bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of oestrogenic activity in red clover (Trifolium pratense) using ovariectomized immature mice
Authors: Munford R. E. , Flux D. S.
Published: June 2009

Two experiments concerned with the testing of plant material for oestrogenic activity, utilizing vaginal reactions and uterine weight changes in immature ovariectomized mice are reported.

In the first experiment the effects of varying the feeding period of an oestrogenic diet, containing 20% of freeze-dried red clover, and of varying the interval between the last feeding of this diet and slaughter were investigated. In general, uterine weight increased linearly with increased period of feeding and decreased linearly with delay in slaughtering. A feeding period of 4 days was satisfactory for comparisons based on uterine weight. If vaginal reactions were also to be utilized a feeding period of not less than 6 days was desirable.

In the second experiment the dose-response relationships of diethylstilboestrol, genistein and oestrogenic red clover were investigated. All materials were incorporated in the diet of mice, and the level of plant material was kept at 20% of the mixed feed by adding inactive plant material where necessary. In general, either diethylstilboestrol or genistein could form a satisfactory standard for biological estimation of oestrogenic activity in red clover. Relative potencies based on uterine weight response and occurrence of vaginal opening and oestrus-type vaginal smears are given.
Studies on the properties of new zealand butterfat: VI. Comparison of the properties and vitamin A potencies of butterfats produced by clover-fed and ryegrass-fed dairy cows
Authors: McDowall F. H. , McGillivray W. A.
Published: June 2009

In an indoor feeding trial with three sets of monozygotic twin cows during late spring the effects of H1short rotation ryegrass and white clover as feeds for the cows on the characteristics and the carotene and vitamin A contents of the butterfat were compared. The butterfat from the cows fed ryegrass had a lower iodine value and refractive index, higher Reichert and saponification values, and lower carotene and vitamin A contents than the butterfat from the cows fed clover. The carotene and vitamin A contents of the blood of the cows fed ryegrass were also lower than those of the cows fed clover

In a subsequent outdoor feeding trial with four sets of monozygotic twins the feeding of pure H1short rotation ryegrass or of perennial ryegrass was compared with the feeding of mixed pastures containing a high but varying proportion of clover. The results for the spring and early summer months were similar in direction but smaller in magnitude than those from the indoor feeding trial. In the result for the autumn months there was a reversal of the relationship for the characteristics and the carotene and vitamin A contents of the butterfat and for the carotenoid contents of the blood.

It is suggested that the lack of consistency between the spring and autumn results could have been due to differences in the stage of growth of the ryegrass fed and that butterfat characteristics may be influenced more by the stage of maturity than by the botanical composition of the pasture.
Studies on thek-casein complex: I. The release of sialic acid-containing material by rennin
Authors: Beeby R.
Published: June 2009

Whenk-casein was treated with rennin at neutral pH all the sialic acid contained in the protein was found in the glycopeptide released by the enzyme. From the known molecular weight of the glycopeptide and its proportion ink-casein, a molecular weight of the order of 50000 was calculated for the protein
Formation of methyl ketones as artifacts during steam distillation of Cheddar cheese and butter-oil
Authors: Lawrence R. C.
Published: June 2009

A complete range of methyl ketones with odd numbers of carbon atoms from C3 to C15 was isolated by steam distillation at atmospheric pressure from fresh butter-oil, cream and Cheddar cheeses of various ages. Evidence was produced to show that the greater part of these methyl ketones was formed during the heat treatment of milk fat. The maximum quantities of methyl ketones obtainable from butter-oil, determined by exhaustive steam distillation at atmospheric pressure, averaged from 14 ppm. for undecan-2-one to 46 ppm. for pentadecan-2-one. Some artifact formation of methyl ketones also occurred, although to much less extent, when dairy products containing milk fat were steam distilled under reduced pressure at 40 °C. Possible mechanisms of formation of the methyl ketones are discussed.

Since it proved possible to extract methyl ketones in low concentration from mature cheese at room temperature, it is evident that milk fat may contain precursors which break down to methyl ketones slowly during cheese ripening, this breakdown being accelerated at higher temperatures. Methyl ketones may therefore play a part in Cheddar flavour, but a previous report from this Institute that the time of first appearance of certain methyl ketones of odd numbers of carbon atoms above C5 in steam distillates, at atmospheric pressure from Cheddar cheese, coincided with the appearance of the typical Cheddar flavour was not confirmed.
The effect of the replacement of concentrates by roots on the intake and production of dairy cows
Authors: Castle M. E. , Drysdale A. D , Waite R. , Watson J. N.
Published: June 2009

To investigate the effect of replacing part of the concentrates by roots, a 16-week winter-feeding experiment was made using twelve Ayrshire cows. All the cows received 8 lb of hay per day and enough grass silage for a measurable residue to be left at each feed. Two rations were supplemented with 45 lb of fodder-beet per day but the other two contained no roots. At each level of root feeding, concentrates were fed at either 3·50 or 1·75 lb per 10 lb of milk.

All the fodder-beet was eaten (8·4 lb dry matter) and, as this caused a reduction in the intake of silage dry matter of only 3·4 lb per day, there was a net increase in drymatter intake. The level of concentrate feeding had little effect on the intake of the other feeds. Rations which included roots contained significantly less crude fibre than rations without roots.

