bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheology of whey protein concentrate solutions as a function of concentration, temperature, pH and salt concentration
Authors: Tang Qingnong , Munro Peter A. , McCarthy Owen J. 
Published: June 2009

SummaryRheological properties of whey protein concentrate (WPG) solutions were studied in steady shear, using a Bohlin VOR Rheometer, as a function of concentration, temperature, shear rate, shearing time, pH, salt type, salt concentration and solution age. At 22 °C and pH 7, the WPC solutions exhibited Newtonian behaviour up to a concentration of 10% total solids, pseudoplastic behaviour between 10 and 30% and time-dependent shear thinning at 35% and above. The apparent viscosity of solutions at 22 °C and pH 7 was linearly related to concentration up to 8%. The effect of temperature on apparent viscosity in the range 5–60 °C was closely described by the Arrhenius equation. The viscosities of WPC solutions were independent of solution age in the pH range 4–8 at all concentrations up to and including 20%, the precise pH range narrowing as concentration increased. At pH values above or below this range apparent viscosity became dependent on both pH and solution age, the age effect becoming more marked at higher WPC concentrations. Apparent viscosity at pH 7 increased markedly with both CaCl2 concentration and solution age at concentrations above 0·6 M-CaCl2, the age effect in this case increasing with CaCl2 concentration. In contrast, NaCl concentrations of up to 0·8 M-NaCl had little effect on apparent viscosity. The rheological behaviour of WPC solutions changed from time-independent to time-dependent shear thinning at high concentration, at extreme pH values, at high CaCl2 concentration (after ageing) and on heating to above ∼ 60 °C. This change is considered to be caused by the formation of structure in solutions; a 40% solution (at 22 °C and pH 6·75) exhibited classic thixotropic behaviour in a step–shear rate experiment.
Toxin production byBacillus cereusin dairy products
Authors: Sutherland Alastair D. 
Published: June 2009

SummarySpores of a known toxigenic and psychrotrophic dairy isolate ofBacillus cereus(HRM 44) were unable to grow and produce diarrhoeagenic toxin at 6 °C in creams and dairy-based products. These findings suggest that the production ofB. cereusdiarrhoeagenic toxin is unlikely to occur in creams and dairy-based products maintained within the cold chain. Growth and toxin production were readily demonstrated in creams and some desserts stored at 21 °C. Growth in creams was associated with obvious spoilage. However, in the flavoured desserts, spoilage was not always obvious before significant growth ofB. cereusand toxin production had occurred. Dairy desserts with high sugar content and/or low pH did not support toxin production and these findings are discussed.
Milk whey proteins in plasma of sows: variation with physiological state
Authors: Dodd Susan C. , Forsyth Isabel A. , Buttle Hugh L. , Gurr Michael I. , Dils Raymond R. 
Published: June 2009

SummaryThe whey proteins α-lactalbumin and βMactoglobulin have been investigated as potential markers of mammary development in sows by measuring their concentrations in plasma. The whey proteins were isolated from porcine milk by gel filtration, ion-exchange and hydrophobic interaction chromatography, characterized by several criteria and used to raise antibodies. Specific radioimmuno-assays were set up for porcine α-lactalbumin and β-lactoglobulin and validated for use in porcine blood and milk. Plasma levels of the whey proteins were measured in sows that were pregnant, suckling litters post partum, weaned abruptly at birth or were pregnant but mastectomized. Both whey proteins showed similar patterns in plasma post partum, falling from a maximum 1 d after parturition to values < 0·02% those in milk by day 4–5 post partum in suckling sows and showing a transient peak associated with early involution before declining to very low concentrations in non-suckling sows. α-Lactalbumin was first detected in the last week prepartum, rising markedly in the 3 d before parturition, correlated with rising prolactin (r= 0·986) and falling progesterone (r= –0·998). β-Lactoglobulin rose much earlier from 5 weeks prepartum, at the time when lobulo-alveolar mammary development is occurring, and correlated (r= 0·929) with oestradiol-17β. In mastectomized sows, concentrations of whey proteins in plasma were reduced by 90% or more when compared with intact animals, though following a similar pattern. This study shows that whey protein concentrations in plasma vary with physiological state and reflect aspects of the development of the mammary gland. The very different profiles for α-lactalbumin and β lactoglobulin prepartum indicate that they are differently controlled.
Distribution and density ofα– andβ–adrenergic receptor binding sites in the bovine mammary gland
Authors: Hammon Harald M. , Bruckmaier Rupert M. , Honegger Ulrich E. , Blum Jürg W. 
Published: June 2009

