bluuebunny/crossref_metadata_2025 huggingface dataset:
555. Aroma-producing group ‘N’ streptococci isolated from Cheddar cheese curd
Authors: Zielinska M. , Hiscox E. R.
Published: June 2009

A high proportion of the group ‘N’ streptococci, isolated from Cheddar cheese curd, produced volatile acids and acetoin, in varying degrees, in milk culture. The active acetoin-producing strains closely resembled type strains of Str. diacetilactis (Matuszew-ski) and Str. citrophilus P.R.M. but differed from them in producing acetoin in lactose broth. The weak acetoin-producing strains resembled Str. cremoris HP in this characteristic, but in their morphological and cultural reactions, mor e closely resembled Str. lactis. The titratable acidity in milk cultures varied inversely with the production of volatile acids and acetoin.
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appear that the rise in iodine value following partial inanition does not result from increased uptake of fatty acids withdrawn from the more highly unsaturated glycerides of the body reserves.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.
667. Synthesis of lactose in vitro by mammary gland slices from lactating rats, guinea-pigs and sheep
Authors: Duncombe W. G.
Published: June 2009

There can now be little doubt that glucose is the principal precursor of lactose in the mammary gland. Evidence for this comes form in vivo and in vitro studies, using both analytical and isotopic techniques (1), though considerable species differences have been noted.
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.
730. A note on the pediococci in New Zealand Cheddar cheese
Authors: Dacre J. C.
Published: June 2009

Organisms identified asPediococcusstrains were found to constitute about a quarter of the normal lactic-acid flora of ripening New Zealand Cheddar cheese. The development and the frequency distribution of these pediococci, in relation to the starter streptococci and lactobacilli were briefly studied.
Observations by anoptral contrast microscopy of casein in milk, condensed milk and milk powder
Authors: King N.
Published: June 2009

Anoptral contrast, a modification of phase-contrast microscopy, appears to be suitable, particularly perhaps when used in conjunction with fluorescence microscopy, for studying casein particles above 0·1–0·2μ in diameter, and different aggregation and coagulation forms of casein, which may comprise irregular flocks of aggregated particles, thin membranes and micro-fibres, nodulated or smooth.
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 concentration

2. 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.
Relations between composition and viscosity of cow's milk
Authors: Cox C. P. , Hosking Zena D. , Posener L. N.
Published: June 2009

Theoretical and practical aspects of the apparent or effective viscosity of milk have been studied by many workers: see reviews by Scott Blair(1,2,3). Seidler & Elke(4), Cox(5), and others have considered the relations between observation temperature and viscosity measurements; Mohr & Oldenburg(6) and Puri & Gupta(7), for example, have investigated the effects of differences between individual viscometers. Other workers, including Puri & Gupta(7), Kobler(8) and Spöttel & Gneist(9), have examined the viscosity of whole raw milk after different times and temperatures of storage; and Weinlig(10), Trout & Weinstein(11) and Whitnah, Rutz & Fryer(12,13) have studied changes in viscosity values in connexion with various processes such as pasteurization and homogenization.
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

The 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

In 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

The 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

A 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

Lactose 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

The 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

Casein 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

Strains 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

Batch 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%.
The effects of acetate and of pyruvate on the pathways of glucose catabolism in lactating mammary tissue: 1. Rat tissue
Authors: Smith R. W. , Glascock R. F.
Published: June 2009

A study was made of the changes in the pathways of glucose catabolism in slices of lactating rat mammary gland which occurred when acetate or pyruvate was added to the medium.

When acetate was added there was an increase in the rates of oxidation of the C(2)and C(6)atoms of glucose but little change in that of the C(1)atom. The amounts of these carbon atoms which were incorporated into fatty acids, lactic acid and glyceride glycerol were reduced, but the results showed that the relative proportion of the glucose converted to these substances which passed through the pentose phosphate pathway was increased.

