bluuebunny/crossref_metadata_2025_split huggingface dataset:
Yogurt production from reconstituted skim milk powders using different polymer and non-polymer forming starter cultures
Authors: Wacher-Rodarte Carmen , Galvan Marcia V. , Farres Amelia , Gallardo Francisco , Marshall Valerie M. E. , Garcia-Garibay Mariano 
Published: June 2009

SummaryUsing polymer producing (ropy) strains of lactic acid bacteria it was possible to reduce considerably the syneresis of yogurt, even with 12% total milk solids. The viscosities obtained with these strains were also similar to those obtained using normal strains and milk with 17% total solids content. The concentration of milk and the polymer produced by ropy starters had a synergic effect in increasing viscosity. Polymer production was not affected in most cases by milk concentration. One type of ropy culture (Wiesby) seemed to produce a different kind of polymer as it could not be determined by alcohol precipitation, in spite of being able to reduce syneresis and increase viscosity in yogurt. A limited number of yogurts were evaluated organoleptically, one prepared with a ropy starter strain (NCFB at 12, 14·5 and 17% total solids) and one prepared with a non-ropy strain (LL-I at 17% total solids). The results suggest that the ropy strain yogurts had different mouthfeel from the non-ropy strain yogurts; the most acceptable product overall was the ropy strain made with 12% total solids.
Bromocriptine treatment of periparturient goats: long-term suppression of prolactin and lack of effect on lactation
Authors: Forsyth Isabel A. , Lee Philip D. 
Published: June 2009

SummaryBritish Saanen dairy goats (n = 10) were treated with bromocriptine or vehicle from day 147 of pregnancy to day 4 post partum, a treatment duration of 8·8±1·7 d (mean ± SEM). The periparturient prolactin surge was abolished by this treatment, but there were no significant effects on plasma growth hormone or insulin concentrations. Lactogenesis was delayed in the bromocriptine-treated goats, milk yields being significantly depressed (P < 0·01) for the first week of lactation. Yields had recovered to control values by day 10 when prolactin concentrations were still significantly depressed. Mammary gland biopsies were taken on day 4 post partum from five animals in each group. Using this tissue, no significant differences could be shown in mammary morphology or DNA synthesis, but the RNA:DNA ratio was significantly reduced (P < 0·05). After week 1, there were no significant differences between bromocriptine-treated and control goats in milk yield, milk composition, udder volume, time of peak yield or persistence. The goats given short-term bromocriptine treatment at parturition showed prolonged effects on prolactin secretion, their seasonal prolactin rise being severely blunted (P < 0·001). A normal lactation is therefore not prevented in goats by a delay in lactogenesis, suppression of prolactin at parturition or the resulting prolonged depression of circulating prolactin. Goats in established lactation given bromocriptine for 8 d showed, by contrast, a rapid recovery of plasma prolactin concentrations within 5 d post treatment. Milk yield declined significantly (P < 0·03) compared with pretreatment values during and for 1 week after bromocriptine but then began to recover, with no significant change in vehicle-treated goats.
Concentration of citrate in the mammary secretion of sows during lactogenesis II and established lactation
Authors: Holmes Mark A. , Hartmann Peter E. 
Published: June 2009

SummaryThe functional significance of citrate in the mammary secretion of six sows was investigated during the second stage of lactogenesis (lactogenesis II) and established lactation. The changes in the concentrations of progesterone and lactose in the maternal blood, and lactose, Na and K in the mammary secretion, suggested that lactogenesis II began during the final day of pregnancy. The concentration of citrate in the mammary secretion of the sows during lactogenesis II was high and varied from 5·4 (SEM 0·5) mai at day 0·5 post partum to 6·8 (SEM 0·4) mM at day 1·5 post partum. There was a decline of ˜ 30% in the concentration of citrate in the milk of sows during the first week of lactation. These findings suggest that, in contrast to all other species studied previously, milk citrate is not a harbinger of lactogenesis II in the sow. However, the changes in the concentration of citrate in the mammary secretion of sows may reflect changes in the rate ofde novosynthesis of fatty acids that take place in the mammary glands of sows during lactogenesis II and established lactation.
Proteolysis during storage of UHT milk: differences between whole and skim milk
Authors: López-Fandiño Rosina , Olano Agustin , Corzo Nieves , Ramos Mercedes 
Published: June 2009

