bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of ultra-high-temperature (UHT) processing and of subsequent storage on the vitamin content of milk
Authors: Ford J. E. , Porter J. W. G. , Thompson S. Y. , Toothill Joyce , Edwards-Webb J.
Published: June 2009

The vitamin content of ultra-high-temperature (UHT) processed milk was compared with that of the original raw milk. Three processes were used. In the first, which caused no change in oxygen content, the milk was heated and cooled in a plate-type heat exchanger. In the second, the milk was again heated indirectly and then evaporatively cooled, leaving in the milk about one-third of the initial oxygen content. In the third process the milk was heated by direct steam injection and cooled by evaporation and contained little or no residual oxygen.

On processing and during subsequent storage for 90 days there was no loss of vitamin A, carotene, vitamin E, thiamine, riboflavine, pantothenic acid, biotin or nicotinic acid. There was little or no loss of vitamin B6or vitamin B12on processing, but up to 50% of each of these vitamins was lost during 90 days' storage. All the dehydroascorbic acid (DHA) and about 20% of the ascorbic acid (AA) was lost on processing. There was no further loss of AA during 90 days’ storage when no residual oxygen was present, but in milks containing more than about 1 ppm oxygen all the AA was lost within 14 days. About 20% of the folic acid was lost on processing; thereafter, as with ascorbic acid, the extent of the loss on storage depended on the residual oxygen content of the milk: in the absence of oxygen the folic acid was stable.
The digestion of fatty acids in the stomach and intestines of sheep given widely different rations
Authors: Sutton J. D. , Storry J. E. , Nicholson J. W. G.
Published: June 2009

The amounts of total lipid and fatty acids consumed, leaving the stomach and excreted in the faeces were examined in 4 sheep fitted with rumen and re-entrant duodenal cannulas. Diets of high (HM1) and low (CM1) roughage content were given at 0·9 times maintenance and the low-roughage diet was also given at 1·7 and 2·3 times maintenance. With all the rations more fatty acid left the abomasum than was consumed in the food, the difference being greater on ration CM1 than on ration HM1 and increasing irregularly with the amount of the low-roughage ration fed. Of the fatty acid entering the duodenum in the chyme, 72–89% was digested in the intestine. About 80% of the increase in fatty acids in the stomach was stearic acid and most of the remainder was palmitic acid. Almost all the polyunsaturated C18acids ingested in the food were hydrogenated in the stomach, and the amounts of oleic acid were also greatly reduced, although more oleic acid entered the duodenum in the chyme with ration CM1 than with ration HM1. The possible origins of the increase in fatty acids in the stomach are discussed.
The effect of the periodic feeding of linseed oil on the production and iodine value of milk fat
Authors: Wadsworth J. C.
Published: June 2009

A study was made of the changes in the iodine value of milk fat from cows following the feeding of linseed oil (450g) at intervals of 6 days. Three cows in midlactation and of differing age and breed were used. The experiment consisted of a series of 3 collection periods, each of 6 days' duration, with 12 days between periods. Three doses of oil were given (6 days apart) between periods 1 and 2, the last dose of oil being given immediately before the start of period 2. The mean iodine values for the 3 periods were 35·5, 40·5 and 34·7 respectively. There was a distinct pattern of change in iodine value with time after feeding the oil, a maximum of 45·5 being attained on the second day with a subsequent decline to 38·5 on the sixth day. Analysis of variance showed that these effects were significant and due to oil-feeding, whereas changes in yield and content of fat and production of milk could be accounted for by normal decline in lactation. It was concluded that the periodic feeding of a large dose of linseed oil produces a significant increase in the iodine value of milk fat and avoids the possible disadvantages of continuous fat supplementation.
Comparison of milks processed by the direct and indirect methods of ultra-high-temperature sterilization. II. The sporicidal efficiency of an experimental plant for direct and indirect processing
Authors: Franklin J. G. , Underwood H. M. , Perkin A. G. , Burton H.
Published: June 2009

The variation of sporicidal efficiency with processing temperature was determined for an experimental ultra-high-temperature (UHT) milk sterilizer operating alternatively as an indirect or as a direct heater. Whole milk was inoculated with large numbers of spores of Bacillus subtilis 786 and Bacillus stearothermophilus TH24, and the proportion of spores surviving the sterilizing process was calculated from dilution and colony counts on the untreated and treated milk. The results for B. subtilis spores were unreliable, and the dilution count results for B. stearothermophilus spores were influenced by the inhibitory effect of the UHT processed milk. The results for the colony counts of B. stearothermophilus spores were preferred as a basis for the comparison of the direct and indirect processes. Over the range of processing temperatures 137–145 °C it was found that the sterilizing temperature had to be 3–4 degC higher with direct heating than with indirect heating to give equal spore destructions.
Apparatus and milking techniques used in lactation studies with sheep
Authors: Treacher T. T.
Published: June 2009

A description is given of a simple milking apparatus for collecting the yields of individual ewes, and of the milking procedure used in studies of lactation in ewes of ‘mutton’ breeds. The incidence of mastitis, level of milk yield, some of the non-nutritional factors affecting the milk yield and the coefficients of variation of milk yield and composition are discussed in relation to data from 6 experiments in which ewes of mutton breeds were machine-milked twice daily for 6–9 weeks of lactation.
The composition of ewe's milk fat during early and late lactation
Authors: Noble R. C. , Steele W. , Moore J. H.
Published: June 2009

The composition of ewe's milk during the first 4 days of lactation and on the 100th day of lactation was investigated. The total fat content was highest (17· 9%) on the day of parturition but decreased rapidly to reach a level on the 2nd day after parturition that was similar to that observed on the 100th day of lactation (9·9 %).