When pyruvate was added, the rates of oxidation of the C(1), C(2)and C(6)atoms were all reduced to about the same extent. The incorporation of the glucose carbon into fatty acids was almost abolished and its incorporation into lactic acid and glyceride glycerol was very much reduced. The results showed that most of the glucose incorporated into these compounds under these conditions passed through the pentose phosphate pathway.

Evidence is presented which suggests that the triose phosphates are not in complete isotopic equilibrium in lactating rat mammary tissue.

These results are discussed in relation to the existence of 2 pools of acetyl coenzyme A, one intra- and the other extra-mitochondrial, and to the possible inhibition of certain steps of the glycolytic pathway.
The effects of acetate and of pyruvate on the pathways of glucose catabolism in lactating mammary tissue. II. Sheep tissue
Authors: Smith R. W. , Glascock R. F.
Published: June 2009

A study was made of the changes in the rates of oxidation of the C(1), C(2) and C(6) atoms of glucose and in the pathways of glucose catabolism in sheep udder tissue in vitro which occurred when acetate and pyruvate were added.

Whereas in rat mammary tissue the rate of oxidation of the C(1) atom of glucose was very much greater than that of the C(6) atom, the ratio of the rates of oxidation of these 2 atoms in sheep tissue was less than 2 when glucose was the only substrate.

The addition of acetate resulted in an unequal stimulation of the oxidation of these 2 atoms, with the result that the ratio of their rates of oxidation was about doubled. The rate of oxidation of the C(2) atom was also increased.

Acetate also increased the participation of the pentose phosphate pathway in glucose catabolism as measured by the incorporation of the C(1) and C(6) atoms of glucose into fatty acids, lactic acid and glycerol.

Pyruvate produced little effect on the rate of oxidation of the C(1) atom but somewhat depressed that of the C(6) atom of glucose. At the same time, it caused a large increase in the participation of the pentose phosphate pathway.

These results are discussed with reference to re-cycling of glucose carbon in the pentose phosphate pathway and to the relationship between that pathway and fatty acid synthesis. It is noted that the incorporation of glucose carbon into the 3 intermediates used gave values for the participation of that pathway which were in better agreement than was obtained in rat tissue. It is concluded that triose phosphates are more nearly in equilibrium in sheep than in rat mammary tissue.
Utilization of citrate by lactobacilli isolated from dairy products
Authors: Fryer T. F.
Published: June 2009

Twenty-five strains of lactobacilli isolated from dairy products, includingLactobacillus casei, Lactobacillus plantarumandLactobacillus brevisspecies, were grown in semi-defined media and examined for their ability to ferment citrate and produce formate. Of 7 strains ofL. casei, all utilized citrate to varying extents, as did 9 of 10 strains ofL. plantarumand 3 of 8 strains ofL. brevis.L. caseiproduced 19–35% of the theoretical yield of formate from the citrate utilized,L. plantarum0–11% andL. brevis0–28%. Of 2 strains ofL. caseitested for their abilities to ferment citrate in the presence of 2% lactose, strain C 5 was unaffected by lactose whereas strain C 2 showed a 45% decrease in the citrate utilized. However, lactose used at 2% concentration greatly reduced formate production byL. caseiC 5, which produced 62% of the theoretical yield of formate from citrate after 35 days in the absence of lactose and only 8% in its presence. The yield of diacetyl produced byL. caseiC 5 from citrate plus lactose (both at 2% concentration) was 145 times that produced from citrate alone, and 800 times that from lactose alone.
Observations on the use of 2,4-dinitrophenylhydrazine and of 2,6-dichlorophenolindophenol for the determination of vitamin C in raw and in heat-treated milk
Authors: Toothill Joyce , Thompson S. Y. , Edwards-Webb J.
Published: June 2009

A study has been made of methods using 2,4-dinitrophenylhydrazine (DNPH) or 2,6-dichlorophenolindophenol (DCP) for the determination of vitamin C (ascorbic acid+dehydroascorbic acid) in raw, UHT processed, evaporated and sterilized milk.