SummaryProteolysis during storage of UHT skim and whole milks processed by either direct or indirect systems has been studied. All the proteolysis indices determined (measurement of free amino groups, PAGE of caseins and PAGE and reversed-phase HPLC of the fraction soluble at pH 4·6) revealed greater proteolytic degradation during storage of skim milks compared with that of whole milks subjected to the same UHT treatments. Increased activities of both native milk proteinase and proteinases of bacterial origin were observed in skim UHT milks. The different behaviour of UHT skim and whole milks on storage would have to be taken into account in establishing the process conditions.
Interactions of temperate bacteriophages ofStreptococcus salivariussubsp.thermophiluswith lysogenic indicators affect phage DNA restriction patterns and host ranges
Authors: Fayard Blandine , Haefliger Moritz , Accolas Jean-Pierre 
Published: June 2009

SummaryAfter treatment with mitomycin C, 12 of the 120 strains of the French Collection of Lactic Acid Bacteria (CNRZ) belonging to the speciesStreptococcus salivariussubsp.thermophiluswere found to be inducible and lysogenic. The corresponding temperate phages were multiplied on indicator strains and further characterized. It is noteworthy that some of the indicators were themselves lysogenic. The temperate phages belonged to Bradley's group B, or to theSiphoviridaefamily of the International Committee on Taxonomy of Viruses. Seven of them were shared among the two protein profiles previously established for virulent phages ofStr. salivariussubsp.thermophilus. Seven different DNA restriction profiles were found for ten native temperate phages examined just after mitomycin C induction. Genome sizes varied from 40 to 45 kb and were classified into four related homology groups by DNA cross-hybridization, but there was no clear-cut relationship with the protein clusters previously shown. DNA homology with representatives of virulent phages was also found. The DNA restriction profiles of seven native temperate phages, examined just after mitomycin C induction of the lysogenic hosts, were noticeably different from those of the corresponding phages once they had been propagated on lysogenic indicators. Moreover, the host range of the latter phages was extended to a greater number of sensitive strains. The possible role of lysogenic strains ofStr. salivariussubsp.thermophilusin the occurrence of phage outbreaks affecting this dairy streptococcal species is discussed.
Milk removal in familiar and unfamiliar surroundings: concentrations of oxytocin, prolactin, cortisol andβ–endorphin
Authors: Bruckmaier Rupert M. , Schams Dieter , Blum Jürg W. 
Published: June 2009

SummaryEight cows were machine milked either in an operating theatre or in their familiar barn. During the experiments, milk flow curves were recorded and blood samples were taken for determination of concentrations of oxytocin, prolactin, cortisol andβ–endorphin. The milking cluster was attached without udder preparation. After cessation of milk flow, air was blown into the vagina for 2 min. When milk flow had stopped again, 1 i.u. oxytocin and finally 10 i.u. oxytocin were injected to remove the remaining milk. After the start of milking, oxytocin remained basal in unfamiliar, but increased in familiar surroundings. Therefore, during normal milking only 9% of total milk was removed in unfamiliar, whereas 79% was available in familiar surroundings. In response to subsequent vaginal stimulation in the operating theatre, oxytocin increased transiently in five cows and 15–71% of the milk was removed in these animals. In the other three cows in the operating theatre, oxytocin remained basal during vaginal stimulation, and no more milk was available. After injection of 1 i.u. oxytocin, 56 and 11%, and after injection of 10 i.u. oxytocin, 13 and 8% of milk was removed in unfamiliar and familiar surroundings respectively. Concentrations of prolactin increased during the course of milking in both treatments. Premilking concentrations of cortisol andβ–endorphin were elevated in unfamiliar as compared with familiar surroundings. During the course of milking, cortisol increased slightly andβ–endorphin decreased in unfamiliar, whereas both hormones increased markedly during milking in familiar surroundings. We conclude that disturbed milk removal in unfamiliar surroundings is due to central inhibition of oxytocin release during normal milking and partly also to a response to vaginal stimulation. This blockade is possibly associated with elevated concentrations ofβ–endorphin.
Influence of pH and sugars on the growth and production of diarrhoeagenic toxin byBacillus cereus
Authors: Sutherland Alastair D. , Limond Ann M. 
Published: June 2009

