bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth of lactic acid bacteria and bifidobacteria on lactose and lactose-related mono-, di- and trisaccharides and correlation with distribution ofβ–galactosidase and phospho-β–galactosidase
Authors: Smart John B. , Pillidge Christopher J. , Garman Jean H. 
Published: June 2009

SummarySpectrophotometric assays ofβ–galactosidase (EC 3.2.1.23) and phospho-β–galactosidase (EC 3.2.1.85) activity were used to survey the lactose utilization pathways of lactic acid bacteria and bifidobacteria.β–Galactosidase activity was found in all six genera represented (Lactococcus, Streptococcus, Leuconostoc, Lactobacillus, PediococcusandBifidobacterium) while phospho-β–galactosidase was restricted to the lactococci, twoLactobacillusand twoLeuconostocspecies. A number of strains ofLactococcus lactis, Lactobacillus caseiandLeuconostocspp. contained both enzymes. Enzyme activities varied when cells were grown on different sugars, but in general were low or absent for cells grown on glucose compared with lactose. Two lactose-related compounds, lactulose and galactosyl lactose, believed to be specific growth factors for bifidobacteria, supported growth amongst a wide range of lactic acid bacteria in addition to bifidobacteria. Growth on galactosyl lactose was restricted to some but not all strains containingβ–galactosidase, implying that the presence ofβ–galactosidase is insufficient by itself to ensure utilization of galactosyl lactose. DNA fragments that encoded theLactococcus lactissubsp.cremorisphospho-β–galactosidase gene or theβ–galactosidase genes ofStreptococcus salivariussubsp.thermophilusorLactobacillus delbrueckiisubsp.bulgaricuswere isolated and used as probes in DNA-DNA hybridizations. Little or no hybridization was detected between these probes and plasmid or genomic DNA isolated from heterologous species, despite the presence of the corresponding enzyme activity in the strains probed.
Hormonal induction of α–lactalbumin and β–lactoglobulin in cultured mammary explants from pregnant pigs
Authors: Dodd Susan C. , Forsyth Isabel A. , Buttle Hugh L. , Gurr Michael I. , Dils Raymond R. 
Published: June 2009

SummaryMammary tissue from pigs on days 60, 80, 90, 100 and 100+ (days 106–111) of pregnancy has been cultured in vitro as explants. The total accumulation in tissue and culture medium of the whey proteins α-lactalbumin and β-lactoglobulin has been measured using specific radioimmunoassays. The control, uncultured tissue showed progressive morphological development from sparse, non-secretory epithelial tissue on day 60 to full lobulo-alveolar development with some accumulated secretion from day 100. In uncultured explants β-lactoglobulin could be detected consistently from day 90 (13 ± 12 ng/μg DNA, n = 4) and α-lactalbumin from day 100 (1·3 ± 0·5 ng/μg DNA, n = 11). At all stages of pregnancy, both whey proteins increased markedly during the period of culture (up to 7 d). Stimulation of α-lactalbumin appeared to be primarily under prolactin control. Prolactin increased α-lactalbumin accumulation to a similar extent alone, or in the presence of insulin and/or corticosterone. The response to prolactin was dose-dependent over the range 0·4–20 nM (10–500 ng/ml). Porcine prolactin was more potent than ovine prolactin. There was no effect of porcine growth hormone and no synergism detected between prolactin and tri-iodothyronine. By contrast, no specific hormonal requirements were established for accumulation of β-lactoglobulin, which appeared to increase in vitro if tissue remained viable in various combinations of insulin, corticosterone and prolactin. It was not stimulated by growth hormone. There was some indication of a prolactin-sensitive component in longer term cultures after day 4.
Milk accumulation and distribution in the bovine udder during the interval between milkings
Authors: Knight Christopher H. , Hirst David , Dewhurst Richard J. 
Published: June 2009

