bluuebunny/crossref_metadata_2025_split huggingface dataset:
631. Variations in iodine value of milk fats
Authors: Mayhead J. W. , Barnicoat C. R. 
Published: June 2009

Iodine values of milk fats of grazing cows show wide variations which are chiefly determined by differences in oleic acid content. Among the factors promoting the variations are: individuality of the cow, stage of lactation, breed differences, diurnal and incidental (irregular) day-to-day effects, nature of the food and plane of nutrition.Results of experiments with feeding an unsaturated vegetable oil indicate that considerable proportions of the unsaturated long chain acids of milk fat were derived from the ingested oil. It is deduced that herbage lipids may contribute materially to the production of milk fat of grazing cows.From comparisons of the extents to which dietary long chain unsaturated acids are incorporated into milk fats of grazing and semi-fasting cows, it would appear that the rise in iodine value following partial inanition does not result from increased uptake of fatty acids withdrawn from the more highly unsaturated glycerides of the body reserves.
656. Factors influencing the vitamin content of milk fat: II. The influnce of botanical composition of the pasture
Authors: Worker N. A. , McGillivray W. A. 
Published: June 2009

1. The effect of the level of clover intake on the vitamin A potency of milk fat has been studied, using Jersey cows from the herd of the Dairy Research Institute (N.Z.).2. In preliminary experiments in which composite bi-weekly butterfat samples were obtained from the whole herd of thirty-eight cows no relationship could be established between level of clover intake and potency of fat produced. This was assumed to be due to the rapidity with which the level of clover intake varied, since under normal grazing management the cows were moved to a fresh paddock (which was often of widely different botanical composition from that previously grazed) after every second milking.3. In later experiments in which three pairs of monozygous twins from the herd were used, a clear-cut relationship was established between clover intake and potency of fat produced and between clover intake and iodine value, oleic acid percentage and tocopherol content. Diets high in clover tended to depress total potency, iodine value, oleic acid percentage and tocopherol content of the fat, while diets low in clover had the reverse effect. The clover used in these experiments was mainly an improved strain of white clover containing approximately 0·03% cyanide. Repetitive experiments using improved strains of red clover produced negative results.4. The mechanism by which diets high in clover depress fat potency, iodine value, oleic acid percentage and tocopherol content is not clear. It is suggested, however, that it may be due to (i) the low tocopherol content of clover relative to grass, (ii) the high HCN content of certain species, and (iii) the possibly lower oleic acid content. The possibility is also considered that it may be due to some factor (or group of factors) associated with the stage of development of the pasture as a whole at a time when clover happens to be the dominant pasture species.5. Drenching cows with thiocyanate, the probable detoxication product of HCN in the ruminant, could not be shown to have any effect on the levels of vitamin A alcohol, ester, carotene, or xanthophyll in the blood and milk fat.Some of the results of this investigation form a section of a thesis submitted by one of us (N.A. W.) in partial fulfilment of the requirements for the degree of M.Agr.Sc. of the University of New Zealand. The authors are indebted to the Department of Scientific and Industrial Research for a grant towards the investigation and to Mr M. R. Patchell and farm staff of The Dairy Research Institute (N.Z.) for assistance in collection of milk and blood samples. The technical assistance of Miss Fay Frecklington is gratefully acknowledged.
693. A rejection test for raw milk
Authors: Taylor Peggy B. , Clegg L. F. L. 
Published: June 2009