SummaryRadioreceptor binding studies were designed to localize and determine the number of α and β-adrenergic receptors in the mammary gland of lactating cows.3H-prazosin,3H-rauwolscine and3H-dihydroalprenolol were used for the regional characterization of α1, α2- and β-adrenergic receptors by competitive inhibition of binding of3H-ligands with unlabelled adrenergic agonists and antagonists. The α1-, α2- and β2-adrenergic receptor subtypes could thus be demonstrated in the regions of the teats, large mammary ducts and parenchyma. Tissues of the teat wall, of the large mammary ducts above the gland cistern and of the mammary parenchyma were prepared to determine the density of α1, α2- and β-receptors by saturation binding assays using3H-prazosin,3H-rauwolscine and3H-dihydroalprenolol respectively. Binding to high affinity sites was reversible within minutes and saturable. Equilibrium was reached within minutes. The number of α1-and α2-adrenergic receptors decreased from the teat to the mammary ducts to the parenchyma. Most of the α1- and α2-adrenergic receptors were found in the teat wall, whereas in the parenchyma α-adrenergic receptors were absent or barely detectable. The density of β-adrenergic receptors was similar in the teat wall and the large mammary ducts, but much lower in the parenchyma. Thus, α1, α2- and β-adrenergic receptors were found mainly in the milk purging system and hardly at all in mammary parenchyma. Inhibition of milk removal by α-adrenergic stimulation is possibly due to constriction of teat wall and to constriction of the mammary ducts, whereas enhanced milk flow after β-adrenergic stimulation is possibly due to relaxation not only of the teat sphincter and teat wall, but probably also of the large mammary ducts.
Rapid, sensitive two-site ELISA for detection of cows' milk in goats' or ewes' milk using monoclonal antibodies
Authors: Levieux Didier , Venien Annie 
Published: June 2009

SummaryA sandwich ELISA (enzyme-linked immunosorbent assay) of the two-site type has been successfully developed for the detection of cows' milk in goats' or ewes' milk. The assay uses two monoclonal antibodies (MAb) raised in mice against cows' β-lactoglobulin (β-lg). These MAb recognize different epitopes of the β-lg, which are sufficiently distinct to allow simultaneous binding of the corresponding antibodies. One of the MAb recognizes a species-specific epitope of the bovine β-lg and was adsorbed to a plastic microtitration plate (capture antibody). The second MAb was labelled with peroxidase and used to detect the captured cows' β-lg. Factors affecting assay performance were investigated. The optimized assay is highly specific, reproducible (intra- and inter-assay CV were 8 and 13% respectively) and sensitive: as little as 5 ng β-lg/ml or 1 part cows' milk per 100000 parts goats' or ewes' milk can be detected. The technique is robust, cheap, rapid, reliable and suitable for high sample throughput, semi-automation and screening surveys. The MAb used guarantee the high specificity of the assay and indefinite reagent supply of constant quality once approved by collaborative national or international trials.
Some aspects of measuring the size and rate of dispersion of milk powder agglomerates using the Malvern Particle Sizer 2600c
Authors: Chen X. Dong , Lloyd Richard J. 
Published: June 2009

SummaryThe Malvern Particle Sizer, which applies Fraunhofer light diffraction theory, has recently become popular for measuring particle size distributions in dried milk and other powders. The size distribution is obtained by dispersing the powder in air or a suitable liquid in the laser light beam of the instrument. The suitability of the dry powder dispersion system (DPD system) of the Malvern Particle Sizer 2600c for characterizing agglomerated milk powders was examined. It was found that, although the instrument gave reproducible and reliable results for non-agglomerated powders (standard milk powders), milk powder agglomerates could be broken in the standard DPD system and erroneous size distributions might be obtained. However, the DPD system had potential for providing an objective test of the mechanical stability of milk powder agglomerates. In addition, the transient size distribution during dispersion of an instantized agglomerated milk powder in water was measured at intervals of about 20 s.
Thermostability of yeast lactase (Kluyveromyces marxianus) in milk
Authors: Mahoney Raymond R. , Wilder Teresa 
Published: June 2009

