bluuebunny/crossref_metadata_2025 huggingface dataset:
The melting properties of milk fat fractions obtained by double fractionation using a commercial process
Authors: Sherbon J. W. , Dolby R. M. , Russell R. W.
Published: June 2009

Solid fractions obtained by a commercial process from anhydrous milk fat were refractionated and the softening point (SP), iodine value (IV), and melting thermograms determined. The content of high melting fats and liquid fat content at the SP were calculated for each fraction from its thermogram. Refractionation at 28 °C did not alter the properties of the resultant solid fat. The small amount of liquid fat obtained by refractionation resembled intact milk fat in the properties measured. Refractionation at 31–32 °C yielded a solid fat having a higher SP, lower IV, and increased high melting fat content. Triple refractionation resulted in a solid fraction having a restricted melting range and capable of crystallizing in an unstable polymorphic form upon quick cooling. Tempering the refractionated solid fats at the melting gap temperature of 20–22 °C resulted in elimination of phases melting below −10 °C and enhancement of the melting gap. The content of high melting fat was correlated with the SP. The SP occurred when 95 % of the fat (S.D.±2·7 %) had melted.
The effects of the protein content of the diet on the performance of lactating cows
Authors: Paquay R. , Godeau J. M. , De Baere R. , Lousse A.
Published: June 2009

Four experiments were carried out with Friesian cows in different stages of lactation to determine the influence of the crude-protein content of the diet on the digestibility and utilization of dietary constituents and on the cow's performance and milk composition.

The rations were composed so that they met the energy requirements of the cows, but crude-protein content was widely variable.

Our findings on the digestibility of the dietary constituents were in agreement with the data given in the literature.

The utilization of dietary N for milk secretion was influenced by the level of N intake only when the crude-protein content of the diet was lower than a limiting value, which varied according to stage of lactation. When this value was not attained the daily milk production was affected, but not the protein content of the milk.

The optimal crude-protein content of the diet was 15–16% (dry-matter basis) when milk production exceeded 20 kg/d, 12–13% for a production of 15–17 kg/d and 11–12% for cows giving less than 10 kg of milk daily.
A technique for evaluating reconstitution properties of milk powders
Authors: Wyeth T. C. , Cheeseman G. C.
Published: June 2009

An accurate and reproducible technique involving a continuous aqueous elution from a bed of dried-milk powder was developed to evaluate reconstitution characteristics. Quantitative data for the determination of reconstitution behaviour were obtained by analysis of the eluate for protein, lactose and Ca constituents. A reconstitution coefficient (P) was derived from the formula (W1+ΣWi)/T, where W1 was the amount reconstituted in the first eluate fraction, ΣWi the total amount reconstituted in 8 fractions, and T the time taken for 1/3 of the constituent to be reconstituted. Values obtained for P were thus related to the reconstitution properties and could be used to grade the powders. A freeze-dried skim-milk gave the ideal reconstitution behaviour with W1 values in the range 42·0–44·2, ΣWi values in the range 93·6–101·3, T values in the range 3·0–3·3 and reconstitution coefficients in the range 41·1–46·3 for the 3 constituents. All the other preparations tested gave lower values for W1 and P, although some gave ΣWi values in the same range, whilst all T values were higher than those for the freeze-dried sample.
Proteolysis detection in milk: I. Interpretation of tyrosine value data for raw milk supplies in relation to natural variation, bacterial counts and other factors
Authors: Juffs H. S.
Published: June 2009

A method for detection of proteolysis in milk was evaluated. Amino acids and peptides soluble in trichloroacetic acid were estimated by the Lowry–Folin procedure with expression of results in terms of colour yield equivalent to that of tyrosine (the ‘tyrosine value’ (TV)). Some variables and alternatives in the method of estimation were investigated.

TVs for milk freshly drawn from individual cows were extremely varied (0·31–0·92 mg/ml). TVs for samples of refrigerated milk from daily supply farms were in the range 0·40–0·58 mg/ml; no relationships between TV and bacterial counts were evident with these samples. With bulk refrigerated raw milk supplied to Brisbane for liquid consumption from country depots and local farms equipped with bulk vats, significant positive relationships were found between TV and total bacterial count (TBC) for supplies from some sources, but in no instance was a significant relationship found between TV and psychrotroph or proteolytic psychrotroph count. Significant positive relationships were found between TV of bulk milk supplies from some sources and atmospheric temperature, and between TBC of the supplies and atmospheric temperature. The significance of these various relationships for bulk milks is discussed.

