bluuebunny/crossref_metadata_2025 huggingface dataset:
A note on the serological typing of some strains of Streptococcus cremoris
Authors: Reiter B. , Di Biase Constanza , Newbould F.H.S.
Published: June 2009

The serological identity of group N streptococci was established by Shattock & Mattick (1943), who discovered that Streptococcus lactis and Str. cremoris had a common antigen, which differentiated them from the rest of the Lancefield groups of streptococci. Although phage typing of these organisms has met with some success (Nichols & Hoyle, 1949; Whitehead & Bush, 1957) attempts to type these organisms with rabbit antisera so far have failed (Briggs & Newland, 1953).
Neutral volatiles in cheddar cheese made aseptically with and without starter culture
Authors: McGugan W. A. , Howsam Shirlie G. , Elliott J. A. , Emmons D. B. , Reiter B. , Sharpe M. Elisabeth
Published: June 2009

Analyses of the neutral volatile components from 3 Cheddar cheese are presented. Two were made aseptically in an aseptic vat, with and without starter culture; the third was made with starter culture in an open vat. Gas–liquid chromatography and mass spectrometry detected the same volatiles in starterless cheese having little or no Cheddar flavour as in cheese made with starter and having a characteristic Cheddar flavour. Methyl disulphide and dimethyl sulphide were the only compounds consistently detected in higher concentrations in the cheese made with starter than in the cheese made without starter. However, using a total trapping technique, it was found that the combination of components recovered from the effluents of the chromatographic columns did not have the cheese-like aroma of the distillate vapours that were injected. Reasons for this are discussed.
The digestibility coefficients of myristic, palmitic and stearic acids in the diet of sheep
Authors: Steele W. , Moore J. H.
Published: June 2009

The apparent digestibility coefficients of the various constituents of diets containing myristic, palmitic or stearic acids have been determined in an experiment with 8 sheep.

The inclusion of myristic acid in the diet had no effect on the digestibility coefficient of total dry matter or crude protein, but it decreased the digestibility coefficients of crude fibre and nitrogen-free-extractives and increased the digestibility coefficients of fat and minerals. When palmitic acid was included in the diet there were decreases in the digestibility coefficients of total dry matter, crude fibre and nitrogen-free-extractives. The inclusion of stearic acid in the diet resulted in decreases in the digestibility coefficients of dry matter and nitrogen-free-extractives. There was an inverse relationship between the melting points and the digestibility coefficients of the added fatty acids.

The findings of this investigation are discussed in relation to the results of a previous study on the effects of these dietary fatty acids on the yield and composition of cow's milk.
Density-gradient electrophoresis of native and of rennet-treated casein micelles
Authors: Green Margaret L. , Crutchfield G.
Published: June 2009

Analytical electrophoresis of native and of rennet-treated casein micelles was carried out at 26 and at 5°C in a sucrose density gradient in a medium of the same ionic composition as milk. Under normal circumstances, the micelles were negatively charged and showed little heterogeneity in the electric field, the fastestmoving ones having at 26°C a mobility not more than 30% greater than that of the slowest. Native micelles were more highly charged at 5 than at 26°C; at each temperature, the mobility was approximately halved by rennet treatment. The results suggest that the effects of rennet treatment and of alterations in temperature on the tendency of the micelles to clot can be entirely explained as being caused by changes in charge.
The formation of 2-butanone and 2-butanol in Cheddar cheese
Authors: Keen A. R. , Walker N. J. , Peberdy M. F.
Published: June 2009

The bacteriological formation of 2-butanone and 2-butanol was investigated. The data suggest that 2-butanol is formed in cheese via 2-butanone in 3 steps, each step being carried out specifically by a different microbial species. Suitable species have been isolated from a single cheese. The first step could be carried out (in the present investigation) either by certain starter organisms or by a strain ofPediococcus cerevisiae. This strain formed substantial amounts of 2,3-butylene glycol in milk, presumably from citrate, but could not metabolize this compound further. A second micro-organism, a strain ofLactobacillus plantarum, was isolated which, in Cheddar cheese, could convert 2,3-butylene glycol into 2-butanone. The final reduction of 2-butanone to 2-butanol could be readily carried out in MRS medium by a strain ofL. brevis. Results from cheese made aseptically indicate that 2-butanone is formed in Cheddar cheese only when non-starter organisms are present.
Molassed sugar-beet pulp nuts supplemented with urea and phosphate used as a milk production concentrate for dairy cows
Authors: Parkins J. J. , Hemingway R. G. , Ritchie N. S.
Published: June 2009

A cubed molassed sugar-beet product with added urea, dicalcium phosphate, trace elements and vitamins was prepared containing 17% crude protein and up to 0·53% P. The product was evaluated in 3 changeover trials with lactating cows and the treatments involved comparisons with a low protein (10%) concentrate and one supplemented with groundnut plus cottonseed meals. When the product was included at 35–62% in milk production diets the mean daily yield of about 15 kg was about 0·5kg less than when full supplementation was as vegetable protein. This was considered more likely to be associated with inefficient utilization of urea rather than because of an energy difference between molassed sugar-beet pulp and barley.
Some operating characteristics of a simple homogenizing poppet valve; pressure profiles and separation: zone of fat globule dispersion
Authors: Phipps L. W.
Published: June 2009

The influences of different operating parameters upon the distribution of pressure across a simple homogenizing poppet valve have been investigated. Regions of contracted and separated flow were defined by detailed probing of static pressures and found to correlate well with the results from previous visual and photographic observations.