SummaryThe half-life (∼ 2 h) of commercial yeast lactase (Kluyveromyces marxianus) in milk at 45 °C was 20 times greater than in milk salts and 50 times greater than in phosphate buffer. K was a more effective stabilizer than Na, both in milk salts and buffer. Stability was markedly reduced by the absence of divalent cations. Lactose and caseinate both stabilized the enzyme about 5-fold in milk salts, but together they stabilized it almost 50-fold. At equimolar concentrations, galactose was almost as effective as lactose as a stabilizer, but glucose was much less effective and sucrose had no effect. Stability in milk was independent of enzyme concentration, but varied with concentration of milk solids, reaching a maximum at about 25% solids. In milk, enzyme denaturation was more sensitive to changes in temperature in the range 42–53 °C than in the range 30–40 °C. At a concentration of 10O-nitrophenyl-β-d-galactopyranoside units/ml it took 19 min at 45 °C to achieve 80% hydrolysis of lactose in milk, compared to 87 min at 30 °C.
Influence of lactic cultures in denaturation of whey proteins during fermentation of milk
Authors: Vaitheeswaran Nataraja Iyer , Bhat Gajanan S. 
Published: June 2009

SummaryUndenatured whey protein (UWP) content of skim milk acidified with lactic acid or cultured with lactic cultures was estimated by a dye-binding method. The UWP content decreased with increase in acidity and the denaturation was only partly reversible on neutralization to the original acidity. The decrease in UWP was higher in cultured milk than in the milk acidified to the same extent with lactic acid, indicating the effect of lactic cultures in denaturation of whey proteins during fermentation of milk. Among the lactic cultures the denaturation effect of Lactobacillus delbrueckii subsp. bulgaricus was highest, followed by Streptococcus salivarius subsp. thermophilus, Lactococcus lactis subsp. lactis and Lact. lactis biovar diacetylactis. Denaturation of whey proteins by lactic cultures was found to be partly irreversible.
Laboratory simulations of a commercial UHT treatment using an oil bath and a programmable, electronically temperature-controlled oven
Authors: O'Connor Robyn E. , O'Connor Colin 
Published: June 2009

SummaryHeat stability of secreted bacterial proteinase is normally assessed using an oil bath test in which the sample is heated at a temperature and time representing the commercial UHT treatment of milk. The temperature/time (T/t) profiles of the oil bath and the commercial UHT process being represented are not taken into account. Two laboratory procedures were used to simulate a commercial UHT process in which milk was heated to 140°C and held for 3 s in a Spiroflo heat exchanger. They consisted of a conventional oil bath test and the use of a programmable, electronically temperature-controlled oven.T/tprofiles were established for each heat treatment. TheT/tprofile of the oil bath test was predicted accurately using the governing heat transfer equation.B*andC*values, which measure the severity of a heat process, were calculated from theT/tprofiles and used to compare the three different heat treatments.B*andC*values of 4·95 and 1·92 respectively were calculated for the Spiroflo heat exchanger. An oil bath test, in which the sample was immersed in a bath at 136°C for 73 s, gave approximately the sameB*andC*values as calculated for the Spiroflo heat exchanger.B*andC*values of 5·01 and 1·73 respectively were calculated for the oven procedure. The oven test gave the better laboratory simulation of the Spiroflo UHT treatment. Despite the slight difference in each of theB*andC*values between the oven and the Spiroflo, theT/tprofile of the oven test closely resembled that of the Spiroflo. TheT/tprofile of the oil bath was completely dissimilar. Although it was possible to use an oil bath test to replicate simultaneously both theB*andC*values of this particular UHT treatment, this would not be the case for other commercial processes.
Effect of plane of nutrition on insulin sensitivity during lactation in the ewe
Authors: Metcalf John A. , Weekes Timothy E. C. 
Published: June 2009

SummaryThe hyperinsulinaemic euglycaemic insulin clamp technique was used to compare insulin sensitivity in lactating ewes at two levels of feeding. Clamps were performed at two (restricted intake) or three (ad libitum intake) stages of lactation and also 30 d after drying off. Dose response curves for insulin were constructed using the glucose metabolic clearance rate (MCR) as the measure of glucose metabolism and these were statistically compared between stages of lactation within the feeding levels, and also between feeding regimes. Animals on a restricted feed intake showed a weight loss throughout lactation, coupled with a lower insulin sensitivity, as measured by the ED50 (concentration of insulin required to produce a half maximal increase in MCR), while those on ad libitum feeding showed a weight gain and a decreased insulin sensitivity in the dry period. Endogenous glucose production was less sensitive to inhibition by insulin in the animals subjected to restricted food intake, compared with those on the ad libitum regime, which suggested a major role for the plane of nutrition in adjusting the homeorhetic control of metabolism during lactation.
Bacteriological investigations of clinical mastitis in heifers in Sweden
Authors: Jonsson Per , Olsson Sven-Ove , Olofson Ann-Sophie , Fälth Christer , Holmberg Olof , Funke Hans 
Published: June 2009

