bluuebunny/crossref_metadata_2025 huggingface dataset:
Lactobacilli in raw milk and in Cheddar cheese
Authors: Perry K. D. , Sharpe M. Elisabeth
Published: June 2009

The lactobacillus flora of the mixed morning and evening milk of a single herd and of sixty Cheddar cheese made from this milk, unheated, was examined over a period of 12 months. Few lactobacilli (usually not more than 1/ml) were found in the milk samples, and were identified asLactobacillus plantarum, L. casei, L. brevis, L. fermentiand unclassified strains. In addition,Pediococcus cerevisiaeand leuconostoc species were isolated on the selective medium used, the leuconostocs occurring more frequently than either the lactobacilli or the pediococci. The lactic-acid bacteria in the cheese varied considerably, both quantitatively and qualitatively. Although in general the same species of organisms were isolated from the cheese as from the milks, the relative frequencies of occurrence were not the same, leuconostocs being found much more often in milk than in cheese, andL. plantarumandL. caseimore frequently in cheese. No association between numbers or types of lactic-acid bacteria and flavour of the cheese was noted, nor did the season of the year or the ration fed to the milking herd affect the lactobacillus flora of the milk.
Genetical aspects of maximum rate of flow during milking
Authors: Donald H. P.
Published: June 2009

Rates of flow of milk during milking have been observed on twin and single-born dairy cows with the aid of a device for continuous recording of weight of milk extracted. Each cow has been characterized by a maximum rate arrived at by averaging morning and evening observations on 2 days. Only this maximum rate has been studied.

Repeatability was high (0·8–0·9) whether measured from day to day or from lactation to lactation. Maximum rate of flow was 10–16% higher in second than in first lactations. The range extended from under 2 lb/min to over 7 lb/min.

Lactation yield of milk varied significantly with rate, rising about 50 gal for an increase of 1 lb/min. This relation is reduced or eliminated by taking into account by partial regression analysis either maximum weekly yield or the increase from the second to the peak week of lactation.

Although the higher yielding cows had larger udder areas bounded by the four teats, the regression of 305-day milk yield on rate was not changed much by taking udder area into account. Cows with short teats milked faster and had higher yields than cows with longer teats.

Differences in yield among the four quarters widened slightly between 1 and 3 months of lactation regardless of rate of flow, except possibly in the three slowest milking cows. In these the differences increased three times as much as in the other cows. The wider the inter-quarter differences in yield the less the proportion of milk obtained at the maximum rate.

Heritability of maximum rate of flow derived from observations on paired singleborn cattle and twins was 85%. Field data would probably yield a value of 60–70%. Appropriate selection of breeding stock would effectively alter rate of flow, but there is no reason yet to expect yield of milk to change except perhaps by reducing the incidence of very slow milking cows.
Fishy flavour in dairy products: III. The volatile compounds associated with fishy flavour in washed cream
Authors: Forss D. A. , Dunstone E. A. , Stark W.
Published: June 2009

When washed cream was treated with copper and ascorbic acid and held at 2°C for 1–5 days a strong metallic, fish-oil flavour developed. Compounds responsible for the flavour were isolated and identified. Gas chromatographic separation of a flavour concentrate on a silicone oil column gave six characteristic flavour fractions which, in order of elution, were described as painty or drying oil, oily, mushroom, metallic, tallowy and cucumber. The flavours of all fractions were predominantly caused by carbonyl compounds and the oily and metallic fractions were the main contributors to the typical fish-oil flavour. The following compounds were characterized: n-pentanal and pent-2-enal in the painty fraction; n-hexanal, n-heptanal and hex-2-enal in the oily fraction; hept-2-enal and a carbonyl compound with a mushroom odour in the mushroom fraction; a carbonyl compound with a metallic odour in the metallic fraction; n-octanal, n-nonanal, oct-2-enal and hepta-2,4-dienal in the tallowy fraction; and non-2-enal in the cucumber fraction.
The effect on milk yield of three times a day milking and of increasing the level of residual milk
Authors: Elliott Gillian M.
Published: June 2009

Experiments were made to determine the effects on yield and butterfat percentage of three times a day milking and of inefficient milking using cows whose milk secretion rates had been shown to be unaffected by the milk accumulation involved. The milking treatments were applied to half-udders of the same cow to ensure that there was no difference between each pair of experimental units in the amount of oxytocic hormone released by the pituitary gland.

Milking three times a day compared with twice a day over a 39-day period resulted in an increase of 12% in both milk and butterfat yields. Increasing the residual milk by 1 lb in each half-udder for a 39-day period caused a 15% decrease in both milk and butterfat yields. It was concluded that since the cause of these findings could be neither the direct effect of differences in milk accumulation nor the effect of different amounts of oxytocic hormone, some local cell effect was involved, activated either by differences in the amount of residual milk or by long-term effects of differences in milk accumulation.
The occurrence and significance of blood in bovine milk
Authors: Rammell C. G.
Published: June 2009

Results are given of the examination for blood of 3214 milk samples from 935 cheese factory supplies. Over 75% of the milks contained less than 2·5 ppm. blood. Excessive blood was due to factors largely controllable by an efficient farmer, and so may be used as an indicator of poor dairy herd management and shed hygiene. No evidence could be obtained that the concentrations of blood likely to be found in commercial milk have any adverse effect on the keeping quality of whole milk or butter.
The estimation of dissolved oxygen in anhydrous milk fat
Authors: McDowell A. K. R.
Published: June 2009

Dissolved oxygen in anhydrous milk fat is reacted with an aqueous manganous-ferrous hydroxide suspension at 50 °C. The mixture is acidified and after separation into two layers the amount of ferric iron in the aqueous layer is estimated by iodometric titration. The procedure is relatively simple and is suitable for routine testing of milk fat.
The effect of feeding dried sugar-beet pulp on the intake and production of dairy cows
Authors: Castle M. E. , Drysdale A. D. , Watson J. N.
Published: June 2009

Three rations were compared in a 15-week winter feeding experiment using 12 Ayrshire cows. All the cows received silage 3 times a day and concentrates; ration A contained no sugar-beet pulp whilst ration B contained 6 lb of pulp and ration C 12 lb.

