bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscometric measurements of the activities of commercial rennets using sodium caseinate as substrate
Authors: Blair G. W. Scott , Oosthuizen J. C. 
Published: June 2009

SummaryThe considerable falls in viscosity of sodium caseinate solutions under the action of rennet are shown to be due to changes in volume and shape (or either alone) of loosely coiled long chain molecules, resulting from the discharge of ionization (‘Third-type electro-viscous effects’). This reduction may be as well effected by small amounts of NaCl or by the separated decomposition products of the rennin-caseinate reaction. Even at the highest practicable caseinate concentrations (9–10% by weight) the solutions are truly fluid over the range of shear-rate of the Ostwald viscometers usedThe initial rate of fall of viscosity is found to be proportional to the maximum (initial) specific viscosity, leading to an equation Xk1 = 1/τ where X the proportional viscosity loss, varies with the source of caseinate but is constant for all normal rennets; k1, the first-order reaction constant, varies with the rennet but is independent of the source of casein over a wide range; and τ, which has the dimensions of time, varies with both caseinate and rennet.The parameter k1 may be found either from the exponential viscosity fall or calculated from the asymptotic initial slope and has been shown to serve as a useful index of rennet activity. This method of rennet testing does not depend on the keeping qualities of rennins, rennets, milks or caseinates. Details of the preparation of caseinates and of the methods for practical testing of commercial rennets are given.
A simple spectroturbidimetric method for the determination of the fat content of homogenized ice-cream mixes
Authors: Goulden J. D. S. , Sherman P. 
Published: June 2009

SummaryA rapid spectroturbidimetric method for the determination of the fat content of homogenized ice-cream mixes using a simple filter absorptiometer has been devised. Turbidities are measured at two different wavelengths to allow for changes in the degree of homogenization. The standard deviation of the differences from the values obtained by the Werner-Schmid method was found to be 2·5% of the mean fat content value. The method also enables the mean fat globule diameter to be determined.
Studies on the properties of New Zealand butterfat: VII. Effect of the stage of maturity of ryegrass fed to cows on the characteristics of butterfat and its carotene and vitamin A contents
Authors: McDowall F. H. , McGillivray W. A. 
Published: June 2009

SummaryIn two outdoor feeding trials with monozygotic twin cows during the spring and early summer months the effects of mature and immature H1 short rotation ryegrass on the composition of the butterfat produced and on the carotene and vitamin A contents of the butterfat and the blood were compared. In both trials the characteristics investigated were markedly affected by the stage of maturity of the grass. The butterfat from cows receiving immature ryegrass was more unsaturated and had higher carotene and vitamin A contents than that from cows receiving mature ryegrass. The blood of cows fed immature ryegrass also contained more carotene than the blood of cows fed mature ryegrass.It is suggested that variation in the stage of maturity of New Zealand dairy pastures throughout the year is an important factor contributing to the seasonal variations in the characteristics and the carotene and vitamin A contents of commercial butterfat. The influence of stage of maturity is probably associated with the quantity and nature of the pasture lipids.
The effect of preparative conditions on the composition of the k-casein complex
Authors: Hill R. D. , Hansen Raione R. 
Published: June 2009

SummaryThe effects of changes in the conditions of preparation on the composition of the k-casein complex have been studied and a method of preparation is suggested which embodies the optimal conditions. The varied conditions include temperature of precipitation of the acid casein, the pH, temperature, CaCl2 concentration and duration of the CaCl2 treatment, and the conditions of centrifuging. Changes in composition caused by alcohol fractionation are reported and the results are discussed from the point of view of k-casein as a complex of three or more proteins.
The effect of pre-partum feeding of heifers on milk composition
Authors: Foot A. S. , Line C. , Rowland S. J. 
Published: June 2009