Direct confirmation was obtained of the conclusion, first reported by Loo & Carleton (1953), that fat globules in milk are disrupted chiefly in a zone between the valve and seating surfaces which is close to the seating inlet boundary. Progressive coarsening of the globule suspension was detectable in the flow downstream from this zone.
The concentration of lactate in relation to other components of bovine mammary secretion during premature regression and after resumption of milking
Authors: Mackie R. I. , Giesecke W. H. , Lück H. , de Villiers P. A.
Published: June 2009

An experiment lasting 42 d was performed in 4 consecutive stages on 6 healthy Friesian cows during mid-lactation. Mean values for the different components of mammary secretion during normal lactation were established. Milking was then suspended on all quarters from d 1–14. The mean values for lactate increased 20- to 30-fold over the mean value for normal lactation. Over the same period the leucocyte count (polymorphonuclear leucocytes and lymphocytes) also increased, whereas the mean values for glucose and the estimated redox potential decreased. From d 15–28 milking was resumed on one half of the udder and from d 29–42 milking was also resumed on the other udder-half. When milking was resumed the above-mentioned changes were reversed, taking 5–7 d to reach values obtained during normal lactation in the udder-half which had not been milked for 14 d, but at least 14 d in the udderhalf which had not been milked for 28 d. The changes in the levels of lactate, glucose, leucocyte count and estimated redox potential are discussed in relation to changes in the secretory activity of the mammary gland (lactose, β-lactoglobulin and epithelial cell count), permeability changes of the mammary epithelium (Na+, K+and serum albumin) and the immune defence mechanism in the udder (immunoglobulins). The results indicate that lactate is formed during anaerobic glycolysis by the leucocytes in the mammary secretion, most probably due to reduced blood flow to the udder and the accumulation of secretion in the gland and teat cisterns on cessation of milking.
Chemical changes in ultra-heat-treated milk during storage: III. Methods for the estimation of lysine and sugar-lysine derivatives formed by the maillard reaction
Authors: Möller A. B. , Andrews A. T. , Cheeseman G. C.
Published: June 2009

Four chemical methods were used in a comparison of the measurement of the extent of modification of lysine residues in casein during storage of ultra-heat-treated (UHT) milk. Determination of homoarginine after reaction with o-methylisourea appeared to be the best measure of total lysine modification. Reduction with borohydride before acid hydrolysis prevented recovery of lysine from lactuloselysine (ε-N-deoxylactulosyl-L-lysine) and fructoselysine (ε-N-deoxyfructosyl-L-lysine). This procedure gave values for these derivatives which were in good agreement with those obtained from the determination of furosine (ε-N-(2-furoylmethyl)-L-lysine) in acid hydrolysates. Determination of lysine after acid hydrolysis showed that lysine loss was accounted for by lactuloselysine and fructoselysine formation in most of the samples.

Browning was most apparent in UHT milk stored at 37 °C for 3 years and in this sample only part of the lysine residues was accounted for as lactuloselysine and fructoselysine, thus indicating that lysine had become involved further in sugar degradation products.
An examination of the factors affecting the reverse osmosis of milk with special reference to deposit formation
Authors: Skudder P. J. , Glover F. A. , Green Margaret L.
Published: June 2009

Changes in the dependent variables flow velocity, inlet pressure and temperature affected the rate of concentration of separated milk by reverse osmosis; their values were measured for minimum fouling at the membrane, resulting in maximum rates of concentration. Most of the deposit formed at an early stage of concentration and its extent depended on the operational variables.

Electron micrographs showed that the major component of the deposit was casein micelles linked by bridges to form a lattice. Chemical analysis of the deposit confirmed a high casein content and showed that Ca phosphate was precipitated in the deposit throughout concentration. When fat globules and fat globule membrane were present in the feed, they appeared to be caught up in the deposit, but did not affect its initial formation.
The composition of whole casein from the milk of Ayrshire cows
Authors: Davies D. T. , Law A. J. R.
Published: June 2009

The composition of whole casein of 5 herd-bulk and 42 individual-cow milks from a single herd of Ayrshire cows has been determined. The percentage composition of the herd-bulk samples varied relatively little over a period of more than a year with the whole casein consisting on average of 38·4 % αs1,0-casein, 36·5 % β-casein, 12·5 % κ-casein, 10·5 % minor αs-caseins and 2·1 % γ-casein. For the individual-cow samples from mid-lactation, casein composition also was relatively constant, but in early and late lactation composition varied more with the relative amount of β-casein often being lower and those of κ- and γ-caseins often higher than in mid-lactation, these differences tending to be more marked in samples from older cows. Stage of lactation appeared to have little effect on the relative amounts of αs1,0-and minor αs-caseins.

The concentrations of all casein fractions were significantly positively correlated (P < 0·001) with the concentration of whole casein in the milk. Also, there were significant negative correlations (P < 0·001) between the percentages of whole casein present as β- and κ-caseins, β- and γ-caseins and minor αs- and γ-caseins, and a significant positive correlation (P < 0·001) between the relative amounts of κ- and γ-caseins. The relative amount of the major αs1,0-casein fraction, however, was not closely related to those of any of the other fractions.