The mean daily milk yields for the treatments with the low and high concentrate levels were 29·5 and 33·9 lb, respectively, without roots and 31·8 and 35·8 lb with roots. The fat percentages of the milk were similar on all four treatments whereas the solids-not-fat (S.N.F.) increased significantly from 8·42% on the treatment without roots and low concentrates to 8·64% on the treatment with roots and high concentrates. The response per 1 lb of extra S.E. was 1·0 lb milk and 0·02% S.N.F. between the low and high concentrate treatments and 0·7 lb milk and 0·05% S.N.F. between the two root treatments. The analysis of milk from individual quarters of all the cows during each period showed the continuous presence of some subclinical mastitis. It was estimated that this lowered the general level of S.N.F. percentage by 0·2% but did not bias the results from any one feeding treatment. For milk from healthy quarters only, the response to 1 lb extra S.E. from concentrates was 0·03% S.N.F. and from beet it was 0·08% S.N.F.
Inherited casein variants in cow's milk: II. Breed differences in the occurrence of β-casein variants
Authors: Aschaffenburg R.
Published: June 2009

A survey was made of the frequency of β-casein variants in the milk of cows of five major British breeds. Three variants A, B and C differing in electrophoretic mobility were found to occur either singly or in pairs, as expected if each were determined by a single allele. The A variant was the most common and found in all breeds. Ayrshires and Shorthorns produced no other variant, whilst the B variant occurred in Jerseys and, at low frequency, in Guernseys and Friesians. Production of the C variant was restricted to the Guernsey breed in which it occurred at low frequency. The technique of paper electrophoresis, used for β-casein ‘typing’ of some 600 cows, is described in detail.
Lactic casein whey powder in rations for pigs: I. The substitution of un-neutralized lactic casein whey powder for barley meal in an all-meal ration for growing pigs
Authors: Dunkin A. C.
Published: June 2009

The results of 2 experiments indicated that casein whey powder can successfully constitute a relatively high proportion of an all-meal diet for growing pigs. Pigs given a diet consisting of a basal meal allowance per day of ½ lb meat meal and 1½ lb barley meal plus increasing amounts of casein whey powder took significantly less time and required significantly less food to grow from 50 lb to 120—140 lb liveweight, than either the control pigs or those given diets containing smaller basal meal allowances but correspondingly more whey powder. In the best diet whey powder comprised approximately 40% of the total food consumed. In one experiment, diets containing more whey powder than this resulted in slower growth rates, relative to that of the controls, from 110 lb liveweight onwards.

There was a little more scouring on the diets containing the greater amounts of whey powder; but even where whey powder formed approximately 83% of the total food consumed, the incidence of scouring was not of great practical importance. Moreover, there was considerable variation among animals within treatment groups in this respect.
Transduction inStreptococcus lactis
Authors: Allen Lois K. , Sandine W. E. , Elliker P. R.
Published: June 2009

Transduction experiments were carried out using recipient strainStreptococcus lactisC2Ss(streptomycin-sensitive) and virulent phages prepared on donor strainStr. lactisC2Sr(streptomycin-resistant). At a high multiplicity of infection of 10, transduction to streptomycin resistance occurred at a frequency approximately 1 in 30 surviving cells and the recombinant character exhibited a delayed expression. Transduction did not occur when phages propagated onStr. lactisC2Sswere used or when phage antiserum was added to the transducing phage suspension. The transducing phage manifested an altered lytic cycle following passage through theStr. lactisC2Srdonor which rendered it incapable of reinfecting the donor but did not alter its virulence for theStr. lactisC2Ssrecipient.
A comparison of hay and silage for milk production
Authors: Murdoch J. C. , Rook J. A. F.
Published: June 2009

In a series of 3 trials there was little or no difference in milk yield when cows were fed the same quantity of dry matter in the form of well-preserved hay or silage from the same sward.

A higher milk yield was obtained from silage made from grass at an early stage of maturity than from silage or hay made from the same crop 5 weeks later.

In 2 trials when hay or silage was fed ad lib. the dry-matter intakes of the cows were higher with hay than with silage, and there was a consequent increase in milk yield and S.N.F. content in favour of hay.

Some of the results indicated that with certain silages a depression in the S.N.F. content of the milk, due to a decrease in the casein content, could occur, although this was not associated with an inadequate energy intake.
Greenish discoloration of butterfat during an extended period of cold storage
Authors: Lück H.
Published: June 2009

Dry butterfat occasionally develops a greenish colour when stored for at least 1½ years at −12°C whereas samples of the same fat kept for 2 years at +2 or +15°C do not show this colour defect. Spectrophotometrical measurements have shown that the defect is accompanied by a chemical change of the carotene. Its absorption maxima are shifted towards the shorter wavelengths, and a new absorption is observed at 400–410, 430–435 and 450–460 mm. The possible involvement of oxidation products of carotene, such as isomeric diepoxides or furanoid oxides is discussed. The colour defect can be observed before any change in flavour is noticed.
The para-caseinate-phosphate complex of washed rennet curd: its composition and its decomposition by water, sodium chloride solutions, and lactic acid solutions
Authors: Ling E. R.
Published: June 2009

Washed rennet curd releases significant quantities of calcium phosphate and relatively small quantities of calcium para-caseinate when shaken with water. Treatment with small quantities of sodium chloride in aqueous solution similarly differentiates between these 2 components, but larger quantities attack both phosphate and para-caseinate with equal severity. A more extensive release of Ca and inorganic Poccurs when the curd is treated with lactic acid solutions; the comparative ease with which Mg is removed under these conditions suggests that Mg is present as magnesium citrate.
The effect of varying the interval between milkings on milk secretion
Authors: Wheelock J. V. , Rook J. A. F. , Dodd F. H. , Griffin T. K.
Published: June 2009

The effect of 6-, 12-, 18-, 24-, 30- and 36-h milking intervals on milk secretion has been investigated. The effect of the previous milking intervals was eliminated by interposing a recovery period consisting of 12-h milking intervals between the experimental intervals. Bias due to the carry-over of residual milk was reduced by removing the residual milk at the end of each milking, after an injection of oxytocin.

