bluuebunny/crossref_metadata_2025_split huggingface dataset:
A rapid colorimetric assay for the extracellular lipase ofPseudomonas fluorescensB52 using β-naphthyl caprylate
Authors: McKellar Robin C. 
Published: June 2009

SUMMARYConditions necessary for the determination of crude extracellular lipase activity fromPseudomonas fluorescensB52 using β-naphthyl caprylate (β-NC), an 8-carbon ester, as the substrate were examined. Maximum enzyme synthesis occurred at 20 °C in pyruvate mineral salts medium containing 1 mM-CaCl2. Bile salts were necessary for enzyme activity; 6 mM-Na taurocholate or Na deoxycholate gave maximum activity but the latter compound was inhibitory at higher concentrations. Activity was optimal in N-Tris[hydroxymethyl]methyl-2-aminoethane sulphonic acid buffer pH 8·0 at 40 °C. A comparison of β-NC with β-naphthyl butyrate (a 4-carbon ester) and β-naphthyl myristate (a 14-carbon ester) showed that β-NC was the best substrate;Kmvalues of 0·0415, 0·141 and 0·200 mM andVmaxvalues of 67·2, 20·1 and 5·28 μmol ml-1h-1were obtained for those substrates respectively. The enzyme was inhibited 50% in its activity against β-NC by 0·009 mM-EDTA, 0–0007% (w/v) mixed alkyltrimethylammonium bromide and 0·00275% (w/v) Triton X-100. The biochemical properties determined using β-NC as substrate are consistent with those reported for the lipases of other strains ofPs. fluorescensusing natural substrates.
Heat stability of milk: further studies on the pH-dependent dissociation of micellar κ-casein
Authors: Singh Harjinder , Fox Patrick F. 
Published: June 2009

SUMMARYWhey protein complexed and became co-sedimentable with casein micelles after heating milk at ≥ 90°C for 10 min at pH ≤ 6·9 while at higher pH values (7·3) whey proteins and κ-casein-rich protein dissociated from the micelles on heating. κ-Casein-deficient micelles were more sensitive to heat, Ca2+or ethanol than whey protein-coated or native micelles and were readily coagulable by rennet. Isolated κ-casein added to skim milk before preheating (90°C for 10 min) did not associate with the micelles at pH ≥ 6·9. Sodium dodecyl sulphate increased the level of both non-sedimentable N (NSN) andN-acetylneuraminic acid (NANA) and shifted the NSN-pH and NANA-pH curves to more acidic values while cetyltrimethylammonium bromide had the opposite effect. It is suggested that the pH-dependent dissociation in micellar κ-casein, which appears to be reversible, depends on the surface charge on the micelles; at a certain negative charge, disruption of hydrophobic and electrostatic forces could result in the dissociation of κ-casein from the casein micelles.
Metabolism of the lactating cow: III. Properties of mechanistic models suitable for evaluation of energetic relationships and factors involved in the partition of nutrients
Authors: Baldwin R. Lee , France James , Beever David E. , Gill Margaret , Thornley John H. M. 
Published: June 2009

SummaryTWO models of lactating dairy cows were constructed by combining mechanistic models of digestion and metabolism reported previously and by adding elements to allow simulation of changes in tissue metabolic capacities over time. One model (day version) had an integration interval of 0·005 d and was suitable for simulation of within-day dynamics of nutrient supply and partition. The other (lactation version) had an integration interval of 1 d and was suitable for simulation of full lactation cycles. A number of simulation analyses were conducted to characterize and evaluate the models, to examine quantitative and dynamic properties of mechanisms which influence partition of nutrients, to identify aspects requiring further study, and to illustrate the potential usefulness of mechanistic, as compared to empirical, models in analyses of energy balance in lactating dairy cows.
Failure of cortisol injected prior to milking to inhibit milk ejection in dairy cattle
Authors: Mayer Harald K. , Lefcourt Alan M. 
Published: June 2009

