bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interrelationships of chemical composition and coagulating properties of renneted milks from dairy cows grazing ryegrass or white clover
Authors: Grandison Alistair S. , Ford Graeme D. , Millard David , Anderson Malcolm 
Published: June 2009

SUMMARYThe chemical composition and rennet coagulation properties at pH 6·4 of bulked milks from two groups of dairy cows grazing ryegrass or white clover swards were monitored over a period of 14 weeks commencing at the fifth week of lactation. There was considerable variation in the concentrations of many components and large variations in the rennet clotting time (RCT), coagulum strength and rate of syneresis. The relative proportions of αs-, β- and κ-casein were also subject to considerable variation. Many statistically significant correlations were found between concentrations of protein fractions, minerals and citrate, some of which may be of physiological significance whereas others may be incidental. The coagulum strength displayed significant correlations with concentrations of total casein, αs-casein, inorganic phosphate (Pi), whey protein and RCT, but not with β-casein or η-casein. The syneresis time was significantly related to the concentrations of fat, citrate, η-casein and the original milk pH. RCT displayed a significant correlation with the concentration of Pi.
Determining the energy of activation for the formation of lactulose in heated milks
Authors: Andrews Geoffrey R. 
Published: June 2009

SUMMARYTime/temperature profiles were obtained for commercial ultra high temperature (UHT) and sterilized milk processing plants and for a pilot UHT plant operating under nine different conditions. Samples of milk from each process were analysed for lactulose by an enzymic method, yielding concentrations of lactulose of 4 to 118 mg/100 ml. The measured lactulose concentration could be derived from the corresponding time/temperature profile by assuming an Arrhenius relationship with an activation energy of 152 kJ mol-1, for the whole range of UHT and in-container processes examined.
Effect of reaming the papillary duct of cows' teats on keratin removal and penetrability of the duct to implantedEscherichia coliendotoxin
Authors: Schultze W. Donald , Bramley A. John 
Published: June 2009

SUMMARYPenetrability of the bovine teat duct toEscherichia coliendotoxin solution was measured before and after reaming the duct with a polypropylene tube, a steel twist drill bit, or a fluted drill point. There was some evidence of a transient increase in penetrability for one or two milkings following reaming but most ducts were not rendered penetrable to endotoxin. Histological examination of ducts after reaming showed that although the loosely packed superficial keratin was effectively removed a continuous smooth keratin layer remained covering the epithelium. These observations are discussed with respect to the possible mechanisms responsible for maintaining the defensive barrier of the duct to bacterial penetration.
Studies on the thermostability of lactase (Streptococcus thermophilus) in milk and sweet whey
Authors: Greenberg Norman A. , Wilder Teresa , Mahoney Raymond R. 
Published: June 2009

SUMMARYThe stability of lactase fromStreptococcus thermophilusat 55 °C increased 7-fold, 2-fold and 1·5-fold in the presence of lactose, galactose and glucose respectively; maltose had no effect. Total stability over an 8 h period was more than 10-fold better in milk and sweet whey than in lactose solution, owing to the stabilizing influence of the milk proteins and the milk salts. Ovalbumin and reduced glutathione provided some extra stability but were not as effective as the milk components. In the absence of lactose the enzyme was less stable in milk and was not protected at all by sweet whey constituents. None of the milk protein fractions was as effective in the absence of lactose as when it was present. Enhanced thermostability of the enzyme in milk and sweet whey is due to contributions by all major milk components, but binding of lactose to the enzyme is the major factor controlling the extent of stabilization by other components.
Heat stability of milk: pH-dependent dissociation of micellar κ-casein on heating milk at ultra high temperatures
Authors: Singh Harjinder , Fox Partick F. 
Published: June 2009

SUMMARYPreheating milk at 140 °C for 1 min at pH 6·6, 6·8, 7·0 or 7·2 shifted the heat coagulation time (HCT)/pH profile to acidic values without significantly affecting the maximum stability. Whey proteins (both β-lactoglobulin and α-lactalbumin) co-sedimented with the casein micelles after heating milk at pH < 6·9 and the whey protein-coated micelles, dispersed in milk ultrafiltrate, showed characteristic maxima–minima in their HCT/pH profile. Heating milk at higher pH values (> 6·9) resulted in the dissociation of whey proteins and κ-casein-rich protein from the micelles and the residual micelles were unstable, without a maximum–minimum in the HCT/pH profile. Preformed whey protein–casein micelle complexes formed by preheating (140 °C for 1 min) milk at pH 6·7 dissociated from the micelles on reheating (140 °C for 1 min) at pH > 6·9. The dissociation of micellar-κ-casein, perhaps complexed with whey proteins, may reduce the micellar zeta potential at pH ≃ 6·9 sufficiently to cause a minimum in the HCT/pH profile of milk.
Seasonal variation and characterization of Micrococcaceae present in ewes' raw milk
Authors: Bautista Lydia , Bermejo Monserrat P. , Nuñez Manuel 
Published: June 2009

