bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical composition and coagulating properties of renneted Friesian milk during the transition from winter rations to spring grazing
Authors: Grandison Alistair S. , Ford Graeme D. , Owen A. Jane , Millard David
Published: June 2009

The chemical composition and rennet coagulation properties at pH 6·4 of milks from 2 commercial herds of Friesian cows were monitored during the change from winter diet to spring grazing. There was considerable variation both in composition and in coagulation properties during this period. There were significant trends for increasing concentrations of casein, Na and lactose, and decreasing concentrations of fat, citrate, K and Mg following the change. Many correlations occurred between concentrations of components, some of which may have physiological significance. Coagulum strength increased after the change to spring grazing and was related to the concentrations of casein, citrate and some of the minerals. Syneresis time did not follow any trend during this period, but was significantly related to concentrations of fat, Na and K. Rennet clotting time did not follow a significant trend immediately after the dietary change, but tended to increase as the summer progressed; it was significantly related to concentrations of Ca, PiNa and K, as well as to the original pH of the milk. When the concentration of lactose in milk was adjusted, variations in lactose concentration did not affect the coagulation properties of milk.
Application of polymer cross-linking theory to rennet-induced milk gels
Authors: Johnston Donald E.
Published: June 2009

A general theory of gel formation by cross-linking of polymer molecules, orginally developed for the study of rubber vulcanization, is proposed as a model for milk gel formation. The model divides gel formation and development into 4 stages, an enzymic and a non-enzymic stage preceding gelation, then a stage of material transition from the sol to the gelled state and a stage of increase in gel strength due to internal cross-link formations. The 2 post-gelation stages overlap to a variable degree depending upon particular circumstances. Gel formation and properties are interpreted in terms of the number of initial units which combine to form the gel and the number of cross-links eventually formed by each unit. When combined with a kinetic expression for the rate of cross-link formation the time course of gel shear modulus development or of the incorporation of material into the gel may be predicted. The classical asymmetric sigmoid shape of gel shear modulus development curves results from the third stage of material transition into the gel, which in turn depends upon the number of cross-links eventually formed by each initial unit. The modulus of mature gels is found to depend upon the square of material concentration, and gel breaking strength is found to be proportional to the modulus, in agreement with the predictions of the theory.
A microassay for the syneresis of cheese curd
Authors: Pearse Martin J. , Mackinlay Antony G. , Hall Robert J. , Linklater Peter M.
Published: June 2009

A micro scale syneresis assay, using the natural optical density of the whey released as a trace, is reported. This assay is suitable for use with raw, reconstituted skim-milk (RSM) or artificial milk. Using RSM the reproducibility and accuracy of the method compared favourably with larger scale laboratory assays. When the method was used to investigate the syneresis properties of artificial micelle milk (AMM), the rate and extent of syneresis and response to a major variable such as pH were very similar to those of RSM. This suggests that the assay used in conjunction with AMM is suitable for investigating the mechanism of syneresis at a molecular level.
Changes in viscosity of processed creams during storage at 5 °C
Authors: Langley Keith R.
Published: June 2009

The viscosity of heat treated creams increased with time (t). The rate (k) was dependent on homogenization pressure, fat content and heat treatment temperatures. Viscosity and its rate of increase could be related by the expressions:

log η = log η0 + kt

(where η0 is the viscosity at t = 0),

log η0 = a1 + b1φ/d

(where φ is the fat volume fraction, d is the globule diameter) and

k = a2 + b2φ/d.

Different values of a1b1a2 and b2 were found for homogenized and unhomogenized creams.
Effect of inclusion of different forms of dietary fatty acid on the yield and composition of cow's milk
Authors: Banks William , Clapperton John L. , Girdler Anne K. , Steele William
Published: June 2009

In addition to a control diet, lactating cows were offered saturated fatty acid mixtures in three forms, free acids, free triglycerides and protected triglycerides, i.e. triglyceride encapsulated within a protein matrix which was cross linked by exposure to formaldehyde. Relative to the control diet, all three supplements increased milk yield. However, only the free fatty acids gave rise to increased yields of the three major milk components. The free fat and the protected fat caused significant increases only in the lactose yield. The different effects of the supplements on the yield of milk fat are suggested to be due to the types of long chain acid reaching the mammary gland rather than to any change in rumen activity. Changes in the concentrations of the soluble multivalent ionic constituents of the milks were consistent with this conclusion.
Isolation and characterization of heat stable proteinases fromPseudomonasisolate AFT 21
Authors: Stepaniak Leszek , Fox Patrick F.
Published: June 2009