SummaryTO test the potential for Cortisol to inhibit milk ejection directly, 18 Holstein cows were divided equally into control and treatment groups based on milk yields. For treated animals, a single injection of Cortisol was made into the saphenous vein 15 min before milkings. Increasing amounts of cortisol (0, 25, 50, and 100 mg) were injected for one morning and one evening milking, with the exception that the treated cows received only one 100 mg injection. Control animals received injections of 0·9% (w/v) NaCl. Cortisol injections had no effect on milk yields. However, a potential inhibitory mechanism might involve a delay, perhaps due to the necessity of synthesizing a regulatory protein. Therefore, to test the potential for increased cortisol over a period of hours to inhibit milk ejection, six of the nine cows in the treatment group were injected with 100 mg of cortisol at 3·25, 2·25, 1·25 and 0·25 h before sequential morning and evening milkings. In blood samples taken 1 min before and after injections, base-line cortisol concentrations averaged 10·2 mg/ml; after injection they were 984·1 ng/ml, and before subsequent injections they were 37·6 ng/ml. Again cortisol injections had no effect on milk yields.
ACTH initiation of mammary secretion in pregnant goats is influenced by the stage of gestation and pre partum milking
Authors: Stewart Harriet J. , Walker Felicity M. Maule 
Published: June 2009

SummaryPregnant goats were treated with ACTH by intramuscular injection (1 mg/d for 2 d) at various stages of pregnancy to investigate its effect on initiation of mammary secretion. ACTH stimulated lactose secretion and increased udder volume at or after 84 d of gestation, when compared with untreated controls. Treatment with ACTH between d 109 and 127 of gestation increased circulating plasma glucose concentration, mammary blood flow and mammary uptake of glucose which returned to pre injection levels 6 d after treatment. Arterial concentrations of progesterone were not affected by ACTH but mammary progesterone uptake increased 2-fold. Pre partum milking alone stimulated mammary secretion in eight of 13 goats. Subsequent treatment with ACTH resulted in no further change in the composition of the secretion but increase in yield was maintained. ACTH stimulated mammary secretion in those goats which did not respond to pre partum milking. It was concluded that ACTH initiated mammary secretion in pregnant goats by mechanisms which interact with the stimulation of milking but which are independent of circulating progesterone levels.
Comparison of a gelation and a chromogenicLimulus(LAL) assay for the detection of Gram-negative bacteria, and the application of the latter assay to milk
Authors: Svensson Annelie , Hahn-Hägerdal Bärbel 
Published: June 2009

SummaryWhen a chromogenicLimulusAmoebocyte Lysate (LAL) assay and a tube gelation LAL assay were compared for the detection of Gram-negative bacteria, using a strain ofPseudomonas putida, the detection level (∼ 103cfu/ml) and cost of the assays were approximately the same for both assays but the reading was more precise for the chromogenic substrate assay. A modified chromogenic assay was devised for detection ofPs. putidain milk.
Synthesis, effectiveness and metabolic fate in cows of the caesium complexing compound ammonium ferric hexacyanoferrate labelled with 14C
Authors: Arnaud Maurice J. , Clement Charles , Getaz Françoise , Tannhauser Fritz , Schoenegge Rainer , Blum Jürg , Giese Werner 
Published: June 2009

SummaryAdding ammonium ferric hexacyanoferrate (AFCF) to cows' fodder produced after the Chernobyl nuclear accident prevented milk contamination by increasing the faecal elimination of 137Cs. Synthesis of ammonium ferric hexa[14C]-cyanoferrate (AF14CF) and its purification were performed for the study of the metabolic fate of this complex, and the evaluation of the possible release of cyanide. The stability of this colloidal product, tested by anaerobic incubation in rumen juice in vitro, showed no release of free cyanide from AF14CF, but hexacyanoferrate was identified in the rumen juice and 0·13% of the added radioactivity was converted to labelled CO2. AF14CF administered per os to two cows showed a nearly quantitative excretion of radioactivity in faeces during the first 3 d (91–95%). A very low but significant level of radioactivity appeared in plasma, blood cells, expired CO2 and was detected in organs taken 9 d after administration. Total cumulative radioactivity in urine and milk amounted to 0·19–0·47% and 0·068–0·071% respectively for the two cows. Labelled hexacyanoferrate and thiocyanate were identified in the urine and also in faeces. In spite of this relative instability of AFCF in the rumen of cows, the poor absorption of AF14CF degradation products showed that AFCF constitutes an efficient and safe food additive to prevent the absorption of radioactive caesium from ruminant feed and its secretion in milk.
An in-line sampling technique to measure the bacterial contamination of milk during milking
Authors: McKinnon Charles H. , Bramley A. John , Morant Steven V. 
Published: June 2009