Natural variation in TV imposed limitations on reliability of the method to provide an index of proteolysis; in general the results indicated that its application was restricted to bulk milk cold-stored for at least 3 days.
The release of intracellular dipeptidase from starter streptococci during Cheddar cheese ripening
Authors: Law B. A. , Sharpe M. Elisabeth , Reiter B.
Published: June 2009

Intracellular dipeptidase ofStreptococcus cremorisNCDO 924 has been investigated as a marker enzyme for detecting the release of starter enzymes into Cheddar cheese during maturation. Dipeptidases were produced extra- and intracellularly byStr. cremorisin broth cultures, but the intracellular enzyme was distinguishable by its relatively high activity against L-alanylglycine at low temperatures. The presence of dipeptidase activity of intracellular origin was demonstrated in extracts of Cheddar cheese freed from whole starter cells, opaque material of high molecular weight and free amino acids by a combination of centrifugation and gel filtration on Sephadex G200. The enzyme was not detected in cheeses made without starter (δ-gluconic acid lactone cheeses). In fresh curd with a high viable count of starter the dipeptidase activity was low and mostly extracellular. As the count declined the proportion of intracellular enzyme activity increased, reaching a maximum when 90% of the starter cells had died. The total dipeptidase subsequently decreased until the level remained 30% higher than that of the original curd, and changed little on further ripening up to 120 d. There remained a significant proportion of extracellular dipeptidase activity throughout the maturation period studied.
Interspecies study on the effect of perphenazine on milk yield and composition
Authors: Shani (Mishkinsky) J. , Cowie A. T. , Broster W. H.
Published: June 2009

The effects on lactation of perphenazine, a tranquillizer which increases the level of prolactin in the blood, have been studied in cows, goats, guinea-pigs and rabbits. The drug caused a significant depression of milk yield in cows, goats and rabbits, but was without effect on the milk yield of guinea-pigs. It seems probable that the inhibitory effects on lactation were due to the actions of the drug on appetite and behaviour. It is concluded that perphenazine, because of its other actions, is not a suitable agent for studying the physiological effects of increased levels of endogenous prolactin.
Proteolysis in Cheddar cheese: influence of the rate of acid production during manufacture
Authors: O'Keeffe R. B. , Fox P. F. , Daly C.
Published: June 2009

Data are presented which show that the use of glucono-δ-lactone as a chemical acidulant in cheese manufacture results in a much more rapid decrease in pH than that occurring in biologically acidified cheese. One of the consequences of the excessive early acid development was a very marked increase in the level of proteolysis during cheese-manufacturing operations. Consequently, chemically acidified cheese, as manufactured by the technique of Mabbitt, Chapman & Berridge (1955) (expt 17), does not appear to be a suitable ‘reference cheese’, especially for studies in which proteolysis during ripening is under investigation. The technique of Mabbitt et al. Avas modified to simulate the pH development pattern of starter cheese more closely; the level of proteolysis in curd made by the modified method was approximately equal to that in starter curd.

An attempt was made to link the propensity to develop bitterness of cheese made with fast acid-producing cultures with excessive early proteolysis in such cheese. The results show that fast- and slow-culture strains differed significantly in their acid-producing capability only after the cooking stage and consequently such cheeses differed little with respect to early proteolysis. Further, cheeses made with 0·5, 1·0, 2·0 or 4·0% of ML8 culture which differed considerably in rate of acid development and consequently in the level of early proteolysis did not develop bitterness, even when 4·0% starter was used.