The concentration of octadecenoic acid, which was the major fatty acid of ewe's milk, was very much higher in early lactation than in late lactation. As the concentration of octadecenoic acid decreased the concentration of the shorter chain fatty acids (6:0−14:0) increased. The major octadecenoic acid was the cis-9 isomer. However, the proportion of the trans-11 isomer increased from 5·5 % of the total octadecenoic acid concentration in early lactation to 11·9 % in late lactation. Although linoleic acid remained a minor component of the fatty acids of the milk during lactation, its concentration increased from less than 1 % during early lactation to 1·4 % by the 100th day of lactation.
The temperature-dependent dissociation of β-casein from bovine casein micelles and complexes
Authors: Downey W. K. , Murphy R. F.
Published: June 2009

The temperature-dependent dissociation of β-casein from the casein micelles of milk and from the soluble casein complexes of colloidal phosphate-free (CPF) milk was investigated by high-speed centrifugation and gel-filtration. The percentage of the total casein in supernatants prepared by high-speed centrifugation of mid-lactation milks increased from approximately 6 to 15% on cooling the milks from 30 to 5 °C; β-casein accounted for about 46% of this increase, while αs-and κ-casein constituted 30 and 23%, respectively. On gel-filtration both of skim-milk and CPF milk on Sepharose 2B at 0, 2, 5, 10 and 25 °C, maximum amounts of free β-casein (c. 60% of total) were obtained at 5 °C. The remainder of the β-casein appeared to be more strongly bound to the αs- and κ-casein and may be involved in the internal cohesion of casein micelles. The free β-casein of both milk preparations appeared to be in equilibrium with the bound β-casein. On Sephadex G-200 columns at 5 °C, approximately 5 and 60% of the β-casein of skim-milk and CPF milk, respectively, was eluted in the free form in the expected position for a globular protein of molecular weight about 200000. At low temperatures, particularly at 5 °C, colloidal phosphate appeared to play an integrating role in the association of over half the total β-casein with the other casein components of native micelles. However, when the equilibrium between micellar and free β-casein was disturbed by gel-filtration on Sepharose 2B, the presence of colloidal phosphate did not prevent the release of most of the β-casein from casein micelles. Some problems encountered in the use of densitometry for the estimation of individual caseins on electropherograms are described.
Low resolution nuclear magnetic resonance in the determination of moisture in cheese curd
Authors: Berridge N. J. , Crean Elizabeth , Mansfield P. B.
Published: June 2009

Nuclear magnetic resonance was used to follow the decrease in moisture in curd cooled to solidify the fat as whey was exuded. The results did not correlate closely with those of moisture determinations by drying at 98 °C partly because of the relaxing effect of the solid curd structure when in close proximity to the whey. This effect was diminished as the whey left the curd, so that whey out of the curd was more readily saturated with radio-frequency energy and therefore absorbed less energy than whey in the curd when high intensity fields were used. The saturation effect could also be used to follow approximately the exudation of the whey.
Nutritional deficiencies of co-precipitate for the growth of a strain of Lactobacillus acidophilus
Authors: Keogh Barbara P.
Published: June 2009

The nutritional deficiencies of co-precipitate as a growth medium for a strain of Lactobacillus acidophilus have been studied. Acid production by this organism was insignificant in a medium composed of 4% low-calcium co-precipitate and 5% lactose.

Additions of the amino acids phenylalanine, tyrosine, valine, cysteine and threonine as well as of nicotinic acid, manganese, magnesium and citric acid all increased acid production.

When only half the milk solids of skim-milk powder was replaced by the coprecipitate, fortification with manganese only was required.
A study of methods for estimating the cell content of bulk milk
Authors: Pearson J. K. L. , Wright C. L. , Greer D. O.
Published: June 2009

Four methods of estimating the cell content of bulk milk were studied, correlated statistically and their degree of reproducibility estimated. The relative merits of the 4 methods are discussed, and the need for defining the object of testing before selecting a test is stressed. If designed for use in a programme for mastitis control, or the control of milk quality based on cell content, each country must choose a screening test or a precise cell-counting technique, depending on the availability of laboratory resources, extension advisory services and other economic factors.

Screening tests studied were the California Mastitis Test (CMT) and the Brabant Mastitis Test (BMR), the former showing a correlation coefficient of 0·817 against the Electronic Cell Count (ECC) method in 320 samples. The more objective BMR correlated well with the ECC method, showing a correlation coefficient of 0·987 for 406 samples. Direct microscopic counts (DMC) were correlated with a centrifugal method and with a chemical method of preparing samples for electronic cell counting. For 430 samples in each case the correlation coefficients obtained were 0·930 and 0·966 respectively. The 2 ECC techniques were compared using 430 samples, and a very close relationship was found (r=0·988).