The rate of secretion of milk and of the individual constituents decreased curvilinearly, with duration of the interval, but the degree of curvilinearity differed between constituents. The rates of decrease were in the following increasing order: sodium, chloride, fat, whey proteins, casein N, water, non-protein N, lactose and potassium. The effects of the treatments persisted for some time after the end of the experimental intervals, but the original rates of secretion were regained by the end of the recovery period. The differing effects on the secretion of individual constituents resulted in increases in the concentrations of sodium, chloride and whey proteins in the milk and decreases in those of lactose and potassium.
A comparison between a hot-wire laboratory apparatus and a plate heat exchanger for determining the sensitivity of milk to deposit formation
Authors: Burton H.
Published: June 2009

Using several milk supplies, a comparison has been made between the amount of deposit formed under standard conditions in a small plate type ultra-hightemperature heater, and the results from the hot-wire laboratory apparatus described previously. It is shown that the laboratory apparatus reproduces the variations in the sensitivity to deposit formation found using the plate heater. The relationship is linear if the criterion derived from the hot-wire results is taken as the square of that proposed previously. A decrease in the sensitivity to deposit formation during the ageing of fresh milk, and a seasonal variation, are indicated.
A method of detecting dissimilation of citrate by lactic acid bacteria usingStreptococcus lactisvar.diacetilactisNCDO 1007
Authors: Garvie Ellen I.
Published: June 2009

In suitable media the relationship between the citrate content and the acetoin formed by the growth ofStreptococcus lactisvar.diacetilactisNCDO 1007 is linear. An assay method for citrate is described which is based on this relationship. It has been used to assay the residual citrate in cultures of lactic acid bacteria and, therefore, to assess the ability of these bacteria to dissimilate citrate. Some suitable media for the test are described.
The persistence of cloxacillin in the mammary gland when infused immediately after the last milking of lactation
Authors: Smith A. , Neave F. K. , Dodd F. H. , Jones A. , Gore D. N.
Published: June 2009

A series of experiments has been carried out in order to develop antibiotic preparations which, when infused into the udder at drying-off, eliminate established infection and prevent new infection from occurring in the dry period. It has been shown that the persistence of antibiotic in the dry udder is affected by the solubility of the antibiotic salt, the quantity of antibiotic infused and the base in which it is formulated. Whereas 0.2 g cloxacillin as the sodium salt infused in a 3% aluminium monostearate in mineral oil base after the last milking of lactation persisted for less than 1 week, 0.5 and 1.0 g cloxacillin in the form of the benzathine salt, in a similar base, usually persisted for 3 weeks.

Secretions removed from the udders of dry cows inhibited the growth ofBacillus subtilisandSarcina luteabut not 2 strains of staphylococci.
n-Pent-l-en-3-ol and n-Pent-en-3-one in oxidized dairy products
Authors: Stark W. , Smith J. F. , Forss D. A.
Published: June 2009

Pent-1-en-3-ol and pent-l-en-3-one were isolated in approximately equal amounts from buttermilk obtained from oxidized cream. The two vinyl compounds were identified by combined gas chromatography and mass spectrometry. The flavour of pent-1-en-3-ol is comparatively mild being detectable in water, skim-milk, butter oil and butter at 3 pts in 106, 3 pts in 106, 1 pt in 105 and 1 pt in 105, respectively. The flavour of pent-1-en-3-one is approximately 1000 times stronger being detectable in water, skim-milk, butter oil and butter at 1 pt in 109, 3 pts in 109, 5 pts in 109 and 5 pts in 109, respectively: these concentrations are of the same order of magnitude as for the compound responsible for metallic flavour, oct-1-en-3-one.

The formation of pent-1-en-3-ol and pent-1-en-3-one is discussed.
The effect of a temporary suspension of milking in mid-lactation on milk secretion after the resumption of milking and in the following lactation
Authors: Wheelock J. V. , Smith A. , Dodd F. H.
Published: June 2009

After the suspension of milking for 2 weeks in 2 ‘experimental’ quarters of each of 4 Friesian cows, there was a reduction in the yield of milk from these quarters. Although subsequently there was a marked recovery, for the remainder of the lactation the yield was lower than that of the corresponding control quarters in which milking had not been suspended. Throughout the next lactation, in all 4 cows, the experimental quarters produced more milk than the corresponding control quarters. At the first milking after the suspension, there were marked increases in the concentrations of sodium and chloride and decreases in those of lactose and potassium in the milk obtained. Within 8 weeks, the composition recovered, and for the remainder of the experiment the composition of the milk from the control quarters was similar to that from the experimental quarters of each cow.
The interrelationship of the viscosity, fat content and temperature of cream between 40° and 80°C
Authors: Phipps L. W.
Published: June 2009