SUMMARYSamples (120) of ewes' raw milk collected over a 12-month period on arrival at the dairy and freshly drawn ewes’ milk samples (30) collected at the farm were analysed for total viable counts and staphylococci. Total viable counts reached on the average 54 × 106/ml in dairy samples and 6·0 × 105/ml in farm samples, whereas mean levels of staphylococci were 5·9 × 104/ml and 3·3 × 103/ml, respectively. A high proportion (62%) of coagulase-positive isolates from Baird-Parker agar plates was detected in spring months.Staphylococcus aureus(42%),Staph. haemolyticus(23%) andStaph. epidermidis(10%) were the predominant species in 210 characterized isolates of staphylococci from ewes' raw milk. Seven coagulase-positive, maltose-negative staphylococci could not be identified with any of the recognizedStaphylococcusspecies. EighteenMicrococcusstrains were identified asM. varians, whereas 111Micrococcusstrains of uncertain taxonomic status were separated into three groups, according to their physiological characters.
Factors affecting the ethanol stability of bovine skim milk
Authors: Horne David S. , Parker Thomas G. , Donnelly William J. , Davies D. Thomas 
Published: June 2009

SUMMARYMilk samples from three groups of cows were taken at frequent intervals throughout lactation following autumn-, winter- or spring-calving. The ethanol (EtOH) stability/pH profile was determined for each sample and its characteristic parameters calculated. The lactational trends in these parameters were examined. Asymptotic maximum EtOH stability (Smax) was low in early lactation but rose rapidly to a value which showed no further lactational trends. Asymptotic minimum stability (Smin) for samples from autumn- and winter-calving cows showed a decrease which could be associated with the transition to summer grazing but no obvious lactational effects. The slope parameter increased slowly during lactation. The profile pK value decreased in early lactation, but thereafter increased throughout lactation giving the most obvious effect observed in direct measurement, namely an alkaline shift in the profile as lactation progressed. The EtOH stability calculated at a fixed pH of 6·6 passed through a maximum, characteristic for each cow, in the first weeks of lactation but declined steadily thereafter. This behaviour mirrors the lactational behaviour of the soluble salt balance ratio calculated from the original data of White & Davies (1958).
Production of cream from ultrafiltered milk
Authors: Scurlock Peter G. 
Published: June 2009

SUMMARYBovine whole milk was concentrated up to 5-fold by ultrafiltration and separated conventionally to produce protein enriched creams with fat contents ranging from 20 to 50 % (w/w). The measured viscosity of the concentrates increased with the degree of concentration. This led to inefficient centrifugal separation, as measured by the loss of fat into the skimmed milk, which was further worsened when damage to the fat globules occurred during ultrafiltration. The viscosity of the creams, at constant fat percentage, increased as the concentration factor of the milk from which it was separated rose.
An inhibitor typing scheme forStreptococcus uberis
Authors: Tagg John R. , Vugler Leone G. 
Published: June 2009

SUMMARYA typing scheme was used to test 15 strains ofStreptococcus uberisaccording to their production of (P-type) and sensitivity to (S-type) bacteriocin-like inhibitory substances. Twelve of the strains were inhibitor producers and nine different P-types were detected. All of the strains were typable according to inhibitor sensitivity, ten different S-types being distinguished. Both the P-type and S-type designations of the strains were reproducible on repeated testing. By combination of P-typing and S-typing, highly discriminatory inhibitor ‘fingerprints’ of the strains could be obtained. This scheme would appear to have considerable potential for typing isolates ofStr. uberisas an aid to investigations into the epidemiology ofStr. uberismastitis in dairy cattle.
Effect of combined ultrasonic and heat treatment (thermoultrasonication) on the survival of a strain ofStaphylococcus aureus
Authors: Ordoñez Juan A. , Aguilera M. Angeles , Garcia M. Luisa , Sanz Bernabe 
Published: June 2009