For regular examination of large numbers of milk samples using the electronic cell counter we consider the chemical method of sample preparation more suitable than the centrifugal method. Differences in the reproducibility and accuracy of both tests are negligible, but the former procedure is quicker, more economical in terms of cost, and more adaptable to a national testing programme.
The specificity for κ-casein as the stabilizer of αs-casein and β-casein II. Replacement of κ-casein by detergents and water-soluble polymers
Authors: Green Margaret L.
Published: June 2009

The cationic detergent cetyltrimethylammonium bromide (CTAB), the anionic detergents sodium lauryl sulphate and sodium deoxycholate, and the nonionic detergents Tween 20, Tween 80 and Brij 35, and lecithin, starch, glycogen, chondroitin sulphate and polyethylene glycol, were tested for their ability to replace κ-casein in stabilizing αs- and β-caseins against precipitation by Ca2+. Of the materials tested, CTAB and Tween 20 stabilized both caseins and Brij 35 stabilized only αs-casein. Analytical ultracentrifugation of mixtures of CTAB with each casein and of Brij 35 with αs-casein indicated that both detergents acted by disrupting the casein aggregates and complexing with the monomers. Addition of CaCl2 did not aggregate the Brij 35–αs-casein complex. It is concluded that the basis of the stabilization phenomenon involves specific interactions between κ-casein and αs-casein or β-casein at mainly hydrophobic sites.
Efficiency of utilization of energy and nitrogen for milk secretion by buffaloes fed various levels of concentrates
Authors: Shukla K. S. , Ranjhan S. K. , Netke S. P.
Published: June 2009

Twenty-four Murrah buffalo cows were divided into 4 groups and were fed 0·3, 0·4, 0·5 or 0·6 kg of concentrate mixture per litre of milk produced. Energy and N balance studies were conducted on 2 animals from each group in the sixteenth and seventeenth weeks of the study. The efficiency of conversion of gross energy into milk energy ranged from 10·9 to 12·7%. The efficiency of conversion of metabolizable energy (ME) and ME above maintenance into milk energy ranged from 25·0 to 32·2% and from 51·7 to 78·6% respectively. Differences amongst groups were not significant for all the 3 parameters.

The conversion of digestible N into milk N varied between 23·6 and 27·3% in different groups. The efficiency of utilization of metabolizable N for milk production ranged between 47·6 and 56·4%. Various groups however did not differ significantly from each other in these respects.
The removal of fission products from milk: The use of the baby monkey (Macaca irus) for the nutritional evaluation of milk treated by 2 processes
Authors: Cohen B. , Ashworth Margaret , Glascock R. F. , Bryant D. T. W.
Published: June 2009

The nutritional quality of milk treated by 2 previously described processes for the removal of cationic fission products has been evaluated by the use of the baby monkey (Macaca irus).

The first process involves acidification of the milk to pH 5·2–5·3 and, when the treated milk was tested on baby monkeys, it was found to be nutritionally unsatisfactory. This result confirmed those previously obtained with baby pigs, from which it was concluded that the process cannot be recommended for the treatment of milk intended for young babies.

Two resin beds are used in the second process and no acidification is involved. Milk treated by this process was first tested on baby rats and pigs and then on baby monkeys. No change in the nutritional value of the milk was detected and it was concluded that this is the process which should be used if it should ever become necessary to remove fission products from milk intended for young babies.
An electron-microscope study of the structure of Domiati cheese
Authors: Abd El-Salam M. H. , El-Shibiny Safinaz
Published: June 2009

A technique is described for preparing ultrathin sections from cheese for electron-microscopic examination. The internal structure of fresh Domiati cheese was found to be composed of a framework of large, spherical casein aggregates held by bridges and enclosing fat.

After pickling, the casein aggregates were partly disintegrated into small spherical particles forming a loose structure.
The influence of some physical characteristics of the milking machine on the rate of new mastitis infections
Authors: Thiel C. C. , Cousins Carol L. , Westgarth D. R. , Neave F. K.
Published: June 2009

Large differences in new infection rates occurred with half-udder milking machines in which one half of the cluster operated substantially free from vacuum fluctuations while the other half was subjected to various combinations of different types of fluctuation in vacuum. To increase the rate of new infection all teats were contaminated before and after each milking by immersion in a suspension of Streptococcus agalactiae and Str. dysgalactiae. A series of short-duration trials indicated that neither irregular nor cyclic fluctuations in vacuum acting alone were able to increase new infection rate. However, either the Nyhan and Cowhig irregular fluctuation, or a variant of it in combination with cyclic fluctuations in vacuum, was able to do so under the particular experimental conditions used.
Seasonal variations in the composition and thermal properties of New Zealand milk fat: I. Fatty-acid composition
Authors: Gray I. K.
Published: June 2009

The fatty-acid composition of 17 samples of New Zealand milk fat obtained throughout one dairy season is reported.

The weight percentage of butyric (C4:0) acid was significantly correlated with that of caproic (C6:0) acid and that of caprylic (C8:0) acid. Percentages of C6:0and C8:0showed a highly significant correlation with each other and with weight percentages of capric (C10:0) and lauric (C12:0) acids.