SummaryBroth cultures supplemented with high levels of sugars, particularly glucose at > 50 g/1, did not support diarrhoeagenic toxin production by psychro-trophicBacillus cereusdespite growth to high counts ( ∼ 107/ml) over a 4 d period of incubation at 21 °C. In contrast, starch levels of 10 and 50 g/l actually enhanced toxin production. Toxin production was also affected by pH levels of broth cultures, and was concomitant with alterations in bacterial growth. These findings help to explain variations in toxin levels previously found in some dairy desserts, which were thought to be associated with pH and sugar content (Sutherland, 1993).
Changes in the gelation mechanism of whey protein concentrate with pH and temperature
Authors: Taylor Stephen M. , Gladden Lynn F. , Fryer Peter J. 
Published: June 2009

SummaryThe percolation model of Steventon et al. (1991) successfully detected changes in the mechanism of whey protein concentrate gelation with pH and temperature by comparing simulated with experimental gelation times. The results demonstrated that at 71 °C and pH 5·2 the formation of an aggregate from two denatured protein molecules (initiation) was the rate-determining step in the gelation process, while at pH 7·0 the addition of denatured protein molecules to an aggregate (propagation) was rate-determining. At pH 5·9, the gelation process was also initiation limited, with the rate being slower than for pH 5·2 solutions, probably owing to electrostatic effects. Analysis of the temperature dependence of the gelation time, and percolation analysis both showed that there was a change in the rate-controlling reaction at 73 °C for gelation at pH 5·2 and 7·0. In the case of pH 7·0 gelation, this change in rate-controlling reaction was not due to a change from denaturation- to aggregation-controlled gelation, but was probably due to a change in the relative rates of interactions between protein molecules. Gelation at pH 5·2 was aggregation-controlled at temperatures below 73 °C, and denaturation-controlled at higher temperatures; there appeared to be another change in rate-limiting reaction at 80–85 °C without a change in mechanism (i.e. it remained denaturation-limited). The activation energies of the rate-limiting reactions determined from analysis of the temperature dependence of gelation time and from percolation analysis were in agreement. This is evidence that the changes in the rate-controlling reaction of whey protein concentrate gelation with temperature and pH were real.
Arsenic content of Spanish cows' milk determined by dry ashing hydride generation atomic absorption spectrometry
Authors: Cervera M. Luisa , Lopez J. Carlos , Montoro Rosa 
Published: June 2009

SummaryThe arsenic content of cows' milk consumed in Spain was determined. A procedure using dry ashing hydride generation atomic absorption spectrometry was developed for the purpose. Experimental conditions for the destruction of organic matter were established and an interference study was carried out. The method developed has a detection limit of 0·1 ng/g, a relative SD of 5%, and a recovery (mean ± CSI) of 100 ± 4%. The accuracy of the method was checked by analysis of a certified sample of IAEA milk powder (mean ± CSI: certified, 4·85 ± 0·32 ng/g; found, 5·04 ± 0·81 ng/g). The proposed procedure was used to analyse cows' milk samples. The extremely low arsenic levels found do not present toxicological problems.
Identification of the unsaturated oxo fatty acids in cheese
Authors: Brechany Elizabeth Y. , Christie William W. 
Published: June 2009

SummaryThe nature and composition of the unsaturated (monoenoic) oxo fatty acids in Cheddar cheese have been re-evaluated. Following isolation by column chromatography and silver ion HPLC, the fatty acids were identified in the form of their picolinyl ester derivatives by gas chromatography–mass spectrometry. For confirmation, they were analysed similarly following deuteration of the double bonds with deuterium and Wilkinson's catalyst. Fifteen fatty acids were identified fully, only five of which corresponded to those reported in an earlier study. Isomers with double bonds in positions 5, 7, 9 and 11–15 were identified, with oxo groups in positions 8, 9, 10, 13, 16 and 17, and with chain-lengths varying from C14 to C18, but with C18 predominating.
Thermal gelation and denaturation of bovine β-lactoglobulins A and B
Authors: McSwiney Mary , Singh Harjinder , Campanella Osvaldo , Creamer Lawrence K. 
Published: June 2009