The determination of apparent lactic acid has been used as a basis for a rejection test for raw milk. The method consists of precipitation of milk proteins with barium chloride, sodium hydroxide and zinc sulphate, and the addition of ferric chloride to the filtrate to produce the yellow colour of ferric lactate. Lactic acid is not solely responsible for the production of the yellow colour, which, nevertheless, gives a good relationship with keeping quality of milk (measured as hours to the C.O.B. end-point at 22° C.) and the values have been expressed as ‘apparent lactic acid’.The relationship of winter and summer milks to keeping quality has been studied, and a value of 0·03% apparent lactic acid in milk is equivalent to an average keeping quality of 5¾ and 8½ hr. for winter and summer milks, respectively. A value of 0·03% is recommended as the earliest value of apparent lactic acid at which milk could be rejected.The apparent lactic acid in colostrum and late-lactation milk and in milk from cows suffering from mastitis has been determined, and only in late-lactation milk were the values found to be significantly higher than usual in fresh raw milk, and an inverse relationship between yield and apparent lactic acid is suggested.Permanent glass matching disks have been prepared for use in a Lovibond comparator. This permits the intensity of the yellow colour produced with 1% ferric chloride to be determined and the apparent lactic acid in milk estimated.Grateful acknowledgement is made to the management and staff of the Dairy Department of the Reading Co-operative Society and the Farmer's Clean Milk Dairy, Reading, and local milk producers for supplying samples for experiments; to the N.M.T.S. staff in Reading for help in finding suitable farmers, and to the Dairy Husbandry Department of the N.I.R.D. for information about and samples of abnormal and late-lactation milk. Our particular thanks are due Miss Marie Gruber for technical assistance, to Dr N. J. Berridge for the suggestion and help on the work on pH change as an indication of keeping quality (given in the appendix), and to Dr A. T. R. Mattick for the advice given in this work.
695. On the composition of the phospholipids of cows' milk
Authors: Rhodes D. N. , Lea C. H. 
Published: June 2009

1. The phospholipids of skim-milk, buttermilk and butter prepared from one bulk of Friesian milk were examined, using chromatographic methods. No major differences were found between the three products.2. The phospholipids of buttermilk contained (in moles %) phosphatidylethanolamine 29, phosphatidylserine 10, phosphatidylcholine 33, sphingomyelin 19. The content of lipid-bound inositol was 5 moles % and of plasmalogens 3 moles %. Nitrogen, associated with the kephalin fraction, equivalent to 14 moles % of the lipid P was not identified. No lysoglycerophospholipids were present.3. Unsaturated fatty acids were present in both the α'- and β-positions of the milk glycerophospholipids, in contrast to those from other animal sources which have usually been found to contain unsaturated acids in the α'-position and predominantly saturated acids in the β-position.The authors are indebted to Prof. H. D. Kay for providing facilities at the National Institute for Research in Dairying, Reading; to Dr R. H. Smith for advice on processing, and to Miss H. R. Chapman and the staff of the Experimental Dairy for carrying out the dairy work.This work forms part of the programme of the Food Investigation Organization of the Department of Scientific and Industrial Research. Mr P. Whiteley contributed to the experimental work.
696. The chemical composition of the colostrum and milk of the ewe
Authors: Perrin Dawn R. 
Published: June 2009

1. The composition of the milk of six low-plane and six high-plane ewes has been studied. Definite lactational trends have been observed for all the major constituents.2. For all the ewes the initial colostrum was characterized by very high protein and fat contents and by low lactose content.3. Analyses of the mineral constituents—calcium, magnesium, sodium, potassium, phosphorus, and chloride—are reported covering the whole lactation of twelve sheep. The colostrum of the low-plane animals was higher in total mineral content than that of the high-plane animals.The author wishes to thank Mr L. J. Lambourne for providing the milk samples and Mr J. E. Allen for the spectographic analyses.
704. The properties of New Zealand butters and butterfats: V. Milks and butterfats from monozygotic twin cows
Authors: McDowall F. H. , Patchell M. R. 
Published: June 2009