SummaryThe proportions of milk stored within the gland cistern (cisternal milk) and within secretory alveolar tissue (alveolar milk) were determined at various intervals after milking in peak lactation cows and late lactation cows. The rate of milk secretion remained constant up to 12 h in both groups. Cisternal milk remained low (600 g or less) until after 4 h in both groups, then increased gradually to values at 12 h of 5·08 (peak lactation) and 2·60 kg (late lactation). Alveolar milk exceeded cisternal milk in both groups and at all time points up to 12 h, and was greatest in the peak lactation cows. A further measurement was made at 20 h in the late lactation group. Milk secretion rate remained constant between 12 and 20 h and most of this additional milk accumulated in the cistern. Alveolar fraction, defined as alveolar milk as a proportion of total milk, ranged from 0·43 to 0·94 at 8 h. There was a highly significant correlation between 8 h and 20 h alveolar milk fraction results, but not between 1 h and 8 h values, nor between alveolar milk at 0 h (effectively residual milk) and alveolar fraction at any time point. The milk volume results were used to construct a mathematical model describing milk flow between cisternal and alveolar compartments, and hence the pattern of milk accumulation. The results are discussed in relation to current hypotheses regarding local autocrine control of milk secretion by a feedback inhibitor in milk.
Effect of milking interval on secretion rate and composition of camel milk in late lactation
Authors: Alshaikh Muhammad A. , Salah Mahmoud S. 
Published: June 2009

SummaryThe effect of milking interval on secretion rates of milk and milk constituents was studied in four milking camels during late lactation. An interval of 4 h produced the highest milk secretion rate compared with 8, 12 and 16 h intervals, and rates tended to decline with increasing milking intervals. Secretion rates of organic (lactose, SNF, fat and protein) and inorganic milk constituents (sodium, potassium, calcium and magnesium) generally followed similar patterns of decreasing secretion with increasing milking intervals. Many of the values for different intervals were significantly different.
Response to phage infection of immobilized lactococci during continuous acidification and inoculation of skim milk
Authors: Passos Flavia M. L. , Klaenhammer Todd R. , Swaisgood Harold E. 
Published: June 2009

SummaryA laboratory scale bioreactor was used for continuous acidification and inoculation of milk with a proteinase-negative, lactose-fermenting strain,Lactococcus lactissubsp.lactisC2S. Calcium alginate-entrapped cells were immobilized on a spiral stainless steel mesh incorporated into a column bioreactor and used to acidify and inoculate reconstituted skim milk. Characteristics of the immobilized cell bioreactor (ICB) were compared with those of a free cell bioreactor (FCB) during challenge with a virulent phage. Steady state biomass and lactate productivities were respectively 25-fold and 12-fold larger with the ICB than with the FCB. The ICB and the FCB were inoculated with the prolate phage c2 at multiplicities of infection of 0·25 and 0·02 respectively. Within 90 min of the infection, the FCB viable cell concentration dropped by five orders of magnitude and never recovered, while the plaque forming units/ml increased dramatically. In the ICB, released cells decreased immediately after infection, but subsequently increased, while the plaque forming units/ml steadily declined, indicating that phage were being washed out of the bioreactor. Productivity of FCB decreased to zero, whereas productivity of the ICB only decreased ∼ 60% and subsequently recovered to its initial steady state value.
Enhanced inactivation of bacterial lipases and proteinases in whole milk by a modified ultra high temperature treatment
Authors: Bucky Anthony R. , Hayes Patrick R. , Robinson David S. 
Published: June 2009

SummaryCultures ofPseudomonasspp. strains P10, P12 and P15 grown in whole milk which contained ∼ 1 × 108viable bacteria ml−1demonstrated near linear increases in the concentration of short-chain free fatty acids and trichloroacetic acid soluble free amino groups at 20 °C, following either ultra high temperature (UHT) treatment (140 °C for 5 s) or dual heat treatments (140 °C followed by either 57, 60 or 65 °C). The dual heat treatments reduced the rates of lipolysis and proteolysis compared to the UHT treatment by up to 25-fold. The dual heat treatment utilizing 60 °C for 5 min also effectively limited both lipase and proteinase activities in raw milk culture samples which had contained either 6 × 106, 5 × 107or 1 × 108viable bacteria ml−1. In this system enzyme activities were reduced by up to 10-fold following dual heat treatment compared to UHT treatment alone.
Study of calcium binding to phosphoserine residues of β-casein and its phosphopeptide (1–25) by 31P NMR
Authors: Baumy J.-J. , Guenot P. , Sinbandhit S. , Brulé G. 
Published: June 2009