SummaryThe effect of the level of pre-partum feeding of Friesian heifers on the yields and composition of the milk in the subsequent lactation has been investigated using 23 heifers on each of 2 treatments. For 1 treatment, over a period of 6 weeks before calving, generous grazing on good pasture was supplemented with 8 lb/cow daily of concentrates, and for the other only restricted grazing of an already sparse sward was allowed.For the period 3—8 weeks from calving the heifers fed at the high plane pre-partum produced significantly more milk than those fed at the low plane (36·8 compared with 31·9 lb/cow daily). The solids-not-fat (S.N.F.) and fat contents of their milk were also significantly higher (8·71 compared with 8·47%, and 3·72 compared with 3·38%, respectively). For the period 3—14 weeks from calving the effect of milk yield was slightly greater but the effect on composition was less. For the period 3—30 weeks from calving the difference in milk yield remained significant (31·3 compared with 26·1 lb/cow daily), but the average differences in S.N.F. and fat contents over this period (8·63 compared with 8·51%, and 3·75 compared with 3·59%, respectively) were not significant.The heifers fed at the higher plane increased in liveweight before calving at a rate which was highly significantly greater than that of the heifers fed at the low plane. After calving, the heifers which had been on the higher plane remained almost constant in weight during the first 12 weeks whilst the others regained some of their losses, a difference which was highly significant. This recovery was apparently made at the expense of milk yield and composition.
The effect of concentrates on the voluntary intake of roughages by cows
Authors: Campling R. C. , Murdoch J. C. 
Published: June 2009

SummarySeven changeover experiments were conducted to examine the effect of giving restricted amounts of concentrates on the voluntary intake of different roughages by non-lactating dairy cows. The addition of up to 6 kg concentrates daily to the diet of cows receiving roughage ad lib. caused little change in the intake of hay and a small increase in the intake of barley straw. Larger amounts of concentrates of 6 and 8 kg daily reduced hay intake by between 0·2 and 0·4 kg dry matter/kg concentrate dry matter given. When concentrates were given to the cows the rate of decline in intake of hay tended to be greatest with the hays of highest digestibility. The daily addition of up to 8 kg concentrates to the diet of cows offered silage ad lib. caused only small depressions in the intake of silage. The results are discussed in relation to recent work on this subject with cattle and sheep.
The effect of mammary gland denervation on the fatty acid composition of goat's milk
Authors: Ward P. F. V. , Huskisson N. S. 
Published: June 2009

SummaryMilk was analysed from twin Saanen goats. In one of the goats one mammary gland was transplanted to the neck. The milk yields and fat content from each gland were recorded and the composition of the fat examined using gas-liquid chromatography. The yield and fat content of the milk from all the glands fell within the normal range. With the operated goat, the milk from the transplanted gland differed little in fatty acid composition from that from the non-transplanted gland. Milk from either gland differed little in this respect from milk from the normal goat.
The stability of milk protein to heat: I. Subjective measurement of heat stability of milk
Authors: Davies D. T. , White J. C. D. 
Published: June 2009

SummaryA subjective test for the determination of the stability of milk protein to heat is described. In the test, the time required for particles of coagulated protein to become visible throughout a 2·5-ml sample of separated milk maintained at 135°C in a glass tube rocking at 8 c/min is taken as a measure of stability. The precision of the test was such that single determinations were generally adequate.Coagulation time decreased by about 12% as rocking speed was increased over the range 4–12 c/min and increased by a factor of about 3 for a decrease in heating temperature of 10 degC over the range 140–105 °C; with some milks the Q10°C value increased to 5–8 a temperature decreased. As sample volume was increased over the range 1–3 ml coagulation time increased, especially With milks whose coagulation was poor (initial clots small). This volume effect appeared to be a consequence of the accompanying decrease in the proportion of headspace oxygen to volume of milk.
Serological differentiation of cow's, buffalo's, goat's and sheep's milks
Authors: Pinto F. C. 
Published: June 2009