1. Seven sets of monozygous twins were kept under the same open-grazing conditions for one year. Milks were analysed for fat, solids-not-fat, lactose and total protein contents, and butterfats were isolated at fortnightly intervals for estimation of iodine value, refractive index, softening point, saponification value, Reichert value, carotene content and vitamin A content. The results are presented both graphically and statistically.2. Consistent differences in body weights of the cows of a twin set did not render the twin set unsuitable for use in experimental work on causes of changes in milk yield, fat yield, milk composition or butterfat characteristics.3. The advantages of monozygous twins over unrelated cows was shown: (a) by the close general correspondence of the within-twin-set results as compared with the between-twin-set results throughout the period of the trial; (b) by the similarity in the forms of the curves for the different sets of twins; (c) by the marked similarity of the reaction of the cows of a twin set to change in environmental conditions—this applied particularly for butterfat characteristics such as iodine value and refractive index; (d) by the ‘twin efficiency values’ for butterfat properties computed from the whole-lactation weighted means, viz. iodine value, 7·8; saponification value, 3·4; Reichert value, 5·5; carotene content, 7·8; vitamin A content, 1·7; and vitamin A potency, 2·5.4. There were wide differences in the degree of approach to ‘identicality’ with different sets of twins. The cows in two of the sets showed a consistently close within-twin-set relationship for all characteristics studied.
716. Physical changes in milk caused by the action of rennet: I. Description of apparatus for measuring rigidity moduli and internal viscosities, tests of reliability and some observations on syneresis
Authors: Blair G. W. Scott , Burnett J. 
Published: June 2009

A method for measuring the increasing rigidity moduli and internal viscosities of milk during rennet setting is described. Curves are given showing the degree of reproducibility on replicate samples of dried and liquid milks, and of the effects of changes in calcium levels in the case of the former.A tentative interpretation of the shape of the main part of the setting curve is proposed. The upper part of the curve generally becomes erratic with the onset of syneresis, but some dried milks do not show this behaviour.Some curious phenomena concerning the production of syneretic liquid (whey) are described and methods for obviating the disturbing effects of syneresis are discussed.
Physical changes in Milk caused by the action of rennet: V. Effects of varying concentrations of milk powder and of low-temperature pretreatment
Authors: Blair G. W. Scott , Burnett J. 
Published: June 2009

1. When the concentration of fat-free milk-powder is increased, other factors being kept constant, the elastic and viscous setting-parameters of the curd also progressively increase, being related to the concentration by power-equations. The intercepts, which correspond closely to ‘coagulation times’, likewise increase, but nearly linearly with concentration2. These effects depend mainly on protein concentration. Quite large quantities of added lactose make little difference to the parameters.3. The slopes of the logarithmic setting curves vary quite independently of their intercepts, so that ‘coagulation times’ provide a very incomplete indication of the rate of setting of curd.4. A comparison of setting data obtained in the ordinary way at a series of temperatures with those from experiments in which the rennet is first allowed to act on the milk at near freezing-point, show that, in the latter case, there is considerable delay before the normal equation of setting is established in the curd. It is also clear that high temperatures are detrimental to this process of setting, just as they are when the usual procedure is followed.5. The general law that the rate of setting is, at any time, proportional to the amount of still unset casein, is established much sooner if the time zero is defined in such a way as to take all the processes involved together. If an ‘induction period’ is subtracted, either by letting the rennet first act in the cold, or by taking the time zero in the normal process at the coagulation, and not the renneting, time, a much longer time elapses before the curves become linear.We are indebted to many colleagues at the N.I.R.D. for helpful discussions, especially Dr S. J. Rowland and Dr R. Aschaffenburg.
Viscosity changes in concentrated skim-milk treated with alkali, urea and calcium-complexing agents: I. The importance of the casein micelle
Authors: Beeby R. , Kumetat K. 
Published: June 2009

The viscosity of concentrated skim-milk changed markedly with time upon the addition of urea, calcium-complexing agents or alkali, the viscosity-time curve passing through a distinct maximum. Also, the characteristic opacity of the milk disappeared in the presence of these reagents.These phenomena are explained in terms of a postulated expansion of the casein micelles followed by their disintegration into ‘molecular’ units.Electrostatic repulsions within the casein micelles are considered to be the cause of expansion.Calcium, either in the ionic atmosphere of the casein micelle or as calcium bridges within the micelle, and hydrogen bonds are regarded as two of the major factors responsible for maintaining the stable structure of the casein micelle.The authors wish to thank Mr E. F. Woods, Division of Protein Chemistry, C.S.I.R.O., Melbourne, and various staff members of the Dairy Research Section, C.S.I.R.O., Melbourne, for helpful discussion during the preparation of the manuscript. The technical assistance of Miss Audrey K. Morris is also gratefully acknowledged.
Strontium-90 from fallout in the diet and milk of a dairy herd
Authors: Cox G. W. , Morgan A. , Tayler R. S. 
Published: June 2009