SummaryBacterial analyses were carried out of 2069 udder secretions, isolated from 1481 heifers with mastitis in eight veterinary districts in Sweden. Streptococci, e.g. Streptococcus dysgalactiae and Str. uberis, dominated the bacterial flora, being isolated from 34·4 and 19·5% respectively of heifers with clinical mastitis occurring from puberty up to 14 d post partum. Bacterial species generally regarded as important pathogens in the summer mastitis complex, e.g. Actinomyces pyogenes, Stuart–Schwan coccus and strictly anaerobic bacteria such as Peptostreptococcus indolicus, Fusobacterium necrophorum and Bacteroides melaninogenicus were isolated at low frequencies (13·2, 6·3, 9·4, 3·8 and 1·3% respectively). When the cases of mastitis studied were restricted to those appearing in heifers pre partum, May 15 to October 14 (summer mastitis), these bacterial species were isolated at higher percentages (27·1, 14·4, 21·4, 13·5 and 5·2% respectively). These figures were, nevertheless, still lower than those published in reports from other countries. Whether considered up to 14 d post partum or only pre partum, there were no significant differences in the frequencies of A. pyogenes isolated at different seasons. There were geographical differences in bacterial incidence, e.g. Staphylococcus aureus was isolated significantly more often in northern regions whereas Str. dysgalactiae was more common in the south. This and other Swedish investigations support the theory that A. pyogenes and strictly anaerobic bacteria are ‘secondary invaders’ that depend on Str. dysgalactiae to cause a primary infection. It is stressed that the udders of all heifers should be examined daily so that cases of mastitis can be treated immediately.
Influence of milk flow rate and streak canal length on new intramammary infection in dairy cows
Authors: Grindal Robert J. , Walton Andrew W. , Hillerton J. Eric 
Published: June 2009

SummaryEighteen cows with a wide range of quarter peak flow rates (0·35–2·22 kg/min) were inoculated with Streptococcus agalactiae and Str. dysgalactiae 4 mm into each streak canal every 3 d for 12 d. Thirty of the 72 quarters developed intramammary infection. Mean peak flow rate and length of streak canal of those quarters that became infected were 1·26 ± 0·08 kg/min (mean ± SEM) and 11·47 ± 0·41 mm respectively, compared with 1·01 ± 0·05 kg/min and 12·05 ± 0·35 mm for those that remained uninfected. Logistic regression analysis showed that the probability of infection increased significantly with the increase in peak flow rate (P = O·O1). The influence of streak canal length on new infection, after allowing for the effect of peak flow rate, was not significant at the 5% level (P = 0·07), suggesting that there may be an inverse relationship between teat duct length and infection, but that it is of secondary importance to peak flow rate. If increased mass of milk distends the teat duct by raising intramammary pressure, then quarter susceptibility to infection is further compromised. These results strongly suggest that the benefits of reduced infection from mastitis control, achieved despite dramatic increases in milk flow rate and milk yield, are significantly underestimated.
Effects of α- and β-adrenergic agonists on intramammary pressure and milk flow in dairy cows
Authors: Bruckmaier Rupert , Mayer Harald , Schams Dieter 
Published: June 2009

Summaryα-Adrenergic mimetics inhibit milk removal whereas β-adrenergic mimetics have a favourable effect upon milk removal in dairy cows. This work aimed to relate these effects to the milk ejection reflex mechanism and/or milk flow from the cisternal cavities only. The α-adrenergic agonist phenylephrine and the β-adrenergic agonist isoproterenol were injected prior to and after milk ejection. Applied after milk ejection, the phenylephrine treatment reduced intramammary pressure (IMP) and milk yield markedly. Phenylephrine application before milk ejection prevented IMP from rising during teat stimulation or after oxytocin injection. Milking produced small amounts of milk at minimal milk flow rates. The very different responses to phenylephrine application prior to and after milk ejection indicate separate adrenergic inhibitory mechanisms for milk ejection and milk flow. The application of the β-adrenergic agonist isoproterenol did not alter the IMP. Nevertheless, this compound improved milk removal by increasing milk flow. The observation of bimodal milk flow at milkings without preceding teat stimulation indicates a delayed milk ejection. Isoproterenol injection without teat stimulation enhanced milk flow rates, but the bimodality remained unchanged. We conclude that isoproterenol enhances milk flow without affectiiig milk ejection.
Enzymic modification of αs1-casein with peptidylarginine deiminase: preparation of less acid-coagulable and less calcium-sensitive casein
Authors: Azuma Norihiro , Nara Kazutoshi , Kanno Choemon 
Published: June 2009