Generally, milks with high lactose and low Na values yielded casein which was comparatively rich in β-casein and comparatively poor in κ- and γ-caseins.
Fractionation and characterization of the membranes from bovine milk fat globules
Authors: Kitchen B. J.
Published: June 2009

Bovine milk-fat globule membrane (MFGM) has been fractionated in to 3 membrane components by isopycnic sucrose density gradient centrifugation. The 3 components, designated as heavy, medium and light material, were characterized by particular polypeptide, lipid, carbohydrate and enzyme compositions.

The heavy material (density > 1·145 g/ml) was red-brown in appearance and consisted of 63% protein, 32% lipid and 5% carbohydrate. The lipid moiety contained 40% triglyceride and 60% phospholipid, while the protein consisted of 3 major polypeptides (apparent mol. wt 135000, 70000 and 53000) in the ratio of 3:6:1. This membrane class was also characterized by the presence of both xanthine oxidase and acid phosphatase. The medium density material (density 1·055–1·145 g/ml) was light red to pink in colour and consisted of 35% protein, 58% lipid and 6% carbohydrate. The lipid contained 45% triglyceride and 55% phospholipid, with nearly 70% of the original MFGM phospholipid being found in this material. The ratio of the 3 major polypeptide bands was 2:4:4 and high levels of both alkaline phosphatase and 5'-nucleotidase were present. The light material (density < 1·055 g/ml) was white to pale pink in colour and was composed of 88% lipid of which 94% was triglyceride, together with 8% protein and 4% carbohydrate. There were virtually no enzymes present and 70% of the protein consisted of a polypeptide with apparent mol. wt of 53000. The 3 membrane classes also differed in carbohydrate content and in the fatty acid composition of their triglycerides.
Lipoprotein lipase of goat mammary tissue: comparison of extraction methods
Authors: Chilliard Yves
Published: June 2009

Mammary lipoprotein lipase of lactating goats was extracted by 3 methods: homogenization of tissue acetone-ether powders; aqueous homogenization of crude tissue using an Ultra-Turrax apparatus; aqueous homogenization of crude tissue using a Sorvall Omni-mixer microhomogenizer. Although there were differences between absolute values obtained by the 3 methods, each type of homogenate had a lipolytic activity with lipoprotein lipase characteristics (i.e. more than 90% inhibition by serum omission or NaCl addition). Furthermore, the 3 methods were highly correlated and presented similar variations with the stage of lactation, in parallel with long-chain fatty acid secretion into milk. Repeatability of the measure of homogenate lipolytic activities was about 8%, whereas day-to-day repeatability of enzyme extraction and assay was about 20% for each method.
Biospecific chromatography of chymosin on quinonated Sepharose and its application to enzyme content determination in rennets
Authors: Gregorio Francesco Di , Sisto Raffaello , Morisi Franco
Published: June 2009

An insoluble benzoquinone derivative, obtained by reacting benzoquinone with Sepharose 4B and subsequent deactivation with ethanolamine, selectively absorbed chymosin from a mixture of milk-clotting enzymes and other proteins such as in rennets. This selective absorption has been used for developing a purification method and for quantitatively estimating the chymosin content of commercial rennets. Thus, from a powdered calf rennet, it was possible to obtain in one step an 8-fold purified chymosin free of bovine pepsins. The proposed analytical test involves 2 milk-clotting activity measurements and a chromatographic elution of the sample on a quinonated Sepharose column. It can be applied directly to commercial rennets, because it does not require pre-dialysis of the sample against the elution buffer. Furthermore, a combination of quinonated Sepharose and DEAE-cellulose chromatography gave a method for isolation of bovine pepsin I from rennets.
The effect of chloroform introduced into the rumen of the lactating goat on the yield and composition of the milk
Authors: Basmaeil Saeid , Clapperton John L.
Published: June 2009

In 2 experiments, chloroform was introduced into the rumen of lactating goats given a mixture of 40% chopped hay and 60% barley-based concentrates. The effects on food intake, apparent digestibility, rumen fermentation and the yield and composition of milk were measured. In expts 1 and 2 food intake was reduced by 7% and less than 1% respectively. There were no significant effects on apparent digestibility in expt 1, but there were significant increases in the apparent digestibility of the dry matter and organic matter in expt 2. The results of in vitro determinations suggested that the loss of energy in combustible gas was reduced by 52 and by 25% in expts 1 and 2 respectively. As a result of these changes, the metabolizability of the dietary energy was increased by 2·1 and 4·8% respectively. In both experiments, the total volatile fatty acid concentration in the rumen was reduced when chloroform was added and there were changes in the molar proportions of the individual fatty acids, principally a reduction in acetic acid and an increase in propionic acid. Milk yield was not affected, but the fat content of the milk was reduced and, in expt 1, the protein content was increased.
Properties of single-strain cheese starter bacteria grown in diffusion culture
Authors: Osborne Raymond J. W. , Brown John V.
Published: June 2009

