bluuebunny/crossref_metadata_2025_split huggingface dataset:
The transfer ofN-acetyl-4-aminoantipyrine and of thiocyanate from blood to milk
Authors: Wheelock J. V. , Rook J. A. F. 
Published: June 2009

SummaryThe entry into milk from blood ofN-acetyl-4-aminoantipyrine (NAAP) and urea, compounds known to be distributed evenly throughout the whole of body water, and thiocyanate and thiosulphate, the distribution of which is confined largely to extracellular fluid, has been investigated. The concentrations of NAAP and urea in blood and in milk were similar, but the concentrations of thiocyanate and thiosulphate in milk were much lower than the concentrations in blood plasma. A progressive increase in the ratio of the thiocyanate concentration in milk to that in blood occurred with advancing lactation and marked variations in the thiocyanate ratio of the milk of the separate quarters were observed in some cows, and these variations in the ratio were closely related to variations in the chloride content of the milk; similar inter-quarter variations in the ratio for NAAP were not observed. With NAAP, there was a continuous equilibrium between blood plasma and milk within the udder, whereas with thiocyanate the content in milk after its secretion into the ducts and cisterns of the udder appeared to be largely independent of later changes in the concentration of thiocyanate in blood plasma. These results are discussed in relation to the secretion of chloride in milk.
Acetaldehyde and diacetyl production by Streptococcus thermophilus and other lactic streptoccocci
Authors: Bottazzi Vittorio , Dellaglio Franco 
Published: June 2009

SummaryThe quantities of acetaldehyde and diacetyl produced in skim-milk and MRS media are reported for strains of Streptococcus lactis, Str. cremoris, Str. diacetilactis, Str. faecalis and Str. thermophilus obtained from culture collections or freshly isolated from natural milk cultures used in cheese manufacture. The diacetyl: acetaldehyde ratio in skim-milk medium was found to be approximately 0·1:1 for Str. lactis and Str. cremoris, 0·5:1 for Str. diacetilactis (5:1 for Str. diacetilactis PIM 13 and K.2 strains) and for Str. thermophilus 0·3:1, in skim-milk medium, and 0·8:1, in MRS medium; in the latter species cultured in MRS medium the ratio varied from 3·5:1 to 0·04:1 and when cultured in milk from 1·2:1 to 0·03:1.In both media all strains of Str. thermophilus formed more acetaldehyde and diacetyl than other homofermentative lactic streptococci.The ratio diacetyl: acetaldehyde in 9 strains of Str. diacetilactis was found to be unsuitable for a good culture flavour.
The effect of milking throughout pregnancy on milk secretion in the succeeding lactation
Authors: Smith A. , Wheelock J. V. , Dodd F. H. 
Published: June 2009

SummaryIn each of 5 cows, 2 quarters which had been regularly milked throughout the whole of pregnancy produced less milk in the next lactation than the other 2 quarters which had a normal dry period. The concentrations of the individual constituents in the milk of all 4 quarters of each cow were similar. The effect appears to be due to factors located within the individual quarter of the mammary gland rather than to factors such as the hormonal background or plane of nutrition which affect the whole animal.
Effects of some protein modifying agents on the properties of rennin
Authors: Cheeseman G. C. 
Published: June 2009

SummaryLoss of milk clotting activity when rennin was treated with urea at several concentrations and at different pH values was compared with the change in UV absorption of the protein. The change in absorption at 287 and 293 nm did not correlate with loss in activity, indicating that the loss of enzymic properties was not related to the extent of unfolding of the molecule but was related to the reaction of susceptible groups to the environmental conditions.Reactions of modifying agents, for example N-bromoacetamide, 2-hydroxy-5-nitrobenzyl bromide and mercuric ions with tryptophan groups and the relationship of these changes to enzyme activity suggested that tryptophan was not specifically associated with enzyme action but was important in maintaining tertiary structure.Rennin was not inhibited by the pepsin inhibitors p-bromophenacyl bromide and α-diazo-p-bromoacetophenone which suggested that the active site did not possess a reactive carboxyl group as in pepsin. However, the reversible inhibition with 1-cyclohexyl-3(2morpholinoethyl)-carbodiimide metho p-toluenesulphonate together with the results of oxidation by N-bromoacetamide indicated that a tyrosine group or groups was important in enzyme activity.
The heat stability of milk as affected by variations in pH and milk salts
Authors: Morrissey P. A. 
Published: June 2009