The dynamic viscosity coefficients η of creams containing up to 50% fat have been determined at temperatures of approximately 40, 50, 60, 70 and 80°C. All the creams behaved as Newtonian liquids, the shear stress being proportional to rate of shear up to the maximum rate used of 100 sec−1. At a given temperature a linear dependence of log η on (φ+φ5/3) was obtained for φ < 0·4, where φ is the concentration (w/w) of fat. Interpolation formulae have been derived to enable η to be calculated at any temperature between 40 and 80°C and for any fat content up to 40%. Formulae for the density ρ of cream have also been deduced to permit kinematic viscosities η/ρ to be computed. Nomograms have been constructed to enable η and ρ to be readily determined without the use of the interpolation formulae and when slight loss in accuracy is unimportant.
Determination of moisture in dairy products by near infra-red absorption of methanol extracts
Authors: Goulden J. D. S. , Manning D. J.
Published: June 2009

Absorbance measurements at the 1·93 μm water band on methanol extracts from butter, cheese and dried milk enabled moisture contents to be determined with coefficients of variation of 1·0, 1·1 and 2·0%, respectively. Butter, cheese and cheese curd analyses could be completed within a few minutes, but a 2-h standing period was required for dried milk to overcome difficulties associated with lactose precipitation.
The effects of intravenous infusions of insulin and of sodium succinate on milk secretion in the goat
Authors: Rook J. A. F. , Hopwood J. B.
Published: June 2009

The effects of intravenous infusion of insulin and of sodium succinate on milk yield and composition and on the yields of milk constituents was investigated in the goat. Depression of plasma glucose concentration to less than 40 mg/100 ml in response to infusion of insulin was associated with a decrease in milk volume and lactose yield, and increases in the contents of fat and casein and in the yield of fat. The increase in fat yield was the result of an increased output of C12–C18 fatty acids; the output of C4–C10 acids was slightly reduced. Infusion of succinate caused a reduction in the yields of milk and of lactose, protein and fat. There was no consistent change in milk composition.

The origin of the effects is discussed.
Measurement of the quantity of lactose passing into mammary venous plasma and lymph in goats and in a cow
Authors: Kuhn N. J. , Linzell J. L.
Published: June 2009

Lactose in the plasma of 12 lactating goats and one cow with healthy udders has been measured by a sensitive and specific enzymic assay. Mean values (±S.E.) for arterial and venous concentrations were 52±11 µM and 70±11 µM respectively. Simultaneous measurement of mammary blood flow, milk yield and milk lactose concentration showed that 2·70±0·25% (mean±S.E.) of the total lactose production passed into the plasma. This rose to 42·7% in a goat when milking was suspended for 46 h. No lactose was found in the plasma of male and non-lactating female goats, but it was detected 4 days before parturition in a nulliparous goat.
The effect of fatty acids on the metabolism of pyruvate in lactic acid streptococci
Authors: Anders R. F. , Jago G. R.
Published: June 2009

The metabolism, of pyruvate by resting whole-cell suspensions of Group N streptococci was studied over the pH range 4·0–7·0, in the presence and absence of oleic acid. In the absence of oleic acid pyruvate was utilized maximally at pH 4·5 with the formation of acetate (volatile acid), acetoin + diacetyl and carbon dioxide. The formation of acetate took precedence over the formation of acetoin + diacetyl. In the presenoe of oleic acid the utilization of pyruvate was maximal at pH 6·5 and completely inhibited at pH 4·5. The only products detected at pH 6·5 were acetoin + diacetyl and carbon dioxide. This effect of oleic acid on the metabolism of pyruvate was also obtained after treating the cells with acetone. The mechanism of action of oleic acid on cells of Group N streptococci and its possible influence on the formation of flavour compounds in cultured dairy products is discussed.
Effect of varying enzyme concentration on the action of rennin on whole milk
Authors: Castle A. V. , Wheelock J. V.
Published: June 2009

The kinetics of the release of glycopeptides by the action of rennin on bovine whole milk have been studied. The initial rate of release of glycopeptides was proportional to the concentration of rennin. Using the integrated form of the Michaelis–Menten equation, values have been obtained forKmandV. These values varied between milk samples from individual cows, and for a single milk sample the value forKmincreased with increasing rennin concentration. It is suggested that theKmvalue is partly dependent on the carbohydrate composition of individual κ-casein molecules.
The status of casein micelles in chilled milk from the buffalo and the cow
Authors: Sabarwal Pershotam Kumar , Ganguli N. C.
Published: June 2009

When milk was chilled for 12 and 24 h at 0 °C, a decrease in the calcium and phosphorus contents of the casein micelle of both buffalo and cow's milk was observed. This decrease was directly proportional to the cooling period. A proportionate increase with cooling in the sialic-acid content of the casein micelle of chilled milk was noticed. Casein micelle isolated from chilled milk exhibited low opacity compared with the normal counterpart.

A decrease in micellar casein and an increase in soluble casein were observed in both buffalo and cow's milk, in proportion to the cooling period. Similar results were obtained when casein micelles were resuspended in milk dialysate and centrifuged.

Casein micelles from chilled milk showed different patterns on starch-gel electrophoresis compared with normal micelles. The intensity of the κ-casein band was relatively higher in the chilled samples. Gel-filtration studies suggest that some molecular rearrangement occurs in the casein micelle when milk is chilled.