The total weights of dry matter consumed were 29·7, 32·3 and 33·4 lb/day, respectively, on treatments A, B and C. For every 1 lb of extra sugar-beet pulp dry matter eaten the decline in the dry weight of the other feeds consumed was 0·50 lb on treatment B and 0·55 lb on treatment C. The main decrease was in the silage part of the ration. The weights of starch equivalent (S.E.) consumed daily were 18·0, 19·8 and 20·7 lb on rations A, B and C, respectively, with mean daily milk yields of 38·2, 39·3 and 39·7 lb, giving a response of 0·55 lb milk/lb extra S.E. between rations A and C. The corresponding fat percentages of the milks did not differ significantly from each other but the solids-not-fat (SNF) percentages increased significantly from 8·76% on ration A to 8·88% on ration C. The average response per lb extra S.E. was 0·044% SNF and the increase was in the protein fraction of the milk. The cows were significantly heavier on rations B and C than on ration A. The inclusion of beet pulp in rations B and C had no adverse effect on the taste of the milk.
Studies on the effect of heat treatment during processing on the viscosity and stability of high-fat market cream
Authors: Rothwell J.
Published: June 2009

The viscosity of cream increased with increasing fat content, and higher values were obtained if the cream was separated at 38–43 °C rather than above 55 °C, and if the cream was cooled to below 15 °C before storage at 20 °C. The ‘type’ of viscosity varied with cooling and storage conditions; for example, cream cooled below 20 °C and stored at 20 °C gave increased viscosity readings with increased rates of shear due to churning of the cream, while the behaviour of cream cooled only to 20 °C was Newtonian.

Cream stability as measured by free fat content decreased with increasing fat content above about 42%, with low temperature separation (38–45 °C), with cooling to below 15 °C before storage at 20 °C, and with increased pressure at temperatures below 15 °C.

Dilatometric study of the amount of fat crystallization indicated that larger amounts of crystallization resulted in higher final viscosity and free fat content.
Estimation by gas chromatography of 5β-pregnane-3α, 20α-diol in the urine of normal lactating and ketosed cows
Authors: Heitzman R. J.
Published: June 2009

The measurement by gas chromatography of pregnanediol in the urine of normal and ketosed cows in the first 3 months of lactation is described. Mean pregnanediol levels, corrected for recovery losses, are reported for 3 groups of cows, namely: normal lactating cows 30·7 μg/1 urine; experimentally induced ketosed cows 22·3 μg/1 urine; and primary spontaneously ketosed cows, 31·4 μg/1 urine. No significant differences between the 3 groups of animals were found.
The production of L(+) and D(−) lactic acid in cultures of some lactic acid bacteria, with a special study ofLactobacillus acidophilusNCDO 2
Authors: Garvie Ellen I.
Published: June 2009

A study of the production of L(+) and D(−) lactic acid in cultures of DL forming lactic acid bacteria has shown that they can be divided into 2 groups. The first includes the thermobacteria andPediococcus cerevisiaein which the percentage of L(+) lactic acid is high initially but decreases as the cultures grow. The second includesLactobacillus plantarumand the heterofermentative lactobacilli and in cultures of these species the percentage of L(+) acid changes little during growth and is generally below 50% of the total.

In a strain ofLactobacillus acidophilusit has been found that if the pH is kept constant during growth the proportion of L(+) lactic acid decreased. However, when acid production stopped the proportion of total acid which is the L(+) isomer is greater than the proportion at the same stage of development in cultures where the pH was not adjusted. Cells harvested from young cultures formed more L(+) acid than cells harvested from older cultures.

There is some evidence that the composition of the medium can affect the ratio of L(+):D(−) lactic acid.
The persistence of penicillin G in the mammary gland when infused immediately after the last milking of lactation
Authors: Smith A. , Neave F. K. , Jones A.
Published: June 2009

Penicillin G at a dose level of 1 and 5 million units infused in a quick release base or an aqueous solution into quarters of cows after the last milking of the lactation persisted in infused quarters for about 4 days. From 1 h after infusion penicillin was detected in the venous blood and from 2 h after infusion in non-infused quarters.
Volatile compounds in butter oil: I. Lower boiling compounds
Authors: Forss D. A. , Stark W. , Urbach Gerda
Published: June 2009

The following compounds were isolated from best-quality Australian butter oil by high vacuum degassing, and identified by the combination of gas chromatography and mass spectrometry: the C3,5,7,9 alkan-2-ones, the C2,4,6,8,10,12 n-alkanoic acids, the C6,8,10 5-lactones (or their hydroxyacids), dimethyl sulphone, all isolated in amounts above 1 pt in 108 of butter oil, and butanone, undecan-2-one, 5-dodecalactone, diacetyl, n-nonanoic acid, a decenoic acid, methyl n-decanoate, toluene, o-methoxyphenol, a cresol, phenol, benzaldehyde, methyl benzoate and benzothiazole, all isolated in amounts between 1 pt in 1011 and 1 pt in 108 of butter oil.