SummaryMilks of the closely related species ox, buffalo, goat and sheep were differentiated by the precipitin test using antisera to blood serum proteins. The antisera were made specific for the homologous species by absorption. The component of milk tested was the lactalbumin–lactoglobulin fraction present in whey. Fraudulent sale of diluted buffalo's milk, cow's milk–buffalo's milk–water mixtures and reconstituted whole and skim-milk powders as genuine cow's milk was detected. Of 270 milks serologically tested, 233 were cow, 26 buffalo, 1 goat, 3 cow–buffalo mixtures, 2 reconstituted whole-milk powders and 5 reconstituted skim-milk powders. Of the samples serologically identified as cow, 135 had analytical figures for fat and solid-not-fat (SNF) only just outside or within the buffalo range.Milk from any one species was detected in a concentration of 5% (v/v) in milk of a related species. Species identification was made of human milk stains in 2 medicolegal cases. Fresh cow's milk, reconstituted whole-milk powder and reconstituted skim-milk powder were differentiated.
Occurrence of milk proteins in the urine of cows during an extended milking interval
Authors: Lyster R. L. J. , Wheelock J. V. 
Published: June 2009

SummaryImmunological methods have been used to test samples of urine from 5 cows for the presence of milk proteins. None could be detected when the cows were milked twice daily at the usual intervals, but during an extended milking interval α-lactalbumin was found in the urine of all 5 cows and β-lactoglobulin in the urine of 2 cows. The urine of one cow during and after a milking interval of 39 h contained 1·63 g α-lactalbumin, 1·12 g β-lactoglobulin and a small amount of casein. One of the factors affecting the transfer of these milk constituents from the udder to the urine appears to be their molecular weight.
Seasonal variation in deposit formation from whole milk on a heated surface
Authors: Burton H. 
Published: June 2009

SummaryThe variation in deposit formation from milk of 2 herds was measured over a period of more than 12 months using a hot-wire laboratory apparatus. A marked minimum was found in May–June, with high deposit levels between September and April. There was a difference of 2 to 1 between maximum and minimum levels. The amount of deposit was not positively correlated with the mineral or protein contents of the milk, but was strongly positively correlated with fat content. It is suggested that the controlling factor is closely associated with fat content and varies with it.
Some skin characteristics in British Friesian pedigree bulls and their correlation with relative breeding value
Authors: Nay T. , Johnson Helen 
Published: June 2009

SummaryA possible relationship between the Relative Breeding Value (R.B.V.) and some skin characteristics has been investigated in 89 British Friesian pedigree bulls made available by the Milk Marketing Board of England and Wales.It was found that there was a statistically significant correlation between the R.B.V. and the follicle diameter. There was also a correlation between the thickness of the papillary layer and the R.B.V. The possible value of the results for selection purposes is discussed.
The action of rennet on whole milk
Authors: Wheelock J. V. , Knight Dorothy J. 
Published: June 2009

SummaryThe release, by the action of rennet, of peptides which are soluble in trichloroacetic acid (TCA) has been studied using milk samples from individual cows. This release showed an initial marked increase with time of rennet action. After the milk clotted there was no further increase for at least 30 min. There was considerable variation in the total amount of N and of sialic acid released from milk samples taken from individual animals at different times during the lactation.For a given milk sample treated with rennet, the amount of sialic acid in the filtrate obtained after precipitation with 2% TCA was similar to that obtained with 10% TCA, whereas the amount of nitrogen was much greater with the 2 % TCA. It appeared that the peptides containing sialic acid were released at a slower rate.On average, about half the total sialic acid in the casein was recovered in the TCA filtrate after rennet action, which suggests that either a proportion of the κ-casein was not accessible to enzyme action or the technique used did not permit full recovery of the sialic acid-containing peptides.
Metabolism of [U-14C]D-fructose by the isolated perfused udder
Authors: Verbeke R. , Massart-Leën Anne-Marie , Peeters G. 
Published: June 2009

SummaryA lactating mammary gland of a sheep and a goat were perfused for several hours in the presence of [U-14C]D-fructose and received adequate quantities of acetate, glucose and amino acids.In both experiments, there was a small incorporation of14C in the expired CO2. Smaller radioactivities were measured in milk citric acid, lactose, casein and fat, the activities decreasing in that order. The specific activities of the amino acids from one casein hydrolysate were determined. The highest radioactivities were found in alanine and serine; methionine, glutamic acid and aspartic acid showed a smaller incorporation of14C.These results indicate that fructose is metabolized only to a very limited extent by the mammary gland. The relative distribution of14C observed among the different substances isolated may be explained by a direct splitting of fructose into two C3-fragments, glycolysis and metabolism via the Krebs cycle.
The winter decline in the solids-not-fat content of herd bulk-milk supplies
Authors: Wright J. A. , Rook J. A. F. , Panes J. J. 
Published: June 2009

