bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

SummaryAn 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

SummaryIn 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

SummaryThe 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

SummaryTen-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

SummaryThe 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

SummaryThe 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

SummaryThe 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

SummaryCheese 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

SummaryThe 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

SUMMARYFreeze 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

SUMMARYThe 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

SUMMARYBulk 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

SUMMARYThe 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

SUMMARYWith 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

SUMMARYImplantation 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

SUMMARYThe 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

SUMMARYMice 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

SUMMARYSeveral 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

SUMMARYDestabilization 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

SUMMARYCheesemaking 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

SummaryThe 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.