No compound was isolated in an amount greater than flavour threshold, in fact most compounds were below one-tenth threshold level. However, the distillate obtained by degassing produced a very attractive creamy flavour when added to bland non-cultured butter.
Some effects of process treatment on the body of cream
Authors: Prentice J. H. , Chapman Helen R.
Published: June 2009

Effects of age and agitation of milk, temperature of separation, heat treatment and cooling, homogenization and ageing on the body of double cream were studied. Homogenization and temperature of heat treatment gave rise to the greatest effect. The effects of most treatments were inter-related to some extent, but this was most pronounced with cooling and ageing.
The folate-binding protein in milk
Authors: Ford J. E. , Salter D. N. , Scott K. J.
Published: June 2009

The folate in cow's milk was strongly and specifically bound to a minor whey protein (FP), forming a complex of primary M of about 38000, but exhibiting concentration-dependent reversible aggregation. The binding protein was present in excess, and the milk had the capacity to bind about 50μgadded folic acid/l. An enriched concentrate of FP was prepared by ammonium sulphate fractionation—FP was precipitated at between 50 and 60% saturation—and further purified by chromatography in DEAE-cellulose and filtration in Sephadex gel G150. Its identity as a distinct minor whey protein was confirmed by comparative starch gel electrophoresis at various pH values.

Some properties of the protein are described, and its physiological significance discussed.
The interaction of bovine milk caseins with the detergent sodium dodecyl sulphate. I. The relationship between the composition and the size of the protein–detergent aggregate
Authors: Cheeseman G. C. , Jeffcoat Joan
Published: June 2009

Study of the dissociation of high-molecular-weight aggregates of preparations of αs1-, β-, κ-, and para-κ-casein by the detergent, sodium dodecyl sulphate (SDS), showed that there are differences in the aggregation properties of the individual caseins. Binding of detergent led first to the dissociation of casein aggregates and then to further interaction with the casein molecules. The amounts of detergent required to give the minimum sized protein-detergent aggregate when expressed as mg/mg casein were similar for κ-, para-κ- and αs1-casein but much less for β-casein. However, expressed as mole/mole the requirement for κ- and αs1-casein was similar but was twice that found for para-κ- and β-casein. The maximum amount of SDS bound was about twice that required for complete dissociation of the aggregates for κ-, para-κ- and αs1-casein but was 13 times greater for β-casein.

Complete dissociation of κ-casein aggregates by SDS alone was not possible due to the presence of aggregates formed by disulphide linkages. These aggregates, which consisted of 3±1 protein molecules, accounted for about one-third of the κ-casein in the preparations examined.
Milk enzymes—their distribution and activity
Authors: Kitchen B. J. , Taylor G. C. , White I. C.
Published: June 2009

The distribution and activity of alkaline phosphatase (E.C. 3.1.3.1), acid phosphatase (E.C. 3.1.3.2), catalase (E.C. 1.11.1.6), xanthine oxidase (E.C. 1.2.3.2), aldolase (E.C. 4.1.2.7 and 4.1.2.13), ribonuclease (E.C. 2.7.7.16) and carbonic anhydrase (E.C. 4.2.1.1) were studied in the major components of bovine milk. Fractionation was accomplished by centrifugation of milk, skim-milk and buttermilk, and ammonium sulphate precipitation of skim-milk serum. The range of activities found for the enzymes studied are tabulated together with the activities of some of the enzymes in mastitic milk, and the significance of the results obtained is discussed. No carbonic anhydrase activity was detected in any of the samples tested. The other enzymes studied were found to have a greater proportion of their total activity located in the skim-milk fraction. However, all of these enzymes except ribonuclease had a higher specific activity in the fat fraction.
The inactivation of lactoperoxidase by group N streptococci
Authors: Hogg D. McC. , Jago G. R.
Published: June 2009

The inactivation of lactoperoxidase (LP) by cultures of Group N streptococci was originally reported by Kiermeier & Kayser (1960). However, Pickering, Oram & Reiter (1962) found that incubation ofStreptococcus cremoris803 with LP did not completely inactivate the enzyme, but only modified its activity with certain substrates. This observation was subsequently confirmed by Kiermeier & Lechner (1966, 1967). In the present investigation, several strains of Group N streptococci were found to modify LP in such a way as to cause total or partial loss of enzymic activity with guaiacol. This loss of LP activity was found to be a consequence of the production of hydrogen peroxide by these organisms.
Comparison of milks processed by the direct and indirect methods of ultra-high-temperature sterilization. IV. The vitamin composition of milks sterilized by different processes
Authors: Burton H. , Ford J. E. , Perkin A. G. , Porter J. W. G. , Scott K. J. , Thompson S. Y. , Toothill Joyce , Edwards-Webb J. D.
Published: June 2009

A comparison was made of the effects of direct and of indirect ultra-high-temperature (UHT) processing of milk, under standardized operating conditions giving equal sporicidal effects, on some of the more labile water-soluble vitamins and on vitamin A and carotene. The effects of processing per se were negligibly small, and the method of processing was important only in so far as the presence of residual oxygen in the sterilized milk has been found to cause losses of folic acid and ascorbic acid during storage subsequent to sterilization. The incorporation of a de-aerator vessel, to reduce the oxygen level in the indirectly heated milk and so eliminate the adverse effects of oxygen during storage, had no effect on the vitamin loss occurring during heat treatment. It is concluded that milk produced by indirect heating plant incorporating a de-aerator should be similar in vitamin content to milk produced on a direct heating plant, both immediately after processing and after storage.
Influence of the physical form of a barley grain and barley straw diet on nitrogen metabolism in sheep
Authors: Jackson P. , Rook J. A. F. , Towers K. G.
Published: June 2009

(1) Two wether sheep fitted with ruminal and duodenal re-entrant cannulas were used to study the influence of the physical form of a barley grain and barley straw diet and intraruminal addition of ammonium salts (mainly acetate) on digestibility of dietary constituents, the flow of digesta to the duodenum and the composition of digesta from the rumen and duodenum.