The production of a range of single-strain cheese starter concentrates by diffusion culture and some of their subsequent properties are described. Five strains ofStreptococcus cremorisand 4 strains ofStr. lactiswere grown to concentrations of above 1.0 × 1011cells/ml, these concentrates all being of satisfactory cheese-making potential. Ammonium lactate accumulation in the system appeared to be the limiting factor to growth, although some strains were more tolerant than others. A continuous harvesting experiment demonstrated that the equipment was potentially capable of this mode of concentrate production. A cheese-making trial was carried out with concentrates produced by diffusion culture; a higher proportion of extra and upper selected cheese was obtained than from control cheese produced with conventionally propagated commercial mixed starters.
Effect of drought condition on the quality of camel milk
Authors: Yagil Reuven , Etzion Zipora
Published: June 2009

Ten-day periods of water restriction followed by 2 h ad lib. water caused radical changes in camel milk. The changes were different from those reported in other mammals. At the end of each dehydration period there were increased water percentages in the milk when compared with milk of hydrated camels. The content of fat, lactose and protein declined. Concentrations of Na, K, phosphate and chloride in milk increased while Ca and Mg concentration declined. The urea concentration of the milk was unchanged. The young suckling calves showed no signs of stress during the dehydration periods. It was concluded that the milk of dehydrated camels is an excellent human food in arid areas, as the water and salt content are high while the nutritive value remains good.
Effect of selected amides on heat-induced changes in milk
Authors: Fox Patrick F. , Nash Bridget M. , Horan Timothy J. , O'brien Jeremiah , Morrissey Patrick A.
Published: June 2009

The effect of 15 amides and related compounds on the heat stability of milk was investigated; of these urea, biuret, triuret, methyl urea and ethyl urea had a similar stabilizing effect. These 5 compounds reacted with lysine to form a ninhydrin-positive compound, possibly homocitrulline, and with lactose produced Maillard-type browning, but some of the other compounds studied were also capable of participating in one or both of these reactions. The only effect which the 5 stabilizing amides had in common and which the other compounds did not share was a significant pH-buffering capacity in synthetic systems and in milk. It is suggested that urea exercises its stabilizing influence in milk principally through its ability to buffer the pH of the system during heating.
Metabolic significance of milk glucose
Authors: Faulkner Anne , Chaiyabutr Narongsek , Peaker Malcolm , Carrick David T. , Kuhn Nicholas J.
Published: June 2009

The free glucose concentration in the aqueous phase of samples of goat, sheep, cow, rat and rabbit milk was about 0·1–0·3 mn, while that in human milk was about 2 mM. During starvation the glucose concentration of goat milk fell considerably (by about 80 % in 2 d) in parallel with the decreased rate of lactose production. With rats fed ad lib., glucose concentration in the milk was greater at 12.00 h than at 18.00 h, when lactose synthesis has been shown to decrease. 3-O-Methyl-D-glucose injected into the goat mammary gland via the teat canal specifically entered the blood. These findings support the idea that glucose equilibrates across the apical membrane of mammary secretory cells, so that milk glucose concentrations reflect intracellular glucose concentrations.
Mineral balance in skim-milk and milk retentate: effect of physicochemical characteristics of the aqueous phase
Authors: Brule Gerard , Fauquant Jacques
Published: June 2009

The effect of physicochemical characteristics (pH, temperature, composition) of the aqueous phase on the mineral balance in milk and milk retentate has been studied. The ratio of colloidal Ca to total protein decreased with pH, but at any given pH the higher the protein concentration, the higher was the ratio of colloidal Ca to total protein. The solubilization of Ca during cooling and the decrease in soluble Ca during heating were approximately the same in retentates and in milk. Among the components of the aqueous phase, soluble Ca and citrate ions were related to the amount of colloidal Ca.
Growth of morel mushroom mycelium in cheese whey
Authors: Kosaric Naim , Miyata Nabuo
Published: June 2009

Cheese whey was used as substrate for submerged cultivation of 8 strains of 6 species of edible mushrooms (morel mushroom):Morchella crassipes(3 strains),M. angusticeps, M. rotunda, M. deliciosa, M. esculentaand an unidentifiedMorchellasp. Best growth of morel mushroom mycelium was obtained with one of theM. crassipesstrains. The optimum growth conditions for the selected mycelium were as follows: initial pH, ~ 5·0–5·5; temperature, 25–28°C; inoculum size, 150–250 mg mycelium/100 ml whey; N sources: peptone and yeast extract; trace elements: K and Fe. More than 20 g/l mycelium was harvested in the form of pellets. Some growth kinetics studies were also performed. The initial carbohydrate (lactose) content was reduced from 5 to 0·4% at the end of the cultivation period. The specific growth rate ofM. crassipesATCC 13227 was from 1.0 to 6·4 x 10–2, depending on the growth phase. The harvested biomass contained about 45% protein, 5% fat and 8·5% ash (on a dry-weight basis). Essential amino acid content was comparable to the FAO standard, except for methionine, and unsaturated fatty acids predominated in the fat. The results with whey are compared with previously reported data on morel mushroom mycelium growth on waste sulphite liquors.
Role of Penicillium roqueforti proteinases during blue cheese ripening
Authors: Le Bars Dominique , Gripon Jean-Claude
Published: June 2009