Summary(1) A survey of the composition of the milk of individual cows in 4 commercial herds in the West Riding of Yorkshire was undertaken from October 1967 to May 1968.(2) In 3 of the 4 herds there was a decline in solids-not-fat (SNF) content throughout the winter feeding period. Milk protein content was at a minimum in January–February but in all 3 herds lactose content also declined and in 2 of the herds this was the major cause of the fall in SNF content.(3) The decline in lactose content was the result partly of the characteristic effect of an advance in lactation, partly of an increase in the incidence of mastitis throughout the winter period. In all herds there was a significant inverse relationship between lactose content and cell count in the bulked milk of individual cows.(4) In 3 of the herds autumn-calving (October–December) animals showed a pronounced fall in milk protein content in the early months of lactation which was not observed in summer-calving (July–September) animals. There was no response in SNF or protein content to supplementary concentrates offered towards the end of the winter-feeding period, whereas with the commencement of grazing in the spring there was an immediate increase in both protein and SNF contents.
Milk-clotting and proteolytic activities of rennet, and of bovine pepsin and porcine pepsin
Authors: Fox P. F. 
Published: June 2009

SummaryThe milk-clotting and proteolytic activities of rennet, bovine pepsin and porcine pepsin were compared. The milk-clotting activity of porcine pepsin was extremely pH-dependent around pH 6·6 and coagulation did not occur above pH 6·68. The clotting activity of bovine pepsin was slightly more dependent on pH than that of rennet but no rapid drop-off in activity occurred as with porcine pepsin. Temperature influenced the clotting activity of rennet and bovine pepsin similarly but the behaviour of porcine pepsin was markedly different.For equal milk-clotting activity, the proteolytic activities of rennet and bovine pepsin were approximately equal and substantially lower than that of porcine pepsin. Electrophoretic examination showed that the proteolysis products of rennet and bovine pepsin were similar and quite different from those produced by porcine pepsin.The suitability of bovine pepsin as a rennet substitute is discussed.
Studies on the mechanism of the whiteside mastitis test reaction
Authors: Nageswararao G. , Derbyshire J. B. 
Published: June 2009

SummaryThe contribution of certain components of leucocytes and milk to the viscosity and precipitate which develop in the Whiteside mastitis test was studied to obtain information on the mechanism of the reaction. The viscosity obtained in the Whiteside test reaction was considerably less than that in the California mastitis test reaction and the Whiteside test was found to be more dependent on precipitation than increased viscosity.Leucocyte nuclei were mainly responsible for the formation of the precipitate in the Whiteside reaction and CaCl2 dispersed the precipitate formed by the leucocyte nuclei into small clumps. Leucocyte protein and fibrinogen increased the amount of precipitate formed by the leucocyte nuclei. Fat globules also increased the amount of precipitate, probably by being trapped in the precipitate.The addition of non-gelable or gelable nuclei resulted in the formation of similar amounts of precipitate in the modified Whiteside reaction. Furthermore, storage of milk for 5 days did not decrease the amount of precipitate formed, indicating that the DNA-protein complex of the leucocyte nuclei need not be present in the native form to contribute to the precipitate in this reaction.
The pattern of release of free fatty acids from milk fat under the action of intrinsic and added lipases
Authors: Hemingway E. B. , Smith G. H. , Rook J. A. F. 
Published: June 2009