(2). Grinding and pelleting of the diet depressed the digestibility of crude fibre and increased that of the nitrogen-free extract and addition of ammonium salts increased the digestibility of crude fibre. The effects of the physical form of the diet on the composition of the short-chain fatty acids of rumen liquor were not consistent and the addition of ammonium salts produced changes over and above those attributable to the small amounts of acids in the mixture. The extreme values observed for the molar proportion of propionic acid were 12·3 and 38·1% and the corresponding values for η-butyric acid were 28·1 and 9·0%.

(3). Variations in the flow of nitrogenous materials to the duodenum were related more to the pattern of fermentation established in the rumen than to the experimental treatments. There was a highly significant relationship between the molar proportion of propionic acid and the abomasal output of nitrogen and also the abomasal output of α-ε-diaminopimelic acid and α-linked glucose polymers. The amino acid composition of duodenal digesta differed from that of the diet—in particular the proportion of glutamic acid was decreased and the proportions of aspartic acid, alanine, lysine and histidine were increased—but differences in composition between treatments and between animals were small.

(4). The faecal output of nitrogen differed little between animals and between treatments, but nitrogen retention was significantly increased during the intraruminal infusion of ammonium salts.
Volatile compounds in butter oil: II. Flavour and flavour thresholds of lactones, fatty acids, phenols, indole and skatole in deodorized synthetic butter
Authors: Urbach Gerda , Stark W. , Forss D. A.
Published: June 2009

The flavours of the following compounds were determined in synthetic butter prepared from 84% steam-deodorized butter oil and 16% water: C6, 8, 10, 12, 14 δ-lactones, C12 γ-lactone, C2, 4, 6, 8, 10, 12, 14n-alkanoic acids, phenol, m- and p-cresols, o-methoxyphenol, indole and skatole. C6, 8, 10 δ-lactones, C2, 4, 6, 8, 10, 12, 14n-alkanoic acids, phenol, m- and p-cresols, o-methoxyphenol and volatile fractions from butter oil were also evaluated in bland butter. None of the compounds listed constitute basic butter flavour on their own, but C8, 10 δ-lactones, C10 acid, phenol, p-cresol, indole and skatole contribute to butter flavour.
Influence of temperature and composition on some physical properties of milk and milk concentrates. I. Heat capacity
Authors: Fernández-Martín F.
Published: June 2009

An isothermal jacket calorimeter was set up and apparent heat capacities of skim-milk, half-and-half milk, whole milk, and their concentrates up to about 30 % total solids were measured throughout the 5–70°C temperature range. Above the butterfat melting interval, the heat capacity of every sample was linearly related to temperature and a linear regression equation was found to relate heat capacity and total solids content for each one of the 3 milk sets. By means of an overall approximation, a single expression relating heat capacity, temperature and total solids content was also derived. To facilitate calculations of relative heat content for practical purposes, an average apparent heat capacity was computed for the whole temperature range and a nomogram was constructed for its determination from fat and solids-not-fat contents in any sample.
Influence of temperature and composition on some physical properties of milk and milk concentrates. II. Viscosity
Authors: Fernández-Martín F.
Published: June 2009

Ten different types of milk, arranged in 3 sets, were observed to be pseudoplastic fluids with linear behaviour at high shear rates in a coaxial cylinder rheometer; at low rates of shear all the samples could be considered sufficiently Newtonian and a Höppler viscometer was used for their study. Dynamic viscosity coefficients of skimmilk, half-and-half milk, whole milk and their concentrates up to about 30% total solids were determined every 5°C between 0 and 80°C. For every milk type a quadratic equation relating t to log η was obtained. At a given temperature the concentration dependence of η for the 3 milk sets was expressed by a single relation of the same mathematical model as in the previous case. A general expression was derived to enable η to be calculated at any temperature (0–80°C), and for any concentration (0–30% total solids) whatever the fat to solids-not-fat ratio (0·01–0·4). A nomogram was also constructed for the immediate computation of η without any practical loss of accuracy.
Growth studies on the lactic streptococci: III. Observations on continuous growth behaviour in reconstituted skim-milk
Authors: Keen A. R.
Published: June 2009

The behaviour ofStreptococcus cremorisAM1and AM2, andStreptococcus lactisML8in continuous growth in reconstituted skim-milk medium under controlled conditions of pH has been investigated.

At 20°C under aerobic conditions small quantities of oxygen were found to stimulate the growth rate ofStr. lactisML8between pH 5·05 and 5·45. Growth between pH 5·45 and 6·35 became erratic due to the accumulation of hydrogen peroxide. Above pH 6·35 hydrogen peroxide could not be detected in the continuously growing culture and below pH 5·05 the growth rate of the culture was not affected by small quantities of oxygen. An effect of direct oxygen toxicity on growth, distinct from that of hydrogen peroxide accumulation, was observed over the limited pH range investigated. After 48 h growth in the presence of small concentrations of oxygen the effect disappeared.