The release of sialopeptide from micellar casein by rennet was not influenced by chilling. However, a decrease in the rate of turbidity development in renneted suspensions of casein micelles was noted in chilled milk, which suggests a change in the structure of the casein micelle.

No difference was noticed between buffalo and cow's milk in these respects.
Adsorption of casein components by halloysite and kaolinite
Authors: Mills O. E. , Creamer L. K.
Published: June 2009

The adsorption of whole casein and some of its constituent caseins by halloysite and kaolinite in the presence and absence of urea and 2-mercaptoethanol has been studied. The order of adsorption generally observed for both clays in the absence of urea and 2-mercaptoethanol was temperature sensitive casein component (TS) > αs1-casein B > αs1-casein A > β-casein in the pH range 7·5–9·5, confirming that these two clays have structurally similar surfaces. In the presence of urea and 2-mercaptoethanol the rate of adsorption on to halloysite increased, although the quantity adsorbed decreased and the relative affinities of the major casein components at pH 8 were altered. However, urea and 2-mercaptoethanol did not alter the relative affinities of the caseins to kaolinite, although the quantity adsorbed did decrease. The casein components are probably adsorbed as monomers, and it may be the superior dispersing properties of the urea solution that decrease the amount adsorbed. The halloysite structure was altered by absorption of urea and the altered relative affinities of the various casein components in the presence of urea can be ascribed to that effect.

The results support the hypothesis that adsorption occurs because the energy of the system is lowered due to changes in protein-solvent, clay-solvent and solvent-solvent (solvent structuring), as well as to electrostatic interactions.
Flavour defects in edible casein and skim-milk powder: II. The role of aliphatic monocarbonyl compounds
Authors: Walker N. J.
Published: June 2009

Aliphatic monocarbonyls have been quantitatively estimated in casein and skim-milk powder during storage. Concurrently these products have been evaluated organoleptically. A close relationship was evident between monocarbonyl level and the flavour or age of the lactic casein. Furthermore, the greater flavour stability of rennet casein and skim-milk powder was coupled with reduced monocarbonyl content. Fractionation of monocarbonyls into classes and individual compounds has shown that the higher levels in lactic casein compared with other low-fat products can be accounted for by a high level of acetone. The absence of appreciable quantities of other odd-numbered methyl ketones suggests that either acetone is derived from a non-lipid constituent of acid casein or decarboxylation of acetoacetate is specifically catalysed at acid pH. All methyl ketones identified in these low-fat dairy products were present in subthreshold concentrations. Saturated and unsaturated aldehydes were present at similar levels in stored lactic casein, rennet casein and skim-milk powder samples irrespective of their degree of musty or stale flavour.
Basal levels of prolactin in goat blood measured throughout a 24-h period by a rapid double antibody–solid phase radioimmunoassay
Authors: Hart I. C.
Published: June 2009

The development of a rapid, highly sensitive double antibody–solid phase (DASP) radioimmunoassay for ovine/caprine prolactin is described. The assay was applied to the measurement of basal levels of prolactin in the blood of 4 anoestrous lactating female, 4 anoestrous virgin female and 4 castrated male goats. For several hours after milking there was a chronic gradually decreasing release of prolactin in the lactating goats, such that the circulating levels of prolactin were, for 14–16 h of the day, at a much higher level than those in the virgin female or castrated male goats. The basal levels of prolactin in the castrated male goats (87–200ng/ml) were somewhat higher than those in the virgin females (47–77ng/ml). The effects of feeding and stress on prolactin levels are discussed.
The effect of manufacturing conditions on the setting rate of butter
Authors: Taylor M. W. , Dolby R. M. , Russell R. W.
Published: June 2009

The setting rate of butter during the first 5 h after manufacture was found to be increased by a higher maximum temperature during working, e.g. 15 as compared with 12·5 °C, or by a temporary rise in temperature to 18 °C for 30 min after working. A temporary lowering of temperature to 7 °C for 30 min, however, had no effect. The amount of working did not affect setting rate except where more prolonged working resulted in a higher final temperature in the butter.

When temperature conditions during and after working were standardized, it was found that temperature of pasteurization in either a Vacreator or plate pasteurizer or the presence of clumped fat in the cream had no effect on setting rate. The setting rate, however, was increased by Vacreator treatment as compared with plate pasteurization of cream or by low-pressure homogenization of cream after plate pasteurization.

Microscopic examination of butter samples showed much fewer intact fat globules in butter from Vacreator-treated or homogenized cream than in that from platepasteurized cream.

It is suggested that Vacreator treatment or homogenization of cream affect the setting rate of butter by causing changes in the fat-globule membrane which, in turn, influence the type of crystallization in the fat globules and the stability of the globules.
Carbohydrates of bovine κ-casein
Authors: Wheelock J. V. , Sinkinson G.
Published: June 2009

Comparison of the carbohydrates of κ-casein with those of the glycopeptides released by the action of rennin on whole milk showed that there are consistent differences between them, which are due to the presence of carbohydrates in para-κ-casein. d-Mannose, d-galactose, 2-acetamido-2-deoxy-d-galactose andN-acetyl neuraminic acid were invariably present in κ-casein.N-acetyl neuraminic acid was located almost entirely on the glycopeptides whereas the greater proportion of d-mannose was attached to the para-κ-casein. d-Galactose and 2-acetamido-2-deoxy-d-galactose were detected in both para-κ-casein and the glycopeptides. In the glycopeptides there are usually about 2 molecules of d-galactose to 1 molecule of 2-acetamido-2-deoxy-d-galactose. Carbohydrates are attached to only a proportion of para-κ-casein molecules. Carbohydrates could not be detected in αs- and β-casein.
Purification and properties of an extracellular proteolytic enzyme fromBacillus cereus
Authors: Islam M. A. , Blanshard J. M. V.
Published: June 2009