SummaryThe development of devices to sample milk at the clawpiece and at the end of the pipeline during milking are described. The results of tests to compare the bacteriological and compositional quality of milk collected from the sampling devices or from the recorder jar or milk cans were similar, demonstrating that the samples provided accurate and representative values. The use of the in-line sampling technique, whereby samples of the milk are taken at three points during its passage through the milking plant, to assess accurately the sources of bacterial contamination of bulk tank milk on farms is discussed.
Effect of acidification of sheep's cheese whey with organic acids on the retention of protein and on the quality of Myzithra cheese
Authors: Pappas Christophoros , Voutsinas Leandros 
Published: June 2009

SummaryWhen 10% citric, lactic or acetic acid was added to sheep's milk cheese whey during its heating for Myzithra cheese preparation, protein retention in the cheese was increased. Acidification of whey to pH 5·2 with lactic acid before heating followed by readjustment to pH 5·8 with NaOH was considered to be the best treatment for practical use, increasing whey protein retention in the cheese and yield without loss of flavour, aroma or texture.
Effect of different oxygen concentrations in the gas phase on biochemical activities of goat mammary tissue in organ culture
Authors: Škarda Josef , Urbanová Eva 
Published: June 2009

SummaryNon-secretory mammary expiants from virgin goats showed higher RNA and protein synthesis in a low O2 gas phase (air) than in high O2 (95% O2). Lipid and casein synthesis was not affected significantly by the concentration of O2 in the atmosphere during culture. on the other hand, the more developed mammary tissue from primigravid goats showed higher lipid, casein and protein synthesis in 95% O2. The relative response of mammary tissue to hormones was not substantially different when cultured in the presence of a low or high O2 gas phase. As Hepes-buffered medium was found not to need a supply of CO2 to maintain the correct pH and as Hepes did not interfere with biochemical activities of cells, it is recommended to use it for cultures in a low O2 gas phase.
Compression and impact strength of gels, prepared from fractionated whey proteins, in relation to composition and microstructure
Authors: Langley Keith R. , Green Margaret L. 
Published: June 2009

SummaryGels varying in protein content and composition were prepared from whey proteins by a standard method and their compression and impact strengths were determined. No surface friction could be observed between the gels and the compression plates, and the Poisson's ratio was close to 0·5. Thus, the elastic moduli of the gels were determined. Compression and impact strengths and elastic moduli were related logarithmically to the β-lactoglobulin content of the protein powders. The strength and manner of fracture of the gels depended on the gel microstructure. Strong gels had a honeycomb structure consisting of a very tightly bound network, and failed by cracking on impact and by shear along cleavage planes in compression. Weaker gels had a loose open network with no definite means of fracture.
Effect of dietary unsaturated fatty acids in various forms on the de novo synthesis of fatty acids in the bovine mammary gland
Authors: Banks William , Clapperton John L. , Girdler Anne K. 
Published: June 2009

SummaryFree and protected soya oil and soya oil fatty acids were included in the rations of dairy cows and from outputs in the milk of 18:1 trans and of polyunsaturated acids conditions in the rumen have been deduced. Similarly, the content of citrate in the milk has been used to evaluate changes occurring in the synthesis of fatty acids in the mammary gland.
Ripening changes in Kopanisti cheese
Authors: Kaminarides Stelios E. , Anifantakis Emmanuel M. , Alichanidis Efstathios 
Published: June 2009

SummaryChanges in a Greek traditional soft cheese, Kopanisti, were followed during ripening. Mature cheese contained > 52% moisture, 22·7% fat and 19·3% protein. The as-casein content was hydrolysed faster than the β-casein so that in mature cheese only 23% and 35% respectively of these proteins remained intact. Soluble N, TCA-soluble N, amino acid N and NH3 were present to the extent of 28·9, 24·6, 14·3 and 6·6% of total N respectively. Leucine, γ-aminobutyric acid, valine and alanine were the dominant free amino acids in the mature cheese. Lipolysis was intense and the total free fatty acid content of ripe cheese was ∽ 50 g/kg cheese. The rate of liberation of short-chain (C4–C8) fatty acids was higher than that of the long-chain. The characteristic rich flavour and peppery taste appeared after 16 d ripening and the best overall cheese quality was produced after 32 d maturation.
Effect on cow performance and milk fat composition of including full fat soyabeans and rapeseeds in the concentrate mixture for lactating dairy cows
Authors: Murphy John J. , McNeill Gerald P. , Connolly James F. , Gleeson Patrick A. 
Published: June 2009

