bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the extracellular lipases ofPseudomonas fluorescensspp. in skim milk with the β-naphthyl caprylate assay
Authors: McKellar Robin C. , Cholette Hilaire 
Published: June 2009

SUMMARYA method based on the hydrolysis of β-naphthyl caprylate (β-NC) has been developed for quantitating extracellular lipase fromPseudomonas fluorescens. The assay was extremely sensitive to skim milk (SM); as little as 0·02 ml raw SM in a 2·0 ml reaction mixture resulted in an apparent loss of 50% of the lipase activity. Activity improved 3-fold when trypsin (50 μg/ml) was included in the reaction mixture. When super-simplex optimization was used to determine the optimum levels of β-NC, Na taurocholate (NaTC), SM/lipase mixture and trypsin for maximum activity, NaTC was found to be unnecessary for activity. Subsequent addition of 15 mM-NaTC resulted in 80% loss of activity. On the other hand, NaTC was required for native lipase activity in the presence of SM. Native lipase was completely inhibited by heating at 70 °C for 2 min, while B52 lipase retained 75% of its activity under the same conditions. The assay was able to detect lipase produced byPs. fluorescensB52 in SM at 5 °C when the cell density exceeded 108colony forming units/ml. The presence of butterfat (3°5%) in the SM assay inhibited B52 lipase by 97%. The β-NC assay gave results comparable to the tributyrin agar diffusion assay using cell-free extracts of ten strains of common dairy psychrotrophs. The results suggest that the β-NC assay may be useful for determining lipase activity in raw SM.
Effect of casein micelle composition and casein dephosphorylation on coagulation and syneresis
Authors: Pearse Martin J. , Linklater Peter M. , Hall Robert J. , Mackinlay Antony G. 
Published: June 2009

SUMMARYThe effect of varying the casein composition of artificial micelle milk on rennet coagulation time and syneresis was examined in order to determine whether either of these processes is dependent on the concentration of particular casein components. It was found that the levels of κ-and β-caseins had a significant effect on coagulation, whereas syneresis was only affected by the level of β-casein. Partial dephosphorylation of preformed micelles or the incorporation of dephosphorylated or partly dephosphorylated β-casein into artificial micelle milk was found to have an adverse effect on both coagulation and syneresis. It was concluded that the phosphate groups of casein, particularly those of β-casein, are directly involved in the micelle-micelle interactions which occur during coagulation and syneresis.
Identification of cheese-smear coryneform bacteria
Authors: Seiler Herbert 
Published: June 2009

SUMMARYThree groups of coryneform bacteria isolated from the rind of nine soft and semi-hard cheese varieties, i.e. the orange, white and yellow strains, were studied with regard to morphological and physiological features. The 115 orange isolates of the Brevibacterium linens type formed only one homogeneous phenon. The 96 white and 161 yellow pigmented strains were grouped into 15 phena. Five phena (58% of the strains) belong to the species ‘B. ammoniagenes’, Arthrobacter variabilis and A. nicotianae. The other strains were arranged into five Arthrobacter spp. and four Corynebacterium spp. groups as well as a Rhodococcus sp. group. Usually specific forms for the individual cheese varieties were involved. In cheeses of poor surface-smear quality B. linens was found in reduced numbers.
A glyco-phosphoprotein in human milk
Authors: Azuma Norihiro , Yamauchi Kunio 
Published: June 2009

SummaryA highly glycosylated phosphoprotein (HGPP) was isolated from a human casein fraction by reversed-phase high-performance liquid chromatography. This component contained carbohydrates to ∼ 38·2% (w/w) and phosphorus to ∼ 1·6% (w/w). The molecular weight of this HGPP as estimated by sodium dodecyl sulphate–polyacrylamide gel electrophoresis ∼ 41000. Ultracentrifugal analysis revealed that the sedimentation coefficient of the HGPP was 2·6S in a 10 mM-imidazole-HCl buffer at pH 7·0 and 27 °C, but this component interacted with human κ-casein and formed a complex with s = 10·4S.
Effect of the protein, citrate and phosphate content of milk on formation of lactulose during heat treatment
Authors: Andrews Geoffrey R. , Prasad S. Krishna 
Published: June 2009