There was a highly significant negative correlation between palmitic (C16:0) and stearic (C18:0) acids and between C4:0and C16:0acids. Oleic (C18:1) acid showed significant negative correlations with C8:0, C10:0, C12:0, myristic (C14:0) and C16:0acids.
A rennin-sensitive bond in αs1Β-casein
Authors: Hill R. D. , Lahav E. , Givol D.
Published: June 2009

Rennin acts on a specially sensitive bond in αs1B-casein to produce a basic peptide containing residues 1–23 of the original protein. At pH 6·4 and 30°C, the action is specific and rapid, the kinetic constants beingKm4·5×10−4M,Kcat3·8 s−1, andkcat/Km0·85×104s−1M−1. Pepsin, and a protease impurity in the acid phosphatase from wheat germ, have a similar action.
Influence of sympathomimetic drugs on the motility of bovine teat muscles
Authors: Peeters G. , de Bruycker Regina
Published: June 2009

Spontaneous rhythmical contractions of the teats of living cows were recorded by a plethysmographical method. These contractions were inhibited by isoproterenol, adrenaline, isoxsuprine and phentolamine, but were activated by phenylephrine. Noradrenaline induced activation which was often followed by inhibition.

These results obtained in vivo were in agreement with responses obtained in vitro. Apparently beta sympathomimetic effects are evoked easily under in vivo conditions.
Heat stability of milk: influence of colloidal calcium phosphate and β-lactoglobulin
Authors: Fox P. F. , Hoynes M. C. T.
Published: June 2009

Reduction of the level of colloidal calcium phosphate (CCP) progressively increased the heat stability of milk at pH values <~7·0 and increased the pH of maximum stability. Removal of 40% CCP also stabilized the system at the pH of minimum stability, but removal of ≥60% CCP rendered milk very unstable at pH values >7·2, an effect not offset by a 4-fold increase in κ-casein concentration. Doubling CCP had a slight destabilizing effect in the pH range 6·5–7·5.

Addition of β-lactoglobulin to serum protein-free casein micelles had a marked destabilizing effect at pH values > ~6·8, but increased stability in the pH range 6·4–6·8. β-Lactoglobulin had a similar and more apparent effect on the heat stability of Na caseinate dissolved in milk diffusate.

It is suggested that rather than being a stabilizing factor responsible for the maximum in the heat stability-pH curve, the true effect of β-lactoglobulin is to shift the curve to more acid pH values (reason unknown) and to sensitize the caseinate system to heat-induced Ca phosphate precipitation at pH values > ~7·0. Low stability at ~pH 7·0 introduces an apparent maximum in the heat stability-pH curve at ~pH 6·8, but this has no independent existence. At pH values >7·2, increased protein charge more than off-sets the influence of heat-precipitated CCP and stability again increases in micellar but not in soluble casein systems.
Milk-gel structure. IV. Microstructure of yoghurts in relation to the presence of thickening agents
Authors: Kalab Miloslav , Emmons D. B. , Sargant A. G.
Published: June 2009

The effects of 3 different thickening agents on the microstructure of yoghurt were examined by scanning and transmission electron microscopy. Unsupplemented yoghurt consisted of casein micelles fused together and linked in long chains; they seldom appeared in clusters. The addition of 0·5% gelatin caused no observable change in the yoghurt structure. Carrageenan (0·4%) formed a markedly fibrillar microstructure which connected large clusters of casein micelles. The fibres were thin and long and no free terminations were observed. Pregelatinized waxy maize starch (2%) appeared under scanning electron microscopy in the form of short fibres and sheets. The fibres frequently had free terminations and only some of them were connected with small clusters of casein micelles. Transmission-electron microscopy did not distinguish between pregelatinized starch and carrageenan additives.
Variations in the susceptibility of lactating and non-lactating bovine udders to infection when infused with Escherichia coli
Authors: Bramley A. J.
Published: June 2009

Small numbers of Escherichia coli were infused into both lactating and non-lactating udders. Twelve of the 17 lactating quarters infused became infected, and all 12 showed clinical symptoms of udder disease. The 5 lactating quarters which did not become infected all had pre-infusion somatic cell counts > 300000 cells/ml milk, whilst all the quarters which became infected had cell counts < 300000 cells/ml milk. E. coli was subsequently recovered from only 6 of the 16 non-lactating quarters infused. In only 2 of these quarters did clinical infection follow, both quarters being in a cow infused 2 d before calving. The remaining 4 quarters from which E. coli was recovered were all negative within 5 d of infusion. These differences in susceptibility are discussed, particularly with reference to the frequent occurrence of coliform mastitis at and shortly after calving.
Heat stability characteristics of ovine, caprine and equine milks
Authors: Fox P. F. , Hoynes M. C. T.
Published: June 2009

Ovine and caprine milks showed a marked stability maximum at ~ pH7 in their heat-stability/pH curves, but became very unstable at higher pH values. A low level of κ-casein appears to be responsible for this low stability of ovine milk; β-lactoglobulin offsets the stabilizing influence of κ-casein at lower pH values. Removal of colloidal calcium phosphate from ovine or caprine milks had very little influence on their heat stabilities and it was necessary to reduce the concentration of soluble salts to a very low level before an effect was observed. At the pH of maximum stability ovine and caprine milks, although quite variable, had stabilities in the same range as bovine milks. Equine milk was very unstable to heat and the shape of the heat-stability/pH curve of most individual samples was similar to ovine and caprine milks.
Inhibitory effect of adrenaline on oxytocin release in the ewe during the milk-ejection reflex
Authors: Barowicz Tadeusz
Published: June 2009