SummaryEnzymic modification with peptidylarginine deiminase (EC 3.5.3.15) enabled five out of six arginyl residues in αs1-casein to be convcrted to citrullyl residues, only the N-terminal arginyl residue remaining unaffected. An increase in the net negative charge was confirmed by PAGE. The isoelectric point was decreased from 4·46 for the intact αsl-casein to 4·30 for the deiminated type, while simultaneously lowering the acid-precipitation starting point from pH 5·17 to pH 4·62. The deiminated αs1-casein self-associated less in the absence of Ca and was less Ca-sensitive than the native type, although its Ca-binding ability was slightly enhanced. In the presence of 25 mM-CaC12andK-casein, Ca-induced precipitation of αs1-casein did not occur, the solution of the mixture remaining transparent. Deimination of αs1-casein resulted in altering its characteristics, possibly by interfering with interactions through hydrophobicity and/or hydrogen bonding. The positive charge of the arginyl residues might play an important role in casein micelle formation.
Immunoadjuvant activity of oralLactobacillus casei: influence of dose on the secretory immune response and protective capacity in intestinal infections
Authors: Perdigón Gabriela , Alvarez Susana , de Ruiz Holgado Aída Pesce 
Published: June 2009

SummaryLactobacilli, often used as effectors of host functions, could play an important role in maintaining human health by controlling other intestinal microorganisms capable of producing harmful effects. Using an experimental model, we studied the effect of different oral doses ofLactobacillus caseion the secretory IgA response and the protective capacity of the microorganism in preventing intestinal infections. The optimization of the protective dose ofLb. caseiby previous feeding and the use of the lactobacillus as an immunological way to control enteric infections were investigated. We found that conventional mice were protected against infection withSalmonella typhimuriumandEscherichia coliby previous feeding for 2 consecutive days with a dailyLb. caseidose of 1·2 × 109cfu/mouse. Previous feeding for 7 d proved less effective, and feeding for 5 d afforded no protection at all. We were also able to demonstrate that the protective effect ofLb. caseiagainstSal. typhimuriumandEsch. coliwas connected mainly with the high level of IgA antipathogen antibodies present in intestinal secretions. β-Glucuronidase (EC 3.2.1.31) and β-galactosidase (EC 3.2.1.23) activities, measured both in the intestinal fluid and histological samples, showed a marked increase in intestinal inflammatory response on day 5 of feeding. These results show thatLb. caseiplays an important role in the prevention of enteric infections, a low dose being enough for protection against intestinal infections by increasing IgA secretion into the intestinal lumen, thus providing adequate defences for the mucosal surface. A previously administered dose of this magnitude could therefore be used as an oral adjuvant in preventing enteric infections.
Somatic cell counts in relation to infection status of the goat udder
Authors: Kalogridou-Vassiliadou Despina , Manolkidis Konstantinos , Tsigoida Afrodite 
Published: June 2009

SummaryBacteriological analyses, cell counts using the Fossomatic method and California Mastitis Test were performed on 1523 goat milk samples taken aseptically at monthly intervals throughout lactation from three goat herds. Of the goat udders, 81·4% were infected, minor pathogens being the most frequent isolates (65·7%). Differences in the level of infection by minor pathogens were found betwccn herds. Cell counts were influenced by stage of lactation and intramammary infection. Cell counts < 106cells/ml were found in 80% of milk samples infected by major pathogens and in 45% infected by minor pathogens. About 81% of udders infected with major pathogens gave California Mastitis Test scores of 2 and 3, compared with 20% for uninfected goats. A high proportion (65%) of udders infected with minor pathogens also produced scores of 2 and 3. A significant positive correlation was found between the California Mastitis Test and cell counts. The use of cell counts for the detection of abnormal goat milk is discussed.