The hydrolysis of isolated αs1- and β-caseins by Penicillium roqueforti aspartyl proteinase produced comparable quantities of pH 4·6 soluble N. The amount of non-protein nitrogen obtained with β-casein was clearly lower than that obtained with αs1-casein, showing that few low molecular weight peptides were released when this casein was hydrolysed. Electrophoresis of αs1-casein hydrolysates produced by aspartyl proteinase showed 5 bands of mobility close to or higher than that of αs1-casein. β-Casein hydrolysates gave 4 bands, 2 of which (βPrapl and βPrap2) showed low electrophoretic mobility. The products corresponding to βPrapl and βPrap2 were purified from a β-casein hydrolysate and identified as fragments Val98-Val209 and Glu100-Val209 of β-casein respectively. The occurrence of the βPrapl and βPrap2 bands in electrophoretic patterns obtained from sterile curd with aspartyl proteinase and controlled-flora curd, where P. roqueforti was the only micro-organism developing, showed the presence of aspartyl proteinase synthesis and activity in cheese. A band of very low electrophoretic mobility (βPrmpl) was present in electrophoregrams of controlled-flora curd inoculated with P. roqueforti. This band, resulting from the action of the metalloproteinase on β-casein, revealed that this enzyme was both synthesized in and active in cheese.
A freeze-fracture study of tight junction structure in sheep mammary gland epithelium during pregnancy and lactation
Authors: Morgan Geoffrey , Wooding F. B. Peter
Published: June 2009

Freeze fractures of the tight junctions at the apices of sheep mammary secretory cells showed that the junction at 72 d of pregnancy was significantly wider than at any later stage. The number of ridges in the junction only increased significantly between 122 and 142 d of pregnancy. The initially even distribution of intramembrane particles across the tight junction changed gradually until in the fully lactating animal there were far more particles on the lateral surface of the plasmalemma. Possible correlations between these changes, the alterations in permeability of the mammary epithelium, and the differences in hormone levels are briefly discussed.
Calcium-induced precipitation of αs1-casein: effect of inclusion of citrate or phosphate
Authors: Horne David S.
Published: June 2009

The calcium-induced aggregation of αs1-casein at pH 7·0 has been studied in the presence of citrate and phosphate anions. The effects of the citrate can be reconciled with the suggestion that the citrate, acting as a Ca chelator, reduces the Ca available for the aggregation reaction, but in no other way interferes with the mechanism of that process. In the presence of phosphate, precipitation is induced below the normal critical Ca concentration. This reaction proceeds to completion at low and high concentrations of phosphate. There is, however, an intermediate range of phosphate concentrations, whose limits depend on the protein concentration, where a colloidally stable precipitate is produced. The significance of these observations is discussed in terms of the currently held theories of micellar structure and formation.
Particles in bulk milk capable of causing falsely high electronic cell counts
Authors: Hill Alan W. , Hibbitt Kenneth G. , Davies Jonathon
Published: June 2009

Bulk milk with an apparently high electronic cell count (ECC) was found to have a normal cell count when the latter was determined directly with a microscope or when cell nuclei were counted with a Fossomatic apparatus. Particles in the form of collapsed spheres formed by aggregated casein micelles were found in bulk milk which accounted for the falsely high ECC values. The ECC value agreed with the values obtained by the other methods if the milk was heated to 55 °C for 15 min before fixation. The shape of the particles and the fact that they were only present after the milk had passed through the milking machine suggested that they may be produced as vacuum vacuoles arising from cavitation in the pump.
The inorganic constituents of milk IV. Diffusible calcium and magnesium concentrations in goat's milk and the effect of starvation
Authors: Ormrod Ian H. L. , Holt Carl , Thomas Phillip C.
Published: June 2009

The concentrations of diffusible Ca and Mg in milk diffusates from 3 goats were determined before, during and after a 2-d period of starvation. Free Ca-concentrations were determined by a murexide method and compared with values calculated from a detailed model of the ion equilibria. It was shown that diffusible Ca increased as citrate increased during fasting and both decreased after refeeding, but there was a difference of about half a day in the response curves, with citrate following Ca. The difference was accounted for mainly by a change in free Ca2+concentration which in turn was related mainly to changes in milk pH. Diffusible Mg underwent changes similar to those of diffusible Ca.
Application of the plastein reaction to caseins and to skim-milk powder: I. Protein hydrolysis and plastein formation
Authors: Sukan Gonca , Andrews Anthony T.
Published: June 2009

With either Na caseinate or skim-milk powder, 1% (w/v) additions of pepsin, chymotrypsin or Alcalase and an incubation time of 24 h at 37°C gave the best hydrolysates for subsequent plastein production. In spite of the fact that peptide species which were produced by treatment with the 3 enzymes were entirely different, they were all capable of producing qualitatively similar amounts of plastein when concentrated and further incubated with proteinase, suggesting that the identity of peptide components was relatively unimportant. αs1-, β- and κ- caseins, Na-caseinate and skim-milk powder all led to plastein products with broadly similar properties, confirming the comparative unimportance of peptide composition. This also indicated that for most practical applications fractionation of initial protein mixtures (as in many food products) would not be justified. Optimum peptide concentration for plastein formation with pepsin and caseinate hydrolysates was 20–35% (w/v) with an optimum pH range of 4–5; the best peptide molecular weight varied between 400 and 800 and the optimum temperature was either 37°C for 24 h or 50°C for 4–6 h. Higher temperatures (70°C) gave more rapid plastein formation but poorer yields. Lower temperatures (e.g. 20°C) gave similar yields, but incubation times required to be extended to at least 48 h. The same proteinase should be used for plastein synthesis as that used in the initial hydrolysis stage, or else further hydrolysis (over hydrolysis) could occur during the plastein formation stage causing lower yields due to differences in the specificity of the 2 enzymes. Even under ideal conditions plastein yields never exceeded 27% of the weight of peptide taken and at the present time it seems unlikely that the plastein reaction will have anything more than curiosity value. Economics must preclude its application in low-cost, high volume situations such as generally exist within the food industry.
Effect ofEscherichia coliendotoxin-mediated inflammation of one mammary quarter of the bovine udder on diapedesis into other quarters
Authors: Schultze W. Donald , Bramley A. John
Published: June 2009