SummaryMilk ultrafiltrate and milks of varying protein, citrate and phosphate concentrations were heated in sealed containers. Protein was found not to be involved in the mechanism of formation of lactulose, but increasing the protein content of milk reduced the concentration of lactulose after heating. This was considered to be due to increased condensation of lactose and lactulose with amino groups of the protein, Less lactulose was formed in milk ultrafiltrate than in skimmed milk accorded the same heat treatment, which was attributed to the buffering capacity of the milk protein in skimmed milk. Activation energies for lactulose formation in skimmed milk and in ultrafiltrate were 128 and 131 kJ/mol respectively. Citrate and phosphate catalysed the formation of lactulose. It is proposed that the formation of free lactulose in heated milk and ultrafiltrate proceeds exclusively by the Lobry de Bruyn-Alberda van Ekenstein transformation with the naturally occurring phosphate and citrate acting as base catalysts.
Improvement in the quality of the dried fermented milk product, oggtt
Authors: Al-Ruqaie Ibrahim M. , El-Nakhal Hamza M. , Wahdan Ahmed N. 
Published: June 2009

SummaryOggtt is a dried fermented milk product made and marketed primitively under uncontrolled conditions in the Arabian peninsula. By applying controlled conditions for production, the keeping quality of oggtt was greatly improved. The two types (cooked and salted) were produced from fresh pasteurized goats' or cows' milk or from skim milk powder. Oggtts flavoured with chocolate, date, mint or different fruits were also produced. Chemical composition and organoleptic properties of the final products were evaluated. Taste panel results indicated that the plain products, including those made from reconstituted milk, were acceptable, but flavoured oggtts, with the exception of date flavour, were not popular.
Lactulose content, colour and the organoleptic assessment of ultra heat treated and sterilized milks
Authors: Andrews Geoffrey R. , Morant Steven V. 
Published: June 2009

Summary24 ultra heat treated (UHT) and 17 in-bottle sterilized milks prepared in commercial plants and of a similar age were presented to taste panels for assessment of flavour and colour. The colour was also analysed instrumentally and the lactulose content of the milks measured by an enzymic method. Flavour defects, other than the cooked flavour, were scored very low. The lactulose content of the milks was negatively correlated with the acceptability of the milks and positively correlated with the cooked flavour. Correlations were also found between the visual and instrumental assessments of milk colour and between some of the instrumental colour parameters and the lactulose content of the milks. UHT and in-container sterilized milks could not always be distinguished on the basis of their organoleptic qualities. The best distinction was observed in the scores for cooked smell and acceptability of taste. The usefulness of the lactulose content and/or the colour of the milks in discriminating between UHT and in-bottle sterilized milks was calculated. Using all the data, sterilized milk could be correctly identified in 96·7% of decisions. The lactulose content of a milk was considered to give a good indication of the organoleptic quality of the milk.
Heat stability of milk: role of β-lactoglobulin in the pH-dependent dissociation of micellar κ-casein
Authors: Singh Harjinder , Fox Patrick F. 
Published: June 2009

SummaryOn heating casein micelle systems containing β-lactoglobulin (β-lg) at 90°C for 10 min, β-lg complexed with casein micelles at pH < 6·9, probably as a result of interaction with κ-casein via sulphydryl-disulphide interchange, and co-sedimented with the micelles on ultracentrifugation. Complex formation with β-lg appeared to prevent the dissociation of micellar κ-casein on heating. However, at pH ≥ 6·9, κ-casein/β-lg complexes dissociated from the micelles on heating, thus enhancing the release of micellar κ-casein. High concentrations of β-lg (≥0·8%) induced coagulation at pH 7·3, essentially by promoting the dissociation of micellar κ-casein. It appeared that αs1-, αs2-, β- and κ-caseins dissociated from serum protein-free casein micelles to equal extents, but the presence of β-lg specifically enhanced the dissociation of κ-casein at pH values ≥ 6·9. Micelle hydration increased slightly when casein micelles were heated in the presence of β-lg at pH 6·7, while at pH 7·3 β-lg decreased the degree of hydration of casein micelles. Formation of a complex between β-lg and κ-casein appeared to stabilize the micelles in the pH range 6·5–6·7, possibly via increased micellar charge or degree of hydration or by preventing the dissociation of κ-casein.
Cardiovascular responses and mammary substrate uptake in Jersey cows treated with pituitary-derived growth hormone during late lactation
Authors: Fullerton Frances M. , Fleet Ivan R. , Heap R. Brian , Hart Ian C. , Mepham T. Ben 
Published: June 2009