Pseudomonasstrain AFT 21 produced three heat stable extracellular proteinases in milk and nutrient broth at 7 or 21 °C, but the proportions depended on medium and cultivation temperature. The three proteinases were EDTA- ando-phenanthroline-sensitive metalloenzymes and were not inhibited byN-ethylmaleimide or phosphoramidon. Proteinases I and II showed maximum activity at pH 7–7·5 and proteinase III at pH 8·5. All three enzymes showed maximum activity at 45–47·5 °C, but had relatively high (19–27% of maximum) activity at 4 °C. They were unstable at 55 °C in phosphate buffer, pH 6·6, or synthetic milk ultrafiltrate (SMUF) containing 12 mmol Ca2+, but were stabilized by short preheating at 100 °C. They were extremely heat stable in both phosphate buffer and SMUF, pH 6·6, at 70–150 °C. Their D-values at 140 °C were 69, 54 and 80 s respectively. The Z-values forPseudomonasAFT 21 proteinase III in phosphate buffer and SMUF were 29·7 and 30·3 °C respectively; the corresponding activation energies for inactivation were 8·7 × 104J mol-1and 9·2 x 104J mol-1.
Lysin production by øC2(W), a prolate phage forStreptococcus lactisC2
Authors: Mullan W. Michael A. , Crawford Robert J. M.
Published: June 2009

A bacteriophage, øC2(W), which attackedStreptococcus lactisstrains C2, ML3 and 712, is described. It had a prolate head and a non-contractile tail and produced large haloes around plaques. Infection of eight paired-strain cultures, each containingStr.lactisC2, with øC2(W) resulted in marked inhibition of acid production for six cultures. Direct phage–nonhomologous ‘host’ contact was not required for inhibition. Lysates of øC2(W) contained a phage-induced lysin. Evidence is presented that the inhibitory effect of øC2(W) against paired and multi-strain cultures is due to the lysis of phage-insensitive strains by phage lysin. An isometric phage, ø712, was shown not to produce such a lysin.
NADP-linked dehydrogenases in secreted milk
Authors: Grigor Murray R. , Hartmann Peter E.
Published: June 2009

The activities of glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, isocitrate dehydrogenase, malic enzyme, lactate dehydrogenase and malate dehydrogenase have been determined in secreted milk from sows, rats and rabbits. Within each species, although there was considerable variation in the absolute activities of these enzymes, the relative activities were similar to those observed for, or previously published for mammary homogenates. The only exception was milk glucose 6-phosphate dehydrogenase which tended to lose activity upon prolonged storage in the mammary gland. These results suggest that the pattern of milk enzymes can be an accurate reflection of that occurring in the mammary gland.
Effects on mastitis of overmilking in conjunction with pulsation failure
Authors: Mein Graeme A. , Brown Murray R. , Williams David M.
Published: June 2009

Half-udder comparisons were made using 56 cows for 2 months, in an experiment involving high bacterial challenge, to assess the combined effects of 5 min overmilking and pulsation failure (resulting from the use of shortened teatcup liners) on teat condition and mastitis. Only three new infections were confirmed in over 12500 quarter milkings in quarters milked with control liners (of 148 mm effective length) indicating little or no effect of prolonged overmilking in these quarters. A 3·5-fold increase in the new infection rate (NIR) based on bacteriological diagnosis alone (P < 0·01), or a 9-fold increase in NIR based on bacteriological diagnosis plus raised cell count and/or N-acetyl-β-D-glucosaminidase (P < 0·01), occurred in quarters milked with the same liners shortened to an effective length of 120–130 mm. The mean interval to infection or teat canal colonization (41 ν. 60 milkings), and for a quarter infection to be confirmed by other diagnostic tests (45 ν. 79 milkings) was significantly less in quarters overmilked with short liners. The results confirm that NIR increases whenever pulsation fails. Overmilking may increase NIR when it is associated with pulsation failure.
Determination of lactulose and soya oligosaccharides in infant formula milk feeds
Authors: Beach Richard C. , Menzies Ian
Published: June 2009

A paper chromatography technique is described for the separation and quantification of minor sugars in infant formula milks. The precision and reliability of the technique are described. Infant milk feeds of various types were analysed and found to contain up to 11·4 mmol/l of the non-absorbed sugar lactulose. Soya derived feeds may contain a significant residue of non-absorbable oligosaccharides.
Studies on the heat stability of milk: II. Association and dissociation of particles and the effect of added urea
Authors: Dalgleish Douglas G. , Pouliot Yves , Paquin Paul
Published: June 2009

The sizes of the casein particles in milk heated at 130°C were measured as functions of heating time and of initial pH. The effect of adding 10 mM-urea to the milks was also studied. Turbidities of the milks before and after dispersing the caseinate particles in 8 m-urea/EDTA/β-mercaptoethanol were measured, the latter measurement giving an indication of the extent of covalent cross-linking. Urea was found to modify the behaviour of the milk: diameters of the caseinate particles were considerably altered, and the extent of covalent cross-linking was diminished. These results agree with the observation that more protein is solubilized from the casein micelles when urea is present, indicating that a competitive reaction scheme involving cross-linking in opposition to micellar dissociation may be responsible for the ultimate precipitation of milk by heat.
Effect of temporary food or water deprivation on milk secretion and milk composition in the goat
Authors: Dahlborn Kristina
Published: June 2009