Interfering substances were not detected in milk that had received a heat treatment no more severe than 145°C for 4 s (UHT process), so that either reagent could be used.

With more drastic heat treatment, interfering substances were formed and only the DNPH method with column and thin layer chromatography of the DNPH derivatives was specific for vitamin C. With in-bottle sterilized milk, the values for ascorbic acid were (in mg/100 ml) 1·16 (DCP method with H2S reduction); 0·58 (DCP method withEscherichia colireduction); 0·64 (DNPH method); 0·33 (DNPH method combined with chromatography).

In our experience the DNPH method combined with chromatography of the derivatives is highly specific for vitamin C and should be used to check the results obtained by other and simpler methods.
The estimation of diacetyl in the presence of other carbonyl compounds
Authors: Lees G. J. , Jago G. R.
Published: June 2009

An examination of the spectra of some volatile carbonyl semicarbazones indicated that only compounds containing vicinal carbonyl groups formed semicarbazones which absorbed at 270 nm. This observation was used for the quantitative estimation of diacetyl. The presence of both acetaldehyde and acetoin did not interfere with the estimation of diacetyl by this method.
A rapid bioassay for penicillin residues in milk
Authors: Cogan T. M. , Fox P. F.
Published: June 2009

A new bioassay for the detection of penicillin in milk which can be completed in 1½ h has been developed. The test depends on measurement of pH changes in milk produced by an antibiotic sensitive organism, Streptococcus thermophilus BC. To measure the changes potentiometrically would require a very sensitive pH meter. Change in the enzymic coagulation time, which is extremely dependent on pH, was used in the present study to measure small changes in pH. The test is highly reliable and should be suitable as a milk selection test.
Metabolism of [1-14C]palmitate and [1-14C]oleate by the isolated perfused mammary gland of the sheep or goat
Authors: Massart-Leën Anne-Marie , Florescu S. , Verbeke R. , Peeters G.
Published: June 2009

Lactating mammary glands of sheep and goats were perfused for several hours in the presence of [1-14C]palmitate or [1-14C]oleate. Adequate quantities of acetate, glucose, amino acids and chylomicrons were added to the perfusate.

The fall in specific activity of [1-14C]palmitic acid or [1-14C]oleic acid across the gland and the labelling of milk triglyceride fatty acids indicates an extensive transfer of radioactivity from plasma free fatty acids (FFA). The plasma triglycerides showed large arterio-venous differences in concentration. The small [14C] incorporation in plasma triglycerides decreased across the gland. In a control experiment triglycerides were also slightly labelled.

There were no significant arterio-venous differences in cholesterol esters and their fatty acid composition showed only slight changes during passage through the gland. Their specific activity showed a small rise across the gland.

In milk components, the [14C] was mainly localized in the triglycerides. An appreciable proportion of the palmitoleate is derived from palmitate by dehydrogenation within the gland, while there is no evidence for the hydrogenation of oleic acid to stearic acid. Elongation of palmitic acid to C18-acids does not occur to any important extent. FFA are catabolized to a variable extent by the gland.

The role of FFA in labelling of milk and blood plasma fatty acid fraction is discussed.
The effects of dietary soybean oil on milk-fat composition in the cow
Authors: Steele W. , Noble R. C. , Moore J. H.
Published: June 2009

The effects of the isocaloric replacement of starch in a low-fat concentrate mixture by 8% soybean oil on the yield and composition of milk fat were investigated in a feeding experiment with 6 cows in mid lactation. Two high-fat concentrate mixtures were given to the cows. In one the requisite amount of soybean oil was given by including 50% coarsely ground soybeans in the concentrate mixture. In the other an equal amount of soybean oil was added directly to the concentrate mixture. The concentrate mixtures were given with a high-roughage diet that supplied 5·5kg hay and 2·7kg of sugar-beet pulp/day.

