistic model
Authors: Baldwin R. Lee , France James , Gill Margaret 
Published: June 2009

SummaryA mechanistic model of dairy cow metabolism is described. The model was constructed as part of a programme directed toward quantitative and dynamic analysis of concepts and data regarding factors which influence the partition of nutrients in lactating dairy cows. Sensitivity and behavioural analyses undertaken using the model indicate that concepts and data arising from tissue level experiments conducted in vitro can be used to structure and parameterize whole-animal models since the quantitative and dynamic behaviour of such a model is acceptable. These analyses indicate further that such models can be used to evaluate factors which influence patterns of nutrient utilization. By way of illustrating the model's utility regarding evaluation of concepts relating to the interpretation of energy balance experiments, results of a simulated energy balance experiment are presented. Apparent costs of milk synthesis are partitioned among biosynthetic costs, physiological costs, ion transport costs and the reductions in energy expenditures in synthesis of body components which accompany increasingly negative energy balances due to feed restriction.
Formation of volatile aroma compounds and carbon dioxide in yogurt starter grown in cows' and goats' milk
Authors: Rysstad Gunnar , Abrahamsen Roger K. 
Published: June 2009

SummaryYogurt starter B3 was grown in cows' milk, goats' milk I (obtained 2–3 weeks after parturition) and goats' milk II (8 months after parturition), and a number of biochemical and bacteriological parameters were recorded at intervals during incubation for 8 h at 43°C. No appreciable differences between the milks were observed for total viable count, bacteriological ratio of rods to cocci, or decrease in pH. Production of acetaldehyde, however, was considerably lower in goats' milk I (6·2 ppm) and goats' milk II (8·9 ppm) than in cows' milk (18 ppm). Formation of diacetyl and acetoin showed similar patterns in all three milks. The highest production of α-acetolactic acid was observed in goats' milk II, apparently coincident with the highest production of CO2 in this milk.
Heat stability of milk: influence of modifying sulphydryl-disulphide interactions on the heat coagulation time–pH profile
Authors: Singh Harjinder , Fox Patrick F. 
Published: June 2009

SummaryAddition of reducing agents such as 2-mercaptoethanol (2-ME), dithio-threitol and Na sulphite to milk markedly reduced its heat stability at pH values below 7·1. 2-ME reversibly destabilized milk or serum protein-free casein micelle dispersions and promoted the release of κ-casein-rich protein from the micelles. Reduction of either casein micelles or β-lactoglobulin (β-lg) with 2-ME and subsequent blocking of the newly formed –SH groups with N-ethylmaleimide irreversibly reduced the maximum to minimum ratio in the heat stability profile. 2-ME disrupted κ-casein/β-lg complexes and stripped κ-casein from the micelles on heating. The milk or caseinate systems were thus destabilized. Addition of KBrO4or iodosobenzoate to milk at 5 HIM eliminated the minimum but destabilized milk in the region of the maximum. However, KIO3at 5 mm had a strong stabilizing effect throughout the pH range 6·5–7·3.
Microbiological quality and composition of two types of Spanish sheep's milk cheeses (Manchego and Burgos varieties)
Authors: García María Camino , Otero Andrés , García María Luisa , Moreno Benito 
Published: June 2009

SummaryThirty six samples of Manchego and 36 of Burgos cheese from retail outlets were examined. The mean log microbiological counts/g in Manchego cheese were 2·6 coliforms, 3·76 enterococci, 7·07 lactic acid bacteria, 8·02 mesophiles, 3·84 psychrotrophs 4·47 yeasts and moulds and 4·11 staphylococci, and in Burgos cheese were 7·17, 3·45, 7·25, 8·89, 8·18, 5·09 and 5·12 respectively. Coagulase-positive staphylococci were detected only in three samples of Manchego cheese, one of these isolates producing enterotoxin A. Staphylococcal thermonuclease was detected in eight samples of Manchego and 12 of Burgos cheese, the mean values of enzyme detected being 0·29 and 0·32 ng/g cheese respectively. Staphylococcal enterotoxins were not detected in any of the cheeses tested. Possible relationships between microbial counts and physicochemical characteristics were investigated by regression analysis.
Histochemical localization and possible antibacterial role of xanthine oxidase in the bovine mammary gland
Authors: Collins Robert A. , Parsons Keith R. , Field Terry R. , Bramley A. John 
Published: June 2009