SummaryPituitary-derived bovine growth hormone (bGH) was administered to Jersey cows during late lactation for 7 d. Milk yield increased significantly during treatment and by a maximum of 49·6% on d 7. The magnitude of the increase was similar to that of mammary plasma flow (47·8±18·3%) over the same period. By 15–21 d after treatment, both variables had returned to pretreatment values. With respect to milk composition, bGH had negligible effect on lactose and fat concentrations but there were significant decreases in protein, sodium and chloride. Arterial plasma concentrations of bGH increased substantially during treatment, but the associated rise in insulin was not statistically significant. Haematocrit decreased significantly, the lowest value being recorded 3 d after bGH treatment ceased. Mammary respiratory quotient fell progressively after the start of bGH treatment and reached the lowest recorded value 3 d after treatment ceased (62·2 ± 7·3% of pretreatment value). Glucose and acetate uptake by the mammary gland increased significantly during treatment, increase in glucose uptake being due both to a greater arterio-venous difference and to mammary plasma flow. There was strong evidence that the acute response in increased milk yield was associated with multiple effects in terms of mammary plasma flow and metabolism, as well as haematocrit changes indicative of increased plasma volume.
Accelerated ripening of Feta cheese, with heat-shocked cultures or microbial proteinases
Authors: Vafopoulou Anna , Alichanidis Efstathios , Zerfiridis Gregory 
Published: June 2009

SummaryAccelerated ripening was successfully achieved in Feta cheese by the addition of a heat-shocked culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, or neutral or acid microbial proteinase. Optimum levels of microbial proteinases were established at which trichloroacetic acid-soluble N (TCA-N) compounds were increased by about 35% in 40 d. Treated cheeses of this age had flavour intensities and body and texture qualities typical of 80 d-old control cheeses. Any further increase in TCA-N by adding larger amounts of enzyme resulted in bitterness. Heat-shocked culture treated cheeses developed similar characteristics to those prepared with neutral or acid proteinases. In contrast to the control cheese, it was necessary in the experimental cheeses to add minute amounts of lamb lipase (0·1–0·2 g/100 kg milk) to the cheese milk to keep the flavour balance. Best organoleptic characteristics were obtained from cheese treated with heat-shocked culture, followed by those treated with neutral or acid proteinase.
Prevention of gastrointestinal infection using immunobiological methods with milk fermented withLactobacillus caseiandLactobacillus acidophilus
Authors: Perdigon Gabriela , de Macias Maria E. Nader , Alvarez Susana , Oliver Guillermo , de Ruiz Holgado Aida A. Pesce 
Published: June 2009

SummaryThe protective effect of feeding milk fermented with a mixture ofLactobacillus caseisp. andLb. acidophilussp. againstSalmonella typhimuriuminfection in mice was compared with that obtained feeding milks fermented with these microorganisms individually. The survival rate obtained after oral infection withSal. typhimuriumwas 100% in mice pretreated by feeding during 8 d with the mixture ofLb. caseiandLb. acidophilusfermented milks. Similar treatments with the individual milks were ineffective. Moreover, mice became more susceptible to infection withSal. typhimuriumafter such treatment. The colonization of liver and spleen with the pathogen was markedly inhibited by the pretreatment with the mixture of fermented milk, while such inhibition was not observed using theLb. caseiandLb. acidophilusmilks. The highest levels of anti-salmonellae antibodies in serum and in intestinal fluid were found in the group of mice fed with the mixture and withLb. caseifermented milk respectively. However, this latter milk was not effective in protecting againstSal. typhimurium. When the mice were first infected withSal. typhimuriumand then fed with the mixture of fermented milks, pathogen colonization was not prevented. The results suggest that the augmentation of resistance to salmonellae caused by the treatment withLb. casei-+Lb. acidophilus-fermented milk was due to the anti-salmonellae protective immunity mainly mediated by the mucosal tissue. Milk fermented with this mixture could be used as an immunobiological method to prevent gastrointestinal infection.
Cost benefit analysis of bovine mastitis in the UK
Authors: Beck Harvey S. , Wise William S. , Dodd Frank H. 
Published: June 2009

