bluuebunny/crossref_metadata_2025_split huggingface dataset:
A procedure for the partial fractionation of the αs-casein complex
Authors: Fox P. F. , Guiney J. 
Published: June 2009

SummaryA method for the partial fractionation of the αs-casein complex is described. It involves removal of κ-casein from iso-electric casein by the method of Zittle & Custer (1963) followed by fractionating the residue (αs- and β-casein) by the urea procedure of Hipp et al. (1952). αs0- and αs1-caseins precipitate from 3·3 M urea at pH 4·6, but much of the αs2-, αs3- and αs4-casein remains in solution and co-precipitates with β-casein from 1·7 M urea at pH 4·9. Chromatography on DEAE cellulose clearly separates β-casein from the αs2-, αs3- and αs4-caseins, which are not resolved by the conditions employed. The method is suitable for the fractionation of iso-electric casein into all its major components (i) κ-casein; (ii) αs0- and αs1-caseins; (iii) αs2-, αs3- and αs4-caseins; (iv) β-casein; (v) γ-casein.
The susceptibility of milked and unmilked udder quarters to intra-mammary infection
Authors: Thomas Carol L. , Neave F. K. , Dodd F. H. , Higgs T. M. 
Published: June 2009

SummaryThe teats of quarters which were milked, and those in which milking had ceased, of 16 cows were exposed to bacteria twice daily for 2 weeks by dipping them in a suspension of streptococci and staphylococci.Of 32 quarters in which milking had ceased 22 became infected in this period. Eighteen infections were with Streptococcus dysgalactiae, 2 with Streptococcus uberis, 1 with Staphylococcus aureus and 2 with organisms not used in the culture. Only 3 of 32 milked quarters became infected in the experimental period: 2 infections were with Str. aureus and 1 with an organism not used in the culture. Animals differed in their susceptibility to infection.Quarters which had been unmilked for 2 weeks were as susceptible to new infectionas those in which milking had just ceased.In this experiment, factors such as intramammary pressure, leakage of milk, concentration of bacterial inhibitors, composition of secretion and cell counts of the secretion did not appear to influence the rate of infection. Yield at drying-off, milking rates and teat patency were not related to the differences in susceptibility between animals. It is suggested that the main reason for the lower new infection rate in the milked quarters is that pathogens entering the streak canal or teat sinus are usually flushed out with the secretion during milking and do not cause infection.
Changes in proteins of Domiati cheese during pickling
Authors: Abd El-Salam M. H. , El-Shibiny Safinaz 
Published: June 2009

SummaryDomiati cheese from homogenized and unhomogenized pasteurized milk was pickled for 4 months at room temperature. During pickling, the soluble tyrosine and tryptophan contents of the cheese gradually increased, indicating progressive proteolysis.Gel filtration of cheese extract on Sephadex G-25 revealed the presence of nitrogenous substances of various molecular weights. The maximum formation of amino acids and related substances was observed after 15 days storage.The changes in the electrophoretic patterns of proteins in the cheese during pickling indicated that both αs- and β-caseins were attacked. β-Casein, however, was much less affected.Homogenization was found to affect the formation of soluble nitrogenous substances, but was without effect on the electrophoretic pattern of the protein in the cheese.
The temperature coefficient of electrolytic conductivity of milk
Authors: Prentice J. H. 
Published: June 2009

SummaryThe temperature coefficient of electrolytic conductivity of normal milk decreased with temperature from 0·0241 ± 0·0003/°C at 15 °C to 0·0173 ±0·0003/°C at 40 °C. The temperature coefficient for a sample of mastitic milk lay within this range.
The melting properties of milk fat fractions obtained by double fractionation using a commercial process
Authors: Sherbon J. W. , Dolby R. M. , Russell R. W. 
Published: June 2009