At 30°C under anaerobic conditions a region in the dilution rate curves was observed withStr. cremorisAM1and AM2andStr. lactisML8which suggested the occurrence of a growth-limiting component. This region of slow growth could be correlated with diminished soluble nitrogen values, and was eliminated by enrichment of the medium with soluble nitrogen.

An unusual feature of the investigation was the dilution rates, indicative of extremely fast specific growth rates, experienced forStr. lactisML8. It was thought unlikely that wall growth contributed appreciably to the dilution rate as a similar phenomenon was not observed withStr. cremorisAM1or AM2.
Variations in the concentrations of free amino acids in the plasma of the dairy cow at parturition
Authors: Verbeke R. , Roets E. , Peeters G.
Published: June 2009

The plasma levels of individual amino acids were studied in 6 dairy cows from 4 days before to 3 days after calving. During this sampling period, the concentrations of 13 amino acids showed significant changes. The levels of several amino acids were depressed markedly in the sample collected immediately before calving. Following parturition, the concentration of most amino acids gradually returned to values obtained 3 days before calving. The glutamine and alanine contents of the plasma rose to a peak value 1 day after calving and subsequently decreased. The mean concentrations of glycine and α-aminobutyric acid did not change before parturition but rose significantly thereafter. These observations are discussed in terms of amino-acid utilization for milk protein synthesis and gluconeogenesis at the onset of lactation. The changes in plasma amino acid levels appear to be synchronized with those reported for prolactin and progesterone in the 24 h before parturition. This may indicate an important influence of both hormones on the lactogenic process in the cow. The highly significant correlations obtained between the concentrations of 14 individual amino acids are discussed.
Kinetics of rennin action on casein prepared by ultracentrifugation
Authors: Castle A. V. , Wheelock J. V.
Published: June 2009

The kinetics of the primary phase of rennin action on casein micelles and on total casein prepared by ultracentrifugation have been studied. It was observed that the values of Km and V varied for the different casein samples. Addition of whey proteins to the reaction mixture or variation of the concentrations of Na+ and K+ had no effect on Km and V and V, but there was a consistent increase in the values of both these parameters when κ-casein was added. It was concluded that these changes were due to an increase in the accessibility of the κ-casein resulting from the rearrangement of the casein micelles. These results are in agreement with our earlier conclusion that the Km for rennin action on casein is dependent on the carbohydrate composition of the molecule.
Casein micelle structure: susceptibility of various casein systems to proteolysis
Authors: Fox P. F. , Guiney J.
Published: June 2009

The susceptibility of the components of various caseinate systems (skim-milk, β-casein-depleted milks, colloidal phosphate-free (CPF) milk, sodium caseinate and isolated β-casein) to proteolysis was investigated. Isolated αs1- and β-caseins were quite susceptible to proteolysis, but their susceptibility decreased in heterogeneous soluble systems and even more so in heterogeneous aggregated systems. In skim-milk and β-casein-depleted milks only about 50% of both αs1- and β-casein was hydrolysable by high levels of rennin, and in CPF milk all αs1- and 70% of the β-casein was hydrolysable. It is suggested that about 50% of micellar β-casein is firmly fixed within the micelle and is unavailable for proteolysis, while the remainder can dissociate from the micelle on cooling and is then readily hydrolysable.

The compatibility of the data with the various published models of the casein micelle is discussed, and a modification of Rose's (1969) model is proposed.
Periodic omission of dairy cow milkings: II. Effect on the composition and processing properties of herd milk
Authors: Bailey L. F. , Radcliffe J. C. , Hehir A. F.
Published: June 2009

Forty-five Friesian cows were assigned to one of 3 milking management treatments: (1) cows milked 14 times weekly, (2) cows milked 13 times weekly (Wednesday morning milking omitted) and (3) cows milked 12 times weekly (Tuesday evening and Wednesday morning milkings omitted). The trial continued for 12 months.

Milking omission led to compositional changes in herd milk similar to those described for subclinical mastitis, including increases in pH, chloride level and cell count. Alterations in processing properties consistent with these changes were encountered. Heat stability and curd firmness were affected by extending the milking interval, but the magnitude and direction of the effects varied.

Where only one milking was omitted weekly, herd milk arriving at cheese or powdered-milk factories would not be expected to cause any serious technical difficulties. Omission of 2 consecutive milkings a week would cause processing difficulties where milk was to be condensed or dried, since the maximum heat stability obtained by pH adjustment was reduced.
Utilization of nutrients by the dairy cow and optimal N:energy ratio in the diet
Authors: Paquay R. , Godeau J. M. , De Baere R. , Lousse A.
Published: June 2009

The dietary and individual animal factors influencing the utilization of digestible nitrogen and of metabolizable energy for milk production were studied and change in the optimal nitrogen:energy ratio during lactation was investigated using 35 different experimental diets and the individual results obtained from 119 Friesian cows whose daily milk production varied from 4 to 30kg.

The amount of N secreted in the milk and the daily milk production depended above all on the metabolizable energy intake and on the stage of lactation. They were related to the dietary N: energy ratio.

The percentages of digestible N and of metabolizable energy utilized for milk production were also related to the dietary digestible N: metabolizable energy ratio of the diet.