A milk-clotting proteolytic enzyme was isolated and purified from the culture filtrate ofBacillus cereusstrain x29 by fractionation with acetone or ammonium sulphate and subsequent column chromatography employing DEAE cellulose and DEAE Sephadex. The purified enzyme was found to be homogeneous by acrylamide gel electrophoresis from pH 3·5 to 8·6, with, a molecular weight of about 50000. The single absorption maximum of the native enzyme was at 277 nm and the value ofat 280 nm was 7·79. Purification resulted in a 9-fold enhancement of activity with 24 % yield. The optimum activity of the enzyme was at pH 8·0 at 40 °C with casein as the substrate. The enzyme was found to be most stable at pH 6·0 and was stable to freezing and freeze-drying. Heavy metal ions were found to inactivate the enzyme, but no metal ion activation was found. Enzyme activity was inhibited irreversibly by EDTA and reversibly by 1,10-phenanthroline. The enzyme has been identified as a Zn-containing neutral protease.
Studies on the milk composition of West African dwarf, Red Sokoto and Saanen goats at different stages of lactation: I. Total solids, butterfat, solids-not-fat, protein, lactose and energy contents of milk
Authors: Mba A. U. , Boyo B. S. , Oyenuga V. A.
Published: June 2009

Nine West African dwarf (Fouta djallon), Red Sokoto (Maradi) and Saanen lactating goats, hand-milked, were used for these studies, which lasted 12 weeks. The Saanen goats' milk was obtained weekly from the Western State Ministry of Agriculture and Natural Resources Urban Dairy Farm at Iwo Road, while similar samples were collected from the herd at the University of Ibadan Teaching and Research Farm. The goats were balanced for stage of lactation, namely early, mid- and late-lactation. They were each maintained on giant star grass (Cynodon nlemfuensis) ad lib.and 1kg dairy concentrate mixture daily.

The mean contents, with standard deviations, of the milks of Saanen, West African dwarf and Red Sokoto goats at mid-lactation respectively were: (in percentages), total solids 12·25±0·078, 18·18±0·392, 15·85±0·077; solids-not-fat (SNF) 8·91±0·142, 10·48±0·471, 10·53±0·140; butterfat 3·34±0·141, 7·78±0·621, 5·32±0·098; protein 3·04±0·139, 5·30±0·292, 4·74±0·021; lactose 4·56±0·167, 5·19±0·176, 4·77±0·053; energy (kJ/g dried milk), 21·08±1·11, 25·51±1·74, 22·17±0·51. Breed differences were significant (P< 0·01). The milk of West African dwarf goats contained more of these milk components than the milk of the Red Sokoto or Saanen goats. The Red Sokoto goats gave milk of higher content than did Saanen goats, even at an early stage of lactation.

Butterfat, protein, lactose and energy values were significantly affected by stages of lactation (P< 0·05) and tended to rise with advancing lactation; this was particularly so with West African dwarf goats.
The acid phosphatases of bovine leucocytes, plasma and the milk of healthy and mastitic cows
Authors: Andrews A. T. , Alichanidis E.
Published: June 2009

Some of the acid phosphatase isozymes of bovine leucocytes and plasma have been separated and partly characterized. About 80% of the phosphatase activity of leucocytes at pH 4·9 was particle-bound and about 8% was extractable with Amberlite CG-50 ion exchange resin. This extractable enzyme existed as a single electrophoretic component with a mol. wt of about 42000 and with optimum activity at pH 5·8. Kmforp-nitrophenyl phosphate was 1·6 mM at pH 5·8 and 0·4 mM at pH 4·9. At pH 5·8 orthophosphate (K1= 1·5 mM) and pyrophosphate (Ki= 4·1 mM) were competitive inhibitors. The enzyme was also strongly inhibited by F−, Al3+, IO4−and S2032−. The enzyme which was not extractable with Amberlite was very heterogeneous with respect to molecular weight. At the pH optimum (4·9), Kmforp-nitrophenyl phosphate was 0·4 mM and orthophosphate (K1= 2·3 mM) and pyrophosphate (K1= 2·1 mM) were competitive inhibitors. Other inhibitors included F−, Al3+, Hg2+, IO4−and tartrate. The enzyme extracted from plasma by Amberlite CG-50 treatment had properties similar to that extracted from leucocytes. Normal bovine milk contained a single acid phosphatase, but milk from cows with mastitis showed 3 electrophoretic isozyme bands, one being the same as in normal milk; the 2 additional bands were of leucocyte origin.
The effect of frequency of feeding on milk secretion in the Ayrshire cow
Authors: Thomas P. C. , Kelly Morag E.
Published: June 2009

Four Ayrshire cows in their second lactation were used in a 4×4 Latin square experiment to determine the effects of frequency of feeding on milk secretion. The animals were given a diet consisting of hay, sugar-beet pulp and dairy concentrates (34·9:19·7:45·5 on a dry-matter basis) either in 2 equal meals/d at 07.00 and 17.00 h or with the hay in 4 meals at 07.00, 12.00, 17.00 and 22.00 h and the sugar-beet pulp and concentrates in 24-h meals. Each feeding frequency was tested at 2 levels of feeding providing either 100 or 80% of the standard requirements for energy.