Milk-ejection activity was determined in the blood plasma of ewes during normal milking and during milking when adrenaline was injected intravenously before or after udder stimulation. It was found that administration of adrenaline either before or after udder washing, decreased the oxytocin concentration and milk yield but increased the yield by hand-stripping. Adrenaline also retards the average time for peak oxytocin concentration. These results and the use of a β-receptor blocker to inhibit the effect of adrenaline at the myoepithelial cell level indicate that in ewes adrenaline can prevent the release of oxytocin from neurohypophysis.
Thermal denaturation of α-lactalbumin and β-lactoglobulin in cheese whey: effect of total solids concentration and pH
Authors: Hillier Robyn M. , Lyster Richard L. J. , Cheeseman Gordon C.
Published: June 2009

Measurements of residual native protein remaining after heat treatment of cheese whey have been made using quantitative polyacrylamide gel electrophoresis. The results have been expressed in terms of kinetic constants. The effect of concentration was investigated up to 3 times the normal total solids content, dialysis treatments were used to study the effect of non-protein constituents, and the effect of pH was studied at pH 4, 6 and 9. The results indicated that increased total solids (TS) concentration slowed the denaturation of β-lactoglobulin A and B (β-lg A, β-lg B) but hastened the denaturation of α-lactalbumin (α-la). However, increased lactose concentration slowed the denaturation of both α-la and β-lg, perhaps by preventing formation of heat-induced complexes. Increased Ca concentration, up to 0.4 mg/ml, tended to slow the denaturation of both proteins, but further increase in Ca up to 0.9 mg/;ml produced little effect. The rate of denaturation of both α-la and β-lg was slower at pH 4 than at pH 6 or 9, and was probably slowest at the isoelectric point. However, not all the changes associated with pH could be explained in terms of net molecular electrostatic charge. The genetic variants of ′β-lg showed different heat stabilities – below 90 °C β-lgA was more stable than β-lgB, but above 90 °C the situation was reversed at all TS concentrations, and pH 6. However, at pH 4 and 9, °-lgA was less stable than °-lgB over the entire temperature range at normal concentration.
The carbohydrate portions of milk glycoproteins
Authors: Jollès Pierre
Published: June 2009

k-Casein is the main glycoprotein of cow's milk. Its polysaccharide part is O-glycosidically linked to threonine residue 133. It contains only 3 different sugars (Gal, GalNAc, NeuNAc), but a microheterogeneity has been detected at the sugar level. Two main polysaccharides have so far been characterized. The structure of the trisaccharide is NeuNAc α → 3 Gal β1 →3 GalNAc; the tetrasaccharide contains one additional sialic acid. The polysaccharide part of ovine k-casein resembles that of bovine k-casein, but contains also N-glycolyl neuraminic acid. Human k-casein contains 3 times more carbohydrate than bovine k-casein with 2 additional sugars, GlcNAc and Fuc. The various polysaccharide parts isolated from bovine colostrum k-caseinoglycopeptide are much more complex than those obtained from the normal glycopeptide, indicating an evolution of the sugar part as a function of time after parturition. Some aspects of the secondary structure of k-casein and the role of the sugar part are discussed. The carbohydrate moiety of another milk protein, human lactotransferrin, is also discussed briefly. It is comprised of 2 identical glycan groups, N-glycosidically linked to the protein, and quite different from the k-casein carbohydrate moiety.
The binding of β-casein to hydroxyapatite: the effect of phosphate content and location
Authors: Sleigh Robert W. , Sculley Thomas B. , Mackinlay Antony G.
Published: June 2009

The elution behaviour of β-casein from columns of hydroxyapatite has been studied and the effect examined of the enzymic addition of an extra phosphate residue. When the additional phosphate is located near pre-existing phosphate residues stronger binding to hydroxyapatite is observed. When the additional phosphate is remote from the pre-existing phosphates no increase in strength of binding is observed. It is suggested that the clustering of phosphate residues which characterizes αs- and β-caseins can be rationalized on the basis that it facilitates cooperative interactions between these phosphates and the Ca phosphate of the casein micelle and/or basic residues within casein polypeptide chains.
Effect of stage and number of lactation on the yield and composition of cow's milk
Authors: Rook J. A. F. , Campling R. C.
Published: June 2009

The effects of stage of lactation and of age on milk and composition yield of cows kept under controlled conditions of feeding and management were investigated. Two groups each of 3 Friesian heifers were used: one group (A) was given a daily diet of 18 lb hay and concentrates at the rate of 3·8 lb/10 lb of milk and kept on experiment throughout the first 3 lactations; a second group (B) was given the same amount of hay and a constant daily amount of concentrates of 10·7 lb and was kept on experiment throughout the 1st lactation only.

The total yields of milk and peak yields for the 1st lactation were similar in both groups. In all the cows, fat content was high early and late in lactation and varied little throughout the mid-lactation period. With cows of group A, the content of solids-not-fat declined until about the 5th week of lactation and then remained steady until a marked rise occurred late in lactation. With cows of group B, however, the content of solids-not-fat was at a minimum between the 5th and 10th weeks of lactation and then increased progressively until late lactation when a more marked rise occurred. Lactose content increased rapidly in the first few days of lactation and then remained constant for several months, eventually declining late in lactation. Characteristic changes were also observed in the contents of total protein, and of the various protein fractions, and of the major minerals of milk.