When the 2 high-fat rations were given to the cows there were reductions in the percentages and yields of 10:0, 12:0, 14:0, 14:1, 16:0 and 16:1 fatty acids and increases in the concentrations and yields of 18:0, 18:1 and 18:2 fatty acids in the milk fat. The direct addition of the soybean oil to the diet also reduced the percentage and yield of 6:0 and 8:0 whilst the inclusion of the soybeans increased the percentage of 4:0 and the yields of 4: 0 and 6:0 in the milk fat.

When both high-fat rations were given to the cows there were increases in the yields and concentrations of as-9–18:1 in the milk fat, whilst inclusion of the soybean oil in the diet increased also the concentration and yield oftrans-11–18:1.

The implications of these findings are discussed.
The relationship between plasma lipid composition and milk fat secretion in cows given diets containing soybean oil
Authors: Steele W. , Noble R. C. , Moore J. H.
Published: June 2009

The effects on the composition of the plasma lipids of the isocaloric replacement of starch in a low-fat concentrate mixture by 8 % soybean oil were investigated in a feeding experiment with 6 cows in mid-lactation. Two high-fat concentrate mixtures were given: in one, the soybean oil was incorporated into the diet by the inclusion of the appropriate amount of coarsely ground soybeans; in the other, the soybean oil was incorporated directly in the concentrate mixture. The concentrate mixtures were given with a high-roughage diet that supplied daily 5·5kg hay and 2·7kg of sugar-beet pulp.

When the cows were given the 2 high-fat diets there were increases in the concentrations of total plasma fatty acids and in the concentrations of fatty acids circulating in the plasma as phospholipids and cholesteryl esters. There were increases in the concentrations of plasma unesterified fatty acids and triglyceride fatty acids when the cows were given the diet containing soybeans but there were decreases in the concentrations of these 2 fractions when the cows were given the diet containing soybean oil.

The inclusion of soybeans in the diet increased the concentration of 18:0 in the plasma triglycerides and unesterified fatty acids whilst the inclusion of soybean oil in the diet increased the concentrations of 18:0 and 18:1 but decreased the concentration of 18:2 in the plasma unesterified fatty acids.

When the cows were given the 2 high-fat diets there were decreases in the concentrations of 16:0 and 16:1 and increases in the concentration of 18:2 in the plasma cholesteryl esters. The inclusion of soybeans in the diet also reduced the concentrations of 18:1 and 20:3 in the plasma cholesteryl esters but increased the concentrations of 18:0 and 18:2 in the plasma phospholipids.

The major fatty acid circulating in the plasma of the cows was 18:2 (46·4–55·3%) on all diets but only about 1% (0·40–1·04%) of the total plasma 18:2 occurred in the plasma triglycerides.

The results are discussed in relation to the changes in the composition of the milk fatty acids produced by the cows when they were given the experimental diets.
Determination of alkaline phosphatase activity in cheese using phenolphthalein monophosphate as substrate
Authors: Rammell C. G. , Joerin M. M.
Published: June 2009

A method is described for determining alkaline phosphatase activity in cheese using phenolphthalein monophosphate as substrate. Results are read with a Lovibond comparator after 1 h incubation. Advisory standards are proposed based on a minimum pasteurization for 15 s at 71°C of the milk used for cheese-making.
A note on the influence of stage of lactation on the response in the lactose content of milk to a change of plane of energy nutrition in the cow
Authors: Dawson R. R. , Rook J. A. F.
Published: June 2009

Three groups of Friesian cows, one of cows in early lactation, one of cows in mid-lactation and one of cows in late lactation, received over successive 4-week periods according to a double changeover Latin square design, rations providing a low, a normal and a high plane of energy nutrition. With the group of cows in early lactation the treatments were repeated again in mid-lactation and in late lactation.

