bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of manufacturing conditions on the setting rate of butter
Authors: Taylor M. W. , Dolby R. M. , Russell R. W. 
Published: June 2009

SummaryThe setting rate of butter during the first 5 h after manufacture was found to be increased by a higher maximum temperature during working, e.g. 15 as compared with 12·5 °C, or by a temporary rise in temperature to 18 °C for 30 min after working. A temporary lowering of temperature to 7 °C for 30 min, however, had no effect. The amount of working did not affect setting rate except where more prolonged working resulted in a higher final temperature in the butter.When temperature conditions during and after working were standardized, it was found that temperature of pasteurization in either a Vacreator or plate pasteurizer or the presence of clumped fat in the cream had no effect on setting rate. The setting rate, however, was increased by Vacreator treatment as compared with plate pasteurization of cream or by low-pressure homogenization of cream after plate pasteurization.Microscopic examination of butter samples showed much fewer intact fat globules in butter from Vacreator-treated or homogenized cream than in that from platepasteurized cream.It is suggested that Vacreator treatment or homogenization of cream affect the setting rate of butter by causing changes in the fat-globule membrane which, in turn, influence the type of crystallization in the fat globules and the stability of the globules.
Carbohydrates of bovine κ-casein
Authors: Wheelock J. V. , Sinkinson G. 
Published: June 2009

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

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

SummaryNine West African dwarf (Fouta djallon), Red Sokoto (Maradi) and Saanen lactating goats, hand-milked, were used for these studies, which lasted 12 weeks. The Saanen goats' milk was obtained weekly from the Western State Ministry of Agriculture and Natural Resources Urban Dairy Farm at Iwo Road, while similar samples were collected from the herd at the University of Ibadan Teaching and Research Farm. The goats were balanced for stage of lactation, namely early, mid- and late-lactation. They were each maintained on giant star grass (Cynodon nlemfuensis) ad lib.and 1kg dairy concentrate mixture daily.The mean contents, with standard deviations, of the milks of Saanen, West African dwarf and Red Sokoto goats at mid-lactation respectively were: (in percentages), total solids 12·25±0·078, 18·18±0·392, 15·85±0·077; solids-not-fat (SNF) 8·91±0·142, 10·48±0·471, 10·53±0·140; butterfat 3·34±0·141, 7·78±0·621, 5·32±0·098; protein 3·04±0·139, 5·30±0·292, 4·74±0·021; lactose 4·56±0·167, 5·19±0·176, 4·77±0·053; energy (kJ/g dried milk), 21·08±1·11, 25·51±1·74, 22·17±0·51. Breed differences were significant (P< 0·01). The milk of West African dwarf goats contained more of these milk components than the milk of the Red Sokoto or Saanen goats. The Red Sokoto goats gave milk of higher content than did Saanen goats, even at an early stage of lactation.Butterfat, protein, lactose and energy values were significantly affected by stages of lactation (P< 0·05) and tended to rise with advancing lactation; this was particularly so with West African dwarf goats.
The acid phosphatases of bovine leucocytes, plasma and the milk of healthy and mastitic cows
Authors: Andrews A. T. , Alichanidis E. 
Published: June 2009

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

SummaryFour Ayrshire cows in their second lactation were used in a 4×4 Latin square experiment to determine the effects of frequency of feeding on milk secretion. The animals were given a diet consisting of hay, sugar-beet pulp and dairy concentrates (34·9:19·7:45·5 on a dry-matter basis) either in 2 equal meals/d at 07.00 and 17.00 h or with the hay in 4 meals at 07.00, 12.00, 17.00 and 22.00 h and the sugar-beet pulp and concentrates in 24-h meals. Each feeding frequency was tested at 2 levels of feeding providing either 100 or 80% of the standard requirements for energy.There were no significant effects of frequency of feeding on milk yield or on the milk content of fat, protein, lactose, solids-not-fat or total solids, but underfeeding depressed the yield of milk and of all milk constituents. Neither the frequency nor level of feeding had appreciable effects on the fatty-acid composition of the milk fat or on the blood glucose concentration, but in animals fed frequently plasma urea levels were lower than in animals fed twice daily and there was no postprandial peak in urea concentration.
Autoxidation in milk rich in linoleic acid: II. Modification of the initiation system and control of oxidation
Authors: Sidhu G. S. , Brown M. A. , Johnson A. R. 
Published: June 2009

SummaryFactors contributing to the initiation of lipid oxidation in cow's and mare's milk containing high levels of polyunsaturated fatty acids were studied. Addition of H2O2just after milking, in slight excess of the stoichiometric amounts required to destroy ascorbic acid, delayed the development of oxidized flavours in cow's milk high in linoleic acid. Hydrogen peroxide treatment followed by the addition of α- or γ-tocopherols prevented lipid oxidation in cow's milk even when 0·1 mg Cu/l milk was added. When used separately in the presence of Cu these treatments were ineffective as was butylated hydroxyanisole treatment.The lipid and ascorbic acid in mare's milk were remarkably stable to oxidation. Addition of 0·05 or 0·1 mg Cu/l, ethylenediamine tetraacetic acid, neocuproine, or H2O2had very little effect on the loss of ascorbic acid and lipid oxidation in mare's milk.
The production of sulphur compounds in Cheddar cheese and their significance in flavour development
Authors: Manning D. J. , Chapman Helen R. , Hosking Zena D. 
Published: June 2009