SummaryThe combined effect of ultrasonic waves (20 kHz, 150 W) and heat treatment applied simultaneously (thermoultrasonication) on the survival of a strain ofStaphylococcus aureuswas studied in 0·05 m-phosphate buffer pH 6·8 and ultra-heat-treated whole milk. This combined process decreased by 63% the decimal reduction times for the heat treatment when the organism was suspended in buffer and by 43% when suspended in milk. These effects were much greater than the additive effect of the two agents considered independently.
Effect on milk production of controlling muscid flies, and reducing fly-avoidance behaviour, by the use of Fenvalerate ear tags during the dry period
Authors: Harris Jeanette A. , Hillerton J. Eric , Morant Steven V. 
Published: June 2009

SummaryFenvalerate ear tags reduced fly loads on dry dairy cattle by 95% between July and September. Fly dislodging behaviour, such as ear flicks which correlated with numbers of Musca autumnalis on the face and stamps/kicks which correlated with numbers of Stomoxys calcitrans on the legs, was also significantly reduced. There was no significant difference between the tagged and untagged groups in the total time spent grazing each day. Milk yields were not statistically significantly different, but the tagged group showed a greater increase in milk yield between lactations, of 1·45 kg/cow daily in the first 12 weeks of the lactation.
Assay of proteinases of psychrotrophic bacteria in milk using Hide Powder Azure and a simple procedure for clarification of milk
Authors: Stead Donald 
Published: June 2009

SummaryThe clarification of milk by addition of solutions of Triton X-100 and EDTA after digestion of added Hide Powder Azure (HPA) was found to provide a simple method of determining the extracellular proteinase activity of Gram-negative psychrotrophic bacteria in pasteurized whole milk. The light absorbance of the clarified HPA digestion product was measured directly, after a brief incubation period, and was stable to storage of samples in diffuse daylight for at least 2 d. Proteinase produced by growth in refrigerated whole milk of as few as 2·5 × 106cfu ml−1ofPseudomonas fluorescensAR11 was detected.
Ethanol stability of casein micelles – a hypothesis concerning the role of calcium phosphate
Authors: Horne David S. 
Published: June 2009

SummaryThe ethanol (EtOH) stability of skim milk and the stability towards aggregation of casein micelles diluted into ethanolic buffer solutions were compared using data obtained from previously published experiments. Differences in absolute stability and in relative response were observed when Ca2+ level and pH were adjusted, the buffer system results lying below those from skim milk in both cases. Increasing the ionic strength of skim milk adjusted to pH 7·0 lowered its EtOH stability whereas increasing the ionic strength of the diluting buffer increased the stability of the casein micelles. The hypothesis is put forward that the differences are due to the simultaneous precipitation of Ca phosphate when EtOH is added to skim milk. This draws calcium from the caseinate sites of the micelle, counteracting the destabilizing effects of the EtOH towards the micelle. Such removal and the consequent restructuring are kinetically controlled and micellar precipitation in skim milk finally occurs when the micellar coagulation time falls within the time scale of the restructuring reactions.
Evidence for temperate bacteriophages in two strains ofLactobacillus bulgaricus
Authors: Cluzel Pierre-Jean , Veaux Monique , Rousseau Micheline , Accolas Jean-Pierre 
Published: June 2009

SummaryLactobacillus bulgaricusstrains LT1 and LT4 previously isolated from a yogurt factory were shown to be lysogenic and inducible by mitomycin C or u.v. irradiation, induction being optimal at the beginning of exponential growth. Five indicator strains (four ofL. lactis, one ofL. bulgaricus) were found in which the two phage lysates propagated well in a liquid medium, but formed plaques on bacterial lawns less readily. Ca2+was required for the phage infection of the indicator strains to reach termination. Phage particles from each strain exhibited a comparable ultrastructural morphology under the electron microscope, having an isometric head, a triple collar and a noncontractile fibre-containing tail.
Distribution of milk in the goat mammary gland and its relation to the rate and control of milk secretion
Authors: Peaker Malcolm , Blatchford David R. 
Published: June 2009

SummaryChanges with time in the distribution of milk between different storage regions of the mammary gland were studied in goats. Milk was allowed to drain from the gland through a catheter (catheter milk); the gland was then milked by hand, before (hand milk) and after the administration of oxytocin (alveolar or residual milk). The hand-milk fraction was of negligible volume. There was an essentially linear increase in the catheter- plus hand-milk fraction from 0 to 16 h. The alveolar fraction increased up to 6 h, but thereafter remained constant to 16 h. There was considerable but consistent variation between animals in the alveolar fraction as a proportion of total milk volume. The proportion of residual milk was inversely related to milk secretory rate per unit weight of mammary tissue. The hourly administration of oxytocin without milking had no apparent effect on the distribution of milk in the gland 1 h later.
Interaction between heated κ-casein and β-lactoglobulin: predominance of hydrophobic interactions in the initial stages of complex formation
Authors: Haque Zahurul , Kinsella John E. 
Published: June 2009