In all experimental groups there were increases and decreases in the treatment mean values for milk yield and solids-not-fat, protein and lactose contents, in response respectively to overfeeding and to underfeeding. The responses in lactose content in early and mid-lactation were small (overfeeding, 0·00 to +0·06 percentage units; underfeeding, −0·01 to −0·08 percentage units) and less than those in protein content, whereas in late lactation they were larger (overfeeding, +0·09 to +0·14 percentage units; underfeeding, −0·13 to −0·19 percentage units) and of the similar size to those in protein content.
Growth studies on the lactic streptococci: II. The effect of agitation on the growth characteristics ofStreptococcus lactisML8in batch culture
Authors: Keen A. R.
Published: June 2009

Investigations on the growth characteristics ofStreptococcus lactisML8in skim-milk medium have indicated that agitation of the medium may decrease the growth rate of the organism by decreasing the availability of CO2(CO2effect) and of soluble nitrogen (soluble nitrogen effect). The former effect was observed only when the CO2concentration was depleted by heat sterilization; the latter occurred when a certain threshold level of agitation was exceeded. Results suggested that the soluble nitrogen affect was caused by an alteration in the rate of diffusion of substances formed in the immediate vicinity of the bacterial cell by the proteolytic enzyme system.
Growth studies on the lactic streptococci: IV. Some observations on redox potential
Authors: Keen A. R.
Published: June 2009

Redox potential changes at 30°C in anaerobic reconstituted skim-milk cultures ofStreptococcus cremorisAM1and AM2andStreptococcus lactisML8have been investigated in batch cultures and continuous cultures maintained at constant pH by the addition of fresh medium.Str. lactisML8was more strongly reducing than eitherStr. cremorisAM1or AM2. The positiveEhvalues which can arise in dense continuous cultures of lactic streptococci are not likely to affect either the lactic acid formation or proteolytic activity of the resultant bacterial concentrate. An electrolytic reduction cell is described which allows variations in redox potential in cultures to be controlled simply and effectively.
Formaldehyde-treated casein–safflower oil supplement for dairy cows: I. Effect on milk composition
Authors: Pan Y. S. , Cook L. J. , Scott T. W.
Published: June 2009

The effects of feeding lactating cows a daily supplement of 1 kg formaldehyde-treated casein–safflower oil (1:1, w/w) on the milk composition are reported. Three breeds, Jersey, Sahiwal and Sahiwal × Jersey crossbred were used.

The formaldehyde treatment not only eliminated the suppressing effect on the milk, fat and protein yields and on the fat and protein contents usually encountered when such a level of unsaturated oil is fed to lactating cows, but also resulted, on the average, in 15 and 6% increases in the fat and protein contents respectively.

The formaldehyde-treated dietary supplement also caused a decline of 5% in the solids-not-fat content, presumably due to a decrease in the lactose content.

It is suggested that the formaldehyde treatment protects the casein from the ruminal proteolysis and this in turn prevents the encapsulated unsaturated oil from biohydrogenation and eliminates the diverse effects on rumen microflora and environment.
Flavour defects in edible casein and skim-milk powder: I. The role of Maillard browning
Authors: Walker N. J.
Published: June 2009

Two chemical tests were used to measure the extent of lactose degradation by Maillard browning in casein and skim-milk powder during storage. At the same time these products were evaluated organoleptically. Highly significant correlations between age, flavour score and level of browning in skim-milk powder were in contrast to the lack of any relationship between the flavour score or age of casein and its level of browning. Maillard browning occurring during storage of skim-milk powder was accompanied by increasing levels of cereal and malty flavours. A stale flavour, which closely resembled the musty flavour common to casein, was not observed in skim-milk powder until after storage for 9 months. A distinct difference in the flavour stability of rennet casein and acid casein could not be accounted for in terms of the relative extent of lactose degradation. Evaluation of casein samples with different lactose contents suggested that Maillard browning does not contribute to flavour defects during storage unless the curd is so insufficiently washed during manufacture as to produce an abnormally high level of lactose in the dried product.
Metabolism of [U-14C]-l-threonine and [U-14C]-l-phenylalanine by the isolated perfused udder
Authors: Verbeke R. , Roets E. , Massart-Leën Anne-Marie , Peeters G.
Published: June 2009