SummaryThe effect of Ca2+. binding and ionic strength on the physicochemical characteristics of phosphoserine residues was studied on O-phospho-DL-serine, bovine β-casein and its phosphopeptide (1–25) using 31P NMR. pK in various experimental conditions were determined.The pK of the phosphoserine residues of β-casein and its phosphopeptide (1–25) respectively ranged from 6·46 to 7·21 and from 6·57 to 7·10. pK of O-phospho-DL-serine, β-casein and its phosphopeptide decreased when Ca2+ was bound to the phosphoserine residue or when ionic strength was increased. The binding of Ca2+ to the phosphopeptide (1–25) took place at first on phosphoserine residues 17, 18, 19 which had the highest pK, then, when these were saturated, on residue 15 whose pK was the lowest. When the four sites had bound Ca2+, peaks corresponding to a different complex form appeared in the spectrum.
Short-term effects of frequent milking of dairy cows
Authors: Van Der Iest Renee , Hillerton J. Eric 
Published: June 2009

SummaryWhen six cows were milked every 4 h over 48 h the average milk yield per cow increased by 1O·7% for the last 24 h period compared with the previous 5 d. Milk composition was similar to pre-experimental values although fat content was 0·5% lower in the last 24 h. The somatic cell count rose to twice the pre-experimental value over the first 24 h but was not significantly different by the second 24 h. It appears that cows responded quickly to an increased frequency of milking and milk of an acceptable composition was produced. This has implications for management of milk production where quotas are in operation and for robotic milking systems.
A method for determination of γ-casein and its use for investigating proteolysis in bovine milk
Authors: Igarashi Yasuo 
Published: June 2009

SummaryA convenient and sensitive method for determining γ-casein content of skim milk is described. It is based on quantitative separation in which the soluble fraction obtained from skim milk (1·5 ml) in a solvent system consisting of 50% (v/v) ethanol, 0·4 M-Na thiocyanate and 0·15 M-CaCl2 was applied to a small column of DEAE-cellulose and eluted with 0·02 M-Tris-HCl buffer (pH 8·0) containing 0·03 M-NaCl and 6 M-urea. Protein in this fraction (5 ml) was measured from its absorbance at 280 nm. The method is applicable also to heated skim milk. Its availability for investigating proteolysis in milk is expected from the fact that incubation of skim milk with porcine plasmin at 37 °C for 3 h increased γ-casein content, an increase that was lowered by addition of soyabean trypsin inhibitor. Incubation of raw skim milk with 0·02% (w/v) NaN3 resulted in increase in γ-casein with time and with increasing temperature. This was accompanied by a time lag, the length of which increased with decreasing temperature. The degree of proteolysis in skim milk, expressed as the amount of increase in γ-casein after 20 h of incubation at 37 °C, showed two pH optima, one at pH 8·0 and the other at pH 7·2–7·5. These results suggested that the present method.of γ-casein determination can be used for more precise studies of the milk plasmin system in which important factors, such as plasminogen activator and inhibitors, are involved.
Serological identification of Streptococcus salivarius subsp. thermophilus
Authors: Nour Maher A. , Abdel-Tawab Gamal , Shalaby Samir , Mohamed Osama A. 
Published: June 2009

SummaryStreptococcus salivarius subsp. thermophilus (Str. thermophilus) has no group-specific antigen. HC1 extracts of 551 strains of streptococci isolated from cheese or yogurt (123 Str. thermophilus and 428 Enterococcus faecalis – Ent. faecium spp.) were examined with three type-specific antisera prepared against representatives of Str. thermophilus and also with Lancefield group D antisera. All typical (80) or atypical (43) strains of Str. thermophilus reacted with at least one type-specific antiserum and none of the enterococci reacted. Only two strains reacted with both type-specific and group antisera.
Factors affecting the thermostability of β-galactosidase (Streptococcus salivariussubsp.thermophilus) in milk: a quantitative study
Authors: Chang Byeong-Seon , Mahoney Raymond R. 
Published: June 2009