When four goats were subjected to total water deprivation for 48 h once in early lactation and once in mid lactation and their voluntary food intake and effects on milk secretion were observed, milk volume decreased and lactose and fat concentration increased during both periods. However, when the goats were then fed the mean of their own food intake at the two previous water deprivation experiments, and were left free access to water, it was found that decreased food consumption had only a minor influence on milk secretion. When six goats were subjected to 48 h of food deprivation and six to 48 h of water deprivation, milk secretion decreased, but the reduction was delayed and of smaller magnitude during water deprivation. During food deprivation lactose concentration decreased and the milk protein and fat increased; the fatty acid composition changed from a greater proportion of short-chain to more long-chain fatty acids. During water deprivation milk fat and lactose concentrations increased, and only after 44 h did a change from short-chain to a larger proportion of long-chain fatty acids become evident. These experiments indicate that not only food intake, but also water intake are concerned with milk production.
Whipping of creams from ultrafiltered milk
Authors: Scurlock Peter G.
Published: June 2009

Creams containing 25–45% fat were made from whole milks which had been concentrated 2- to 5-fold by ultrafiltration. Each series of creams (from any one concentrate) was standardized with its own skimmed milk, giving creams with higher than normal protein contents. These were then pasteurized and cooled for at least 24 h before being whipped. Increasing the fat content of creams gave increased stiffness, an overrun (volume increase) that passed through a maximum, decreased serum leakage and shorter whipping time. Increasing the protein content gave increased stiffness, less serum leakage, reduced overrun and a whipping time that passed through a maximum. Low fat creams, and also creams containing high amounts of fat and protein, did not produce a satisfactory whipped product. However, 35% fat creams from 2-fold concentrated milks compared well with ordinary 38% whipping creams. By lowering the fat content of creams an increase in yield was obtained.
Effect of ultrafiltered milk and use of different starters on the manufacture, fermentation and ripening of Havarti cheese
Authors: Qvist Karsten B. , Thomsen Dorf , Høier Erik
Published: June 2009

When Havarti cheeses were made from milk concentrated 5-fold using ultrafiltration (UF) and with a direct vat set type starter containingStreptococcus lactis, Str. cremoris, Leuconostoc cremorisandStr. lactissubsp.diacetilactis(i.e. a BD-type starter) their colour, texture, body, and flavour were equal to those of traditionally produced Havarti. The somewhat slower flavour development was associated with a retarded breakdown of protein. Although αs1-casein was almost completely broken down in Havarti cheese made with the ultrafiltration method (UF Havarti) and traditional cheeses after 120 d of storage, degradation of β-casein was retarded in UF Havarti. Rennet contents and numbers of starter organisms were similar in the two types of cheese and thus could not explain the difference in ripening rate.Str. lactissubsp.diacetilactiswas dominant in both UF and traditional Havarti cheeses when the BD-type starter was used. By varying the composition of the starter, large variations in the bacterial composition and citrate fermentation in UF Havarti cheeses were obtained. The BD-type starter gave the best organoleptic quality.
Effect of casein and β-lactoglobulin genotypes on renneting properties of milks
Authors: Pagnacco Giulio , Caroli Anna
Published: June 2009

The effects of αs1-, β-, κ-casein and β-lactoglobulin genetic variants on rennet clotting time, rate of curd firming and coagulum strength, measured on the individual milks of 306 Rendena cows by a lactodynamographic apparatus, were evaluated statistically, with simultaneous adjustment for environmental and physicochemical factors. The importance of genetic polymorphism was confirmed, especially for the main effects of casein loci: interaction among them was not found to be significant. For κ-casein, BB genotype showed the best coagulation parameters (lower rennet clotting time, a higher rate of curd firming and higher coagulum strength), with AB in an intermediate position for clotting time and rate of curd firming. However, for αs1-casein and β-casein, dominance and overdominance effects between alleles were observed. Herd by genotype interaction was also found to be significant (herd by β-casein) or close to significance level (herd by κ-casein). From the results of the analyses, suggestions for selection programmes have been made.
Subunit components of casein micelles from bovine, ovine, caprine and equine milks
Authors: Ono Tomotada , Kohno Hideaki , Odagiri Satoshi , Takagi Toshio
Published: June 2009

Subunit components of ovine, caprine and equine casein micelles were separated by gel chromatography using a TSK-G4000SW high-performance column and the subunit components of the fractions analysed and compared with bovine casein. Molecular weights of the casein complexes were determined by the combined use of high-performance gel chromatography and low-angle laser light scattering. The caprine and ovine caseins were separated into three peaks (F2, F3 and F4) which were similar to those of bovine casein with respect to composition and molecular weight (500, 100 and 23 K). These F2, F3 and F4 peaks consisted mainly of αs- and κ-casein, αs- and β-casein and β-casein respectively. The equine casein was separated into two components corresponding to F3 and F4 of bovine casein. These F3 and F4 peaks consisted mainly of αs- and β-casein and β-casein respectively. The molecular weight of equine F3 (850 K) was different from that of the other three species. The contents of F2 and F4 in these caseins were dependent on the contents of κ-casein and β-casein respectively.
Whipping properties of cream in relation to milk composition
Authors: Banks William , Clapperton John L. , Muir D. Donald , Girdler Anne K.
Published: June 2009