SummaryMixtures of κ-casein and β-lactoglobulin (β-lg) were heated at 70 °C in 20 mM-imidazole buffer, pH 6·8 containing 20 mM-EGTA. Aggregation of the κ-casein/β-lg mixture occurred within 90 s and susceptibility to hydrolysis by chymosin decreased significantly within 180 s even though covalent interaction was not detected until after 4000 s. UV-absorbance indicated initial structural destabilization of the heated κ-casein/β-lg mixture followed by a return ( > 350 s) to a spectrum comparable to the native state, indicating molecular rearrangement. Apparent hydrophobicity of κ-casein decreased 80% within 250 s compared to a 38% decrease for β-lg. Under similar conditions, the κ-casein/β-lg mixture (1:1) showed a faster (2·5 times) decrease in apparent hydrophobicity than κ-casein alone with concomitant exposure of acidic (hydrophilic) groups. The results suggested that the driving force for the rearrangement was mainly hydrophobic, i.e. entropic in origin. The tendency of heated and subsequently cooled κ-casein/β-lg to aggregate reached a maximum after heating at 70 °C for 720 s.
Protein synthesis and degradation in the mammary gland of lactating goats
Authors: Oddy V. Hutton , Lindsay Derek B. , Fleet Ivan R. 
Published: June 2009

SummaryLactating goats were given a close arterial infusion of [1-14C]leucine and [4,5-3H]4-methyl-2-oxopentanoic acid into one half of the mammary gland at 2–3 weeks and 34–39 weeks after kidding. Rates of protein synthesis, degradation and net output were determined from measurements of arteriovenous difference and blood flow using a model of leucine metabolism previously developed for muscle (Oddy & Lindsay, 1986). Protein leucine output in milk (Y μmol/min) correlated well with the difference between synthesis and degradation (X μmol/min) derived from the model:There was substantial synthesis and degradation of protein within the mammary gland. Although only an approximate value could be obtained for the partitioning of protein synthesis and degradation between tissue and milk proteins, there was evidence of appreciable turnover of both. There was no significant difference between mammary leucine and protein metabolism in early and late lactation other than that imparted by a greater mass of mammary tissue in early lactation, although there was a tendency for greater oxidation of leucine in late lactation.
Use of light scattering techniques to study the kinetics of precipitation of mineral acid casein from skim milk
Authors: Jablonka Mark S. , Munro Peter A. , Duffy Geoffrey G. 
Published: June 2009

SummaryTwo light scattering methods for monitoring the precipitation of casein from skim milk (9% w/w) with mineral acid are presented. Experiments were carried out at precipitation temperatures in the range 25–53 °C and precipitation pH values in the range 3·9–5·1. The initial stages of precipitation were explored using a light fibre optics system attached to a closed-loop acid/milk mixing system. The later stages of particle formation and growth were examined using a laser doppler anemometer attached to an open-pipe flow system. It was found that there was a lag initially, followed by a period of rapid particle growth. During a third phase a dynamic equilibrium between particle growth, break-up and shrinkage was established. A model for isoelectric casein precipitation based on these observations is proposed and discussed.
Emulsifying capacity of whey proteins produced by ion-exchange chromatography
Authors: Langley Keith R. , Millard David , Evans E. William 
Published: June 2009

SummaryAt pH 7·0, the emulsifying capacity (Ec) of ion-exchange fractionated whey protein powders in corn oil/water systems increased with increase in protein concentration up to 0·l% (w/v), where it was maximal. At higher concentrations Ec decreased because of packing effects of the oil droplets. At low protein concentrations Ec could be determined from linear equations involving the relative concentration of the individual proteins in the powder. The surface coverage of β-lactoglobulin on the oil was ∼ 1 mg m–2. Oil droplet size and Ec were maximal at pH 4·0–6·0, corresponding to the isoionic points of the proteins.
Production of acetolactate byStreptococcus diacetylactisandLeuconostocspp.
Authors: Jordan Kieran N. , Cogan Timothy M. 
Published: June 2009