SummaryXanthine oxidase (XO) was demonstrated to be present in the teat canal and secretory tissue of the bovine mammary gland by histochemical techniques. Homogenates of these tissues were able to replace XO in an antibacterial assay with Streptococcus uberis. The action of XO on its substrate hypoxanthine was shown to provide an essential component for anti-streptococcal activity mediated by lactoperoxidase. A mechanism is proposed whereby the interaction of XO, lactoperoxidase and thiocyanate may provide antibacterial activity in the teat canal.
Partial purification and characterization of an extracellular proteinase fromAeromonas hydrophilastrain A4
Authors: Alichanidis Efstathios 
Published: June 2009

SummaryAn extracellular metalloproteinase fromAeromonas hydrophilastrain A4, isolated from milk, was purified by a factor of 300 by chromatogrpahy on DEAE-cellulose and Sephadex G-150. The enzyme had a mol. wt of 43000 and contained 2 g atom Ca/mol. It was active over a pH range 4·8–9·5 and had optimum activity on casein at pH 7·0 withKm= 0·17 mM. It was strongly inactivated by metal chelators and the apoenzyme was fully reactivated with Ca2+, Mn2+or Co2+. Heavy metal ions such as Ag+, Hg2+, Fe2+, Zn2+, Cd2+, Ni2+and Cu2+totally or partly inactivated the enzymic activity at 5 mM concentration. The enzyme was not inactivated by diisopropylfluorophosphate, soyabean trypsin inhibitor or sulphydryl group reagents. It was optimally active at 45 °C; above 50 °C activity declined rapidly, but significant activity persisted at 4 °C. It was heat labile in phosphate or Tris-maleate buffer but exogenous Ca2+afforded protection.
Uptake of glutamic acid byStreptococcus salivariussubsp.thermophilusCNRZ 302
Authors: Bracquart Patrice , Le Deaut Jean-Yves , Linden Guy 
Published: June 2009

SummaryGlutamic acid uptake inStreptococcus salivariussubsp.thermophiluswas energy dependent, the source of energy and adaptation to sugar being important to efficiency of uptake. The disaccharides, lactose and sucrose, stimulated uptake, but cells grown in glucose were more active. Optimum temperature was ˜ 40 °C and pH ˜ 7·0. NaCl was strongly inhibitory to the uptake of glutamic acid although not to that of isoleucine. High specificity existed because only L-aspartic acid was inhibitory.
Purification and thermostability of β-galactosidase (lactase) from an autolytic strain ofStreptococcus salivariussubsp.thermophilus
Authors: Chang Byeong-Seon , Mahoney Raymond R. 
Published: June 2009

Summaryβ-Galactosidase from an autolytic strain ofStreptococcus salivariussubsp.thermophiluswas purified 109-fold to near homogeneity. The yield of purified enzyme was 41% and the specific activity was 5920-nitrophenylβ-D-galactopyranoside U/mg at 37 °C. Two isozymes were present, but only one subunit was detected, having a mol. wt of 116000. Enzyme stability was 37–83 times greater in milk than in buffer in the range 60–65 °C. At 60 °C the half-life in milk was 146 min. Denaturation in buffer was first-order, but in milk the overall reaction order with respect to enzyme concentration was ˜ 0·5. The activation energy for denaturation was 453 kJ/mol in milk and 372 kJ/mol in buffer. In milk the activation energy for lactose hydrolysis was 35·1 kJ/mol.
Low resolution NMR spectroscopy: a tool to study protein denaturation: I. Application to diamagnetic whey proteins
Authors: Lambelet Pierre , Berrocal Rafael , Ducret Francine 
Published: June 2009