Dietary manipulation was used to produce a similar series of milks from both Friesian and Jersey cows. The gross compositions of the milks, the fatty acid (FA) composition of the milk fats, the distribution of molecular sizes in the triglycerides of the milk fat, the melting properties of the milk fats, and the whipping properties of creams containing 360 and 400 g fat/kg were measured. Changes in gross composition and FA composition were as expected from the use of dietary oil supplements, but it was established that the mathematical relation between 18:0 and 18:1 differed between breeds, the Jersey yielding a milk fat with a lower proportion of 18:1 for a given value of 18:0. Control diets free from added fat produced milk fats with essentially unimodal triglyceride distributions, whereas fatrich diets produced bimodal distributions. The slight differences in these distributions between breeds were merely a reflection of variations in FA composition rather than in synthetic procedures. Differences in the whipping properties of creams containing 360 and 400 g fat/kg were consistent with literature observations. Dietary manipulation had little effect on the whipping properties of creams derived from Friesian cows, but caused considerable changes in the corresponding properties of the creams from Jersey cows. The only property that behaved similarly in the creams from the two breeds was the butter time, i.e. the time taken for butter granules to form on prolonged whipping of the cream. A major determinant of the butter time appeared to be the proportion of the fat that was molten at the temperature at which the whipping experiments were carried out.
Effect of antibiotic resistance on the flavour profile of lactic acid bacteria
Authors: Babu K. S. , Singh R. S. , Chander H.
Published: June 2009

The major problem encountered in the dairy industry is due to the failure of starter in the manufacture of fermented dairy products such as cheese, Yogurt buttermilk and also the Indian fermented milk products srikhand and dahi, in terms of low acid production and absence of flavour and aroma. Usually, in such cases the presence of antibiotics is detected. Little work has been done on the effect of antibiotic resistance in the starter on flavour production, though many workers have investigated acid production and proteolytic activity (Kondratenko et al. 1978 Ottogalli et al. 1975; Shahani & Harper 1958; Wilkowske & Krienke, 1951). The present investigation has been undertaken to develop antibiotic-resistant strains of lactic streptococci, i.e. Streptococcus lactis biovar. diacetylactis and Lactobacillus delbrueckii subsp. bulgaricus which could be used for the preparation of fermanted milk products.
Fractional melting of hydrogenated milk fat
Authors: Banks William , Clapperton John L. , Girdler Anne K.
Published: June 2009

Hydrogenated milk fats have been subjected to a process of fractional melting. In five of the six samples, the procedure yielded two fractions, defined as oil/upper solid and lower solid fractions, whilst in the remaining sample, three fractions (oil, upper solid and lower solid) were obtained. The oil and oil/upper solid fractions were rich in short-chain fatty acids (FA) (4:0 and 6:0), whereas the lower solid fractions contained large amounts of long-chain FA (16:0 and 18:0). Triglyceride distributions reflected these differences in FA composition, the oil and oil/upper solid fractions being dominated by triglycerides with carbon numbers (CN) 36–38; the dominant CN for the lower solid fraction was 48–54. Melting spectra, obtained using differential scanning calorimetry, showed that the ability of the fractionation procedure to separate on the basis of melting properties ranged from excellent to relatively poor, depending on the type of milk fat.
Ion-exchange fast protein liquid chromatography: optimization of the purification of caseins using a non-denaturing detergent
Authors: St-Martin Maryse , Paquin Paul
Published: June 2009

The separation of bovine milk proteins by fast protein liquid chromatography has been studied by ion-exchange chromatography on Mono S and Mono Q columns. The use of a non-ionic detergent, octyl-glucoside, made possible the separation of the four major casein components (αs1, αs2, β and κ) as well as minor caseins on the Mono S column using urea-containing buffers at pH 3·5. There was, however, considerable overlap between the αs1 and αs2-casein peaks. A good resolution was obtained with a low concentration of urea (3·5 M) and detergent (0·1%). These conditions allowed the separation of casein components in their native state in less than 50 min. The purity of isolated κ-casein was further improved by a second separation on a Mono Q column.
Characterization of wild strains ofLactococcus lactissubsp.lactisisolated from Cabrales cheese
Authors: Mayo Baltasar , Hardisson Carlos , Braña Alfredo F.
Published: June 2009

TwentyLactococcus lactissubsp.lactisstrains isolated from cheese made from raw milk have been, studied and compared with well known starter strains. Many of them produced acid bacteriocins resembling those of other lactic streptococci and their patterns of antimicrobial agent susceptibility were also similar to previously studied dairy strains. On the basis of their ability to clot milk they could be divided into two groups. Some strains were rapid fermenters, with highβ-phosphogalactosidase and proteolytic activities. The other group had lowβ-phosphogalactosidase activity and coagulated milk slowly, but seemed to have proteolytic activity. All the strains had plasmid DNA in amounts and sizes similar to starter strains. Aβ-phosphogalactosidase probe was constructed with plasmid DNA from aLc. lactissubsp.lactisNCDO 712 derivative. Southern hybridization located homologous sequences in chromosomal and plasmid DNA from the wild isolates that fermented lactose efficiently, but the degree of homology was lower than that observed between starter strains.
Production of a bacteriocin active on lactate-fermenting clostridia byLactococcus lactissubsp.lactisimmobilized in coated alginate beads
Authors: Zezza Nicla , Pasini Gabriella , Lombardi Angiolella , Mercenier Annick , Spettoli Paolo , Zamorani Arturo , Nuti Marco Paolo
Published: June 2009