SummaryBovine mastitis reduces the yield and quality of milk and increases the rate of culling and veterinary costs. This reduces the profitability of farm milk production but the calculation of the extent of this economic loss is complex because of the many factors involved and deficiencies in the evidence on the relationship between the disease and various production factors. This paper examines the available evidence for the UK and provides a consistent analytical framework within which the benefits arising from reduced mastitis in dairy herds constrained by quota can be considered. It is estimated that since 1970 the farms that have followed the recommended control procedures have reduced the average annual number of cases of clinical mastitis from 135 to 40 cases/100 cows each year, while the quarters remaining uninfected for a whole year has increased from 65 to 80% of the total quarters. The costs of the main control procedures (e.g. £8–60/cow for dry-cow therapy and teat dipping or spraying) are broadly covered by the reduction in clinical mastitis, leaving the benefits of reduced subclinical infection (e.g. £3810 for a 100 cow herd unconstrained by quota and achieving the average reduction in infection) as a substantial bonus. The imposition of quotas reduces the financial benefit of mastitis control but it still remains a worthwhile investment. The results of this analysis can be used to suggest maximum costs of additional new control measures produced by research. It also indicates that there is considerable value in production research which gives more precise knowledge of production Systems, thus allowing producers to respond optimally to quota cuts.
Effects on milk yield and composition of intra-abomasal infusions of sodium caseinate, an enzymic hydrolysate of casein or soya-protein isolate in dairy cows
Authors: Choung Jai-Jun , Chamberlain David G. 
Published: June 2009

SummarySix lactating dairy cows receiving a diet of grass silage and barley were given the following treatments as infusions into the abomasum, in a replicated 3 × 3 Latin square with 10 d periods: sodium caseinate (C), an enzymic hydrolysate of casein (CH) and soya-protein isolate (SPI). The C and CH treatments supplied ~ 185 g/d and the SPI treatment ~ 160 g/d of amino acids. Milk yield was similar for all treatments. Yields of milk protsein were 605, 604 and 582 (P > 0·05) g/d for C, CH and SPI respectively. For C, CH and SPI respectively, concentrations (g/kg) of fat were 39·6, 45·7 and 41·9 and yields (g/d) of fat were 790, 931 and 827; values for CH were significantly (P < 0·01) higher than for either of the other treatments. It is concluded that the form in which amino acid residues of casein are supplied to the abomasum (protein v. peptide–amino acid mixtures) can influence the partition of use of nutrients between body tissues and the mammary gland.
Effect of the A and B variants of both αs1- and κ-casein on bovine casein micelle solvation and κ-casein content
Authors: Anema Skelte G. , Creamer Lawrence K. 
Published: June 2009

SummaryCasein micelle solvation, a micelle characteristic that is sensitive to many factors, has been measured by a centrifugation technique at 30 °C for a series of uncooled fresh skim milks at pH 6·3, 6·6, 6·9 and 7·1. The relative αs-(αs1- plus αs2-), β– and κ-casein contents of all centrifuge pellets and supernatants were determined by a standardized electrophoretic method. The calcium and phosphate contents of a number of the pellets and milk samples were also determined. Solvation of micelles from milks with various genetic variants of β-lactoglobulin (A and B), αs1-casein (A and B) and κ-casein (A and B) was often found to be lower for milks containing either the B variant of αs1-casein or the A variant of κ-casein. It was also found that these two variant caseins were associated with a lower κ-casein content of the milks and the micelles, which is consistent with the lower solvation as κ-casein is associated with smaller micelle size and greater solvation. The solvations also seemed to increase during the lactation period. It is possible that some of the other features of milk and its products that have been ascribed to the differences in functional character between the A and B variants of αs1-casein may be partly caused by the increased level of κ-casein. The reason for the association of the A variant of αs1-casein with higher concentrations of κ-casein (and micelle solvation) is not obvious but possibly the haplotype αs1-casein A, β-casein A1, κ-casein A contains a controlling sequence in the chromosomal DNA that enhances expression of the κ-casein gene.
Effect of the levels of N fertilizer, grass and supplementary feeds on nitrogen composition and renneting properties of milk from cows at pasture
Authors: Hermansen John E. , Ostersen Steen , Aaes Ole 
Published: June 2009