SummarySolid fractions obtained by a commercial process from anhydrous milk fat were refractionated and the softening point (SP), iodine value (IV), and melting thermograms determined. The content of high melting fats and liquid fat content at the SP were calculated for each fraction from its thermogram. Refractionation at 28 °C did not alter the properties of the resultant solid fat. The small amount of liquid fat obtained by refractionation resembled intact milk fat in the properties measured. Refractionation at 31–32 °C yielded a solid fat having a higher SP, lower IV, and increased high melting fat content. Triple refractionation resulted in a solid fraction having a restricted melting range and capable of crystallizing in an unstable polymorphic form upon quick cooling. Tempering the refractionated solid fats at the melting gap temperature of 20–22 °C resulted in elimination of phases melting below −10 °C and enhancement of the melting gap. The content of high melting fat was correlated with the SP. The SP occurred when 95 % of the fat (S.D.±2·7 %) had melted.
The effects of the protein content of the diet on the performance of lactating cows
Authors: Paquay R. , Godeau J. M. , De Baere R. , Lousse A. 
Published: June 2009

SummaryFour experiments were carried out with Friesian cows in different stages of lactation to determine the influence of the crude-protein content of the diet on the digestibility and utilization of dietary constituents and on the cow's performance and milk composition.The rations were composed so that they met the energy requirements of the cows, but crude-protein content was widely variable.Our findings on the digestibility of the dietary constituents were in agreement with the data given in the literature.The utilization of dietary N for milk secretion was influenced by the level of N intake only when the crude-protein content of the diet was lower than a limiting value, which varied according to stage of lactation. When this value was not attained the daily milk production was affected, but not the protein content of the milk.The optimal crude-protein content of the diet was 15–16% (dry-matter basis) when milk production exceeded 20 kg/d, 12–13% for a production of 15–17 kg/d and 11–12% for cows giving less than 10 kg of milk daily.
A technique for evaluating reconstitution properties of milk powders
Authors: Wyeth T. C. , Cheeseman G. C. 
Published: June 2009

SummaryAn accurate and reproducible technique involving a continuous aqueous elution from a bed of dried-milk powder was developed to evaluate reconstitution characteristics. Quantitative data for the determination of reconstitution behaviour were obtained by analysis of the eluate for protein, lactose and Ca constituents. A reconstitution coefficient (P) was derived from the formula (W1+ΣWi)/T, where W1 was the amount reconstituted in the first eluate fraction, ΣWi the total amount reconstituted in 8 fractions, and T the time taken for 1/3 of the constituent to be reconstituted. Values obtained for P were thus related to the reconstitution properties and could be used to grade the powders. A freeze-dried skim-milk gave the ideal reconstitution behaviour with W1 values in the range 42·0–44·2, ΣWi values in the range 93·6–101·3, T values in the range 3·0–3·3 and reconstitution coefficients in the range 41·1–46·3 for the 3 constituents. All the other preparations tested gave lower values for W1 and P, although some gave ΣWi values in the same range, whilst all T values were higher than those for the freeze-dried sample.
Proteolysis detection in milk: I. Interpretation of tyrosine value data for raw milk supplies in relation to natural variation, bacterial counts and other factors
Authors: Juffs H. S. 
Published: June 2009

SummaryA method for detection of proteolysis in milk was evaluated. Amino acids and peptides soluble in trichloroacetic acid were estimated by the Lowry–Folin procedure with expression of results in terms of colour yield equivalent to that of tyrosine (the ‘tyrosine value’ (TV)). Some variables and alternatives in the method of estimation were investigated.TVs for milk freshly drawn from individual cows were extremely varied (0·31–0·92 mg/ml). TVs for samples of refrigerated milk from daily supply farms were in the range 0·40–0·58 mg/ml; no relationships between TV and bacterial counts were evident with these samples. With bulk refrigerated raw milk supplied to Brisbane for liquid consumption from country depots and local farms equipped with bulk vats, significant positive relationships were found between TV and total bacterial count (TBC) for supplies from some sources, but in no instance was a significant relationship found between TV and psychrotroph or proteolytic psychrotroph count. Significant positive relationships were found between TV of bulk milk supplies from some sources and atmospheric temperature, and between TBC of the supplies and atmospheric temperature. The significance of these various relationships for bulk milks is discussed.Natural variation in TV imposed limitations on reliability of the method to provide an index of proteolysis; in general the results indicated that its application was restricted to bulk milk cold-stored for at least 3 days.
The release of intracellular dipeptidase from starter streptococci during Cheddar cheese ripening
Authors: Law B. A. , Sharpe M. Elisabeth , Reiter B. 
Published: June 2009