SummaryEnhanced stability of β-galactosidase (Streptococcus salivariussubsp.thermophilus) in milk is due to several milk components acting in concert. Milk salts stabilized the enzyme 3-fold compared to phosphate buffer. K+was a better stabilizer than Na+. Omission of divalent cations, especially Mg2+, caused a marked drop in stability. Lactose stabilized enzyme stored in the frozen state but destabilized enzyme stored unfrozen. Caseinate stabilized the enzyme 8-fold in phosphate buffer but it stabilized 144-fold in the presence of lactose. In the presence of milk proteins, lactose was 25 times as effective as galactose and 100 times as effective as glucose at promoting stability; sucrose slightly destabilized the enzyme. Stability rose with increasing lactose concentration but declined with increasing enzyme concentration. In milk, soluble casein was the primary stabilizer; whey proteins and peptides had much less effect. Micellar casein had no effect on stability.
Milk yield and mammary function in goats during and after once-daily milking
Authors: Wilde Colin J. , Knight Christopher H. 
Published: June 2009

SummaryStarting in week 5 of lactation, goats were milked unilaterally once daily for 4 ½ weeks, then twice daily for 12 weeks and finally thrice daily for 2 weeks. The control gland was milked twice daily throughout. During less frequent milking, yield fell by 26%. There was a rapid and essentially complete recovery of milk yield on resumption of twice-daily milking, and five of the six goats subsequently responded to thrice-daily milking with a small increase in milk yield. Mammary function was assessed during each phase by determining enzyme activities and in vitro synthesis rates of lactose and casein in mammary biopsies. There was a trend towards reduced differentiation of secretory cells during infrequent milking, with very little recovery during twice-daily milking but complete recovery during thrice-daily milking. The differentiative state of the control gland remained unchanged throughout.
Volatile components of Manchego cheese
Authors: Martínez-Castro Isabel , Sanz Jesus , Amigo Lourdes , Ramos Mercedes , Martín-Alvarez Pedro 
Published: June 2009

SummaryVolatile components of four batches of Manchego cheese were studied throughout their ripening process. Samples were submitted to a micro simultaneous distillation-extraction procedure, and then analysed by capillary gas chromatography (GC) and combined GC and mass spectrometry. Among other components, four homologous series of compounds were found: free fatty acids, methyl ketones, ethyl and methyl esters of even fatty acids. Ripening stage can be approximately estimated from the concentrations of some components.
Structural changes in sweetened condensed milk during storage: an electron microscopy study
Authors: Alvarez de Felipe A. I. , Melcón Berta , Zapico Julián 
Published: June 2009

SummaryThis work aimed to relate changes in rheological behaviour with structural details of different sweetened condensed milk samples as well as to clarify the role of additives in delaying gelation. To study the process of gelation, rheological techniques were applied to fresh and stored condensed milk samples for times and at temperatures known to favour gelation (45 d at 37 °C). Electron microscopy techniques were used to relate the rheological changes with observed structural details. Examination by electron microscopy showed that micellar aggregation and association of casein micelles with fat globules increased during storage. The whey proteins appeared to play an important role in the thickening process.
Effects of speed and duration of cutting in mechanized Cheddar cheesemaking on curd particle size and yield
Authors: Johnston Keith A. , Dunlop Frank P. , Lawson Michael F. 
Published: June 2009

SummaryThe speed and duration of cutting the coagulum were varied during the commercial manufacture of Cheddar cheese in nine Damrow cheese vats on each of 3 consecutive days. The effects of the variations were assessed by determining the curd particle size distribution and fat and fines losses into the whey at draining. Short durations of cutting at slow speeds produced small curd particles and high fat losses into the whey. As the duration and/or speed of cutting was increased, average curd particle size increased while fat losses into the whey decreased. A maximum particle size and minimum fat level were reached after the Damrow's knife panels had completed approximately 37 revolutions. Further increases in speed and/or duration of cutting decreased curd particle size. Fat losses did not increase significantly. The hypothesis suggested to explain the results of these trials is that curd particle size is determined not by the cutting programme alone, but by a combination of the speed and duration of cutting and the subsequent speed of stirring prior to cooking. Fat losses in the whey are also influenced by this combination. Based on this hypothesis, a model is proposed which explains how variation in cutting speed and duration, followed by a constant stirring speed, determines curd particle size distribution in a Damrow cheese vat. Implications of the present findings in relation to cheese yield (losses of fat and fines into the whey) are discussed.
Production, isolation and identification of low molecular mass peptides from blue cheese by high performance liquid chromatography
Authors: de Llano Dolores Gonzalez , Polo M. Carmen , Ramos Mercedes 
Published: June 2009