We report the isolation and immobilization of a nisinogenic strain (NZ1) ofLactococcus lactissubsp.lactis, active on gas-forming lactate-fermenting clostridia responsible for late blowing of Asiago and Montasio cheeses. The bacteriocin (nisin) produced by strain NZ1 is pronase-sensitive and is released in culture media during the growth phase. Using the sensitive indicator strainLactobacillus delbrueckiisubsp.bulgaricusNCDO 1489, a rapid microtitre plate based assay was developed for quantitative determination of the bacteriocin produced by NZ1 cells, either free or immobilized in gel beads. Scanning electron microscopy of cells immobilized in calcium alginate coated beads and viable counts of the surrounding medium showed that no cell leakage occurred during a 24 h assay. The bacteriocin released from immobilized cells reached, after 5 and 24 h, concentrations comparable to that of the free cell system after 3–4 h incubation in culture media.
Evaluation of the use of an artificial teat to measure the forces applied by a milking machine teatcup liner
Authors: Adley Nicholas J. D. , Butler M. Clare
Published: June 2009

An artificial teat containing a force transducer was constructed to study the forces exerted by the liner on the teat during milking. The objective was to develop a method of comparing the action of different liners under a variety of different milking conditions. The rigid structure of the artificial teat did not provide an accurate representation of a real teat but deformable models used in the past have not proved practical. Initial tests of the teat showed that it gave repeatable results during calibration. When placed in a liner, however, repeatable results could not be obtained if the teat–liner interface was disturbed. The forces that were measured under simulated milking conditions varied with liner wall position and with time. There was a peak and trough prior to a stable asymptotie value being attained and a noticeable time lag behind pulsation chamber pressure. This technique can be used to compare liners when a reliable method of locating the artificial teat within the liner has been developed.
Identification ofBacillusstrains isolated from milk and cream with classical and nucleic acid hybridization methods
Authors: Tatzel Ralf , Ludwig Wolfgang , Schleifer Karl Heinz , Wallnöfer Peter R.
Published: June 2009

A total of 529 bacterial strains have been isolated from milk and cream sampled at different sites in a dairy production plant under conditions selective for aerobic sporeforming bacteria. Identification with classical methods based on morphological, physiological and biochemical criteria showedBacillus licheniformisto be the most frequently occurringBacillussp. The investigation also revealed 62 unidentified strains. Classical identification methods were time consuming (3–7d), lacked specificity and —because of their dependence on phenotypic gene expression—sometimes produced ambiguous results. Consequently, a colony hybridization method developed for the identification ofB. licheniformisstrains and using non-radioactive labelled 23S rRNA targeted oligonucleotide probes was also used. Identification ofB. licheniformiswith borth classical and hybridization methods revealed diverging identification results for 70 strains.
A gel electrophoretic study of caprine casein
Authors: Addeo Francesco , Mauriello Rosalba , Di Luccia Aldo
Published: June 2009

To compare the resolving power of starch-urea gel (SUGE) and polyacrylamide-agarose gel electrophoresis (PAAGE) in caprine casein analysis, polyacrylamide gel isoelectric focusing (PAGIF) was used as reference method. The PAAGE or SUGE patterns in the first dimension were allowed to migrate by PAGIF in an orthogonal direction giving rise to two-dimensional (2-D) separations. Using this procedure, some individual bands considered to be homogeneous by SUGE or PAAGE were found to be complex mixtures of casein components. A detailed analysis of the analytical capabilities of SUGE and PAAGE was performed. Procedures based on the densitometric reading of SUGE and PAAGE patterns seemed to give inaccurate results on the quantitative composition of caprine casein. Among the electrophoretic methods assayed, the 2-D procedure gave the best resolution of casein fractions.
Influence of glycosylation on the hydration properties of caseinates
Authors: Le Meste Martine , Colas Bernard , Blond Geneviève , Simatos Denise
Published: June 2009

Glycosylation has been recognized as enhancing some functional properties of caseinates. The present work was aimed at elucidating the structure–function relationship of the functionality of caseinates and, more particularly, the influence of hydration on these properties. Measurements of non-frozen water content derived from sorption isotherms are presented. Using spin-probing Electron Spin Resonance we studied the mobilization pattern of solutes as hydration changed.The protein interactions with bound water were not significantly affected by sugar binding. Changes in the functional properties as, for example, in the water-holding capacity, reflected alterations in the structure, which was looser and more flexible after glycosylation, and in the associative properties (increased solubility) of caseinates. Disaccharides seemed more effective than monosaccharides in inducing these changes.
Milk stability in ethanolic solutions
Authors: Pierre Alice
Published: June 2009

We have investigated the role of pH in the destabilization of milk and sodium caseinate solutions by ethanol. Ethanol shifted the pH of minimum stability of both caseinate and milk to higher values. A linear relation between this pH and the reciprocal dielectric constant of the mixture was observed. The addition of calcium to these alcoholic mixtures also increased the pH of minimum stability. The results are discussed in terms of the alcohol-induced shifts in the pK values of important constituent amino acids and of the effect of alcohol on soluble Ca levels.
Evaluation of a rapid fluorogenic method for the detection ofEscherichia coliin dairy products
Authors: Sarhan Hassan R. , Williams Leslie R. , Foster Howard A.
Published: June 2009