SummaryIntracellular dipeptidase ofStreptococcus cremorisNCDO 924 has been investigated as a marker enzyme for detecting the release of starter enzymes into Cheddar cheese during maturation. Dipeptidases were produced extra- and intracellularly byStr. cremorisin broth cultures, but the intracellular enzyme was distinguishable by its relatively high activity against L-alanylglycine at low temperatures. The presence of dipeptidase activity of intracellular origin was demonstrated in extracts of Cheddar cheese freed from whole starter cells, opaque material of high molecular weight and free amino acids by a combination of centrifugation and gel filtration on Sephadex G200. The enzyme was not detected in cheeses made without starter (δ-gluconic acid lactone cheeses). In fresh curd with a high viable count of starter the dipeptidase activity was low and mostly extracellular. As the count declined the proportion of intracellular enzyme activity increased, reaching a maximum when 90% of the starter cells had died. The total dipeptidase subsequently decreased until the level remained 30% higher than that of the original curd, and changed little on further ripening up to 120 d. There remained a significant proportion of extracellular dipeptidase activity throughout the maturation period studied.
Interspecies study on the effect of perphenazine on milk yield and composition
Authors: Shani (Mishkinsky) J. , Cowie A. T. , Broster W. H. 
Published: June 2009

SummaryThe effects on lactation of perphenazine, a tranquillizer which increases the level of prolactin in the blood, have been studied in cows, goats, guinea-pigs and rabbits. The drug caused a significant depression of milk yield in cows, goats and rabbits, but was without effect on the milk yield of guinea-pigs. It seems probable that the inhibitory effects on lactation were due to the actions of the drug on appetite and behaviour. It is concluded that perphenazine, because of its other actions, is not a suitable agent for studying the physiological effects of increased levels of endogenous prolactin.
Proteolysis in Cheddar cheese: influence of the rate of acid production during manufacture
Authors: O'Keeffe R. B. , Fox P. F. , Daly C. 
Published: June 2009

SummaryData are presented which show that the use of glucono-δ-lactone as a chemical acidulant in cheese manufacture results in a much more rapid decrease in pH than that occurring in biologically acidified cheese. One of the consequences of the excessive early acid development was a very marked increase in the level of proteolysis during cheese-manufacturing operations. Consequently, chemically acidified cheese, as manufactured by the technique of Mabbitt, Chapman & Berridge (1955) (expt 17), does not appear to be a suitable ‘reference cheese’, especially for studies in which proteolysis during ripening is under investigation. The technique of Mabbitt et al. Avas modified to simulate the pH development pattern of starter cheese more closely; the level of proteolysis in curd made by the modified method was approximately equal to that in starter curd.An attempt was made to link the propensity to develop bitterness of cheese made with fast acid-producing cultures with excessive early proteolysis in such cheese. The results show that fast- and slow-culture strains differed significantly in their acid-producing capability only after the cooking stage and consequently such cheeses differed little with respect to early proteolysis. Further, cheeses made with 0·5, 1·0, 2·0 or 4·0% of ML8 culture which differed considerably in rate of acid development and consequently in the level of early proteolysis did not develop bitterness, even when 4·0% starter was used.It is concluded that gross proteolysis and bitterness are not correlated.
Peptidase activities in Group N streptococci
Authors: Mou Lynette , Sullivan J. J. , Jago G. R. 
Published: June 2009

SummarySeveral peptidase activities in the 3 species of Group N streptococci were partly separated by gel filtration on Sephadex G-200. The peptidases identified were a general aminopeptidase of wide specificity, a tripeptidase, a proline iminopeptidase (prolyl-β-naphthylamidase), a proline iminodipeptidase and an aminopeptidase-P. The effects of temperature and pH on the stability of the enzyme activities, and the influence of the type of N source used in the growth medium on the elution pattern of the enzymes were examined.
The effect of oxygen content on flavour and chemical changes during aseptic storage of whole milk after ultra-high-temperature processing
Authors: Thomas E. L. , Burton H. , Ford J. E. , Perkin A. G. 
Published: June 2009