Implantation of 1 μgEscherichia coliendotoxin into one papillary duct of a bovine udder frequently resulted in a mild inflammatory process in the treated quarter which was measured by use of the Wisconsin mastitis test (WMT) on quarter fore milk samples. Inflammation of a fore quarter was usually (18/24) accompanied by a transient elevation in WMT score from the homolateral hind quarter, but rarely (1/25) from the contralateral quarter. Inflammation in a hind quarter rarely (2/26) affected the homolateral fore quarter and never (0/25) the contralateral quarter. The pattern of responses suggests that absorption and initial removal of endotoxin from the mammary gland occurs via the lymphatic rather than the blood system.
Preservation of raw milk by the addition of carbon dioxide
Authors: King Joseph S. , Mabbitt Leonard A.
Published: June 2009

The effects of concentrations of 10–30 mM/1 of CO2on the growth of psychrotrophic milk spoilage organisms were examined, both in untreated whole milk and in pure cultures ofPseudomonas fluorescensgrowing in skim-milk and broth. Spoilage of refrigerated untreated whole milk was found to be inhibited by the addition of CO2and the effect was enhanced with increasing concentrations of CO2and decreasing storage temperature. Experiments with pure cultures ofPs. fluorescensshowed that the inhibitory effects of CO2were not due to increased acidity or to displacement of dissolved O2, but to the presence of CO2per sewhich induced an increase in the duration of the lag phase of growth and had only a small effect on the logarithmic phase.
Effects of fasting during mid pregnancy or early lactation on mammary development and milk yield in mice
Authors: Knight Christopher H. , Peaker Malcolm
Published: June 2009

Mice were fasted during pregnancy or early lactation and the effects on mammary development and milk yield studied on d 13 and d 18 of pregnancy and on d 7 of lactation. Fasting during pregnancy reduced body weight and mammary weight on d 13 of pregnancy but not on d 18. Mammary concentrations and total contents of DNA and RNA ([DNA], [RNA], DNAt, RNAt) were increased or unchanged on d 13 but significantly decreased on d 18. Fasting had no effect on fetal number or weight at either stage of pregnancy. Fasting on d 1 of lactation reduced mammary weight, DNAt and RNAt (but not [DNA] or [RNA]) and the incorporation of tritiated thymidine into DNA on d 2 of lactation. Mammary gland weight and composition on d 7 of lactation were not significantly affected by fasting for 24 h on d 1 of lactation or for 40 h on d 11–13 of pregnancy, except that DNAt was decreased slightly by the latter treatment.

Milk yield (litter weight gain) was depressed markedly during fasting on d 1 of lactation, but thereafter recovered so that it was the same as controls between d 3 and 13 of lactation; after d 13 it fell once more. A 40 h fast on d 11–13 of pregnancy had no effect on milk yield. Thus, although normal mammary development was inhibited by starvation, the gland was subsequently able to compensate so that milk yield was not reduced.
Heat stability of milk: influence of modification of lysine and arginine on the heat stability-pH profile
Authors: Shalabi Samweul I. , Fox Patrick F.
Published: June 2009

Several dicarbonyl compounds (glyoxal, substituted glyoxals, diacetyl and 1, 2-cyclohexadione) had a marked stabilizing effect on the heat stability of milk, especially in the presence of urea. These reagents are believed to modify arginine more or less specifically suggesting an important role for arginine residues in heat stability. In contrast, modification of lysine residiles with dansyl chloride, acetic anhydride or cyanoborohydride had little effect on maximum heat stability although it did alter the HCT-pH profile. Since diacetyl is a natural constituent of fermented milks and cheese, it may be acceptable as an additive to increase the heat stability of ṃilk.
Recent advances in the destabilization of dairy emulsions
Authors: Darling Donald F.
Published: June 2009

Destabilization of emulsion droplets is described in terms of flocculation, coalescence and adsorption processes, and then discussed with reference to various technological aspects of dairy emulsions. A semi-quantitative measurement of homogenization-induced flocculation of cream is described using measurements on the time-dependent decrease in viscosity that occurs during shear. The whipping of cream is discussed in terms of the adsorption of fat droplets to air bubbles and the formation of a fat particle network with the fat directly in contact with air. The whipping of homogenized creams is shown to be dependent upon the structure of the newly formed milk fat globule membrane. Since the major protein component of the membrane is casein, any change in casein micelle stability is reflected in the whipping properties of the cream.

The presence of crystalline fat within emulsion droplets is essential for many destabilization processes. Fat crystals pierce the film between 2 approaching interfaces, thus leading to aggregation. The contact angle between fat crystal, oil and aqueous phase can be used to describe the susceptibility of an emulsion to destabilize.