SummaryThe blue cheese nitrogenous fractions soluble in water and in 5% phosphotungstic acid (PTA) were analysed by HPLC after 3–180 d ripening. In the water-soluble fraction, in addition to four or five major peaks corresponding to amino acids, there were many minor peaks, which increased during ripening. The low molecular mass peptides, soluble in 5% PTA, showed ripening-induced increments. A method combining precipitation with 5% PTA, gel permeation and subsequent HPLC was used to isolate some peptides of cheese. Four peptides containing between seven and ten residues were isolated and their amino acid composition and N-terminal residues determined.
Prediction of responses in milk constituents to changes in the nutrition of dairy cows
Authors: Tran C. Lang , Johnson C. Lewis 
Published: June 2009

SummaryMilk quotas, based on an average fat content, severely limit milk production on UK farms. Predictions of the time-course of lactation are incorporated into most computerized herd management programs but these models take no account of food inputs, body weight change or milk composition. Dynamic models are generally used to simulate metabolic pathways and, as such, have little direct relevance to commercial milk production. Dynamic models can be converted to an adaptive-predictive model that partitions food energy into milk and non-milk constituents. This paper reports the development of an adaptive-predictive model to partition food into milk and non-milk components. Additional functions further partition milk energy into the principal constituents, fat, protein and lactose.
Determination of ovine casein heterogeneity using gel electrophoresis and immunochemical techniques
Authors: Chianese Lina , Mauriello Rosalba , Moio Luigi , Intorcia Nunziatina , Addeo Francesco 
Published: June 2009

SummaryDiscontinuous PAGE at alkaline and acid pH, polyacrylamide gel isoelectric focusing, two dimensional electrophoresis and immunoblotting have been used to study the heterogeneity of sheep caseins. Three main phenotypes were selected either because of mobility at alkaline and acid pH of the individual αs components or because of their relative intensity. On electrophoresis at alkaline pH, one phenotype showed two distinct bands of lower electrophoretic mobility than β,- and β2-caseins. A detailed study of these components using immunospecific detection with β-casein antiserum showed that these minor components of ovine casein may have a polypeptide chain similar to that of β1- and β2-caseins. Complete electrophoretic patterns of the casein components in some individual milks are also presented.
Effect of insulin in conjunction with glucose, amino acids and potassium on net metabolism of glucose and amino acids in the goat mammary gland
Authors: Tesseraud Sophie , Grizard Jean , Makarski Boguslaw , Debras Elisabeth , Bayle Gerard , Champredon Claude 
Published: June 2009

SummaryThe hyperinsulinaemic euglycaemic insulin clamp technique was used to study the effect of insulin on the arterio-venous concentration differences of glucose and amino acids across the mammary gland in dairy goats. Insulin was given in conjunction with K to prevent insulin hypokalaemia. Appropriate amino acid infusion was used to blunt insulin-induced hypoaminoacidaemia or to create hyperaminoacidaemia and maintain this state under insulin treatment. Hyper-aminoacidaemia alone only stimulated mammary leucine uptake but did not significantly modify the net metabolism of other amino acids and glucose. Insulin infusion at physiological level in conjunction with glucose, KCl-NaCl and amino acids failed to alter mammary uptake of glucose and essential amino acids; occasional increase in arginine extraction and decrease in tyrosine extraction were exceptions. Thus these new experimental conditions did not reveal any galactopoietic effect of insulin.
Use of the Cd-ninhydrin reagent to assess proteolysis in cheese during ripening
Authors: Folkertsma Baukje , Fox Patrick F. 
Published: June 2009

SummaryA new method for monitoring the terminal stages of proteolysis in cheese, i.e. the formation of free amino acids, using the Cd-ninhydrin reagent is reported. The assay was very specific for free amino acids and may be performed on citrate-soluble, water-soluble or phosphotungstic acid-soluble fractions of cheese, but not on trichloroacetic acid-soluble extracts; water-soluble extracts were chosen for routine analysis. Application of the assay to several experimental cheeses showed almost linear increases in free amino acids during ripening for up to 12 months with a slightly faster rate of formation during the later stages of ripening.