SummaryIn a 2 × 2 × 3 factorial design grazing experiment we investigated the effect of fertilizer (none or 240 kg N/ha), amounts of clover grass available (low or high) and type and level of daily supplementary feed for each cow (3·5 kg barley, 3·5 kg concentrate mixture rich in protein and fat, or both, 7 kg) on the protein composition and renneting properties of their milk. The experiment was carried out in two successive grazing seasons (years) and included a total of 79 Danish Holstein cows. The effect on milk protein composition was determined in both years whereas the effect on renneting properties was determined only in the second year. Fertilization of the clover grass significantly decreased total milk protein concentration (− 1·4 g/kg; P < 0·01) and tended also to decrease the relative proportion of whey protein N. Fertilization had no effect on renneting properties. Increased availability of clover grass significantly increased milk protein concentration (1 g/kg; P < 0·05) and resulted in significantly poorer renneting properties, that is increased clotting time (P < 0·01) and decreased coagulum development. These effects seemed to be mediated through an effect on the pH of the milk (+ 0·05; P < 0·05) as the effect was markedly reduced when statistical correction was made for the actual pH. Use of the protein- and fat-rich concentrate mix (3·5 kg) significantly reduced the total protein content of the milk (P < 0·05) and increased the proportion of non-protein N (NPN) in total N compared with use of the other supplementary feeds (P < 0·05). We found no effect on renneting properties of the different supplementary feeds. Throughout the grazing season and independent of the main treatments, the NPN proportion of milk N increased at the expense of casein N. At the same time, renneting properties became poorer, especially with high clover grass availability.
Disulphide arrangement in bovine caseins: localization of intrachain disulphide bridges in monomers of κ- and αs2-casein from bovine milk
Authors: Rasmussen Lone K. , Højrup Peter , Petersen Torben E. 
Published: June 2009

SummaryNaturally occurring monomeric κ-casein and αs2-casein in bovine milk were purified by ion-exchange chromatography in order to localize potential intrachain disulphide bridges. Enzymic cleavage of the proteins followed by mass spectrometry and amino acid sequence analysis of cystine-containing peptides revealed the presence of an intrachain disulphide bond in both proteins.
Distribution of lysosomal enzymes within the non-secretory epithelium of the bovine mammary gland
Authors: Mattila Tuna , O'Boyle Denise , Frost Alan J. 
Published: June 2009

SummaryThe levels ofN-acetyl-β-glucosaminidase (NAGase) and acid phosphatase were analysed in tissue from the teat and lactiferous sinus epithelia of dairy cows at different stages of lactation. Enzyme levels were lower in the epithelia of the teat sinus than of the lactiferous sinus. For both enzymes, levels were highest in tissue from post-partum glands, lowest in those from dry and mid-lactation glands. In involuting glands the levels were high, but not as high as the post-partum glands.
Antimutagenic activity of whole casein on the pepper-induced mutagenicity to streptomycin-dependent strain SD 510 ofSalmonella typhimuriumTA 98
Authors: Hosono Akiyoshi , Shashikanth Kunigal N. , Otani Hajime 
Published: June 2009

SummaryWhen the antimutagenic activity of milk or cultured milk components on the pepper-induced mutagenicity to streptomycin-dependent strain SD 510 ofSalmonella typhimuriumTA 98 was investigated, whole casein showed a significant antimutagenic activity. Heating at 121 °C for 15 min completely destroyed the antimutagenic activity of casein, which was temperature dependent. While acid or papain digestion resulted in the loss of antimutagenic activity of casein, trypsin digestion had little effect although the digestion of casein by each proteinase was over 75%. β-Casein, egg albumin, and bovine serum albumin also had a similar antimutagenic activity to that of whole casein.
Small-angle X-ray scattering investigation of the micellar and submicellar forms of bovine casein
Authors: Pessen Helmut , Kumosinski Thomas F. , Farrell Harold M. 
Published: June 2009

SummarySmall-angle X-ray scattering was performed on whole casein under submicellar (Ca2+ removed) and micellar (Ca2+ re-added) conditions. Submicellar scattering curves showed two Gaussian components which were interpreted in terms of a spherical particle with two concentric regions of different electron density, a relatively compact core of higher electron density and a looser shell. Normalized scattering curves and calculated distance distribution functions were consistent with this picture. Micellar scattering data, which can yield only cross-sectional information related to a window of scattered intensities, could be analysed by a sum of three Gaussians with no residual function. The two Gaussians with the lower radii of gyration were again taken to indicate the two concentric regions of different electron density of inhomogeneous spherical particles; the third Gaussian was shown to reflect the packing number of these particles within a cross-sectional portion of the micelle, which was 3:1 for this system. These results are a strong indication that submicellar inhomogeneous particles containing hydrophobically stabilized inner cores exist within the colloidal micelle.