A quantitative measure of emulsion destabilization under shear is described kinetically in terms of reversible flocculation followed by coalescence. The measurement of emulsion viscosity as a function of time at constant shear stress is used to monitor the aggregation processes and the 3 rate constants evaluated by computer curve fitting.
Development of texture and flavour in cheese and other fermented products
Authors: Green Margaret L. , Manning Donald J.
Published: June 2009

Cheesemaking is initiated by specific hydrolysis of κ-casein, followed by random aggregation of casein particles to form a network. The structure of this curd determines its subsequent behaviour and the composition and texture of the cheese. It is affected by previous homogenization or concentration of the milk. The composition of the milk and the distribution of components in it, which are affected by season, mastitic infection and cold storage, also influence its curd-forming properties, and the composition and yield of cheese. During ripening of cheese, the final texture and the development of flavour occur. Both are influenced by the type and extent of proteolysis, catalysed by coagulant, bacterial and milk enzymes. These and other enzymic and non-enzymic reactions responsible for flavour development depend on the composition and environment within the product. Some of these reactions can be accelerated by incorporating enzymes and chemical reagents into the curd, resulting in the production of an enhanced flavour. A number of compounds responsible for the flavour of cheese and yoghurt have been identified and mechanisms for their formation and retention in the product have been postulated.
Dynamic viscosities of milk and cream from 70 to 135 °C
Authors: Bertsch Antonio J. , Cerf Olivier
Published: June 2009

The dynamic viscosities of non-homogenized and homogenized (2-stage) whole and half skim-milk and cream, of unhomogenized skim-milk and of water-diluted milks were measured at temperatures between 70 and 135 °C; this range includes those temperatures used in ultra-high-temperature (UHT) treatments. A tube viscometer was used at the outlet of a continuous flow indirect heater. Above 85 °C the mean residence time of a milk or cream at the test temperature was 3–6 s.

An equation relating viscosity μ and temperature θ of the form In μ = aθ2+bθ+c was derived for each product.

It proved possible to relate μ, θ and fat content (0·03–15·5%) in a single equation which was appropriate for all the homogenized milks and creams as well as the non-homogenized skim-, half skim- and whole milk; the equation is considered valid for these products under conditions of indirect UHT sterilization. Viscosity values calculated with the equation, even those relating to temperatures as low as 50 °C, were comparable with those reported in the literature.
Influence of homogenization of concentrated milks on the structure and properties of rennet curds
Authors: Green Margaret L. , Marshall Richard J. , Glover Frank A.
Published: June 2009

Whole milk was concentrated by ultrafiltration in a plant causing some homogenization of the fat. Comparisons were made with milk concentrated in a plant causing little homogenization and with milk homogenized conventionally. None of the processes appreciably affected the casein micelle size distribution. On rennet treatment of homogenized milk, casein micelle aggregation occurred more slowly, the protein network in the curd was less coarse and the rate of whey loss was reduced, compared with non-homogenized milk at the same concentration. In using concentrated milks for cheesemaking homogenization improved the composition of Cheddar cheese, because of increased fat and moisture retention, but curd fusion was poorer. Some aspects of the texture of the mature cheeses were improved, but the free fatty acid levels were higher. Values for the firmness of curds, formed from milks processed in different ways, did not relate to the extent of aggregation of the casein micelles. It is suggested that the complete cheesemaking process is driven by the tendency of the casein to aggregate.
Suitability of some microbial coagulants for Feta cheese manufacture
Authors: Alichanidis Efstathios , Anifantakis Emmanuel M. , Polychroniadou Anna , Nanou Marinela
Published: June 2009

Three microbial rennets, Noury rennet (Mucor pusillus, Lindt), Rennilase (M. miehei) and Suparen (Endothia parasitica), were assessed as calf rennet substitutes for Feta cheesemaking, in comparison with calf rennet. Cheeses prepared were all of good quality with similar organoleptic properties. Yield (referred to 55% moisture), moisture content, NaCl and protein content did not differ significantly. Different rates of proteolysis were observed in the cheeses, the highest of which was exhibited by calf rennet followed by Rennilase, Noury rennet and Suparen preparations. These calf rennet substitutes are well suited for Feta cheese manufacture.
Effect of prazosin on the function of the teat sphincter in lactating cows
Authors: Messom Georgette Vandeputte-Van , Bernabé Jacques , Burvenich Christian , Peeters Georges
Published: June 2009

Oxytocin was infused for 60 min into the jugular vein of 8 lactating cows with full udders before milking. Under these circumstances milk loss occurred spontaneously in 3 cows and was evoked in 5 cows by reducing pressure around one teat (–30 cm water) using a plethysmographic chamber. Milk loss was measured continuously. The postsynaptic α-blocking agent prazosin (PRZS) injected either into the udder artery (2 or 5 mg) or into the jugular vein (200 mg) consistently induced a significant increase in milk leakage. It is suggested that PRZS effectively inhibits α-adrenoceptors in the teat sphincter muscles and thus promotes the action of β-adrenoceptors, in this way inducing relaxation of the teat sphincter.
Isolation and composition of milk fat globule membrane material
Authors: McPherson Avis V. , Dash Mary C. , Kitchen Barry J.
Published: June 2009