SummaryA method using low resolution NMR spectroscopy is described for investigating whey protein thermal denaturation. The method is based on measuring at 20 °C changes in water proton transverse (T2) relaxation parameter following the denaturing treatment. This parameter is shown to be sensitive to protein denaturation and not to other phenomena such as gelation. Examples are given for the qualitative study of protein thermal denaturation in whey protein concentratc, β-lactoglobulin, α-lactalbumin, bovine serum albumin and immunoglobulins aqueous solutions and for the quantitative determination of thermal denaturation in whey protein concentrate solutions.
Influence of chromatographically pure bovine chymosin and pepsin A on cheese curd syneresis
Authors: Andersson Hans , Andrén Anders 
Published: June 2009

SummaryThe influence of chromatographically pure bovine chymosin and pepsin A on cheese curd syneresis has been studied. The enzymes were compared in experiments using a microscale syneresis assay, where the light absorbance of the released whey was used as a measurement of the syneresis. The following parameters were investigated: reconstituted skim milk powder (RSM), bulk raw milk, CaCl2 addition and cutting time of the curd. The gelling (clotting) time was held constant under all experimental conditions to eliminate its influence on syneresis. The differences in influence on syneresis of the two enzymes were neither obvious nor uniform. As regards the syneresis of RSM, the influence of chymosin and pepsin seemed to be very similar, while the syneresis of bulk raw milk seemed to be more enhanced by chymosin. However, results were not sufficiently clear to prove any distinct differences between the enzymes. As long as the cheese curd is cut at a proper firmness, there are probably no practical problems in using bovine rennets with varying chymosin: pepsin ratio.
Ultraviolet spectroscopic studies and the prediction of the feathering of cream in filter coffees
Authors: Hamboyan Lucie , Pink David 
Published: June 2009

SummaryCream feathering was studied in sixteen samples made from six brands of filter coffee. We have used a predictive rule, deduced from our studies of instant coffees, to determine the likelihood of feathering occurring in filter coffee samples upon the addition of coffee cream. The predictive rule makes use of 1,3,4,5-tetra-hydroxycyclohexane carboxylic acid-3-[(3,4) dihydroxycinnamate] (chlorogenic acid) concentration in the coffee, and the ratio of ultraviolet absorbances at 261 nm and 340 nm. We found good agreement between the predicted and observed behaviour of samples of filter coffee and conclude that the predictive rule is reliable for both instant and filter coffees. The effect of increased fat content in the cream was also studied.
A model heat exchange apparatus for the investigation of fouling of stainless steel surfaces by milk II. Deposition of fouling material at 140 °C, its adhesion and depth profiling
Authors: Foster Carole L. , Green Margaret L. 
Published: June 2009

SummaryFormation and adhesion of fouling deposit during heating of milk at a stainless steel surface were studied separately using a model apparatus. The amount of deposit and proportion of minerals present increased with increase in surface temperature. At 140 °C, the amount of deposit formed increased linearly with heating time, becoming more uneven in appearance. The variations of deposit formation at 140 °C with pH of the milk, with fat removal and with preheating were similar to those observed in the final heating section of continuous UHT plants. Deposits containing a higher proportion of protein were easier to remove. The remaining inner layer had a smoother appearance and contained a higher proportion of minerals than the original deposit. Depth profiling, using secondary ion mass spectrometry, showed that protein was concentrated on the outside of deposits with calcium phosphate being concentrated closest to the steel surface.
Acidic coagulation of casein micelles: mechanisms inferred from spectrophotometric studies
Authors: Bringe Neal A. , Kinsella John E. 
Published: June 2009