There were no significant effects of frequency of feeding on milk yield or on the milk content of fat, protein, lactose, solids-not-fat or total solids, but underfeeding depressed the yield of milk and of all milk constituents. Neither the frequency nor level of feeding had appreciable effects on the fatty-acid composition of the milk fat or on the blood glucose concentration, but in animals fed frequently plasma urea levels were lower than in animals fed twice daily and there was no postprandial peak in urea concentration.
Autoxidation in milk rich in linoleic acid: II. Modification of the initiation system and control of oxidation
Authors: Sidhu G. S. , Brown M. A. , Johnson A. R.
Published: June 2009

Factors contributing to the initiation of lipid oxidation in cow's and mare's milk containing high levels of polyunsaturated fatty acids were studied. Addition of H2O2just after milking, in slight excess of the stoichiometric amounts required to destroy ascorbic acid, delayed the development of oxidized flavours in cow's milk high in linoleic acid. Hydrogen peroxide treatment followed by the addition of α- or γ-tocopherols prevented lipid oxidation in cow's milk even when 0·1 mg Cu/l milk was added. When used separately in the presence of Cu these treatments were ineffective as was butylated hydroxyanisole treatment.

The lipid and ascorbic acid in mare's milk were remarkably stable to oxidation. Addition of 0·05 or 0·1 mg Cu/l, ethylenediamine tetraacetic acid, neocuproine, or H2O2had very little effect on the loss of ascorbic acid and lipid oxidation in mare's milk.
The production of sulphur compounds in Cheddar cheese and their significance in flavour development
Authors: Manning D. J. , Chapman Helen R. , Hosking Zena D.
Published: June 2009

A method is described for determining H2S, methanethiol and dimethyl sulphide in Cheddar-cheese headspace. Cheeses ranging in age from 2 to 12 months were analysed using a gas chromatograph equipped with a photometric detector. These cheeses were presented to a trained flavour panel for the assessment of quality and intensity of Cheddar cheese flavour.

An attempt is made to correlate the concentration of sulphur compounds in the headspace with the average flavour scores. The results suggest that the flavour intensity of the cheese is related to the concentration of methanethiol in the headspace.
Reproducibility of electronic cell counts in milk; a study of 5 further factors
Authors: Greer D. O. , Pearson J. K. L.
Published: June 2009

This paper is a sequel to a previous one in which a number of factors likely to influence the accuracy of counting somatic cells in milk was assessed; in the present work the effects of 5 other factors are investigated. In a study of storage time and temperature of milk samples fixed in formalin, a significant increase in cell count occurred after 5–7 d when samples were stored at room temperature (17–23°C), compared with those maintained at 4 °C. When manual and mechanical mixing of fixed samples were compared only marginal differences in cell counts were observed. An increase in cell counts followed manual dilution of milk samples in comparison with automatic dilution. The temperature of samples prepared for counting was also studied and no significant variations occurred between mean temperatures of 12·7 and 32·9 °C. The final factor evaluated was that of holding time before counting; using 4 cell-count levels it was observed that counts were acceptable up to 1½ h.
The reaction of αs1- and β-casein with ferrous ions in the presence of oxygen
Authors: Manson W. , Cannon J.
Published: June 2009

The reaction of αs1- and β-casein with ferrous ions and O2 has been studied. It has been found that phosphoseryl residues present in these proteins rapidly catalyse the oxidation of iron from the ferrous to the ferric state with the formation of stable ferric-phosphoprotein complexes and the consumption of the theoretical amount of O2. When, however, the phosphoseryl residues occurred in groups, the formation of ferric complexes was accompanied by uptakes of O2 in quantities significantly in excess of that required for the oxidation of ferrous to ferric iron.

The significance of these findings is discussed in relation to hypotheses which have been advanced concerning the possible biological function of phosphoprotein.
Heat stability of milk: influence of dilution and dialysis against water
Authors: Fox Patrick F. , Hearn Catherine M.
Published: June 2009

The marked precipitation of Ca phosphate found to occur at ~ pH 6·8 when milk is heated to high temperatures may account for the minimum in the heat coagulation time (HCT)–pH curve at ~ pH 6·8. Dialysis of milk against water for about 3 h converted a normal type A milk to one with type B heat stability characteristics by reducing stability in the region of the HCT maximum while increasing stability in the region of the minimum. Reduction of the concentration of urea, lactose, Na or chloride did not cause these changes and gross micelle structure appeared to be intact following short dialysis as indicated by turbidity and sedimentability. Dilution of milk with water increased stability at the minimum without significantly affecting stability at the maximum. Pre-heating at 80°C for 10 min precluded the effect of dilution but not of dialysis.
The effect of diet on the γ- and δ-lactone and methyl ketone potentials of bovine butterfat
Authors: Urbach Gerda , Stark William
Published: June 2009