It is concluded that gross proteolysis and bitterness are not correlated.
Peptidase activities in Group N streptococci
Authors: Mou Lynette , Sullivan J. J. , Jago G. R.
Published: June 2009

Several peptidase activities in the 3 species of Group N streptococci were partly separated by gel filtration on Sephadex G-200. The peptidases identified were a general aminopeptidase of wide specificity, a tripeptidase, a proline iminopeptidase (prolyl-β-naphthylamidase), a proline iminodipeptidase and an aminopeptidase-P. The effects of temperature and pH on the stability of the enzyme activities, and the influence of the type of N source used in the growth medium on the elution pattern of the enzymes were examined.
The effect of oxygen content on flavour and chemical changes during aseptic storage of whole milk after ultra-high-temperature processing
Authors: Thomas E. L. , Burton H. , Ford J. E. , Perkin A. G.
Published: June 2009

Indirectly heated ultra-high-temperature (UHT) processed milk was prepared with initially high, medium, and low dissolved O2 contents of 8·9, 3·6 and 1·0 ppm respectively, aseptically bottled, and tested at intervals during storage at room temperature for 150 d. Flavour acceptability increased to a maximum after a few days, but declined slowly after about 6 d; the increase was associated with less off-flavour described as ‘cabbagey’, and the decrease with more ‘stale’ off-flavour descriptions. Milks with higher initial O2 contents were preferred up to 8–13 d, but thereafter acceptability was independent of initial O2 content. Sulphydryl group (–SH) contents rapidly decreased and O2 levels correspondingly declined in the first few days as the flavour improved. Loss of –SH was lower with lower initial O2 contents, and moderate –SH content remained in low O2 samples for several weeks. Ferricyanide reducing (FR) values did not satisfactorily measure stale flavour development. They were initially high and decreased during the first 13 d at rates dependent on O2 content. After 20 d the FR values began to rise in high O2 samples, but continued to decline slowly in low O2 samples up to 90d although stale flavour was increasing.

High initial O2 contents resulted in rapid depletion of ascorbic acid and folic acid during storage. Losses of vitamin B12 were small, but were higher with high O2 contents than with low.

The beneficial effect of O2 on flavour, therefore, appears to be so slight and confined to such a short period in the early life of the milk as to be completely outweighed by the adverse nutritional effects.
Relationships between stage of lactation and pregnancy and blood composition in a herd of dairy cows and the influences of seasonal changes in management on these relationships
Authors: Rowlands G. J. , Manston R. , Pocock Rita M. , Dew Sally M.
Published: June 2009

Blood samples, taken on 6 occasions during 1 year from 172 cows resident in a dairy herd, were analysed for packed cell volume, blood glucose, haemoglobin (Hb), serum albumin, urea N, total protein, Ca, inorganic phosphate, Mg, Na and K. The data were analysed statistically, firstly with respect to date of sampling, stage of pregnancy or lactation and the interaction between stage of pregnancy or lactation and date of sampling, and secondly with milk yield as an additional factor for the data for lactating cows.

Concentrations of all constituents except inorganic phosphate and K varied significantly (P<0·001) with stage of lactation and/or pregnancy. The most significant changes in concentrations were confined to the periods up to 3 months either side of calving. The greatest changes in concentration during these periods occurred for Mg which rose during late pregnancy and for albumin which fell at or near calving. Albumin, urea and glucose were all, on average, lowest in concentration during the first month of lactation; globulin concentrations showed the reverse trend. Haemoglobin concentrations decreased during late pregnancy and early lactation and were lowest in the period 30–120 d post partum. Calcium concentrations decreased during late pregnancy and rose during early lactation. Sodium concentrations rose during late pregnancy. Interactions between dates of sampling and stages of lactation or pregnancy were significant (P<0·001) for all constituents, and most marked for glucose, urea, albumin, Hb, Ca and Na.

Haemoglobin and K concentrations fell and Mg concentrations rose with increasing milk yield, but the proportions of the total variance accounted for by differences in milk yield were small in relation to those accounted for by stage of lactation. These findings are of significance in relation to the selection of animals for sampling in the Compton Metabolic Profile Test.
Artificial induction of lactation by hypothalamic implantation of perphenazine in virgin goats
Authors: Vandeputte-van Messom Georgette , Peeters G. , Lauwers H.
Published: June 2009