SummaryThe acidic coagulation of casein micelles was monitored turbidimetrically at 400 nm using a Cary 219 spectrophotometer. Following acidification with HCI, the rate of coagulation during the initial stage of coagulation was proportional to the rate during the immediate subsequent stages, indicating that progressive stages of coagulation were controlled by similar factors and the slope at any portion of the reaction profile could be used to characterize the kinetics of the coagulation reaction. The rate of coagulation following acidification by glucono-δ-lactone was proportional to the reciprocal of the rate of acidification. The effects of environmental factors on the rate of the acidic coagulation of casein micelles over a range of pH values were evaluated from the smooth, hyperbolic profiles of pH v. coagulation rate. Determination of the pH required to initiate coagulation of casein micelles in skim milk ultrafiltrate at 5–25 °C, together with the maximum rates of coagulation at 5–25 °C, suggested that repulsive forces are reduced by acidification and con-sequently facilitate hydrophobic interactions resulting in the coagulation of casein micelles.
Characterization and kinetics of gastric emptying of peptides derived from milk proteins in the preruminant calf
Authors: Scanff P. , Yvon M. , Thirouin S. , Pelissffir J.-P. 
Published: June 2009

SummaryThe gastric emptying kinetics of peptides derived from milk protein were studiedin vivoin preruminant calves by collecting and characterizing the whole effluent leaving the stomach for 12 h after ingestion of crude skim milk. Peptides were isolated by reversed-phase HPLC and identified. Particular attention was paid to biologically active peptides and to peptides that could be precursors of biologically active sequences. A gastrin inhibitor, the caseinomacropeptide, was emptied from the stomach only during the first 0·5 h of digestion and rapidly hydrolysed. Precursors of immunostimulatory peptides from αs1- andβ-caseins were emptied throughout digestion in the gastric effluent. A precursor ofβ-casomorphins (peptide 58–93 ofβ-casein) was emptied from the stomach 3·5 h after the meal when it was taken on an empty stomach. From this precursor, peptides that may be resistant to hydrolysis by intestinal peptidase were obtained afterin vitrohydrolysis by pancreatic enzymes. A phosphopeptide (fragment 110–142 of αs1-casein) was also found in digesta after a few hours of digestion. When the meal was not taken on an empty stomach, these peptides were emptied in the first digesta at a low concentration. The potential activity of these peptides is discussed. The results support the hypothesis that active sequences could still be present in the gut after the action of pancreatic enzymes.
Effect of breed, protein genetic variants and feeding on cows' milk coagulation properties
Authors: Macheboeuf Didier , Coulon Jean-Baptiste , D'Hour Pascal 
Published: June 2009

SummaryOne hundred and thirty-seven (Holstein (41), Montbéliarde (42) and Tarentaise (54)) dairy cows in first or second lactation received during winter one of two levels (high, H; low, L) of energy intake, and were later fed identically at pasture. Thrice in winter and twice at pasture, the chemical composition and coagulation properties of individual milks were measured. Milk from Holstein cows had lower casein and calcium contents, and poorer coagulation properties (curd firming time and curd firmness) than that from Montbéliardes and Tarentaises (P< 0·01). These differences practically disappeared when taking into account the distribution of the differentκ-casein variants and milk casein content.κ-BB milks had coagulation properties 20–50% superior, according to characteristic, to those of AA milks. In the three breeds, animals from the H group had casein contents higher by 1·4 g/l than those of the L group, which induced a significant improvement in curd firming time, curd firmness and cheese yield. Turning out to pasture induced an increase of 0·02 in milk pH, and improved milk coagulation properties. These changes did not appear to result entirely from the parallel increase in milk casein content.
Effect of heat treatment and other milk proteins on the interaction of lactoferrin with monocytes
Authors: Oria Rosa , Ismail Maznah , Sánchez Lourdes , Calvo Miguel , Brock Jeremy H. 
Published: June 2009