SummaryThe diet and milk from a herd of dairy cows were analysed regularly for 90Sr and calcium. The ‘observed ratio’ (the ratio of 90Sr to calcium in the milk divided by the ratio of 90Sr to calcium in the diet) was found to be 0·10 against 90Sr in favour of calcium, which corresponds well with the results of other workers. The amount of 90Sr secreted into the milk was 1·2% of the total ingested. Similar values were obtained using stable strontium data.Soil samples from different depths and herbage were taken from three areas with different cultivation histories and analysed for 90Sr and calcium. The effect of ploughing on the vertical distribution of 90Sr in soil and on the 90Sr levels in vegetation was examined.
A viscometric study of the breakdown of casein in milk by rennin and rennet
Authors: Blair G. W. Scott , Oosthuizen J. C. 
Published: June 2009

SummaryIn the later stages of the reaction between rennin and casein drastic viscometric methods are undesirable, but in the first stages there is a fall in viscosity which may be satisfactorily measured in an Ostwald viscometer. Using fat-free milk, the viscosity at first falls linearly with time. At low rennet concentrations (Ce) this may be said to constitute a zero-order reaction (constantk0). At higher rennet concentrations and after longer times, the reaction passes to first order (constantk1). After very long times it doubtless becomes more complex.The values ofk0are proportional, over a considerable range, to the milk concentration (Cm), those ofk1being independent ofCm.For pure rennink0andk1are proportional toCe, but for commercial rennets they vary as a power (N) ofCeand the value ofNappears to measure the rennin purity. The potentialities of the method for assessing rennet activities are also discussed.If the reduced viscosity (specific viscosity÷Cm) of fat-free milks is plotted againstCm, good straight lines are obtained which may be extrapolated to zero concentration to give a reliable value of intrinsic viscosity. The intrinsic viscosity falls progressively during the protein breakdown process but the slope of the curves (‘second order term’) remains unchanged.
Some effects of ionizing radiations on the alkaline phosphatase in cow's milk
Authors: Glew G. 
Published: June 2009

SummaryThe effects of ionizing radiation on the alkaline phosphatase activity of milk have been studied under different environmental conditions. Twenty-five megarads were required to inactivate the enzyme completely. A combination of heat treatment and irradiation given either before or after heating showed that inactivation of the enzyme was greater when heating occurred after irradiation, this effect of the different forms of energy possibly indicating different mechanisms of heat inactivation. Varying the dose rate over the range 12–250 krad/min did not affect the amount of enzyme inactivated. After irradiation, activity declined during storage at 30°C but not at 5°C. Irradiation did not change the value ofKmyet theVmaxfell, indicating that there are fewer active sites present after irradiation but that affinity of the remaining sites for the substrate remains unchanged.
The relationship between milk yield, composition and tissue damage in a case of subclinical mastitis
Authors: Waite R. , Blackburn P. S. 
Published: June 2009

