bluuebunny/crossref_metadata_2025 huggingface dataset:
Relation between micelle size and formation of soluble casein on heating concentrated milk
Authors: Aoki Takayoshi , Kako Yoshitaka
Published: June 2009

In order to examine the influence of micelle size on the formation of soluble casein brought about by heating concentrated milk, casein micelles were separated into 3 fractions by differential centrifugation. The micelles were dispersed in the ultrafiltrate of skim-milk and the preparations were concentrated to 1/2·5 of the original volume. When the concentrated milk samples were heated at 135–140 °C, a larger amount of soluble casein was formed from smaller micelles than from larger micelles. Only a slight effect on the formation of soluble casein on heating was observed when colloidal calcium phosphate (CCP) was removed from the large micelles to a level lower than that associated with the small micelles or when the CCP in the small micelles was increased to a level higher than that of the large micelles. The soluble caseins formed on heating from different sizes of micelles were similar in composition. The fact that the formation of soluble casein on heating was affected by micelle size may be ascribed to variation in the κ-casein content of micelles rather than to variation in CCP content.
Proteolysis of caseins and the proteose-peptone fraction of bovine milk
Authors: Andrews Anthony T. , Alichanidis Efstathios
Published: June 2009

The proteolysis of highly purified samples of αs1-, αs2-, β-and κ-caseins by porcine plasmin and by bovine plasminogen with urokinase has been examined principally by gel electrophoresis. The resulting peptide band patterns were compared with those of total proteose-peptone (TPP) samples prepared from fresh and stored raw and pasteurized milk, and also with those obtained during the natural course of proteolysis by indigenous enzymes in milk during storage. TPP was found to contain at least 38 components detectable by a single electrophoresis run. Apart from residual traces of whey proteins and intact caseins nearly all of these components were fragments of caseins produced by indigenous plasmin, with products from the breakdown of αs1- and β-casein predominating. Over 90 % of TPP has been accounted for in this way. A fragment consisting of residues 29–105 of β-casein was isolated and characterized from both stored milk and from plasmin digests of β-casein. This fragment was a relatively major product of the natural proteolysis occurring during storage of milk, but contrary to a report in the literature it was not the same as proteose-peptone component 8-slow. Since many of the components of TPP resulted from proteolysis, the composition of TPP was found to vary according to the time and temperature of storage of the milk from which it was prepared. Thus, while the proteose-peptone fraction of milk can easily be defined operationally it cannot be rigorously defined in terms of its composition unless the history of the milk is also defined.
Lipid composition of milks from cows with experimentally induced mastitis
Authors: Needs Eric C. , Anderson Malcolm
Published: June 2009

Changes in milk lipid composition were measured during the course of mastitis infections induced in cows by infusion of eitherEscherichia coliendotoxin orStreptococcus agalactiaeinto 2 quarters of the udder; untreated quarters were used as controls. Experiments were divided into 3 distinct phases: a pre infusion period during which several samples were collected before infusion; a post infusion period following infusion and corresponding to the occurrence of elevated cell counts in milk from infused quarters; a recovery period followed after a short pause and represented the return of the cell count in milk from infused quarters to the level in the corresponding controls.

Milk total fatty acid composition was unaffected by the infusion. Free fatty acid (FFA) composition did, however, undergo some alteration. There was a significant increase in long-chain saturated acids in milk from infused quarters relative to the corresponding controls during the post infusion period. FFA concentration (mequiv./100 g fat) also increased significantly during this period although the net increase was only slight. Phospholipid and cholesterol concentrations were significantly higher post infusion in milk of infused quarters.

The results suggest that changes in concentration and composition of those milk constituents synthesized and secreted by the mammary epithelium occur after secretion in the alveolar lumen and milk ducts.
A procedure for the complete clarification of milk of various species and its suitability for use with colorimetric measurements
Authors: Owen A. Jane , Andrews Anthony T.
Published: June 2009