A rapid fluorogenic medium was evaluated for the detection ofEscherichia coliin dairy products. The medium was capable of detectingEsch. coliafter 7·5 h incubation at 41·5 °C. Samples of pasteurized milk (136), raw milk (63), soft cheese (60) and pasteurized cream (39) were examined with media based on 4-methylumbelliferyl-β-D-glucuronide (MUG-7) and Violet red bile agar and there were no significant differences between the numbers ofEsch. colidetected on the two media. MUG-7 medium had a specificity of 98·6% and the small number of organisms giving a false positive reaction were identified asKlebsiella pneumoniae. The incidence of false negative results was ∼2%. MUG-7 medium was suitable for pour plate, spread plate and membrane filtration methods. Possible applications of the method are discussed.
Identification of the saturated oxo fatty acids in cheese
Authors: Brechany Elizabeth Y. , Christie William W.
Published: June 2009

The nature and composition of the saturated oxo fatty acids in Cheddar cheese have been re-evaluated following isolation by moern chromatographic procedures, including low-pressure column chromatography and HPLC (adsorption and silver ion modes). The oxo fatty acids were identified and quantified (for the first time) by gas chromatography–mass spectrometry in the form of the methyl ester derivatives and many of the structures were confirmed similarly by preparing picolinyl ester derivatives. Thirty-six saturated oxo fatty acids were identified, ranging in chain length from 9 to 22 with an oxo group on carbons 4–17 (except for 12), of which twenty-one had been identified in a previous study and fifteen were new. Fifteen fatty acids tentatively identified by others did not in fact appear to be present.
Assessment of mammary gland metabolism in the sow: II. Cellular metabolites in the mammary secretion and plasma during lactogenesis II
Authors: Atwood Craig S. , Toussaint Janine K. , Hartmann Peter E.
Published: June 2009

The concentrations of lactose, glucose, glucose 6-phosphate, glucose 1-phosphate, UDPglucose, UDPgalactose, UDP, UMP, inorganic phosphate, ADP and AMP (metabolites involved in the lactose synthesis pathway), and cAMP, galactose and fructose were measured in the mammary secretion from sucked (n = 9) and unsucked (n = 4) mammary glands of nine sows during the first 5 d post partum. The concentrations of lactose, glucose, galactose and fructose were also measured in plasma during this time. The progressive increase in the concentration of lactose, and changes in the concentrations of cellular metabolites in the mammary secretion from sucked glands were consistent with an increase in the metabolic activity of those glands during lactogenesis II. In contrast, unsucked glands showed a progressive decrease in the concentration of lactose, while the concentrations of cellular metabolites in the milk generally remained unchanged. These results indicated that there was no increase in the metabolic activity of unsucked glands (no increase in lactose synthesis or utilization of glucose and ATP) and that the rate of lactose synthesis prior to milk removal was limited by the availability of glucose and/or UDPgalactose. Therefore, the removal of colostrum from the mammary gland was necessary for an increase in the rate of lactose synthesis (and probably de novo fatty acid synthesis) and implies that autocrine mechanisms are operating to control the rate of milk synthesis during lactogenesis in the sow. The low concentration of glucose in colostrum compared with that in plasma is discussed in view of the paracellular pathway.
Assessment of mammary gland metabolism in the sow: III. Cellular metabolites in the mammary secretion and plasma following weaning
Authors: Atwood Craig S. , Hartmann Peter E.
Published: June 2009

The concentrations of lactose, glucose, glucose 6-phosphate, glucose 1-phosphate, UDPglucose, UDPgalactose, UDP, UMP, inorganic phosphate, ADP and AMP (metabolites involved in the lactose synthesis pathway), and cAMP, galactose and sodium were measured in the mammary secretion from four or five mammary glands on each of six sows during the first 5 d post weaning. The concentrations of lactose, glucose and galactose were also measured in plasma during this time. Following weaning, the rapid increase in the concentrations of glucose 6-phosphate and UDPgalactose suggested that the rate of lactose synthesis was regulated by the inhibition of hexokinase and/or lactose synthase, while the decrease in glucose and AMP indicated a subsequent decline in glucose and ATP utilization. The rapid increase in glucose 6-phosphate which plays a pivotal role as a substrate for both lactose and de novo fatty acid synthesis, and the rapid decrease in AMP which reflects ATP utilization, were good markers of decreased metabolic activity. These rapid changes in the metabolic activity of the mammary glands were not observed in a second weaning study when two piglets were removed from selected mammary glands for periods up to 5 h during established lactation. Since concentrations of lactogenic hormones remain elevated following partial weaning, but fall following total weaning (Rojkittikhun et al. 1991), these differences in mammary gland metabolism indicate that endocrine rather than autocrine mechanisms are controlling lactose and fat synthesis during the initial stages of total weaning.
Rheological and structural studies on heat-induced gelation of concentrated skim milk
Authors: Tobitani Atsumi , Yamamoto Haruyoshi , Shioya Toshiaki , Ross-Murphy Simon B.
Published: June 2009