SummaryA chemical, cytological and bacteriological examination of the milk from each quarter of a cow suffering from subclinical mastitis, but giving 5–6 gal of milk per day, was made at weekly intervals during the first 84 days after parturition. The infection, caused by micrococcal and staphylococcal bacteria, resisted repeated treatments with various antibiotics administered via the teat canals and also intramuscularly, although in vitro the bacteria were susceptible to all the antibiotics used. The cow was slaughtered and a histological examination made of the udder in an attempt to establish the cause of the continuing infection and to assess the extent of tissue damage. Two quarters each contained large abscesses in the upper level of the udder and these could have acted as reservoirs of infection; no cause was established for the other two quarters and it can only be assumed that reinfection occurred from the two abscessed quarters.The amount of active lesions in the lobules of all the quarters was small, 1–6%, but half or more of all the lobules were involuted, although only a minority appeared to have involuted as a result of infection. In the two abscessed quarters there was extensive damage to the duct system, 23 and 31% showing lesions.When the milk contained an abnormally large number of cells the chemical composition was also abnormal, containing less lactose (and hence less solids-not-fat) and having a nitrogen distribution in which there was more blood serum albumin and globulin and less casein than usual. Cell content and chemical composition were better indicators of tissue damage than the presence of mastitis organisms. It is estimated that the solids-not-fat content of the milk of the whole udder as a result of the infections was considerably lower than it would otherwise have been (8·0 instead of 8·8%) and that the daily loss in milk yield was about 9 lb.
Lactose in the blood and urine of cows
Authors: Wheelock J. V. , Rook J. A. F. 
Published: June 2009

SummaryLactose could not be detected in the urine of non-lactating cows but was invariably found, though usually in low concentration, in the urine of lactating cows; the highest values were observed with cows of high lactation number. Towards the end of an extended milking interval of 39 h, the lactose concentration in the blood and the excretion of lactose in urine increased markedly, but on milking there was a rapid return to original values. Lactosuria was observed in pregnant cows from about 20 days before parturition, and at parturition there was a temporary, marked increase in the excretion of lactose in urine.
The effect of bacterial infections of the udder on the yield and composition of cow's milk
Authors: Wheelock J. V. , Rook J. A. F. , Neave F. K. , Dodd F. H. 
Published: June 2009

SummaryThe effect of bacterial infections, produced by infusions of Streptococcus dysgalactiae and of Staphylococcus pyogenes into one quarter of the udder, on milk yield and composition in heifers has been investigated. After a quarter became infected there was invariably a decrease in the yield of milk and in the concentrations of lactose and potassium, while there was an increase in those of sodium, chloride and non-casein proteins. These effects persisted into the 2nd lactation if the infection was not eliminated. If the infection was eliminated during the 1st lactation or during the dry period before 2nd calving there was a complete recovery in the composition of the milk in the 2nd lactation, but the recovery in milk yield was not complete.
Partition of casein between polymer phases
Authors: Berridge N. J. , Suett D. L. 
Published: June 2009

SummaryCasein derived from the micelles of milk by removing the calcium has been subjected to partition and counter current distribution between phases containing polyethylene glycol and dextran. The results show that at least 2 kinds of casein complex exist which differ in structure, in size or in both. There are also differences in composition with respect to minor components, though both types contain predominantly α- and β-casein.
Identification of compounds causing symbiotic growth ofStreptococcus thermophilusandLactobacillus bulgaricusin milk
Authors: Bautista Emma S. , Dahiya R. S. , Speck M. L. 
Published: June 2009

SummaryStrains ofLactobacillus bulgaricusandStreptococcus thermophilusisolated from yoghurt culture were used to study the cause of the synergistic effect on acid production by mixtures of the 2 cultures. The beneficial effect was essentially limited to the gradual accumulation of factors in theL. bulgaricuscultures that promoted more rapid acid production byStr. thermophilus. The active factors were identified as glycine and histidine.
Simple methods for the purification of crude κ-casein and β-casein by treatment with calcium phosphate gel
Authors: Green Margaret L. 
Published: June 2009

SummaryBatch methods applicable on a large scale are described for the purification of crude κ- and βκ-Casein, dissolved in urea-containing buffer, was freed from αs- and β-caseins by treatment with calcium phosphate gel and recovered in about 60% yield. β-Casein was freed from most impurities by adsorption on to calcium phosphate gel at pH 7·8 in the presence of urea and elution with 6 M-urea–N-NH4OH at 4°C. The recovery was about 50%.