Bovine, caprine, ovine and human milks have been clarified by addition of Triton X-100 and EDTA followed by a short incubation. Generally, addition of 4·2% Triton X–100 and 5·4% EDTA was sufficient and with skim-milk samples no dilution was necessary. With whole milks some dilution and greater amounts of Triton X-100 or longer incubation times or higher temperatures were required. These factors were interrelated to some extent and the optimum conditions will be determined by convenience and any particular requirements of the experiment. The attainment of optically transparent milk samples greatly facilitates colorimetric measurements; as examples we have shown that total protein may be estimated by the biuret reaction, NH2groups measured with 2,4,6-trinitrobenzene sulphonic acid and SH groups by reaction with 5, 5′-dithiobis(2-nitrobenzoic acid). Acid phosphatase activity in bovine milk was followed colorimetrically by reaction withp-nitrophenyl phosphate to demonstrate the suitability of the clarification procedure in the measurement of enzymic reactions.
Observations onCorynebacterium bovisinfection of the bovine mammary gland: I. Natural infection
Authors: Honkanen-Buzalski Tuula , Griffin Tony K. , Dodd Frank H.
Published: June 2009

Data from experiments in 55 commercial herds have been examined to study the patterns ofCorynebacterium bovisinfection. Such infections are most common in herds that are not subjected to regular control methods but their commercial significance appears to be small. In herds using teat disinfection and dry cow therapy levels of infection with this organism are low. There is no evidence from these data to suggest thatC. bovisinfections protect the udder against invasion by a major pathogen. On the contrary these infections do not persist when major pathogens invade.
Influence of 2-mercaptoethanol on heat stability of concentrated whey-protein-free milk and formation of soluble casein
Authors: Aoki Takayoshi , Kako Yoshitaka
Published: June 2009

The heat coagulation time (HCT) of concentrated whey-protein-free (WPF) milk measured at 120 and 130 °C was reduced toby addition of 5–20 mM-2-mercaptoethanol (ME). However, although the amount of soluble casein formed on heating was doubled by addition of ME, the shape of the HCT–pH profile was affected only slightly. The proportion of κ-casein in the soluble casein from heated concentrated WPF milk containing ME was very high, though it was somewhat lower than that of the soluble casein from heated concentrated WPF milk containing no ME. No solubilization of colloidal Ca phosphate was observed in either unheated or heated concentrated WPF milk on addition of ME. These facts suggest that ME probably promotes the formation of soluble casein with release of κ-casein from micelles on heating, thus destabilizing the casein micelles.
Effect of residues of five disinfectants in milk on acid production by strains of lactic starters used for Cheddar cheesemaking and on organoleptic properties of the cheese
Authors: Dunsmore David G. , Makin Debbie , Arkins Richard
Published: June 2009

The inhibitory effect of five disinfectants on acid production byStreptococcus lactisandStr. cremorisCheddar cheese starters was compared using two techniques, a laboratory scale fermentation tube test, and pilot scale cheese manufacture. Threshold inhibition concentrations (partial, total) of disinfectants (mg/1) on acid production observed in the fermentation tube were: peracetic acid/H2O2(0–5, > 600) iodophor (75–220, > 400), quaternary ammonium compound (QAC), (20–30, > 200), acidic anionic (60–120, 600–1200), and Na hypochlorite (400–1000, > 1000). Threshold inhibition concentrations (partial, total) observed in the cheese vat were (mg/I); peracetic acid/H2O2(0–5, 5–35), iodophor (15–30, 75–200), QAC (10–20, > 200), acidicanionic(30–120, > 600), and Na hypochlorite (35–400, > 400). Flavour threshold concentrations in the cheese at 4 weeks were (mg/l): peracetic acid/H2O25, iodophor 8, QAC 20, acidic anionic 12, and hypochlorite 50. It is concluded that problems in cheese manufacture are unlikely to occur with hypochlorites, iodophors, and acidic anionics, but that care should be taken when using QAC and peracetic acid as sanitizers. A correlation coefficient of 0918 was computed between the two methods of determining partial acid inhibition (P< 0·005).
Effect of ACTH and oxytocin treatment on lactoferrin and citrate in cows' milk
Authors: Thomas Alex S. A. , Fell Lloyd R.
Published: June 2009