The optimal digestible N:metabolizable energy ratio ranged from about 2·2g/MJ during the first 3 months of lactation to about 1·7g/MJ in the sixth and seventh months and 1·3g/MJ from the tenth month. When expressed in g N intake per MJ energy intake, this optimal ratio ranged from 1·6 after calving to 1·1 at the end of lactation.
Separation and estimation of diacetyl and acetoin in milk
Authors: Walsh B. , Cogan T. M.
Published: June 2009

Two methods are described for the separation of diacetyl and acetoin in milk by steam distillation. In the first method, acetoin is measured in the residue remaining in the extraction flask after steam distillation while diacetyl is measured in the first 10 ml of distillate which contains 35% of the acetoin and 100% of the diacetyl. Increases in the volume of residue taken for analysis decreased colour development by acetoin. In the second and preferred method, diacetyl is measured in the first 10 ml of distillate and acetoin in the second 10 ml of distillate which contains about 24% of the added acetoin. Diacetyl in both methods is measured by a modification of the method of Prill & Hammer (Walsh & Cogan, 1974) and acetoin by the Westerfeld (1945) procedure.
Effects of intramammary arterial infusion of essential amino acids in the lactating goat
Authors: Linzell J. L. , Mepham T. B.
Published: June 2009

Experiments were performed on 3 lactating goats, in which mammary arterial plasma amino-acid concentrations were elevated by the infusion of a solution of essential amino-acids into the carotid artery supplying a transplanted mammary gland. In 2 experiments there were marked elevations in the arterial concentrations of most essential amino acids, but in one case only did this result in significantly increased uptake of amino acids by the gland, the arterio-venous difference being significantly correlated with arterial concentration for all except one amino acid. In the experiment in which increased amino-acid uptake was observed, infusion also resulted in a significantly increased milk yield and increased milk protein yield. The results are discussed in relation to data from other laboratories and lead to the suggestion that milk protein synthesis may be limited by the availability of either methionine or tryptophan.
Organochlorine content of milks, dairy products and animal feed ingredients: Ireland 1971–1972
Authors: Downey W. K. , Flynn Mary P. , Aherne S. A.
Published: June 2009

Milks (bovine and human) and dairy products (butter, cheese, skim and whey powders, calf-replacer, casein, butter-oil and dietetic food) were collected during 1971/2 throughout Ireland together with a more limited sample of the 10 major animal feed ingredients, and analysed for organochlorine insecticide residues using electron-capture gas chromatography. The different materials contained low or negligible levels of chlorinated insecticides. Apart from some of the animal feed ingredients the DDT residues were generally the predominant contaminants detected together with lower levels of γ-BHC (lindane), aldrin/dieldrin and heptachlor/heptachlor epoxide. The maximum levels of these insecticides in the bovine milk and dairy products (511, 100, 62 and 21 μg/kg fat respectively) constitute only 50% or less of the Codex Tolerance Limits. The correspondingly low residue levels in the human milk (maxima of 128, 1, 1, and 5 μg/kg fat respectively) which at most represent insecticidal ingestion by infants equivalent to 13, 0·05, 5 and 5% respectively of the WHO/FAO acceptable daily intake for DDT, γ-BHC, aldrin/dieldrin and heptachlor/heptachlor epoxide again pose no obvious health hazards and are strongly indicative of negligible organochlorine contamination in the general diet. The samples of animal feed ingredients examined also contained trace levels of organochlorines (maxima of 0·9, 0·1, 1·6 and 1·0 μg/kg respectively). More extensive monitoring of the residues in animal feed ingredients (the most probable source of milk contamination) is advocated, and the desirability of tolerance limits for insecticides in animal feeds discussed.
Citrate utilization in milk byLeuconostoc cremorisandStreptococcus diacetilactis
Authors: Cogan T. M.
Published: June 2009

Citrate utilization and diacetyl, acetoin and acetaldehyde production by 2 strains each ofLeuconostoc cremorisandStreptococcus diacetilactisin milk were studied. With the leuconostoc bacteria no growth and little citrate utilization occurred unless a stimulant (yeast extract) was present, when complete utilization of citrate without concomitant production of diacetyl or acetoin was obtained. The addition of Mn2+stimulated growth and citrate utilization in the presence of yeast extract. Addition of citric acid after 65-h growth resulted in diacetyl and acetoin production. Destruction of diacetyl and acetoin occurred when the citric acid level fell toc. 1000 and 600 μg/g in the case ofLeuc. cremorisFR8-1 and CAF1, respectively. Only strain FR8-1 produced acetaldehyde. In contrast,Str. diacetilactisproduced diacetyl, acetoin and acetaldehyde concomitant with citrate utilization.
The precipitation of proteins by carboxymethyl cellulose
Authors: Zadow J. G. , Hill R. D.
Published: June 2009