SummaryThe maximum and minimum heat stability exhibited by most milks over a relatively narrow range of pH values is shown also by synthetic colloidal calcium caseinate-calcium phosphate systems and even by simple caseinate systems, provided all possess adequate contents ofβ-lactoglobulin, soluble calcium and phosphate. The phenomenon is not, however, dependent on the presence of the characteristic micellar structure of the casein of milk. The minimum stability observed, usually around pH 6·9, is the most characteristic feature of the phenomenon and arises from heat induced deposition of calcium phosphate on a caseinate/β-lactoglobulin complex. This reaction, which tends to occur to a marked degree at relatively high pH values and calcium ion concentrations, sensitizes the complex to precipitation by calcium ions. The precise pH values at which the maximum and minimum stabilities occur can vary depending on the salt composition of the serum, since the latter can influence the solubility of calcium phosphate.
Fractionation of bovine serum lipoproteins and their characterization by gradient gel electrophoresis
Authors: Brumby P. E. , Welch V. A. 
Published: June 2009

SummaryBovine serum lipoproteins were fractionated by precipitation with dextran sulphate followed by ultracentrifugation and were examined by paper electrophoresis and by disk electophoresis in acrylamide gels. Gels containing concentration gradients of both sucrose and acrylamide gave better resolution of lipoproteins than did gels of uniform composition or gels with a concentration gradient of sucrose and a uniform concentration of acrylamide.The densities of the lipoprotein classes isolated (listed in order of increasing mobility on electrophoresis in acrylamide gels) were as follows:I,d< 1·019; II, 1·039 <d<1·050;III, 1·019 <d<1·039; IVa and IVb,d> 1·050.Lipoproteins of classes I, II and III were precipitated by dextran sulphate. On paper electrophoresis, lipoproteins of class II had β mobility and lipoproteins of classes IVa and IVb had α mobility. Lipoproteins of class I remained at the origin.The lipoprotein classes of bovine sera resembled those of sheep and goat sera in that class IV predominated. In contrast, the sera of several non-ruminant species showed a predominance of lipoprotein classes of low electrophoretic mobility.
An improved method for canning 3-fold concentrated whole milk
Authors: Board P. W. , Mullett J. T. 
Published: June 2009

SummaryA method is described for canning and sterilizing concentrated whole milk containing 36·5% total solids. The product had acceptable organoleptic properties and did not form sediment or undergo age-thickening during storage. The method involved initially increasing the pH of the raw milk and forewarming. The product was not homogenized nor were polyphosphates added.
Determination of nitrite in cheese and other dairy products
Authors: Rammell C. G. , Joerin M. M. 
Published: June 2009

SummaryDetails are given of a spectrophotometric method for determining nitrite in cheese and other dairy products at levels down to 0·05 μg NO2-N/g and of a spectrofluorimetric method for levels down to 0·003 μg NO2-N/g. Nitrite-N levels in cheese varied from 0·003 μg/g to 0·021 μg/g. These levels increased up to 4-fold after UV irradiation of the cheese extracts. No nitrite (< 0·003 μg/ml) could be detected in raw milk.
Metabolism of cod-liver oil in relation to milk fat secretion
Authors: Brumby P. E. , Storry J. E. , Sutton J. D. 
Published: June 2009