Six dairy cows were treated before milkings with either oxytocin (Pitocin, 20 i.u.) or ACTH (Synacthen, 150 i.u.), principally to determine their effect on the ratio of citrate:lactoferrin concentrations in the milk. With ACTH treatment, after 3 d milk yield and citrate concentration decreased significantly, lactoferrin and bovine serum albumin (BSA) concentrations increased significantly. Somatic cell counts (SCC) increased temporarily in the milk of three of the cows which previously had > 100000 cells/ml. Lactoferrin yield remained fairly constant but citrate yield was significantly reduced. The citrate: lactoferrin molar ratio decreased from 1373 to 606. With oxytocin treatment, after 4 d milk yield first increased and then significantly decreased, citrate concentration decreased significantly while there were no significant changes in lactoferrin or BSA concentration or in the yield of any other milk constituents. The citrate: lactoferrin molar ratio decreased from 1621 to 1301. There were no significant changes in SCC either during treatment or 4 d after treatment but there was a significant rise at 16 d after treatment. It was concluded that in lactating cows both hormones affected citrate and lactoferrin concentrations in the direction that would improve the antibacterial properties of milk, but that this was accompanied by adverse effects on milk secretion. The extent of the change was not sufficient to be likely to produce inhibition of coliform bacteria.
Epimerization of lactose to free lactulose in heated model milk solutions
Authors: Greig Barry D. , Payne Gerald A.
Published: June 2009

The kinetics of the epimerization of lactose to lactulose were determined for two ‘model milk’ solutions, one containing lactose and the other lactose and lysine. The lysine was added to lactose to determine whether amino groups of proteins act as base catalysts promoting the production of free lactulose. The presence of lysine actually reduced the rate of production of free lactulose, presumably by the formation of amino-sugar complexes. The rate of production of free lactulose over the range of processing conditions was shown to be first order for both systems. Thermal effects on lactose were shown to be complex. The epimerization of lactose to lactulose was reversible and both sugars were thermally decomposed to their monosaccharides. The difference in the rate of production of free lactulose between the lactose, and the lactose and lysine solutions was also observed in processed milk and its ultrafiltrate (protein free).
Methods for making kefir and fermented milks based on kefir
Authors: Marshall Valerie M. , Cole Wendy M.
Published: June 2009

Flavour, aroma and appearance of milks fermented with commercially available kefir grains were compared with similar characteristics of heat treated (90 ΰC/30 min) milks that had been fermented with aroma producing starters in addition to the kefir grains. The starters used were either a mixture ofStreptococcus lactissubsp.diacetilactisandLeuconostoc cremoris(lactic culture) or ofStr. thermophilusandLactobacillus bulgaricus(yogurt culture).

Two methods of fermentation were investigated involving removal of the grains followed by (i) a second fermentation of the kefir with the aroma-producing organisms and (ii) combining the kefir with aroma-producing organisms for use as a starter to ferment a further sample of heat-treated milk. Products were assessed by a taste panel and marked for acceptability. Addition of lactic or yogurt cultures resulted in products with increased mean scores for aroma and more acceptable flavours.
Short-term associations between disease and milk yield of dairy cows
Authors: Lucey Stephen , Rowlands G. John , Russell Alexander M.
Published: June 2009

Short-term associations between disease and milk yield were studied in 1594 lactations occurring between 1977 and 1982 in 732 Friesian, Ayrshire and Holstein crossbred cows. Statistically significant differences in milk yield between one week before and one week after clinical diagnosis were observed for ketosis (5·l kg/d), hypomagnesaemia (4·1 kg/d), mastitis occurring after peak yield (2·1 kg/d) and lameness (1·1 kg/d). Milk yield declined for as much as 2–4 weeks before diagnosis of disease, and total losses in milk yield associated with ketosis or hypomagnesaemia were estimated to be 60–70 kg. No significant differences were found for endometritis or for mastitis when it occurred before peak yield. Milk yield was suppressed for about 4 weeks after calvings with retained placenta, but there were no corresponding effects of dystocia or hypocalcaemia on milk yield. It is suggested that if automatic daily milk recording is available it may be possible to detect deviations from normal, and hence detect subclinical disease 2 or more weeks before its clinical appearance.
Separation of casein aggregates cross-linked by colloidal calcium phosphate from bovine casein micelles by high performance gel chromatography in the presence of urea
Authors: Aoki Takayoshi , Kako Yoshitaka , Imamura Tsuneaki
Published: June 2009