Heat-induced gelation of milk was studied using both rheological and structural techniques. The sample was a conventional skim milk, concentrated with an ultrafiltration membrane, which formed gels when heated at appropriate pH. We investigated some factors that are considered to affect the gelation, such as concentration, pH and rennet treatment. The gelation process was monitored with a high precision oscillatory shear rheometer and the structure of gels was evaluated with quasi-elastic laser light scattering. From these results the gelation and phase separation behaviour were determined. By combining the results for different concentrations a phase diagram was obtained, which indicated that skim milk had a two-phase region on the higher temperature side. The effects of pH and rennet treatment were also evaluated with the aid of this phase diagram. The results were discussed on the basis of concepts of the phase behaviour of polymers, which were successfully developed in polymer physics.
Acidification test based on the use of biomass for screening ofLeuconostoc. Application toLn. mesenteroidesstrains isolated from French raw milk cheeses
Authors: Demirci Yeter , Hemme Denis
Published: June 2009

Unlike that of other lactic acid bacteria, the growth ofLeuconostocspp. in milk is poor and the resulting acidification cannot be used to distinguish different strains. An acidification test based on the use of high initial numbers (109cfu/ml) has been developed and proved to be an efficient tool for discriminating between 110Leuconostocstrains isolated from French raw milk cheeses. The pH values after 24 h ranged from 6.55 to 4.05 and distinguished four acidification groups. All 34% of the strains that acidified milk to at least pH 5.1, coagulating it and should be considered as Lac+. The differences in rates and degrees of acidification could not be related to the proteolytic activity which was, from all 27 representative strains tested, similar to that ofLactococcus lactisPrt–variants.
Seasonal influences on Cheddar cheese manufacture: influence of diet quality and stage of lactation
Authors: Kefford Bruce , Christian Mary P. , Sutherland Brian J. , Mayes Jeffery J. , Grainger Chris
Published: June 2009

The influence of diet quality and stage of lactation on Cheddar cheese moisture and yield were segregated and the effects of other potential variables (cow breed, milk protein genotype, age and level of mastitis) were minimized. An experiment was conducted using milk of cows in mid lactation or late lactation fed on high or low quality diets. Increased moisture in cheese was largely due to the influence of cow diet. Milk from cows given high quality diets produced lower moisture cheese. Cheese yield was influenced by diet and stage of lactation. Cows in late lactation fed on high quality diets always gave milks yielding the most cheese. Fat and protein recovery in cheese was not influenced by diet or stage of lactation. The results suggest that low quality diets may induce changes in the complex interactions of milk proteins and other components that affect cheesemaking.
A qualitative screening procedure for the detection of casein hydrolysis by bacteria, using sodium dodecyl sulphate polyacrylamide gel electrophoresis
Authors: Hill Susan H. A. , Gasson Michael J.
Published: June 2009

Incubation of bacteria with casein at 30 °C (pH 7·2) resulted in the formation of a number of peptide fragments. The peptides were separable when subjected to electrophoresis. A proteinase-positive strain ofStreptococcus lactispreferentially hydrolysed the β-casein moiety of whole casein, and after incubation for 5 min produced a characteristic pattern of four peptides on sodium dodecyl sulphate (SDS) polyacrylamide gels. After 30 min incubation only one peptide remained. This single polypeptide was then further hydrolysed to produce one (60 min) and eventually two (120 min) lower molecular weight peptides. Hydrolysis was generally complete after about 480 min. Two proteinase-negative variants of this strain did not hydrolyse casein. Crude proteinase preparations gave the same characteristic peptide patterns. SDS-polyacrylamide gel electrophoresis was used to screen more proteinase-positive strains ofStr. Lactisfor casein hydrolysing activity. Of those so far tested all produced the same peptide patterns from β-casein. Proteinase negative variants of all these strains did not hydrolyse casein.
Cardiovascular and metabolic responses during growth hormone treatment of lactating sheep
Authors: Fleet Ivan R. , Fullerton Frances M. , Heap R. Brian , Mepham T. Ben , Gluckman Peter D. , Hart Ian C.
Published: June 2009

Pituitary-derived bovine growth hormone (bGH) was administered to six lactating Friesland ewes for 7 d. There was no consistent galactopoietic response, with changes in milk yield varying from 0 to 33% during treatment compared with the pretreatment period. The major effect of bGH on the concentration of milk constituents was to increase fat by 14·2% (P < 0·05). Treatment resulted in significant increases in arterial plasma concentrations of growth hormone, insulin-like growth factor I and glucose, with decreases in the plasma arterial concentrations of acetate and certain amino acids. There was a marked reduction in haematocrit and in haemoglobin concentration which took at least 3 d to recover. The arterio-venous difference across the mammary gland decreased for O2 during treatment and the veno-arterial difference for CO2 decreased after treatment. Mammary respiratory quotient therefore decreased significantly after bGH treatment. The results suggest that bGH exerts effects at a number of separate loci.
Plastein synthesis by the action of α-chymotrypsin on a peptic hydrolysate of whey protein
Authors: Sciancalepore Vito , Longone Vincenzo
Published: June 2009