SummaryThe effects of daily supplements of 300 g native and 2 hydrogenated cod-liver oils (CLO) to the diets of lactating cows have been examined. Native CLO supplements increased the proportion of propionate and decreased the proportion of acetate in the rumen and also decreased the yields in milk of fatty acids synthesized within the mammary gland and those derived from plasma triglycerides. These effects were reduced or eliminated when the hydrogenated oils were given instead of the native CLO. With all 3 supplements about 15% of the dietary C20and C22acids was secreted in milk.Both native and hydrogenated CLO supplements increased the concentrations of the cholesteryl ester and phospholipid components of the α-lipoproteins in the blood plasma. These components contained most of the C20and C22acids of the CLO supplements that were incorporated into the blood plasma lipids. With the native CLO supplement about half of the C20and C22acids present in the blood plasma were polyunsaturated.There were no differences in the effectiveness of high-density plasma lipoproteins as activators of triglyceride emulsions for lipoprotein lipase hydrolysis whether the lipoproteins were from cows receiving the native or the hydrogenated CLO supplements or the control diets. Significant rates of hydrolysis by lipoprotein lipase could not be demonstrated using as substrates low- or high-density plasma lipoproteins or activated emulsions of their extracted lipids.Additional in vitro experiments using activated triglyceride emulsions as substrates for mammary lipoprotein lipase showed that replacement of a soybean oil emulsion by an emulsion of native CLO reduced the rate of hydrolysis considerably, whereas an emulsion of hydrogenated CLO was without effect unless it was present at levels in excess of 50%.It is concluded that the change in rumen fermentation induced by the polyunsaturated fatty acids of CLO is implicated in the decreased intramammary synthesis of fatty acids, but that additional information is required before the reason for the reduced mammary uptake of plasma fatty acids can be established.
Measurement of the protein content of milk from mastitic quarters by the Amido Black method
Authors: Waite R. , Smith G. M. 
Published: June 2009

SummaryAn investigation was made into the effect of subclinical mastitis on the accuracy of the Amido Black method for measuring the crude-protein percentage of the milk of individual cows. Values obtained by the dye-binding and Kjeldahl methods on a sample of milk from each quarter of 46 cows, 11 of which were sampled at regular intervals during lactation, were compared. It was concluded that, even in cases of severe subclinical mastitis, the effect is so small as to constitute no objection to the use of the dye-binding method. The accuracy of the Amido Black method, irrespective of disease, was less in milk produced in the first and last months of lactation.
Casein micelle structure: location of κ-casein
Authors: Fox P. F. , Morrissey P. A. 
Published: June 2009

SummaryThe effect of heat treatment on the rennet coagulation times (RCTs) of various casein–whey protein systems, the effect of pre-renneting centrifugal serum on the RCT of casein subsequently mixed with such serum, the influence of repeated centrifugation and resuspension at constant protein level on the RCT of such suspensions, and the rate and completeness of the hydrolysis of sialic acid in micellar and non-micellar caseins, all lead to the conclusion that κ-casein does not occur in milk in 2 functionally different states, as proposed by Parry & Carroll (1969).
Periodic omission of dairy cow milkings: I. Effect on milk yield and composition and on udder health
Authors: Radcliffe J. C. , Bailey L. F. , Horne M. L. 
Published: June 2009

SummaryForty-five Friesian cows were assigned to one of 3 milking management treatments: (1) cows milked 14 times weekly, (2) cows milked 13 times weekly (Wednesday morning milking omitted), and (3) cows milked 12 times weekly (Tuesday evening and Wednesday morning milkings omitted). Cows were removed from the trial at the end of their lactations, and newly calved cows were added as they became available. The trial was continued for 12 months.When one milking was omitted weekly, the total lactational milk yield was reduced by 3·5%, fat yield by 2% and protein yield by 1·5%. These reductions were not statistically significant. When 2 consecutive milkings were omitted, the yield of milk and of its main components was reduced by 14% (P < 0·001). The effects were greatest for highly productive cows in early lactation.When one or 2 milkings were omitted the milk yield on the following day was nearly 50% greater than the mean daily yield. No increase in the incidence of subclinioal mastitis was observed in either milking omission treatment.It is concluded that it is practicable to omit one milking each week though it is suggested that the technique should not be used in highly productive herds unless most of the cows are past the sixth week of lactation.
Seasonal variations in the composition and thermal properties of New Zealand milk fat: II. Thermal properties of milk fat and their relation to composition
Authors: Norris Gillian E. , Gray I. K. , Dolby R. M. 
Published: June 2009

SummaryMelting curves were determined by differential scanning calorimetry on 17 samples of milk fat obtained at approximately fortnightly intervals through one dairying season. Liquid-fat content at a number of temperatures was calculated from the melting curves.Correlation between percentage liquid fat at 12 and at 22 °C and weight percentage of short-chain fatty acids (C4–C8) was low (r = 0·45 and 0·58 respectively) as was that with cis-unsaturated acids (r = 0·39 and 0·29). Correlation with the sum of short-chain and cis-unsaturated acids was higher (r = 0·71 and 0·68). With a multiple regression model including short-chain and cis-unsaturated acids the values of the multiple correlation coefficient (R) were 0·75 and 0·78.The softening point showed a high correlation (r = 0·79) with weight percentage of long-chain saturated acids and also with the temperature at which 94 % of the fat was liquid (r = 0·75).Possible explanations of these findings are discussed.
Cavitation and separated flow in a simple homogenizing valve and their influence on the break-up of fat globules in milk
Authors: Phipps L. W. 
Published: June 2009