SummaryThe effect of several parameters on the decarboxylation of α-acetolactic acid (ALA) to diacetyl and acetoin was studied in model experiments. At temperatures > 50 °C, relatively more diacety1 than acetoin was produced. Regardless of temperature, HC1 increased the production of acetoin (58 mol% conversion at max.) and prevented the production of diacetyl. Steam distillation of ALA caused ~ 55 mol%/h conversion to acetoin and 7 mol%/h to diacetyl. Production of acetoin was proportional to the ALA concentration. Based on these results two methods for the quantitative measurement of ALA were developed. Only one of 17 strains ofStreptococcus diacetylactis (Lactococcus lactissubsp.lactisbiovar.diacetilactis, new nomenclature) and three of three strains ofLeuconostocspp. produced ALA. The implications of these findings are discussed.
Species identification of staphylococci and micrococci isolated from ewes' milk cheeses
Authors: García María Camino , Otero Andrés , García María Luisa , García María Rosario , Moreno Benito 
Published: June 2009

SummaryForty-five strains of staphylococci and 6 strains of micrococci isolated from pasteurized ewes' milk cheeses (Manchego and Burgos varieties) were identified to species level. Three strains of staphylococci were identified asStaphylococcus aureus. Amongst the 42 coagulase-negative staphylococci, 8 were novobiocin-sensitive and 34 novobiocin-resistant. The novobiocin-sensitive species found wereStaph. auricularis(5 strains),Staph. caseolyticus(2 strains) andStaph. epidermidis(1 strain). Novobiocin-resistant strains were identified asStaph. gallinarum(5 strains),Staph. xylosus(4),Staph. saprophyticus(9),Staph. cohnii(6),Staph. sciuri(1) andStaph. lentus(3). The other 6 isolates could not be identified. Only 3 strains of micrococci were identified (Micrococcus kristinae, M. variansandM. sedentarius). The possible origin of the isolates is discussed.
Effect of cleaning-in-place disinfectants on wild bacterial strains isolated from a milking line
Authors: Mattila Tiina , Manninen Merja , Kyläsiurola Anna-Liisa 
Published: June 2009

SummaryTwo cleaning-in-place disinfectant Systems (alkaline–acid, alkaline–CI2) were tested on wild bacteria isolated from a milking line. Most of the isolated strains were Gram-negative and capsule-positive. The effect of milk and cream on the resistance of the wild strains to the cleaning Systems was tested. Suspension tests did not show the resistance of bacteria whereas the surface test showed high resistance towards all cleaning-agents. Milk had a protective effect only on the surfaces whereas cream showed mild protection in suspension and complete protection on the surfaces. It was concluded that the growth pattern of contaminants on surfaces needs further attention and the laboratory suspension tests do not correlate with the practical situation. Disinfectant tests based on bacterial growth on the surface are of importance.
Comparison of rapid tests for assessing UHT milk sterility
Authors: Reinheimer Jorge A. , Demkow Maria R. 
Published: June 2009

SummarySamples of UHT milk were contaminated at two levels (102 and 104 cfu/ml) with 52 bacterial strains associated with spoilage. Samples were assayed, using various tests, to determine efficiency in detecting non-sterility after an incubation period shorter than that advised in standard procedures. The tests performed were colony count, titratable acidity and pH modification, organoleptic assessment, stability towards ethanol (68, 80 and 88% v/v), resazurin and nitrate reduction. After 3 d incubation at 30 °C every case was detected by the resazurin test with a good statistical probability (P = 0·999). Reliability was not so high in all other tests, even after 14 d incubation.
Studies on antimutagenic effect of milk cultured with lactic acid bacteria on the Trp-P2-induced mutagenicity to TA98 strain of Salmonella typhimurium
Authors: Hosoda M. , Hashimoto H. , Morita H. , Chiba M. , Hosono A. 
Published: June 2009

SummaryThe inhibitory effects of cultured milk using 76 strains of lactic acid bacteria isolated from milk products were investigated on the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3−b]indole (Trp-P2), a tryptophan pyrolysate for Salmonella typhimurium TA98. Each cultured milk sample displayed its characteristic antimutagenic effect against the mutagenicity of Trp-P2. The milk cultured with Lactobacillus acidophilus LA106 (LA2) showed the highest inhibition of 82·1% among the strains used. Milk samples cultured with Lactococcus lactis subsp. lactis, L11103 (10−3) and L11102 (KM) also exhibited higher inhibition percentages.