High performance gel chromatography of the casein micelles disaggregated by 6 m-urea was carried out on a TSK-GEL G4000SW column using 6 M-urea synthetic milk serum as the effluent. The eluate was divided into two fractions. Fast eluted fraction 1 decreased from 67·5 to 57·3% on reduction of casein micelles and was not observed in reduced colloidal phosphate-free casein micelles. Fraction 1 from reduced casein micelles contained 1·7 times as much Ca and Pibound to casein as did whole casein micelles, while fraction 2 essentially contained only bound Ca. These facts indicated that fraction 1 of reduced casein micelles consisted of the casein aggregates cross-linked by colloidal Ca phosphate (CCP). Polyacrylamide-gel electrophoresis showed that fraction 1 of reduced casein micelles contained more αs1- and αs2-caseins and less β-casein than whole micellar casein. No κ-casein was detected in fraction 1 of reduced casein micelles. It is suggested that the ester phosphate groups of casein are the sites for interaction with CCP.
Development of an objective method for assessing the mechanical strength of casein curd
Authors: Jablonka Mark S. , Munro Peter A.
Published: June 2009

AS the break-up of weak curd during processing leads to fines losses, the mechanical strength of acid casein curd is important. When different techniques were investigated to evaluate objectively the strength of acid casein curd a plate extrusion method was found to require the least preparation of the curd and to give rapid and reproducible results. The optimum condition for mechanical testing of samples was after acidulation or after cooling for 2h at 25 °C.
Effect of precipitation temperature and pH on the mechanical strength of batch precipitated acid casein curd
Authors: Jablonka Mark S. , Murno Peter A.
Published: June 2009

The precipitation stage in acid casein manufacture controls the initial strength of the casein curd, which is an important factor in determining fines losses during processing. A plate extrusion method was used to determine the mechanical strength of casein curd, precipitated batchwise at temperatures from 25 to 53 °C over a pH range of 3·9 to 5·1. Curd strength was determined either immediately after acidulation or after cooling for 2 h at 25 °C. Curd was stronger immediately after acidulation than after cooling and increased in strength as precipitation temperature and pH were increased. Curd precipitated at high temperature and high pH was mechanically strong, had a large particle size, and had high total solids and Ca contents. The relationship between these curd properties is discussed, and it is concluded that Ca retention at high precipitation temperature and pH is largely responsible for the characteristic curd properties under these precipitation conditions.
Effects of iodate, hydrogen peroxide and dichromate on the denaturation of whey proteins in heated milk
Authors: Marshall Richard J.
Published: June 2009

The effect of heating raw milk at 75 °C for 30 min and at 95 °C for 15 s in the presence of varying concentrations of three oxidizing agents on the denaturation of total and individual whey proteins was measured. At 75 °C, ±-lactalbumin could be protected against denaturation by both iodate and H202 and ²-Lactoglobulins A and B by H202 and dichromate. However, at concentrations above ∼ 15 MM, the oxidizing agents tended to increase denaturation. At 95 °C, where the extent of whey protein denaturation was much reduced in the absence of oxidizing agents, little or no protective effect was observed. It is suggested that H202 may prove a suitable alternative to iodate in reducing deposits in ultra high temperature plants.
A rapid colorimetric assay for the extracellular lipase ofPseudomonas fluorescensB52 using β-naphthyl caprylate
Authors: McKellar Robin C.
Published: June 2009

Conditions 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

Whey 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

TWO 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

TO 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

Pregnant 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

When 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

Adding 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

The 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

When 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

Non-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

Gels 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.
A scheme for the partial fractionation of cheese peptides
Authors: O'Sullivan Michael , Fox Patrick F.
Published: June 2009

Although proteolysis is regarded as the most important biochemical event in the ripening of most cheese varieties (Rank et al. 1985; Grappin et al. 1985; Law, 1987), current methods for the fractionation of cheese N, yield very heterogeneous fractions (Rank el al. 1985; Grappin et al. 1985; Fox, 1989). This communication describes the results to date of a study undertaken to develop a comprehensive scheme for the fractionation of cheese N.
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

Free 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

Changes 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

Two 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

The 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

Levels 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

A 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

Penicillium 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

The 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

Three 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

A 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.
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

Using 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

British 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

The 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

Proteolysis 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.