SummaryFlow separation and cavitation effects in a simple homogenizing valve have been studied visually and recorded photographically. The degree of separation depended upon the profile of the seating inlet boundary, the pressure loading and several other interdependent factors. Cavitation did not occur independently of separation; conditions would be suitable for microscale cavitation to occur within the separated flow itself, but this was not discerned with certainty. The suppression of separation and any cavitation, assessed visually, did not influence the homogenizing characteristics of the valve. It was concluded that hydrodynamic forces of cavitation are not responsible for fat globule disintegration in drop-and-lift or poppet types of high-pressure homogenizing valve.
The influence of lysolecithin on the complex formation between β-lactoglobulin and κ-casein
Authors: Korver O. , Meder H. 
Published: June 2009

SummaryUltraviolet difference spectral measurements and some circular dichroism data are reported on the systems (β-lactoglobulin (BLG)/soya-lysolecithin (sll)), (κ-casein (KC)/sll) and (BLG/KC/sll). Sll destabilizes the native conformation of BLG and KC and promotes the interaction between BLG and KC. The influence of sll: protein ratio and time of heating on the complex formation has been investigated.
Studies on the heat stability of milk protein: II. Effect of exposing milk to light
Authors: Sweetsur A. W. M. , White J. C. D. 
Published: June 2009

SummaryIt was found that the increase in heat stability (coagulation time) that occurs when some milks are stored in light was not caused by changes in pH. These labile milks invariably gave a type A heat-stability curve, had a pH in the range corresponding to the coagulation-time minimum of the curve, and showed the expected abnormal 2-stage type of coagulation. The increase in coagulation time following exposure to light resulted from a delay in the occurrence of the first coagulation, the second coagulation time remaining unaltered. The presence of riboflavin in milk and of O2 in the headspace atmosphere during storage were necessary conditions for milk to be labile. Since light, headspace O2 and riboflavin had similar influences on rennet coagulation time it is suggested that in both instances the causative reaction, as proposed by others to account for the increase in rennet coagulation time of H2O2-treated milk, is stabilization of the heat- and rennin-sensitive methionine-phenylalaninebond in κ-casein by photo-oxidation of the methionine to methionine sulphoxide.
Studies on the heat stability of milk protein: III. Effect of heat-induced acidity in milk
Authors: Sweetsur A. W. M. , White J. C. D. 
Published: June 2009

SummaryAn examination was made of the effect of varying the protein, lactose and total serum ion content of milk on the rate of production of heat-induced acidity (as measured by pH decrease), on heat stability (as measured by coagulation time), on the relationship between coagulation time and initial pH of milk (as measured by coagulation time-pH curves) and on the interrelationship of these parameters. In addition, the effect on these parameters and their interrelationship of varying the composition and volume of the headspace atmosphere in contact with the milk was investigated. Explanations are proposed for the observed effects on heat stability of varying the composition of milk and the heating conditions, with special reference to the influence of heat-induced acidity.
Preparation and properties of β-casein from buffalo's milk
Authors: El-Salam M. H. Abd , El-Shibiny Safinaz 
Published: June 2009

Summaryβ-Casein from individual buffalo's milk was found to be homogeneous by starch-gel electrophoresis. β-Casein was separated from buffalo's milk by the method of Warner (1944) and purified by DEAE-cellulose chromatography.Buffalo β-casein possesses identical end-groups to those of cow β-casein; namelyN-terminal arginine and assuming a single polypeptide chain a possibleC-terminal sequence of Ile-Ile-Val. However, the amino-acid composition and the tryptic peptide patterns of the 2 proteins are not the same.
The preparation and assessment of a suitableMucor pusillusLindt proteinase–swine pepsin mixture for Cheddar cheese-making
Authors: Green Margaret L. , Stackpoole A. 
Published: June 2009