Summary(1) The rate of release of fatty acids from milk by porcine pancreatic lipase was studied as a model system for the development of lipase taint. The rate was low initially but then increased logarithmically and later declined. Addition of milk which had been subjected to the action of lipase and then boiled to inactivate the enzyme enhanced fatty acid release. An extract containing monoglycerides from lipolysed milk had a similar action whereas an extract of free fatty acids had an effect mainly in the early stages, increasing the initial rate. Addition of Ca2+, which accelerated lipolysis of fresh milk, enhanced the action of fatty acids and depressed that of monoglycerides.(2) In the early stages of lipolysis there was a preferential release of short-chain fatty acids and a high proportion of these passed into the aqueous phase. These effects were more pronounced at low temperature and at acid to neutral pH. At alkaline pH a greater proportion of the short-chain acids was present in the aqueous phase but the total release of these acids was less.(3) Fresh milks differed in their response to ‘aeration’ and storage at 4°C. In those in which taint was induced there was a considerable release of fatty acids in response to aeration, and a further release and also a redistribution between the aqueous and fat phases during storage. No relationship was apparent between the amount of fatty acids released and the initial fatty acid content.(4) The findings are discussed in relation to the development of lipase taint in commercial milks.
Structure of the casein micelle. A proposed model
Authors: Garnier J. , Dumas B. Ribadeau 
Published: June 2009

SummaryOn the basis of complete permeability by high molecular weight reagents of casein micelles in milk and a uniform distribution of the 3 different casein subunits, a model of the micelle structure is proposed. It is composed of an average repeating unit of 1 κ-, 2 αs1;- and β-casein subunits assembled in a 3-dimensional network or branched polymer made of 130–130000 monomers, in which the trimers of κ-casein occupy the nodes and the copolymers of αs1;- and β-caseins make up the branches. All the associations between subunits are through non-covalent bonds. The chemical composition varies with the number of αs1;- and β;-casein subunits in the branches. This proposed structure is strongly supported by evidence from electron microscopy and a scale model has been made. It leads to an understanding of the role of κ-casein in micelle formation and opens new perspectives in explaining some properties of the caseins. It offers an interesting example of a new type of quaternary structure of protein subunits.
The determination of vitamin C in evaporated and fortified sterilized milks
Authors: Toothill Joyce , Thompson S. Y. , Hill W. B. 
Published: June 2009

SummaryA study has been made of the use of 2,6-dichlorophenolindophenol (DCP) and also of 2,4-dinitrophenylhydrazine (DNPH) with and without chromatography of the DNPH derivatives, for the determination of ascorbic acid (AA) and dehydroascorbic acid (DHA) in evaporated milks, and of AA in AA-fortified sterilized milks.In the DNPH method, when interfering compounds were removed by the chromatographic separation of the DNPH derivatives, absorption curves typical of the pure DHA derivative were obtained.The DCP method gave erroneously high values for the AA and DHA content, and the lower values obtained by the DNPH method with chromatography of the DNPH derivatives were judged correct. Thus for an evaporated milk, the values for vitamin C content (AA + DHA) were, in mg/100ml reconstituted milk, 0·88 (DCP method), 0·66 (DNPH method without chromatography), and 0·48 (DNPH method combined with chromatography). The AA contents (mg/100 ml) of the 2 fortified sterilized milks were 3·63 and 5·78 (DCP method); 3·01 and 4·28 (DNPH method combined with chromatography).The AA contents of the 5 different evaporated milks, determined by chromatography of the DNPH derivatives, ranged from 0·07 to 0·63 mg/100 ml reconstituted milk. The DHA content was negligible.As judged by the shape of the absorption curves after chromatography of the DNPH derivatives, it is concluded that this method is the most reliable of those studied.
Bovine milk protease
Authors: Dulley J. R. 
Published: June 2009

SummaryMilk protease, the naturally occurring proteolytic enzyme from fresh raw bovine milk, was purified 629-fold. Purification methods are described which included acid precipitation, ion-exchange and gel chromatography and ammonium sulphate fractionation. It was necessary to use a large-scale purification as the amounts of enzyme in milk are very low.The basic properties of the enzyme were elucidated from experiments on this partially purified fraction. Under the conditions of assay these showed a wide pH optimum from 6·5 to 9·0 and a temperature optimum of 37°C. The protease was fairly heat stable, the stability being pH dependent.The source of the enzyme appeared to be the mammary gland, where the enzyme was also detected.