SummaryTwo experiments were carried out to determine the effect on milk yield, milk composition and composition and physical properties of milk fat of giving full fat soyabeans (FFS) and full fat rapeseeds (FFR) to dairy cows. In both experiments grass silage was provided ad lib. and constituted over 50% of the dry matter (DM) intake of the cows. In experiment 1, cows received 7·25 kg/d of a concentrate mixture containing 240 g/kg of extruded FFS or 7·25 kg/d of a mixture without soyabeans. Cow performance was not significantly affected by the inclusion of FFS but fatty acid composition of the milk fat was greatly altered. The contents of C8:0 to C16:0 were significantly reduced (P < 0·001) while the contents of C18:0, C18:l and C18:2 were significantly increased (P < 0·001). Milk fat produced during feeding on FFS concentrate had a significantly lower content of solid fat at temperatures between 0 and 25 °C compared with milk fat produced when FFS was not given. In experiment 2, cows received concentrate mixtures containing either no whole rapeseed, 150 g/kg of whole unground FFR or 150 g/kg of ground FFR. Milk yield was significantly higher and silage DM intake significantly lower with the ground FFR concentrate compared with the other two diets but milk composition was not significantly different among treatments. FFR inclusion, either ground or unground, reduced diet digestibility. Changes in fatty acid composition of the milk fat were similar to those observed with FFS inclusion but the effect was larger with ground FFR compared with unground FFR. Nuclear magnetic resonance analysis showed a lower solid fat content when the FFR diets were employed with the effect being greatest with ground FFR.
Effect of threonine and glycine on acetaldehyde formation in goats' milk yogurt
Authors: Rysstad Gunnar , Knutsen Wenche J. , Abrahamsen Roger K. 
Published: June 2009

SummaryThe effect of threonine on the biochemical activity of yogurt starter was investigated by the addition of L-threonine to cows' and goats' milk in two concentrations (5 and 10mg/100g). A separate experiment was conducted to investigate the effect of free glycine on the formation of acetaldehyde from yogurt starter. Increasing amounts of glycine (1, 2, 3, 4 and 5 mg/100 g) were added to samples of cows' milk. Addition of threonine to milk samples did not influence acid production, total bacterial growth, or the balance between cocci and rods in the yogurts. Raised levels of threonine resulted in increased production of acetaldehyde. This increase was more pronounced in goats' milk than in cows' milk. The production of acetaldehyde in cows' milk without added threonine was significantly greater than in goats' milk without addition of threonine. Addition of threonine did not influence the formation of diacetyl and α-acetolactic acid, whereas production of acetoin in both milks was reduced. No marked difference in the formation of C02 was observed in samples with or without addition of threonine. Addition of free glycine to cows' milk had a marked negative effect on the production of acetaldehyde by yogurt starter. Addition of 3 mg glycine/100 g cows' milk gave approximately the same amount of acetaldehyde as obtained in goats' milk yogurt. It is suggested that the relatively low amount of acetaldehyde usually observed in goats' milk yogurt is caused by a feed-back inhibition of threonine aldolase produced by the relatively high amount of free glycine present in goats' milk.
Observations on plasmin activity in cheese
Authors: Farkye Nana Y. , Fox Patrick F. 
Published: June 2009

SummaryLevels of plasmin activity in various commercial cheeses are reported. The effects of some processing conditions (pH, cooking temperature and method of salting) on plasmin activity in cheese were investigated. Neither draining pH nor method of salting affected the activity. However, plasmin activity in cheese, rennet curd and micellar casein dispersions increased with increasing cooking temperature. The results suggest that plasmin activity in cheese depends on cooking temperature used during manufacture.
Low-field nuclear magnetic resonance relaxation study of thermal effects on milk proteins
Authors: Lambelet Pierre , Berrocal Rafael , Renevey Francine 
Published: June 2009

SummaryA recently described nuclear magnetic resonance (NMR) method was evaluated for its usefulness in studying thermal effects on milk proteins. The increase in water proton T2 relaxation rate observed during thermal treatment of aqueous whey protein solutions above the denaturing onset temperature paralleled results obtained with the standard Rowland (1938) method. The influence of milk constituants on NMR characteristics was analysed. The NMR response increased with the ionic strength and the addition of caseinate or casein micelles. The relevance of the T2 relaxation probe for studying thermal modifications of milk proteins is discussed. It is proposed to apply the NMR method for determining either reversible or irreversible thermal denaturation of whey proteins in model Systems.
Effect of culture parameters on the production of styrene (vinyl benzene) and 1-octene-3-ol by Penicillium caseicolum
Authors: Spinnler Henry E. , Grosjean Olivier , Bouvier Isabelle 
Published: June 2009