The concentrations of all major constituents in milk secreted from the 2nd–5th months of lactation tended to decrease from lactation to lactation.

The results are discussed in relation to the development of knowledge of the changes in milk composition throughout lactation.
Steam distillation of taints from cream. XI. The use of benzyl mercaptan (35S) in a study of its vapour/liquid equilibrium relationships
Authors: Walker N. J.
Published: June 2009

Solutions of labelled benzyl mercaptan-(35S) in water and cream were subjected to steam distillation in a continuous vaporization equilibrium still, and the concentrations of mercaptan in distillates and residues were obtained by measurement of the radioactivity in toluene extracts.

In the steam distillation from aqueous solution the vapour/liquid equilibrium relationship was not linear. The vapour/liquid equilibrium coefficient increased from 73 to 108 over the range of concentrations 0·01–0·05 ppm. in the liquid fraction at the time of partition.

In the steam distillation from cream containing 30% fat the relationship was linear, with an equilibrium coefficient of 1·35 over the range 0·1–0·6 ppm. in the cream at the time of partition.

The values of the vapour /liquid equilibrium coefficients are of the same order as those reported previously, 105 and 1·30, respectively, for which estimations were made by an absorption method.

The butterfat/water partition coefficient for benzyl mercaptan was found to be 160, which is consistent with the large difference found between the steam volatilities of the substance from water and from cream.
Seasonal variation in the viscosity index and adhesive strength of casein from the milk of individual cows
Authors: Southward C. R. , Dolby R. M.
Published: June 2009

The viscosity index and adhesive strength of casein from the milk of 6 individual cows were determined on samples collected regularly throughout the 9-month dairying season. The viscosity index of the casein from each cow showed a seasonal decline while the adhesive strength showed a general increase during this time. Casein from one cow had a consistently low viscosity index attributed to the presence in it of a rare genetic variant of α-casein. It is suggested that the variations in viscosity index and adhesive strength are lactational rather than seasonal.
Factors affecting the viscosity of caseinates in dispersions of high concentrations
Authors: Hayes J. F. , Southby Pamela M. , Muller L. L.
Published: June 2009

The physical effects of various cations in caseinate dispersions of high concentrations were investigated over a range of temperature and pH.

With calcium and strontium the temperature-viscosity relationships of the caseinates were abnormal in that the viscosity decreased rapidly from 30 to about 40 °C and a gel formed at temperatures in the region of 50–60 °C. On cooling, the gel reliquefied. No gel formed with barium, aluminium or magnesium. On cooling, magnesium preparations separated into 2 phases.

The supernatant phase from the magnesium caseinate and a corresponding phase prepared by centrifuging the calcium caseinate showed depletion ofα-casein and enrichment ofκ-casein andβ-casein. The supernatant phase from the calcium caseinate showed the reversible gel formation on heating. The magnesium supernatant phase did not.κ-Casein and a mixture ofκ- andβ-caseins gave reversible gels at similar levels of calcium and pH.

For reversible gel formation to occur, calcium caseinate was required to be in fairly high concentration, to have a calcium content of about 1·0% of the protein and to be within the pH limits 5·2–6·0. The temperature at which gelation occurred was affected by the concentration of calcium and protein and by pH.

The behaviour of the material was compared with that of methyl cellulose with and without addition of urea.

Some potential commercial applications of the findings on viscosity relationships are outlined.
The folic acid activity of some milk foods for babies
Authors: Ford J. E. , Scott K. J.
Published: June 2009

Folic acid activity was determined for National Dried Milk and for 5 proprietary dried milk foods for babies, for a proprietary liquid milk baby food and for 8 brands of tinned evaporated milk. For comparison, values were determined for mature breast milk, for raw bulk cow's milk, for bottled pasteurized cow's milk and for goat's milk.

Human milk and raw and pasteurized cow's milk all had much the same folate activity, equivalent to about 54 µg folic acid/1. Values for goat's milk were much lower, around 6 µg/1.

Values for the reconstituted baby milks ranged from 9 to 65 µg/1, though only 2 of the products had markedly lower values than breast milk. The question is discussed whether the folic acid requirement in infants can be met by formulas based on cow's milk without having recourse to folic acid supplementation.
Studies on the change in the properties of the fat globule membrane during the concentrating of milk
Authors: Cheeseman G. C. , Mabbitt L. A.
Published: June 2009

Previous work had shown that when milk is boiled in a climbing film evaporator a reaction occurs between the casein micelles and the fat globule membrane, probably at the liquid–gas interface. It now appears that the micelle–globule complex is formed by combination of the κ-casein components of the micelles and the membrane of the fat globule. The reaction is not significantly affected by increases in concentration of individual constituents, or by changes in temperature or pH.

The history of the milk before its concentration is an important factor in its subsequent behaviour. Thus, cooling and stirring of the milk during storage, as normally occurs in a bulk collection tank, promotes the reaction in the evaporator and, for some milks, is essential for starting the reaction.