SummaryIndirectly heated ultra-high-temperature (UHT) processed milk was prepared with initially high, medium, and low dissolved O2 contents of 8·9, 3·6 and 1·0 ppm respectively, aseptically bottled, and tested at intervals during storage at room temperature for 150 d. Flavour acceptability increased to a maximum after a few days, but declined slowly after about 6 d; the increase was associated with less off-flavour described as ‘cabbagey’, and the decrease with more ‘stale’ off-flavour descriptions. Milks with higher initial O2 contents were preferred up to 8–13 d, but thereafter acceptability was independent of initial O2 content. Sulphydryl group (–SH) contents rapidly decreased and O2 levels correspondingly declined in the first few days as the flavour improved. Loss of –SH was lower with lower initial O2 contents, and moderate –SH content remained in low O2 samples for several weeks. Ferricyanide reducing (FR) values did not satisfactorily measure stale flavour development. They were initially high and decreased during the first 13 d at rates dependent on O2 content. After 20 d the FR values began to rise in high O2 samples, but continued to decline slowly in low O2 samples up to 90d although stale flavour was increasing.High initial O2 contents resulted in rapid depletion of ascorbic acid and folic acid during storage. Losses of vitamin B12 were small, but were higher with high O2 contents than with low.The beneficial effect of O2 on flavour, therefore, appears to be so slight and confined to such a short period in the early life of the milk as to be completely outweighed by the adverse nutritional effects.
Relationships between stage of lactation and pregnancy and blood composition in a herd of dairy cows and the influences of seasonal changes in management on these relationships
Authors: Rowlands G. J. , Manston R. , Pocock Rita M. , Dew Sally M. 
Published: June 2009

SummaryBlood samples, taken on 6 occasions during 1 year from 172 cows resident in a dairy herd, were analysed for packed cell volume, blood glucose, haemoglobin (Hb), serum albumin, urea N, total protein, Ca, inorganic phosphate, Mg, Na and K. The data were analysed statistically, firstly with respect to date of sampling, stage of pregnancy or lactation and the interaction between stage of pregnancy or lactation and date of sampling, and secondly with milk yield as an additional factor for the data for lactating cows.Concentrations of all constituents except inorganic phosphate and K varied significantly (P<0·001) with stage of lactation and/or pregnancy. The most significant changes in concentrations were confined to the periods up to 3 months either side of calving. The greatest changes in concentration during these periods occurred for Mg which rose during late pregnancy and for albumin which fell at or near calving. Albumin, urea and glucose were all, on average, lowest in concentration during the first month of lactation; globulin concentrations showed the reverse trend. Haemoglobin concentrations decreased during late pregnancy and early lactation and were lowest in the period 30–120 d post partum. Calcium concentrations decreased during late pregnancy and rose during early lactation. Sodium concentrations rose during late pregnancy. Interactions between dates of sampling and stages of lactation or pregnancy were significant (P<0·001) for all constituents, and most marked for glucose, urea, albumin, Hb, Ca and Na.Haemoglobin and K concentrations fell and Mg concentrations rose with increasing milk yield, but the proportions of the total variance accounted for by differences in milk yield were small in relation to those accounted for by stage of lactation. These findings are of significance in relation to the selection of animals for sampling in the Compton Metabolic Profile Test.
Artificial induction of lactation by hypothalamic implantation of perphenazine in virgin goats
Authors: Vandeputte-van Messom Georgette , Peeters G. , Lauwers H. 
Published: June 2009

SummaryPerphenazine (0·8–1mg) caused udder growth and artificial induction of lactation, when stereotaxically implanted into the median eminence of virgin female goats. Sham implantations into the median eminence or implantation of perphenazine into sites of the hypothalamus not in the immediate proximity of the median eminence were ineffective. Fourteen–twenty-two d after implantation the goats were milked for the first time. Maximal milk yields of 250–1050 ml/d were achieved 3–5 months later. Udder development and induction of lactation during the premilking period were exclusively due to the action of perphenazine. It is likely that after implantation the milking stimulus played a synergic role with perphenazine in the progressive increase and the maintenance of lactation. Apparently no side effects were caused by the drug. Implantation of small doses of perphenazine in the hypothalamus might be a suitable technique for studying the physiological effects of increased levels of endogenous prolactin in goats.
Effect of storage on the electronic cell count of milk
Authors: Sweetsur A. W. M. , Phillips J. D. 
Published: June 2009