SummaryA method is described for determining H2S, methanethiol and dimethyl sulphide in Cheddar-cheese headspace. Cheeses ranging in age from 2 to 12 months were analysed using a gas chromatograph equipped with a photometric detector. These cheeses were presented to a trained flavour panel for the assessment of quality and intensity of Cheddar cheese flavour.An attempt is made to correlate the concentration of sulphur compounds in the headspace with the average flavour scores. The results suggest that the flavour intensity of the cheese is related to the concentration of methanethiol in the headspace.
Reproducibility of electronic cell counts in milk; a study of 5 further factors
Authors: Greer D. O. , Pearson J. K. L. 
Published: June 2009

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

SummaryThe reaction of αs1- and β-casein with ferrous ions and O2 has been studied. It has been found that phosphoseryl residues present in these proteins rapidly catalyse the oxidation of iron from the ferrous to the ferric state with the formation of stable ferric-phosphoprotein complexes and the consumption of the theoretical amount of O2. When, however, the phosphoseryl residues occurred in groups, the formation of ferric complexes was accompanied by uptakes of O2 in quantities significantly in excess of that required for the oxidation of ferrous to ferric iron.The significance of these findings is discussed in relation to hypotheses which have been advanced concerning the possible biological function of phosphoprotein.
Heat stability of milk: influence of dilution and dialysis against water
Authors: Fox Patrick F. , Hearn Catherine M. 
Published: June 2009

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

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

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

SummarySeparated milk was treated with rennet at 30 °C for known proportions of the visually-determined clotting time. Samples were fixed with glutaraldehyde, which inhibited aggregation of casein micelles, mixed with agar, and stained sections examined. Bias in the preparation of the electron micrographs was minimized by replication, particularly in the early stages of sample preparation, and, for thin (60–90 nm) sections, by systematic selection of the areas examined.Whole casein micelles, viewed in stereo micrographs of thick (about 1 μm) sections, had open, diffuse structures and their appearance did not change on treatment with rennet. Micrographs of thick sections taken at 90° to each other showed that casein micelles form a network-type of gel, with the same structure in all dimensions. Counts of micelles larger than about 20 nm diam. in fields of thin sections showed that each of 3 sets of fields was similar and representative for each sample. The number of micelles/μm2 appeared to increase between 60 and 130 % of the clotting time, but this change was not statistically significant.
Sub-structure of synthetic casein micelles
Authors: Knoop Anne-Marie , Knoop Ernst , Wiechen Arnold 
Published: June 2009

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

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

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

SUMMARYThe theory of branching processes is used to derive a simple kinetic model for the heat-induced coagulation of a type A milk. Coagulation time-pH profiles and N depletion curves for the overall reaction can be fitted with the model, and most of the major properties for a milk exhibiting a type-A behaviour can be accounted for. Possible reactions for the heat-induced coagulation are also discussed in relation to the model.
Titrimetric studies on milk and milk products
Authors: Kirchmeier Otto 
Published: June 2009

SUMMARYPotentiometric acid-base titration is a simple method that can be used successfully in the investigation of the protein system of milk and other protein-containing products. Its applications include the examination of conventional heating procedures, cheese ripening, the investigation of processed cheese and the effect of melting salts. The principle depends on the performance of pH-dependent phase transitions which are recorded by a single titration cycle and evaluated quantitatively by means of hysteresis loops.
Major elements in milk of the West African dwarf goats as affected by stage of lactation
Authors: Akinsoyinu Akintunde O. , Akinyele Isaac O. 
Published: June 2009

SUMMARYTwelve adult West African dwarf (Fouta djallon) does, about 2 years old and weighing from 25 to 28 kg were kept for lactation studies lasting two 19-week periods. During these periods the does were hand-milked twice daily and the daily samples were bulked for each animal for subsequent analysis.The results showed that the colostrum was much richer in its content (g/kg) of Na 1·44 ± 0·17, Κ 3·38 ± 0·22 and Cl 4·83 ± 0·29 than the mature milk which contained (g/kg) Na 0·65 ± 0·09, Κ 1·57 ± 0·19 and Cl 2·46 ± 0·58. The corresponding values obtained for Ca (0·65 ± 0·02) and P (0·36 ± 0·10) in the colostrum were, however, lower than 2·01 ± 0·98 and 1·18± 0·28 g/kg obtained for Ca and P respectively in the mature milk. The composition of these elements in the colostrum approached that of the normal goat's milk on the sixth d after parturition. The results showed a rise in Ca, P, Na and Cl levels with stage of lactation and a fall in Κ content of the milk with advancing lactation with the trends being highly significant (P < 0·01).
Effect of membrane perturbing treatments on the membrane-bound peptidases ofStreptococcus cremorisHP
Authors: Exterkate Fred A. 
Published: June 2009

SummaryThe effects of solubilization, treatment with organic solvents and storage under alkaline conditions on membrane-associated peptidases of intact cells ofStreptococcus cremorisHP were studied. Differences in the response of the peptidase activities towards these membrane perturbing treatments were observed. Pyrrolidonecarboxylylpeptidase (PCP) and an endopeptidase (P50) showed 50% irreversible inhibition at the same concentration of each solvent tested. An amino- and proline iminopeptidase activity and the endopeptidase P37were in this respect much more sensitive to the action of the solvents. Within a homologous series of n-alkanols irreversible inhibition of PCP showed a dependence on the hydrophobicity of the solvent molecules. Only P37activity was increased considerably upon solubilization of the enzyme. Similar levels of activation were found upon treatment of cells with 3% (v/v) n-butanol at 25 °C or storage at 30 °C at an alkaline pH. Optimal activity of P50during n-butanol treatment was at 25 °C using a concentration of 5% (v/v), but no activation was observed upon solubilization. The results are discussed in terms of enzyme–lipid interaction and accessibility of the enzymes in situ. It is concluded that the enzymes apparently occupy different positions within the membrane although they may together constitute a functional peptide-hydrolysing unit.