Perphenazine (0·8–1mg) caused udder growth and artificial induction of lactation, when stereotaxically implanted into the median eminence of virgin female goats. Sham implantations into the median eminence or implantation of perphenazine into sites of the hypothalamus not in the immediate proximity of the median eminence were ineffective. Fourteen–twenty-two d after implantation the goats were milked for the first time. Maximal milk yields of 250–1050 ml/d were achieved 3–5 months later. Udder development and induction of lactation during the premilking period were exclusively due to the action of perphenazine. It is likely that after implantation the milking stimulus played a synergic role with perphenazine in the progressive increase and the maintenance of lactation. Apparently no side effects were caused by the drug. Implantation of small doses of perphenazine in the hypothalamus might be a suitable technique for studying the physiological effects of increased levels of endogenous prolactin in goats.
Effect of storage on the electronic cell count of milk
Authors: Sweetsur A. W. M. , Phillips J. D.
Published: June 2009

Using a standard method, the electronic cell count of formalin-treated milk usually increased during storage. This increase varied with the milk and was found to be due to a corresponding decrease in the effectiveness of the fat-dispersal procedure before counting. A more severe fat-dispersal procedure incorporated into the standard method resulted in a stable cell count being obtained. It was found that formalin must be added to milk within 24 h of milking to prevent lysis of the cells.
Acetaldehyde: an intermediate in the formation of ethanol from glucose by lactic acid bacteria
Authors: Lees G. J. , Jago G. R.
Published: June 2009

Group N streptococci formed acetaldehyde and ethanol from glucose. As the enzymes aldehyde dehydrogenase, phosphotransacetylase and acetate kinase were present this would enable these organisms to reduce acetyl-CoA to acetaldehyde and convert acetyl-CoA to acetyl phosphate and acetate. A pentose phosphate pathway which converted ribose-5-phosphate to glyceraldehyde-3-phosphate was also present. Acetaldehyde could not be formed via the hexose monophosphate shunt or by direct decarboxylation of pyruvate, as the enzymes phosphoketolase and α-carboxylase were absent. Phosphoketolase activity was induced inStreptococcus lactissubsp.diacetylactisafter growth on D-xylose. Group N streptococci also contained an NAD-dependent alcohol dehydrogenase which reduced acetaldehyde to ethanol while both NAD- and NADP-dependent alcohol dehydrogenase activities were found inLeuconostoc cremoris.
Immunochemical, chromatographic, and milk-clotting activity measurements for quantification of milk-clotting enzymes in bovine rennets
Authors: Rothe G. A. L. , Axelsen N. H. , Jøhnk P. , Foltmann B.
Published: June 2009

Monospecific rabbit antibodies were produced against bovine chymosin (rennin) and bovine pepsin A and used for quantitative measurements of these enzymes by rocket immunoelectrophoresis. Bovine pepsin B was identified and measured quantitatively in tandem crossed immunoelectrophoresis, using a polyspecific antibody preparation. Chromatographically purified chymosin B and bovine pepsins A and B were used as standards. The contents of chymosin and bovine pepsin A were also determined by 2 forms of DEAE chromatography, and by an assay utilizing the ratio of milk-clotting activity at pH 6·0 and 6·5. Results obtained by measurements on 3 bovine rennets (calf rennet, adult bovine rennet, and a mixture of such types) by the different methods of analysis were in good agreement. The advantages of the immunochemical methods are direct and simultaneous identification and quantitation of enzymes.
Serological studies on heat-induced interactions of α-lactalbumin and milk proteins
Authors: Baer A. , Oroz M. , Blanc B.
Published: June 2009

The heat denaturation of α-lactalbumin (α-la) in NaCl and KCl solutions, milk ultrafiltrate and milk was studied using the method of micro complement fixation. It was established that this protein was very resistant to heat denaturation and that it was more stable in milk ultrafiltrate than in the other media studied at temperatures up to 70 °C. Of the various milk proteins added to α-la, only β-lactoglobulin (β-lg) formed a heat-induced complex with this protein. This complex was identical in milk ultrafiltrate or in milk and depended on the molar ratio between both proteins; it was not modified by any other milk proteins. The binding of a-la to β-lg changed the ability of the latter protein to bind κ-casein.
A heat-induced change in the ultrastructure of milk and its effect on gel formation in yoghurt
Authors: Davies F. L. , Shankar P. A. , Brooker B. E. , Hobbs D. G.
Published: June 2009