Carboxymethyl cellulose (CMC) formed insoluble complexes with β-lactoglobulin, bovine serum albumin and Na caseinate. Maximum precipitation of the β-lactoglobulin-CMC complex occurred at pH 3·2, whereas maximum precipitation of the bovine serum albumin-CMC complex and the Na caseinate-CMC complex occurred at pH 2·8. The ratio of CMC to protein for maximum precipitation depended on the protein, being greatest for Na caseinate and least for bovine serum albumin. The percentage of protein precipitated by CMC decreased with increasing ionic strength of the solution, the rate of decrease being least for bovine serum albumin. At a given ionic strength, more protein was precipitated by CMC of high degree of substitution than by CMC of low degree of substitution. The change in pH (ΔpH) occurring on mixing CMC and unbuffered protein solutions, each initially at the same pH, was measured. ΔpH was negative for β-lactoglobulin-CMC mixtures over the pH range 7–2 (minimum at pH 5·5). For bovine serum albumin-CMC and Na caseinate-CMC mixtures, ΔpH was positive between pH 7 and 3·2 (maximum at pH 4·5), zero at pH 3·2 and negative between pH 3·2 and 2·0 (minimum at pH 2·8).
Relationship between temperature and sterilizing efficiency of heat treatments of equal duration. Experimental testing with suspensions of spores in milk heated in an ultra-high-temperature sterilizer
Authors: Hermier J. , Begue P. , Cerf O.
Published: June 2009

A relationship between temperature and sterilizing efficiency of heat treatment at constant time is described and checked experimentally using spores of Bacillus coagulans 604 in a pilot ultra-high-temperature plant. The relation is:

whereN0andNare initial and final concentrations of spores,Tthe temperature (°C),zthe temperature coefficient (°C,z=10/logQ10) andAa dimensionless constant. A special effect of the injection of spores into live steam is observed. The sterilizing efficiency curve can be used in determining the heating temperature for a desired sterilizing efficiency and in predicting the influence of temperature fluctuation on sterilizing efficiency.
The quantitative measurement of whey proteins using polyacrylamide-gel electrophoresis
Authors: Hillier Robyn M.
Published: June 2009

A method is described for the quantitative estimation of a mixture of whey proteins by spectrophotometric scanning of the stained protein bands following polyacrylamide-gel electrophoresis. The incorporation of β-lactoglobulin A as an internal standard improves the accuracy of the technique. The method has been used to measure residual native whey proteins in milk after heating. Results are presented for whey protein denaturation in skim-milk after heat treatment at 130 and 140 °C for various periods of time.
Compositional and electrophoretic changes in buffalo milk-fat globule membrane proteins during lactation
Authors: Singh Sukhminder , Ganguli N. C.
Published: June 2009

Chemical analyses, polyacrylamide-gel electrophoresis and isoelectric focusing of milk-fat globule membrane proteins (FGMP) obtained from the milk of 2 Murrah buffaloes were done to determine if any change in composition occurred during lactation. Changes in the levels of sialic acid, hexose, hexosamine, N and P were found in the FGMP obtained at different stages of lactation. On the day of parturition, 8 major proteins in FGMP were determined by sodium dodecyl sulphate polyacrylamide-gel electrophoresis whereas 6 major proteins were obtained in FGMP of middle and late lactation milks. Isoelectric focusing of FGMP showed 8–9, 9–13 and 13–16 proteins from colostrum, middle and late lactation milks, respectively and the isoelectric pH of the proteins varied from 5·25 to 7·80, 5·85 to 8·30 and 5·75 to 8·61 respectively.
A study of cow's milk containing high levels of linoleic acid: isolation and properties of the fat-globule membrane
Authors: Sleigh R. W. , Bain Joan M. , Burley R. W.
Published: June 2009

Properties of whole milk and milk fractions from cows fed a diet that gave a greatly increased proportion of unsaturated fatty acid residues (especially of linoleic acid) in the milk lipids were studied, and this milk (high-linoleic milk) was compared with milk from cows on a control diet (control milk). The milk fractions were isolated by high-speed centrifugation of whole milk or cream and were examined by chemical analysis and electron microscopy. During centrifugation the globules of milk fat were disrupted and the membranes (fat-globule ‘ghosts’) floated as a layer beneath the free lipid. Membrane proteins from the 2 sorts of milk gave the same electrophoretic pattern and the amino acid compositions were the same. Lipid analysis of the membrane fraction from high-linoleic milk showed the expected increase in the proportion of unsaturated fatty acid residues in the neutral lipids, but there was an unexpected decrease in the proportion of unsaturated residues in the membrane phospholipids. No differences were found between high-linoleic and control milk in the ultrastructure of the milk-fat globules or the isolated membranes.
Volatile compounds in butter oil: IV. Quantitative estimation of free fatty acids and free δ-lactones in butter oil by cold-finger molecular distillation
Authors: Stark W. , Urbach Gerda , Hamilton Janet S.
Published: June 2009

Free fatty acids (FFA) and free δ-lactones in butter oil were quantitatively estimated by cold-finger molecular distillation at 35 °C followed by silicic-acid column chromatography of the cold-finger distillate and gas chromatography of the fatty acid and lactone fraction. Typical values for FFA and free δ-lactones in butter oil prepared from export standard sweet-cream salted Australian butter were in the range 0·07–0·24, 0·75–2·4, 4·5–8·6, 34–40 and 44–89 ppm for the C4,6,8,10,12 fatty acids and 0·09–0·18, 1·2–4·9 and 3·0–5·8 ppm for the C8,10,12 δ-lactones. These values are in the range of organoleptically desirable levels.
Volatile compounds in butter oil: V. The quantitative estimation of phenol,o-methoxyphenol,m- andp-cresol, indole and skatole by cold-finger molecular distillation
Authors: Stark W. , Urbach Gerda , Hamilton Janet S.
Published: June 2009