A lactating mammary gland of a goat was perfused for 9 h in the presence of [U-14C]-l-threonine and received adequate quantities of glucose, acetate and amino acids. Two lactating sheep udders were likewise perfused in the presence of [U-14C]-l-phenylalanine: the plasma levels of phenylalanine in the first of these experiments were 4 times higher than in the second.

In the [14C]threonine experiment, 4 % of the casein and 0·4 % of the expired CO2were derived from threonine; 85 % of the threonine and 1·6 % of the glycine residues in casein originated from plasma threonine. Small14C levels were found in glutamic acid, aspartic acid and serine of casein. The relative specific activities amongst the casein amino acids and the appearance of appreciable labelling in plasma glycine are consistent with the view that threonine is split by threonine aldolase.

In the [14C]phenylalanine experiments virtually no radioactivity was detected in CO2, lactose or citric acid, indicating that this substrate is not broken down by mammary tissue. In the second experiment, 96 % of the phenylalanine and 0·3 % of the tyrosine of casein originated from plasma phenylalanine. In the first experiment, a 30-fold higher14C incorporation into casein tyrosine relative to phenylalanine was observed. The possible significance of the phenylalanine concentration in the plasma on the degree of conversion of phenylalanine into tyrosine within the mammary gland is discussed.
The composition of milk of British Alpine and Anglo–Nubian goats imported into Trinidad
Authors: Devendra C.
Published: June 2009

The variations in the composition of milk over an 18-week period from lactating British Alpine and Anglo–Nubian goats imported into Trinidad are reported. The animals were fed Napier grass (Pennisetum purpureum) ad lib. and 2 lb of a proprietary concentrate mixture daily.

The mean percentage contents of the milks of British Alpine and Anglo–Nubian goats were: total solids 11·49±0·22, 12·17±0·28; butterfat 3·42±0·18, 4·06±0·22; total N 0·462±0·04, 0·530±0·07; ash 0·78±0·02, 0·79±0·03 and ‘lactose’ 4·38±0·28, 4·05±0·55. Anglo–Nubian goats had a higher content of percentage total solids, fat, total N and ash. For all constituents the coefficient of variation between weeks was higher for Anglo–Nubian goats. No significant trends were found between weeks for each of the components analysed for both breeds. Statistically significant correlations (P < 0·01) were found between percentage fat and percentage total N for both breeds.

The mean mineral contents (mg/100ml) for the milks of British Alpine and Anglo–Nubian goats were: Na 52·6±4·6, 55·5±1·9; K164·0±8·4, 133·4±11·4; Ca 85·5±11·6, 89·9±9·8; Mg 13·2±3·8, 10·2±1·6 and P 74·7±3·9, 82·1±3·9. British Alpine goat's milk had a higher content of K and that of Anglo–Nubian goats had a higher content of P; both differences were statistically significant (P < 0·01).

The milk composition figures in this study together with those from a similar study in Guadeloupe suggest that the values are low and considerably lower in comparison with the same breeds of goats in a temperate environment. This could be a feature of dairy goats imported into the tropics due perhaps to inadequate nutrition. Much more information is needed to verify this possibility.
Location of proteins within the milk fat globule membrane
Authors: Anderson M. , Cheeseman G. C. , Knight Dorothy J.
Published: June 2009

Radioactive labelling of intact fat globules with125I gave at least one labelled protein in each of the 4 fractions of the fat globule membrane. Similar treatment of isolated membrane gave extensive labelling of all membrane proteins in each fraction.

It was concluded that all fractions are partially exposed at the membrane surface and the existence of well-defined layers is unlikely.