SummaryPenicillium caseicolum has been shown to completely synthesize styrene. A medium was developed to test the capacity of different strains for this synthesis. In a synthetic medium, styrene production began only after the glucose was entirely consumed. This production depended on storage temperature and occurred simultaneously with 1-octene-3-ol formation.
Response of Jersey and Friesian cows to once a day milking and prediction of response based on udder characteristics and milk composition
Authors: Carruthers Vicki R. , Davis Stephen R. , Bryant Arnold M. , Henderson Harold V. , Morris Chris A. , Copeman Peter J. A. 
Published: June 2009

SummaryThe response of dairy cows to once a day (OAD) milking was investigated in four trials. Two trials involved Friesians (F) and Jersey cows selected for high (HP) or low (LP) milk protein concentration. Trial 1 compared 74 HP, LP and F cows milked either OAD or twice daily (TAD) for 2 weeks in both mid and late lactation. Trial 2 compared 98 HP, LP and F cows milked OAD or TAD for 12 weeks in early lactation. Trial 3 investigated the repeatability of production loss by milking identical twin cows either OAD or TAD during three 1 week periods. Trial 4 compared the time course of milk production in 32 cows milked every 12 or 24 h for 72 h. Cows milked OAD produced 10–28% less milk and milk solids in early to mid lactation and 9–13% less in late lactation than cows milked TAD. Losses in fat and protein yield were slightly lower than those of milk. HP, LP and F cows did not differ in percentage loss in milk and milk solids in Trial 1, except for loss in protein yield which was lower for HP than LP and F cows. In Trial 2 the losses in milk and milk solids were lower for HP cows than for F cows but the other differences were not significant. Milk storage ability of the udder (hours worth of secretion) was higher and productivity of the udder was lower for HP cows than F cows. Levels of residual milk did not differ among groups. The loss in udder capacity during lactation was greater for cows milked OAD than for those milked TAD. The correlations for repeated estimates of percentage losses in yields of milk and milk solids between successive OAD periods ranged from 0·29 to 0·49. Secretion rate of cows milked OAD was lower during the second 12 h than the first 12 h during each 24 h milking interval. Prediction of OAD performance based on milk composition and udder characteristics was poor. A high level of residual milk was the factor most consistently associated with high loss on OAD milking.
Purification and characterization of three proteins isolated from the proteose peptone fraction of bovine milk
Authors: Sørensen Esben S. , Petersen Torben E. 
Published: June 2009

SummaryThree major proteins from the proteose peptone of bovine milk were purified by Sephadex G-75 gel chromatography, Q-Sepharose ion-exchange and additional Sephadex G-75 gel chromatography in the presence of urea. From their mobility in a gradient SDS-PAGE, the proteins were found to have molecular masses of 17, 28 and 60 kDa. The N-terminal amino acid sequence of the 17 kDa protein was found to be homologous with a camel whey protein. This protein has not previously been described in bovine milk. From the SDS-PAGE results, the 28 kDa protein was judged to be the major protein of proteose peptone, contributing ~ 25% of the total. The N-terminal amino acid sequence showed no homology to any known protein sequence, but the amino acid composition indicated that the 28 kDa protein is identical with the PP3 component from the proteose peptone fraction of bovine milk, or part of it. The 60 kDa protein was found to be bovine osteopontin, a very highly phosphorylated protein with an Arg-Gly-Asp sequence which mediates cell attachment.
Routine Limulus amoebocyte lysate (LAL) test for endotoxin determination in milk using a Toxinometer ET-201
Authors: Mottar Jozef , De Block Jan , Merchiers Martine , Vantomme Kristien , Moermans Renaat 
Published: June 2009

SummaryA rapid method of performing the Limulus amoebocyte lysate (LAL) test in milk is proposed using the Toxinometer ET-201. This instrument measured the increase in turbidity due to the interaction between the endotoxins of the Gram-negative bacteria and the LAL reagent, monitored the ratio Rt of the sequential to the initial transmission at 12 s intervais and quantified endotoxins by determination of the reaction time Tr required to obtain a 5% decrease in Rt. There was a good correlation between the toxinometrically determined endotoxin concentrations and the number of Gram-negative bacteria (SD, 0·18 log(plate count units)), and the repeatability (CV, 6·10%) was high. The assay may be useful for screening raw materials for UHT milk production, as the endotoxin content of the raw material is related to the rest proteinase activity in the UHT milk.