SummaryHeat-induced gelation, an important functional property of β-lactoglobulin, was studied by measuring the rheological properties of both the A and B variants of the protein during and after heat treatment within a range of pH, temperature and concentration. Gel electrophoresis was used to determine the extent of denaturation and disulphide bond crosslinking of some samples. Both variants formed gel networks on heating at temperatures > 75 °C, and under most conditions the storage modulus (G′) of βlactoglobulin A gels was higher than the G′ of β-lactoglobulin B gels, in particular after cooling to 25 °C. A minimum protein concentration of 50 g/1 was required for gel formation at pH 7·0 in 0·1 M-NaCl by both variants at 80 °C. Increasing the protein concentration above 50 g/1 increased G′, the extent of increase being much greater for the A variant than the B variant. G′ of variant A gels was not much influenced by pH whereas G′ of variant B gels decreased slightly from pH 3 to pH 6 and increased between pH 6 and pH 9. When mixtures of the two variants were gelled G′ increased at the temperature of heating (80 °C) and after cooling (25 °C) as the relative quantity of variant A was increased. Comparisons of the loss of discrete protein bands from electrophoretic gels (native-PAGE, SDS-PAGE and SDS-PAGE of reduced samples) showed that heating β-lactoglobulin solutions of 100 g/1 at pH 7 in 0·1 M-NaCl and at 75, 80 and 85 °C caused a faster loss of both native and SDS-soluble β-lactoglobulin A than of β-lactoglobulin B. It was concluded that the loss of native β-lactoglobulin structure from these solutions during heating was faster than the formation of disulphidelinked aggregates, which was faster than gel formation for both β-lactoglobulin A and β-lactoglobulin B, and that each of these reactions was faster for β-lactoglobulin A than for β-lactoglobulin B. This contrasts with conclusions drawn from some previous studies and may arise from the differences in protein concentration between the present study (∼ 100 g/1) and the previous ones (< ∼ 10 g/1).
Production of volatile compounds in model milk and cheese media by eight strains of Geotrichum candidum Link
Authors: Jollivet Nathalie , Chataud Jean , Vayssier Yves , Bensoussan Maurice , Belin Jean-Marc 
Published: June 2009

SummaryEight strains of Geotrichum candidum isolated from cheese were compared for aroma production. Twenty-four components, including alcohols, methyl ketones, fatty acids and esters, were identified by gas–liquid chromatography and gas chromatography–mass spectrometry of the volatile compounds produced by G. candidum cultures. Strains could be differentiated by their ability to produce dimethyldisulphide, phenol, phenylethanol and methyl ketones.
Autolysis and proteolysis in different strains of starter bacteria during Cheddar cheese ripening
Authors: Wilkinson Martin G. , Guinee Timothy P. , O'Callaghan Daniel M. , Fox Patrick F. 
Published: June 2009

SummaryAutolysis of and proteolysis by variousLactococcus lactissubsp.cremorisstrains were monitored in cheese ‘juice’ extracted by hydraulic pressure up to 63 d ripening. Viability was lowest for strain AM2 (non-bitter), intermediate for strain HP (bitter) and highest for the defined mixed strains G11/C25 (non-bitter). Autolysis monitored by the levels of the intracellular marker enzymes lactate dehydrogenase (EC 1.1.1.27), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and post-proline dipeptidyl aminopeptidase proceeded in the order AM2 > G11/C25 > HP. Differences in autolysis between strains did not appear to be due to differences in stabilities of the marker enzymes, populations of non-starter lactic acid bacteria or levels of the marker enzymes in the strains. Proteolysis, as measured by gel permeation FPLC and free amino acid analysis of the cheese juice was highest for AM2, intermediate for G11/C25 and lowest for HP. The results of this study provided some evidence that differentLactococcusstrains used for cheesemaking had different autolytic patterns during ripening, the effects of which on ripening and flavour development have not yet been clearly demonstrated.
Machine milking of dairy goats during lactation: udder anatomy, milking characteristics, and blood concentrations of oxytocin and prolactin
Authors: Bruckmaier Rupert M. , Ritter Chantal , Schams Dieter , Blum Jürg W. 
Published: June 2009

SummaryForty-four goats were milked and milk flow recorded without or with 1 min manual prestimulation in early, mid and late lactation. Ultrasound measurements of cross sections of the whole mammary gland were performed in a water bath. In additional experiments with 15 goats, milk flow was recorded and frequent blood samples were taken for the determination of oxytocin and prolactin concentrations. Milk yield increased from the first to the third lactation and decreased markedly during the course of lactation. Average and peak milk flow rates were closely related to the actual milk yield. The ultrasound cisternal area was 27·4±1·5% of the entire udder half cross section. Milking characteristics were scarcely different without or with prestimulation, although oxytocin was released within 30 s after the start of prestimulation, whereas oxytocin concentrations without prestimulation increased only after the start of milking. Concentrations of prolactin were higher during July and August than in April, and increased similarly with or without prestimulation during milking. In contrast to dairy cows, prestimulation and an opportune release of oxytocin during milking does not significantly influence the course of milk flow in goats, and this is probably because large amounts of cisternal milk allow milk ejection to be induced only after the start of milking without causing bimodal or otherwise reduced milk flow.
Rennet coagulation of milk in the presence of sucrose
Authors: Famelart Marie-Hélène 
Published: June 2009