A high retention of whey by curds made from the concentrated milks, diluted with water to their original volume before renneting, indicates that curd properties other than fat retention are also altered during concentration.
Errors in fat testing of composite milk samples
Authors: McDowell A. K. R.
Published: June 2009

Analyses were made at the Institute chemistry laboratory over 2 dairy seasons of 900 composite milk samples prepared for routine fat testing at 2 dairy factories and held at ambient temperature. The composites, which were preserved with mercuric chloride, frequently had high free fat acidities and high bacterial and mould counts.

At one factory, where the composites were sampled at 85−90 °F, the samples contained incompletely dispersed fat. Werner Schmid fat values for 83 milks pipetted immediately after factory sampling were lower on average by 0·084±0·089% than values obtained for the same samples after high-speed mixing at 115°F. At the other factory, where the samples were mixed at 98–103°F, Werner Schmid tests on 56 milks showed a corresponding difference of only 0·033±0·047%.

For 273 factory composites, mixed at high speed, results by the Babcock test and by the Gerber test averaged, respectively, 0·015±0·019% and 0·059±0·054% higher than those by the Werner Schmid test.

High bacterial and mould counts in factory composites were attributed to contamination from unsterilized bottles and stoppers and to failure of factory staff to mix the contents of each bottle after the daily addition of milk. Low bacterial and mould counts and negligible increases in free fat acidity were found in composites made up from factory milk in the Institute laboratory in sterilized bottles, kept at ambient temperature and swirled daily. Composites made up from fresh farm milks and held at 38–40°F remained in good condition for sampling after warming to 98–103°F but showed wide variation in free fat acidity.

Rises in free fat acidity occurred only in composites preserved with mercuric chloride. Other preservatives, however, were less effective in preventing bacterial growth at ambient temperatures.

Increases in free fat acidity up to 10 (ml N alkali/100 g fat) had no effect on results in the Babcock tests but caused a slight rise with the Gerber tests. Acidities over 20 caused a decrease in Babcock and a further rise in Gerber values.

It is suggested that fat destabilization in composite samples could be minimized by avoiding rises in temperature during transport of fresh daily samples from farm to factory, by holding composites at 55–60°F and by mixing after each daily addition of milk.
The composition of rumen fluid from cows fed biuret and urea
Authors: Waite R. , Wilson Agnes G.
Published: June 2009

The effect on the chemical composition of rumen fluid of replacing oilcake nitrogen by either biuret or urea N in the concentrate part of the ration for cows has been investigated. The biuret treatment produced the highest concentrations of NPN and the lowest concentrations of ammonia N in the fluid, whereas the urea treatment gave rise to higher concentrations of NPN than did the oilcake treatment and the highest ammonia N concentrations of the 3 diets. It is unlikely, however, that the differences in either peak or mean ammonia concentrations between the biuret and urea diets, if they occurred in lactating cows receiving these diets, would be sufficient to affect milk production. The concentration of ammonia N in the rumen liquor of cows on the biuret diet increased progressively up to the 5th to 8th week of feeding this diet. The different dietary treatments did not result in any marked differences in the concentrations of total volatile fatty acids in the rumen fluids or in the proportions of acetic, propionic and butyric acids in the total fatty acids.
The use of single or composite milk samples for the determination of fat
Authors: O'Keeffe M. G.
Published: June 2009

Samples were tested for fat percentage from every consignment of herd bulk milk from 10 herds over a period of 12 months. The mean monthly within-herd variance was 0·043. Also, triplicate samples were taken from 8 herd bulk supplies for 8 days and tested in duplicate and an analysis of variance was applied to the within-herd fat percentage in order to find the contribution sampling, testing and biological variances. It is shown that when dealing with tanker-collected milk where composite samples are not used the testing accuracy is secondary to frequency of sampling. By combining the variances in the formulae given, the accuracy of different systems may be obtained and compared using either single tested or composite samples.
The prediction of dairy performance of cows from the lactation induced by treatment with oestrogen
Authors: Naito M. , Kano Y. , Okubo E. , Nemoto H. , Miya T. , Kashiwagi K. , Sakurai M. , Katsuki T. , Morita K.
Published: June 2009

Lactation was induced in 30 Holstein heifers by treatment with synthetic oestrogen only. The average age of the heifers at the start of treatment was 16·6 months and the average lactation yield 1072 kg of milk with a fat content of 3·43% given in 241 days. Subsequently, 22 of these animals gave a normal lactation starting at an average age of 31 months, with yields of 3980 kg milk with a fat content of 3·31% given in 294 days. The induced lactation was slightly associated with reproductive problems and growth of the animals was normal. There was a good within-cow correlation between the yield and composition of the milk obtained in the 2 lactations. The correlation coefficients between the total production of the milk in the normal lactation and the total yield and peak production in the induced lactation were 0·718 and 0·785 and that between the average percentages of fat in the milk obtained in the 2 lactations was 0·718.

It is possible to predict dairy performance from the performance during the induced lactation, but before the procedure can be recommended for general use the question whether it may induce reproductive difficulties requires further investigation.
A laboratory study of continuous fermentation of skim-milk for the production of sour curd cheese
Authors: Linklater P. M. , Griffin C. J.
Published: June 2009

The feasibility of 2-stage continuous fermentation of skim-milk to produce sour curd cheese (quarg) has been established. The first stage was a stirred pH-stat fermenter, operated at pH 5·4, 5·6, 5·8 and 6·0, in which the operating pH was maintained by inflowing fresh milk. The remaining fermentation down to pH 4·7 was carried out by a procedure which simulated a second-stage plug flow fermenter (i.e. one in which forward velocity was as constant as possible at all points of the crosssection).