The quantity of γ- and δ-lactones and of methyl ketones produced when bovine butterfat was heated in the presence of water vapour and the absence of air, and hence the flavour quality of the butterfat, varied widely with the diet of the lactating cows. There was a marked increase in the γ-dodecanolactone potential when the cows were transferred from pasture to a mixture of chopped lucerne hay plus crushed oats but not when they were transferred to lucerne hay only. Feeding crushed sunflower seeds, whose oil was protected against biohydrogenation in the rumen, but not feeding sunflower meal from which the oil had been extracted, raised the γ-dodec-cis-6-enolactone potential, lowered the saturated δ-lactone potential and the methyl ketone potential and simultaneously raised the proportion of linoleic acid in the butterfat at the expense of fatty acids up to and including C16.
Effect of incubation temperature on the development of lactic acid bacteria and their phages
Authors: Sozzi Tomaso , Poulin J.-Marc , Maret Roger
Published: June 2009

Thirty-one strains of mesophilic and thermophilic lactic acid bacteria and their respective phages were tested for their minimum, optimum and maximum multiplication temperatures. Culture growth was strongly influenced by temperature during the first few hours of incubation, but less so after 24 h. Most of the phages showed the same pattern of development as their hosts, but one phage lysing a thermophilic lactobacillus and 3 phages lysing mesophilic streptococci proved temperature-sensitive, having a lower maximum temperature than that of their hosts. One phage was unusual in that its minimum development temperature was 7 °C above that of its host. Differences in temperature sensitivity were insufficient to reduce risk of phage infection by temperature control in industrial processes.
Intermicellar relationships in rennet-treated separated milk: I. Preparation of representative electron micrographs
Authors: Green Margaret L. , Hobbs David G. , Morant Steven V.
Published: June 2009

Separated milk was treated with rennet at 30 °C for known proportions of the visually-determined clotting time. Samples were fixed with glutaraldehyde, which inhibited aggregation of casein micelles, mixed with agar, and stained sections examined. Bias in the preparation of the electron micrographs was minimized by replication, particularly in the early stages of sample preparation, and, for thin (60–90 nm) sections, by systematic selection of the areas examined.

Whole casein micelles, viewed in stereo micrographs of thick (about 1 μm) sections, had open, diffuse structures and their appearance did not change on treatment with rennet. Micrographs of thick sections taken at 90° to each other showed that casein micelles form a network-type of gel, with the same structure in all dimensions. Counts of micelles larger than about 20 nm diam. in fields of thin sections showed that each of 3 sets of fields was similar and representative for each sample. The number of micelles/μm2 appeared to increase between 60 and 130 % of the clotting time, but this change was not statistically significant.
Sub-structure of synthetic casein micelles
Authors: Knoop Anne-Marie , Knoop Ernst , Wiechen Arnold
Published: June 2009

Casein micelles of different composition were synthesized in various ways and their sub-structure was investigated with the electron microscope by means of thin sections. Earlier studies of Schmidt et al. (1974) using the freeze-fracturing technique had shown no differences in the sub-structure of natural micelles and artificial micelles containing Ca and casein only. Contrary to these results our present studies showed that for the production of synthetic casein micelles with the same sub-structure as the natural ones it is necessary to add at least 2 other ions to the casein solution besides Ca2+: these are phosphate and citrate. The citrate ions play an important role in forming the material of the dark framework of the micelles visible in electron micrographs of unstained thin sections. This supports the hypothesis of Pyne & McGann (1960) that casein micelles contain a citrate apatite.
Physico-chemical characteristics of casein micelles in dilute aqueous media
Authors: Fox Patrick F. , Nash Bridget M.
Published: June 2009

The heat stability and rennet coagulation time (second stage) of milk were reduced by brief dialysis against water. Destabilization appears to arise from a developed imbalance between Ca and phosphate plus citrate due to the very slow diffusion of Ca on dialysis. Average micelle size as indicated by permeation chromatography in porous glass CPG 10 was slightly reduced by dialysis for 24 h. Direct addition of low levels (10–100 mM) of NaCl to milk markedly reduced heat stability at pH > 7·0 (normal minimum) possibly due to dissociation of κ-casein, but increased rennet coagulation times; higher levels of NaCl decreased heat stability throughout the pH range 6·4–7·4.
Interaction of ionic materials with casein micelles
Authors: Green Margaret L. , Marshall Richard J.
Published: June 2009

A suspension of casein micelles in a milk-salts solution bound highly cationic polypeptides and charged surfactants extensively, and globular proteins and low molecular weight amines less extensively. All additives were bound equally to native micelles and to a rennet coagulum. The distribution of each additive between the micellar and soluble phases was constant over a wide range of concentration, indicating that the micelle contained a large number of equivalent binding sites. Additives that did not bind Ca2+ caused a decrease in the rennet coagulation time which was related to the charge on the additive and the amount adsorbed. Salmine affected the time course of the viscosity of milk treated with rennet in a similar way to increase in temperature, accelerating the aggregation phase. Extensively-bound additives protected milk against loss of coagulability by rennet on heating, but did not affect the extent of whey protein denaturation. They did not cause aggregation of micelles or produce significant changes in their size distribution, but did cause a decrease in micellar hydration. It was concluded that the additives were bound to the apatite and casein components of the micelle, causing a change in the environment of the κ-casein and para-κ-casein, which affected their properties.
Theory for the heat-induced coagulation of a type A milk
Authors: Parker Thomas G. , Horne David S. , Dalgleish Douglas G.
Published: June 2009

The theory of branching processes is used to derive a simple kinetic model for the heat-induced coagulation of a type A milk. Coagulation time-pH profiles and N depletion curves for the overall reaction can be fitted with the model, and most of the major properties for a milk exhibiting a type-A behaviour can be accounted for. Possible reactions for the heat-induced coagulation are also discussed in relation to the model.