Phenol,o-methoxyphenol,m- andp-cresol, indole and skatole have been isolated from good quality butter oil by cold-finger molecular distillation, and separated into phenolic and indolic fractions by solvent extraction and silicic-acid column chromatography. The individual compounds were quantitatively estimated by gas chromatography. When phenol,o-methoxyphenol,m- and;p-cresol, indole and skatole were added to volatile-free butter oil, their recoveries were 94, 47, 90, 75, 71 and 61% respectively. The technique, when applied to fresh butter oil, gave the following ranges of values for the natural levels of these compounds: phenol 0·005–0·022,o-methoxyphenol 0·002–0·10,m-cresol 0·002–0·010,p-cresol 0·002–0·004, indole 0·07–0·13, skatole 0·16–0·22 ppm of butter oil. The results, when compared with flavour threshold studies, showed that indole and skatole are important contributors to the natural flavour of butter oil, but that phenolic compounds are of only borderline significance.
The use of short-term secretion rate measurements for estimating the milk production of suckler cows
Authors: Le Du Y. L. P. , Baker R. D. , Barker J. M.
Published: June 2009

Two experiments with dairy cows and one with suckler cows and their calves were conducted to examine the use of secretion rate measurements for estimating total milk production. In the first experiment both 4- and 6- h intervals between measurements gave similar estimates of total 7-d milk yield. The second experiment compared estimated and measured milk composition as well as yield. Milk and solids-not-fat yields were underestimated with dairy cows as a result of an extended milking interval before measurement. However, fat yield was overestimated, indicating that all residual milk was not removed at the first oxytocinaided milking. It was concluded that for the beef cow, previous interval effects would be eliminated by the frequency of calf suckling, but that residual milk effects might cause a 3–6% and a 16% overestimation of milk and fat yields respectively.

In the third experiment, the milk yield of suckler cows was estimated from measurements of secretion rate and from changes in calf weight; good agreement was obtained provided there were at least 3 consecutive controlled sucklings.
The cell count of milk in relation to milk yield
Authors: Meijering A. , Jaartsveld F. H. J. , Verstegen M. W. A. , Tielen M. J. M.
Published: June 2009

Quarter-milk cell counts and milk yields from 1000 cows in the province of Noord-Brabant were obtained over a 12-month period. The data from 933 animals, mainly heifers, were used to examine statistically the relationship between cell counts, as a criterion for sub-clinical forms of mastitis, and milk yield. Losses in milk were assessed by quarter, by pairs of quarters and by cow. The conclusions were that the losses in milk due to sub-clinical forms of mastitis, as indicated by cell count, can be substantial. The existence of a compensating increase in milk yield from a healthy gland, in response to the loss of milk from a neighbouring quarter with raised cell count, could not be demonstrated.
Bovine milkN-acetyl-β-D-glucosaminidase and its significance in the detection of abnormal udder secretions
Authors: Kitchen B. J. , Middleton G. , Salmon M.
Published: June 2009

A new spectrofluorimetric assay procedure for bovine milkN-acetyl-β-D-glucosaminidase (NAGase) is described for use as a routine screening test for the detection of abnormal uddersecretions. This procedure uses 4-methylumbel-liferyl-N-acetyl-β-D-glucosaminide as substrate. On the basis of the greater sample throughput, increased product sensitivity detection of NAGase and the absence of turbidity problems, it is considered to be superior to a previously reported spectrophotometric procedure (Kitchen, 1976). The correlation coefficient between the somatic cell count and the fluorimetric procedure using 243 quarter fore-milk samples was 0·86. Distribution studies on bovine milk and mammary gland homogenates indicated that this enzyme activity was located predominantly in the soluble whey protein fraction and the post-microsomal supernatant. Mammary gland secretory cells contained high levels of NAGase and appeared to be the major source of the enzyme in milk whilst NAGase from other sources (white blood cells, blood serum) contributed only a minor proportion (5–15%) of the total activity in milk. The implications of these findings on the value of the NAGase test as a means of mastitis diagnosis are discussed.
Seasonal changes in the heat stability of milk from creamery silos in south-west Scotland
Authors: Holt Carl , Muir D. Donald , Sweetsur A. W. Maurice
Published: June 2009

The heat stability of the milk supply to manufacturing creameries in south-west Scotland was examined over 15 months from Nov. 1975 to Jan. 1977. For all but 2 months of this period the heat stability of the milk was very highly significantly correlated with the naturally occurring level of urea. Between 72 and 90% of the variation of coagulation time (CT), measured at the natural milk pH, was accounted for by changes in milk urea alone. For a short period, in May and June, the CT of the milk at natural pH fell within the minimum of the CT–pH profile, but insufficient data were available to allow the occurrence of this phenomenon to be related to changes in milk composition.
Preparation and fractionation of goat κ-casein: analysis of the glycan and peptide components
Authors: Addeo Francesco , Soulier Solange , Pelissier Jean-Pierre , Chobert Jean-Marc , Mercier Jean-Claude , Ribadeau-Dumas Bruno
Published: June 2009

Whole goat κ-casein was prepared by chromatography of whole casein on hydroxyapatite. Chromatography of whole κ-casein on DEAE-cellulose separated 5 fractions. All of them were sensitive to chymosin. Their amino acid and carbohydrate composition, phosphate content and molecular weight were determined. Galactose,N-acetylgalactosamine,N-acetyl andN-glycolyl neuraminic acids were identified in whole κ-casein. It appears that goat κ-casein, like cow, buffalo and ewe κ-caseins, is composed of several fractions having identical peptide chains and differing in their carbohydrate contents. The main fraction, devoid of carbohydrate, was treated with chymosin. The para-κ-casein and caseinomacropeptide were isolated. Their amino acid composition and phosphate content were determined.