SummaryThe interaction of lactoferrin from human and bovine milk with the human promonocytic cell line U937 has been studied. Both human and bovine Fe-lactoferrins bound to the cells. Binding of bovine lactoferrin was inhibited by excess bovine lactoferrin but not by human lactoferrin, suggesting that the binding mechanisms for the two proteins are different. Binding of human but not bovine lactoferrin was inhibited by bovine lactoperoxidase, while a 20-fold excess of human IgA inhibited binding of human but not bovine lactoferrin. Human and bovine α-lactalbumins, bovine β-lactoglobulin, and human lysozyme had no effect on binding of lactoferrin from either species. Samples of bovine Fe- and apolactoferrin in capillary tubes were exposed to temperatures of 72 °C for 20 s, 85 °C for 20 min or 137 °C for 8 s. All the heated samples inhibited binding of native Fe- and apolactoferrin, though to a lesser extent than the native proteins. Both heated and native lactoferrins enhanced [3H]thymidine incorporation by U937 cells, except for Fe-lactoferrin heated at 85 °C for 20 min, which was inhibitory. These results suggest that heat treatment of lactoferrin under conditions used for industrial processing does not greatly affect its ability to interact with and stimulate monocytic cells, and that other milk proteins in general do not interfere with lactoferrin–monocyte interactions. It may thus be feasible to incorporate biologically active lactoferrin into infant formulas.
Polyclonal antibodies with predetermined specificity against bovine αs1-casein: application to the detection of bovine milk in ovine milk and cheese
Authors: Rolland Marie-Paule , Bitri Lotfi , Besançon Pierre 
Published: June 2009

SummaryComparing the primary sequences of bovine and ovine milk proteins, some short peptide fragments are cow-specific, in particular the 141–148 fragment of bovine αs1-casein, which is deleted in its ovine counterpart. The 140–149 peptide was chemically synthesized on a solid phase matrix and directly used as an immunogen to produce polyclonal monospecific antibodies in rabbits. These antibodies recognized this fragment both on the peptidyl resin and in the native protein. They appeared to be monospecific, since no antigen–antibody complex was formed with homologous ovine or caprine proteins. Subsequently, a competitive enzyme-linked immuno-sorbent assay was successfully developed for the detection of defined amounts of cows' milk in sheep's milk from 0·125 to 64% (v/v) and in cheese from 0·5 to 25% (v/v) that was not influenced by heat treatment of milk or the degree of ripening of cheese.
Preliminary stages of fouling from whey protein solutions
Authors: Belmar-Beiny M. Teresa , Fryer Peter J. 
Published: June 2009

SummaryFouling from milk fluids is a severe industrial problem which reduces the efficiency of process plant. The chemistry of fouling has been thoroughly investigated but the sequence of events that occur is not yet clear. Deposit contains both protein and minerals. Experiments have been carried out to determine the sequence of events in the fouling of stainless steel surfaces at 96 °C from turbulent flows of whey. Contact times between 4 and 210 s have been studied, and surface analysis techniques used to detect the distribution of elements. The first layer of deposit, formed after 4 s of contact between the fluid and the surface (fluid temperature 68 and 73 °C), consisted mainly of protein and was identified by X-ray photoelectron spectroscopy analysis. There was a lag phase of up to 150 s for a fluid temperature of 73 °C before deposit aggregates were observed to adsorb on to the surface. These aggregates were identified as protein and Ca by X-ray elemental mapping. No P was found in any experiments for this exposure. After 60 min contact time, however, both Ca and P were found at the interface between deposit and the stainless steel surface, irrespective of the Ca and P content of the test fluid.
Phosphorylation, glycosylation and amino acid sequence of component PP3 from the proteose peptone fraction of bovine milk
Authors: Sørensen Esben S. , Petersen Torben E. 
Published: June 2009

SummaryComponent PP3 is a phosphorylated glycoprotein with an apparent molecular mass of 28 kDa isolated from the proteose peptone fraction of bovine milk. The function of the protein is not known. The primary structure has been determined and shown to contain 135 amino acid residues (EMBL accession no. P80195). It was phosphorylated at Ser29, Ser34, Ser38, Ser40 and Ser46. Two O-linked carbohydrate groups were found at Thr16 and Thr86, while one N-linked carbohydrate group was present at Asn77. Thr16 was only ∼ 50% glycosylated. The amino sugar detected by the amino acid analyser at Thr86 was mainly galactosamine but a small amount of glucosamine was also present. The amino sugars found in the carbohydrate group linked to Asn77 were both glucosamine and galactosamine. A fragment of PP3 has been isolated from milk and shown to correspond to residues 54–135. This fragment was probably generated by plasmin hydrolysing the Arg53–Ser54 bond.