Skim-milk powder was dissolved to give 8, 10, 14 and 20% solids in the reconstituted milk. Maximum productivity of fermented milk solids was obtained with reconstituted milk containing 20% solids and operation of the first-stage fermenter at pH 5·4. This 2-stage continuous fermentation gave a total residence time of about 5 h, which represents a rate of production 4·8 times that obtainable in 24 h in a batch fermenter of the same fluid capacity filled once daily with the same reconstituted milk.
Bovine milk acid phosphatase: II. Binding to casein substrates and heat-inactivation studies
Authors: Andrews A. T.
Published: June 2009

The acid phosphatase of bovine milk was further purified to yield enzyme with an activity of about 2 units/mg. This was almost 105 times the activity present in milk and enabled a detailed study of heat inactivation to be made, together with further measurements on binding to casein substrates.

The effectiveness of caseins as inhibitors of the hydrolysis of p-nitrophenyl phosphate by acid phosphatase paralleled the phosphate content of the casein molecules, so that αs1-casein A was a more potent inhibitor with a K1 of 1·7 mM than β-casein A1A2 (K1 = 4·3 mM), which in turn was more inhibitory than κ-casein A (K1 = 5·9 mM).

The heat inactivation of acid phosphatase followed first-order kinetics at pH 4·9, 5·2 and 6·7 and values of E, the activation energy, were between 2·4×105 and 3·0×105 J mole −1 in all cases, consistent with simple protein denaturation. The presence of 1% αs1-casein A, 1% β-casein A1A2, 1% κ-casein A, 1% isoelectrically precipitated ‘whole’ casein and 1% fresh raw milk provided no substrate protection at pH 5·2 or 6·7. Acid phosphatase was somewhat less heat stable at pH 6·7 than at pH 4·9, but may be expected to survive typical milk pasteurization conditions almost completely. However, conventional milk sterilization or ultra-high-temperature (UHT) processes would be expected to give total inactivation.
Comparison of the rates of proteolysis during ripening of Cheddar cheeses made with calf rennet and swine pepsin as coagulants
Authors: Green Margaret L. , Foster P. M. D.
Published: June 2009

The rates of proteolysis during ripening were followed in cheeses made with either calf rennet or swine pepsin and either starter or δ-gluconic acid lactone (GAL) as a replacement for the starter. A gel-filtration column technique and starch-gel electrophoresis were used for analysis, and bacterial counts were made on all samples. Proteolysis was faster in cheeses made using GAL than in those made using starter and also slightly faster in GAL cheeses made with swine pepsin than in those made with rennet. Further, it was considerably slower in starter-containing cheeses made with swine pepsin than in those made with rennet. It is suggested that these differences were due to the much greater rate of development of acidity in cheeses made with GAL than in those made with starter, which resulted in more of the coagulant being incorporated into the curd in an active state. The rate of proteolysis in starter-containing cheeses appeared to follow a characteristic course, being initially slow, then markedly increasing with a later slow decline. It is suggested that the increase in the rate of proteolysis was due to an increase in the total activity of bacterial proteinases released by lysis of the bacteria. Indications were obtained that the coagulants and bacterial proteinases catalysed broadly similar patterns of protein breakdown in cheese, and that medium-sized peptides (mol. wt 9000–14000) were formed as definite intermediates in the process. The results also showed that rennet and swine pepsin remained active for at least 7 months in GAL cheeses, that rennet contributed significantly to proteolysis in starter-containing cheeses, and that swine pepsin was at least extensively inactivated and possibly completely inactivated during cheese-making with starter.
The precipitation of whey proteins by carboxymethyl cellulose of differing degrees of substitution
Authors: Hill R. D. , Zadow J. G.
Published: June 2009

The complexing of whey proteins in hydrochloric acid whey by carboxymethyl cellulose (CMC) has been studied. The efficiency of precipitation of CMC (the ability to form insoluble complexes with whey proteins) increased with increasing degree of substitution (DOS) of CMC. At a DOS of greater than 1·4, efficiencies of precipitation of whey protein greater than 90% were achieved without the need for dilution of whey. CMC of high DOS would thus be useful in whey protein reclamation schemes. The amount of CMC necessary for maximum efficiency of precipitation also increased with increasing DOS. The composition of the CMC-protein complex varied little over the range pH 2·8–4·0. Under optimum conditions for binding, the complex contained 61–68% protein and more than 95% of the CMC originally in solution was precipitated in the complex.
The potential application of the theory of branching processes to the association of milk protein
Authors: Parker T. G. , Dalgleish D. G.
Published: June 2009

The coagulation of caseins is considered in the light of a polyfunctional condensation model for protein. This model was originally developed to explain aspects of the polymerization behaviour of small molecules, but it is shown here that it can be used to explain certain aspects of the polymerization of caseins, particularly the Ca2+-induced association of αs-casein and the heat-induced coagulation of casein in whole milk.