SummaryA simple test procedure was used to predict the most suitable mixture of Noury rennet (Mucor pusillusLindt proteinase) and swine pepsin for Cheddar cheesemaking. Duplicate cheeses were made with 6 Noury rennet–swine pepsin mixtures and with each enzyme alone, with calf rennet as the control. There were slight differences in the course of the cheese-making process and in the yields of the cheeses. Sensory evaluation showed that the most acceptable cheeses were those made by coagulant mixtures closely similar to the predicted mixture and these were as acceptable as cheeses made with calf rennet. The survival rates of different groups of bacteria were similar in all cheeses. There were differences in the products of proteolysis in the various cheeses throughout ripening, particularly with respect to products derived from αs1-casein. The Noury rennet was characterized for the proportion of milk clotting activity associated with each of 4 components and its stability in solution was determined.
A comparison between the amino acid compositions of 2 chymosin-sensitive polypeptides and C-terminal segments of κ-casein
Authors: Beeby R. 
Published: June 2009

SummaryTwo distinct types of chymosin-sensitive polypeptide were found in the soluble fraction obtained when a solution of crude κ-casein in 0·4 m-NaCl was adjusted to pH 3. One corresponded to a segment of κ-casein comprising residues 94–169. The other was very similar to the section Gln77-Val169 in the protein, but contained a phosphate group plus isoleucine and glycine in the region between the N-terminus and the chymosin-sensitive bond. If these polypeptides form as a result of a specific cleavage of κ-casein, the data indicate that there is a variant of this protein with a number of amino acid replacements on the N-terminal side of the chymosin-sensitive bond. The shorter polypeptide and κ-casein are both rapidly cleaved by chymosin at pH 6·7 which suggests that the contribution of residues 1–93 to the sensitivity of the Phe-Met bond in κ-casein is a minor one.
Cytochemical observations on the extracellular carbohydrate produced byStreptococcus cremoris
Authors: Brooker B. E. 
Published: June 2009

SummaryElectron microscopy showed that a varying proportion of cells ofStreptococcus cremorisNCDO 924 grown in autoclaved skim-milk possessed a layer of extracellular material attached to the cell wall. Occasional filamentous extensions of this layer made contact with neighbouring casein micelles. The same surfacestaining material persisted during the production of cheese-curd, but after maximum scald it was predominantly filamentous in appearance. These filaments made frequent contact with the adjacent curd matrix and with milk-fat globules.Str. cremorisNCDO 1986 produced similar surface material when in curd, but not when grown in skim-milk. In all situations, the extracellular material stained with colloidal iron hydroxide, ruthenium red and periodic acid–thiosemicarbazide–silver proteinate, indicating that it was largely composed of an acidic carbohydrate. It is suggested that this carbohydrate facilitates the adhesion of starter bacteria to the cheese-curd matrix and that during the initial stages of syneresis this serves to prevent their expulsion from the curd with the whey.
Amino acid nutrition of some commercial cheese starters in relation to their growth in peptone-supplemented whey media
Authors: Law B. A. , Sezgin Emel , Sharpe M. Elisabeth 
Published: June 2009

SummarySome strains of commercial cheese starters were obtained in higher yield after batch culture in whey-based media supplemented with soy peptones than in those supplemented with papain digested skim-milk. The soy peptones contained a greater proportion of small peptides than did the skim-milk digest. Also the average size of peptides was lower (3·4–3·9 residues) in soy preparations than in the milk digest (6·8). Small peptides isolated from the soy peptones were utilized by growing starters more completely than the equivalent peptides isolated from the papain digested milk. These observations may account for the difference in cell yields with soy and milk-digest peptones.
Kinematic viscosities of New Zealand skim-milk
Authors: Buckingham J. H. 
Published: June 2009

SummaryThe variation in kinematic viscosity (ν) with solids concentration and temperature has been determined for native skim-milk concentrates and reconstituted New Zealand skim-milk. Below 40% (w/v) total solids, samples reconstituted from a single batch of skim-milk powder model the behaviour of native concentrates obtained from an evaporation plant at all times of the year. Above 40% (w/v) agethickening and seasonal variations in the viscosity of native concentrates become significant. Age-thickening can be reduced by cooling the concentrate. These results are discussed in relation to milk powder manufacture.