SummaryUsing a standard method, the electronic cell count of formalin-treated milk usually increased during storage. This increase varied with the milk and was found to be due to a corresponding decrease in the effectiveness of the fat-dispersal procedure before counting. A more severe fat-dispersal procedure incorporated into the standard method resulted in a stable cell count being obtained. It was found that formalin must be added to milk within 24 h of milking to prevent lysis of the cells.
Acetaldehyde: an intermediate in the formation of ethanol from glucose by lactic acid bacteria
Authors: Lees G. J. , Jago G. R. 
Published: June 2009

SummaryGroup N streptococci formed acetaldehyde and ethanol from glucose. As the enzymes aldehyde dehydrogenase, phosphotransacetylase and acetate kinase were present this would enable these organisms to reduce acetyl-CoA to acetaldehyde and convert acetyl-CoA to acetyl phosphate and acetate. A pentose phosphate pathway which converted ribose-5-phosphate to glyceraldehyde-3-phosphate was also present. Acetaldehyde could not be formed via the hexose monophosphate shunt or by direct decarboxylation of pyruvate, as the enzymes phosphoketolase and α-carboxylase were absent. Phosphoketolase activity was induced inStreptococcus lactissubsp.diacetylactisafter growth on D-xylose. Group N streptococci also contained an NAD-dependent alcohol dehydrogenase which reduced acetaldehyde to ethanol while both NAD- and NADP-dependent alcohol dehydrogenase activities were found inLeuconostoc cremoris.
Immunochemical, chromatographic, and milk-clotting activity measurements for quantification of milk-clotting enzymes in bovine rennets
Authors: Rothe G. A. L. , Axelsen N. H. , Jøhnk P. , Foltmann B. 
Published: June 2009

SummaryMonospecific rabbit antibodies were produced against bovine chymosin (rennin) and bovine pepsin A and used for quantitative measurements of these enzymes by rocket immunoelectrophoresis. Bovine pepsin B was identified and measured quantitatively in tandem crossed immunoelectrophoresis, using a polyspecific antibody preparation. Chromatographically purified chymosin B and bovine pepsins A and B were used as standards. The contents of chymosin and bovine pepsin A were also determined by 2 forms of DEAE chromatography, and by an assay utilizing the ratio of milk-clotting activity at pH 6·0 and 6·5. Results obtained by measurements on 3 bovine rennets (calf rennet, adult bovine rennet, and a mixture of such types) by the different methods of analysis were in good agreement. The advantages of the immunochemical methods are direct and simultaneous identification and quantitation of enzymes.
Serological studies on heat-induced interactions of α-lactalbumin and milk proteins
Authors: Baer A. , Oroz M. , Blanc B. 
Published: June 2009

SummaryThe heat denaturation of α-lactalbumin (α-la) in NaCl and KCl solutions, milk ultrafiltrate and milk was studied using the method of micro complement fixation. It was established that this protein was very resistant to heat denaturation and that it was more stable in milk ultrafiltrate than in the other media studied at temperatures up to 70 °C. Of the various milk proteins added to α-la, only β-lactoglobulin (β-lg) formed a heat-induced complex with this protein. This complex was identical in milk ultrafiltrate or in milk and depended on the molar ratio between both proteins; it was not modified by any other milk proteins. The binding of a-la to β-lg changed the ability of the latter protein to bind κ-casein.
A heat-induced change in the ultrastructure of milk and its effect on gel formation in yoghurt
Authors: Davies F. L. , Shankar P. A. , Brooker B. E. , Hobbs D. G. 
Published: June 2009

SummaryMicelles of milk heated at 95 °C for 10 min or autoclaved at 121·7 °C for 15 min were observed by electron microscopy to bear filamentous appendages, whereas micelles from raw milk had relatively smooth contours with no appendages. Experiments suggested that the appendages were composed of denatured β-lactoglobulin and showed that their development was sensitive to sulphydryl blocking agents. Firmness and syneresis of yoghurt were associated with the extent to which micelles coalesced during fermentation; the appendages of micelles in heated milk appeared to inhibit coalescence giving rise to a firmer curd with a lower tendency to syneresis.