SummaryThe aim of this work was to test the diffusion-controlled hypothesis of milk coagulation kinetics by reducing the diffusion coefficient of casein micelles. This has been achieved by increasing the solvent viscosity of milk through sucrose addition. Milk was reconstituted from skim milk powder and sucrose added at 100–300 g kg–1. Hydrolysis and coagulation were followed by chromatographic determination of caseinomacropeptide content and optical, thermal and viscoelastic measurements. Soluble and ionic calcium were determined by atomic absorption spectrophotometry and ionometry and micelle size was measured by dynamic light scattering. Addition of sucrose resulted in a substantial retardation of both enzymic and aggregation steps, a re-equilibration of calcium because of water reduction, and a micelle size increase. The enzymic rate constant was inversely proportional to the viscosity, according to a diffusion-controlled model, and the lag or characteristic times for the aggregation reaction were inversely proportional to the viscosity. These results are consistent with the involvement of diffusion-controlled steps in the sequence of reactions.
Variability of reduced glutathione levels in Massese ewes and its effect on daily milk production
Authors: Rizzi Rita , Caroli Anna , Bolla Patrizia , Acciaioli Anna , Pagnacco Giulio 
Published: June 2009

SummaryThe variability of the erythrocyte concentration of the tripeptide glutathione was studied in four flocks of Massese sheep. A relationship was found between glutathione level and stage of lactation in which the second month showed the lowest content. Genotype at transferrin and haemoglobin loci was associated with glutathione levels. Homozygotes at the transferrin locus yielded higher levels, while the D allele at the same locus was associated with lower concentrations. Animals with haemoglobin AA showed higher contents of glutathione. Also, a negative correlation was found between daily milk production and glutathione level.
Distribution of cholesterol in milk fat fractions
Authors: Arul Joseph , Boudreau Armand , Makhlouf Joseph , Tardif Rene , Grenier Benoit 
Published: June 2009

SummaryMilk fat was fractionated into liquid (m.p. ⋍ 12 °C), intermediate (m.p. ⋍ 21 °C) and solid (m.p. ⋍ 39 °C) fractions by three different processes—melt crystallization, short-path distillation and supercritical CO2extraction—and the cholesterol content of these fractions determined. Cholesterol was enriched in the liquid fractions from all three processes, in particular about 80% of the cholesterol being found in the liquid fraction obtained by short-path distillation. The basis of migration of cholesterol into various milk fat fractions was explained by its affinity to various triglycerides (melt crystallization) and by vapour pressure and molecular weight (short-path distillation). It was more complex in the supercritical CO2extraction process; the interplay of cholesterol affinity toward CO2and its molar volume, and its vapour pressure enhancement under applied pressure play a role.
Opioid antagonist peptides derived from κ-casein
Authors: Chiba Hideo , Tani Fumito , Yoshikawa Masaaki 
Published: June 2009

SummaryOpioid antagonists were sought in the fragments of κ-casein which were obtained by chemical synthesis and enzymic digestion. A synthetic bovine κ-casein peptide (35–41), Tyr-Pro-Ser-Tyr-Gly-Leu-Asn (casoxin A) showed opioid antagonist activity at 200 μM in the guinea pig ileum assay. A synthetic peptide Tyr-Pro-Tyr-Tyr (casoxin B) which is found in bovine and human κ-casein, also showed opioid antagonist activity at 100 μM. Another opioid antagonist peptide (casoxin C) was isolated from tryptic digests of bovine κ-casein by reverse-phase HPLC. The structure of the peptide was Tyr-Ile-Pro-Ile-Gln-Tyr-Val-Leu-Ser-Arg, which corresponded to κ-casein (25–34). Casoxin C was active at 5 μM in the guinea pig ileum assay. Thus, bovine κ-casein contains three potential opioid antagonist sequences.