Milk fat globule membrane (MFGM) material was isolated from commercial pasteurized milks and pasteurized creams using a procedure specifically adapted for these products (McPhersonet al.1984a). Pasteurized cream membranes contained higher lipid levels while pasteurized milk membrane material had lower lipid contents than fresh raw MFGM. Electrophoretic analysis showed that membrane material from both commercial products contained, in addition to native MFGM polypeptides, significant amounts of β-lactoglobulin with lower levels of caseins and other skim-milk components. The incorporation of β-lactoglobulin was more pronounced in pasteurized cream membranes. Examination of the lipoprotein complexes present in these membrane preparations by linear sucrose density gradient centrifugation showed that pasteurized milk membrane material had a similar profile to fresh raw MFGM except that preferential binding of skim-milk components was found in some of the lipoprotein fractions. Pasteurized cream membranes showed considerably different density gradient patterns with only 2 lipoprotein fractions present, of which the major one was a low density complex.
Measurement of electrophoretic mobilities and zeta-potentials of particles from milk using laser Doppler electrophoresis
Authors: Dalgleish Douglas G.
Published: June 2009

The use of a commercial laser Doppler electrophoresis apparatus to measure electrophoretic mobilities of milk constituents is demonstrated, and calculations of apparent ζ-potentials from these mobilities are given. Systems studied were: native and renneted casein micelles suspended in milk ultrafiltrate and different buffers containing Ca2+, particles from homogenized milk before and after renneting, fat globules, and homogenized fat/caseinate systems. The results confirmed previous estimates of the ζ-potentials of these materials, but also extended to cover the effect of changing the concentrations of Ca2+ and other salts on the electrokinetic properties of the particles. Increasing concentration of Ca2+ caused considerable decrease in the ζ-potentials of native and renneted casein micelles, and temperature increase caused the apparent ζ-potential to increase in both cases. Particles from homogenized milk showed ζ-potentials very similar to those of native casein micelles, and renneting of the homogenized milk gave behaviour similar to renneted casein micelles. The ζ-potential of the homogenized materials could be distinguished clearly from those of native fat globules. Likewise, milk fat which had been homogenized using whey protein showed distinct differences in its surface properties from particles based on caseinate or casein micelles.
Catabolism of L-phenylalanine by some microorganisms of cheese origin
Authors: Lee Chang-Won , Richard Jean
Published: June 2009

The ability of 42 microorganisms isolated from cheese, including strains of yeasts,Geotrichum candidum, Arthrobacter, Moraxellaspp.,Brevibacterium linensandStaphylococcus saprophyticusspp. to produce phenethyl alcohol (PEA) from L-phenylalanine was studied. All the yeast strains produced labelled PEA from L-[U-14C]phenylalanine. Phenylpyruvic acid was detected as an intermediate of PEA production and CO2was produced by decarboxylation of this acid. For five strains tested, the level of PEA which had accumulated in the culture at the end of exponential growth phase represented 39–52% of the L-Phe added. None ofG. candidumstrains nor bacterial isolates produced PEA from L-Phe. Strains ofMoraxellaspp. and four strains of theS. saprophyticusgroup produced phenylacetaldehyde. For three strains ofArthrobacterspp., five ofB. linensand all theMoraxella,14CO2produced from uniformly labelled L-Phe represented more than one carbon atom of the L-Phe molecule, suggesting that Phe was catabolized beyond the stage of phenylacetic acid. Production and disappearance of PEA during Camembert cheese ripening is probably related to the metabolic activity of microorganisms present at the cheese surface.
Yield and composition of milk from Friesian cows grazing either perennial ryegrass or white clover in early lactation
Authors: Thomson David J. , Beever David E. , Haines Michael J. , Cammell Stephen B. , Evans Roger T. , Dhanoa Mewa S. , Austin Anthony R.
Published: June 2009

The yield and composition of milk from Friesian cows grazing either perennial ryegrass (Lolium perenne) (G, ten cows) or white clover (Trifolium repens) (C, nine cows) were evaluated between d 21 and 129 post partum. The two forages, of similar digestible energy content, were the sole source of nutrients and were offeredad lib. (exp. 1). Digestion and flow at the duodenum were measured on 13 occasions in early lactation with comparable cows fitted with rumen and duodenal cannulae and grazing similar forages (exp. 2). The gross milk yield (22·2, G; 25·0, C, kg/dP< 0·05) and the yield of protein (0·66, G; 0·77, C, kg/d,P< 0·01) were higher, but the protein content was similar and the fat content lower for cows fed C compared with G. Cows fed G were heavier at the beginning of the experiment and lost weight more rapidly than cows fed C. Milk energy output, adjusted for tissue energy gain or loss, was 83·9 for cows fed C compared with 71·8 MJ/d for cows fed G (P< 0·001), during the period of tissue energy repletion (weeks 11–18). From week 18 to the end of lactation all cows from exp. 1 were fed silagead lib. and 502 kg dry matter of concentrates. The total (305 d) difference in lactation response to grazing C compared with G was 931 1 (5657 1, C; 4726 1, G); this was a direct response during the experiment of 301 1 and a residual response of 630 1. In exp. 2, more organic matter (6·47, G; 8·01, C, kg/ d,P< 0·001), and more non-ammonia N (433, G; 575, C, g/d,P< 0·001) entered the duodenum of cows grazing C compared with G.