A peptic hydrolysate of proteinaceous material of whey from Mozzarella cheese manufacture was incubated with α-chymotrypsin under conditions leading to the formation of plastein products. The influence of incubation time, concentration and molecular size of substrate was studied. The most favourable conditions for the plastein synthesis were 12 h incubation time and 35% (w/v) concentration of peptides having mol. wt in the range 451–1450.
Effect of forage digestibility and type of concentrate on nutrient utilization by lactating dairy cattle
Authors: Gordon Frederick J. , Porter Michael G. , Mayne C. Sinclair , Unsworth Edmund F. , Kilpatrick David J.
Published: June 2009

Six lactating dairy cows were used in a three period, part balanced changeover design experiment to investigate the effects of forage digestibility and concentrate composition on the efficiency of nutrient utilization in lactating dairy cows. Six treatments comprising three forage regimens and two concentrate types (starch υ. fibre) were examined in a 3 × 2 factorial design. The three forage regimens were high digestibility grass silage offered ad lib. (HA) or restricted to 6·5 kg dry matter/d (HR) and a low digestibility grass silage offered ad lib. (LA). Within each forage regimen animals were offered 10 kg·d of supplements containing either high-starch or high-fibre concentrations. Experimental periods lasted 28 d with a 10 d recording period, during which animal performance, ration digestibility and nitrogen and energy utilization were measured. Respiratory exchange measurements were made over a 72 h period using indirect open-circuit calorimetry. Throughout the experiment, there were no significant forage × concentrate interactions in any of the intake, production or nutrient utilization results. Milk yield was significantly influenced by forage regimen (24·1, 21·7 and 21·9 kg/d for HA, HR and LA respectively) and concentrate type (21·6 and 23·5 kg/d for high-starch and high-fibre respectively). Concentrate type also significantly influenced milk protein concentration (32·8 and 30·9 g/kg for high-starch and high-fibre respectively). Forage regimen significantly influenced the efficiency of utilization of metabolizable energy (ME) for milk production (κ1) with values of 0·62, 0·64 and 0·59 for HA, HR and LA respectively. Concentrate type had no significant effect on ME intake, heat production or κ1, although animals receiving the high-fibre concentrates synthesized proportionately 0·11 more milk energy per unit of available energy (ME intake – heat production) than those receiving the high-starch concentrates. Interpolation of the values obtained with the two high digestibility forage regimens indicated that at similar ME intakes there was a trend towards a higher κ1 with the diet based on high digestibility silage, and this was in line with the higher metabolizability of the overall diet with this silage.
Isolation and quantification of cholesterol oxides in dairy products by selected ion monitoring mass spectrometry
Authors: Nielsen Jacob H. , Olsen Carl Erik , Duedahl Christina , Skibsted Leif H.
Published: June 2009

A method for isolation, detection and quantification of cholesterol oxidation products based on solid phase extraction in combination with preparative HPLC and gas chromatography–mass spectrometry selected ion monitoring has been developed for dairy products. The isolation procedure had a high recovery and artifact formation was minimal, as shown by isotope labelling. The limits of detection ranged from 0.3 to 35 pg/μl of the isomeric forms of 7-hydroxycholesterol, 20α-hydroxycholesterol, the isomeric forms of cholesterol-5,6-epoxides, cholestanetriol, 25-hydroxycholesterol and 7-ketocholesterol corresponding to a limit of quantification of 2–6 ng oxysterol/g lipid in the dairy product, depending on the nature of the cholesterol oxidation product.
On a Rare Cercaria, Cercaria soparkari n.sp., (Transversotrematidae) from Lucknow, India
Authors: Pandey K. C.
Published: June 2009

About 100 specimens of the fresh-water snail, Melanoides tuberculatus (Muller), collected on 30th March, 1962 from “Kukrail”, a tributory of river Gomati, were examined for larval infection. One specimen was found infected with a unique cercaria belonging to the genus Transversotrema. The writer subsequently attempted to collect this cercaria from the same place and 1750 specimens of the said host were examined in the following years (1962–67) without success. Further, a large number of specimens of fishes of the genera Channa Gronov; Colisa Cuv. and Val.; Xenentodon Regan and Nundus Cuv. and Val., common in the tributary were also examined for metacercarial infection of this cercaria but none were found.
Temperature dependent population growth of Gyrodactylus derjavini on rainbow trout, Oncorhynchus mykiss
Authors: Andersen P. S. , Buchmann K.
Published: June 2009

Rainbow trout were experimentally infected with the ectoparasitic monogenean Gyrodactylus derjavini at three temperatures, 5.5°C, 11.6°C and 18.7°C. Subsequently, the infection level was monitored during the following 6 weeks. The population growth was positively correlated with temperature in the initial part of the investigation. At 18.7°C growth of the parasite population was fast reaching a peak abundance within 3 weeks, whereafter the infection level decreased significantly. Peak abundance was recorded in week 5 at 11.6°C. A very slow but steady parasite reproduction was noted at 5.5°C, but no peak abundance was reached within 6 weeks. The decline in parasite population after reaching peak levels is likely to be caused by a host response. The host response is also indicated by the parasites' active selection of particular microhabitats. This anti-monogenean response developed fastest at 18.7°C, more slowly at 11.6°C and was not recorded within 6 weeks at 5.5°C.