Micelles of milk heated at 95 °C for 10 min or autoclaved at 121·7 °C for 15 min were observed by electron microscopy to bear filamentous appendages, whereas micelles from raw milk had relatively smooth contours with no appendages. Experiments suggested that the appendages were composed of denatured β-lactoglobulin and showed that their development was sensitive to sulphydryl blocking agents. Firmness and syneresis of yoghurt were associated with the extent to which micelles coalesced during fermentation; the appendages of micelles in heated milk appeared to inhibit coalescence giving rise to a firmer curd with a lower tendency to syneresis.
The formation of complexes between whey proteins and carboxymethyl cellulose modified with substituents of increased hydrophobicity
Authors: Zadow J. G. , Hill R. D.
Published: June 2009

The precipitation of proteins from whey by modified carboxymethyl cellulose (CMC) was examined. Carboxymethyl cellulose containing acetyl, methoxyl or carboxymethyl secondary amides with iso-propyl, n-propyl, iso-butyl, n-butyl or cyclohexyl side chains precipitated more protein than did CMC of similar carboxyl content. This effect was greatest in CMC containing secondary amide groups. The increase in protein precipitation gained by introduction of secondary amide groups into CMC was no greater however than the increase obtained by introduction of a similar number of carboxymethyl groups into the polymer. Carboxyethyl cellulose did not form insoluble complexes with whey proteins under the conditions examined.
Metabolism of [14C]bicarbonate byStreptococcus lactis: identification and distribution of labelled compounds
Authors: Hillier Alan J. , Jago G. Richard
Published: June 2009

Streptococcus lactisC10, grown in tryptone–yeast extract–lactose broth containing [14C] bicarbonate, incorporated radioactivity into the protein and nucleic acid fractions of the cell as well as into compounds which were excreted by the organism into the growth medium. Aspartic acid was the first compound to be labelled and was the only amino acid labelled in the cell protein. All 4 bases were labelled in the cell RNA. Aspartic, succinic and lactic acids were the radioactive compounds excreted into the growth medium.
Stereospecific distribution of fatty acids in bovine milk fat triglycerides
Authors: Parodi Peter W.
Published: June 2009

Pancreatic lipase deacylation was used to study the variation in distribution of the fatty acids at positionsn-2 of milk fat triglycerides of a series of butters and of the milk obtained from a cow on a restricted feeding regimen. Selected samples were analysed for stereospecific distribution of their triglyceride fatty acids which were found to be esterified in a non-random manner. The percentage of a fatty acid at positionsn-3 generally decreased with increase in the chain length of the acid; the reverse occurred at positionsn-1. There was no major variation in the stereospecific distribution of fatty acids throughout the year; the variation that did occur was exhibited mainly by the medium chain length acids. Variation was greater at positionssn-1 andsn-3 than at positionsn-2 and when the proportion of an acid varied at positionsn-1 it usually varied at positionsn-3 in the reverse manner.

For the milk samples it was found that change in triglyceride fatty acid composition was not associated with random increases or decreases of fatty acids at the 3 stereospecific positions. With changing triglyceride fatty acid composition (6:0, 8:0, 10:0, 12:0, 14:0, and 16:0 decreasing and 18:1 increasing) the percentage of 6:0, 8:0, 10:0, 12:0, 14:0 and 16:0 acids at positionsn-3 decreased while the percentage of 18:0 and 18:1 acids increased. These changes were compensated for by changes in the opposite direction at positionssn-1 andsn-2.
Quantitation of αs1-casein aggregation by the use of polyfunctional models
Authors: Dalgleish Douglas G. , Parker Thomas G.
Published: June 2009

A model for the coagulation of Ca2+ αsl-caseinate is described wherein the casein molecules are considered to aggregate as polyfunctional units. The functionalities on the protein molecules are produced as a consequence of the binding of Ca2+, and the multiple equilibria which are established during this binding produce a distribution in which not all casein molecules have the same functionality. The theory is compared with experimental data of the precipitation reaction, and is shown to provide an adequate quantitative description of the precipitation.
The voluminosity of bovine casein micelles and some of its implications
Authors: Walstra Pieter
Published: June 2009

A comparison of literature results on the voluminosity of casein micelles yields large differences, largely related to the method of determination. After applying some corrections, methods based on hydrodynamic radius yield a value of roughly 3·9ml/g dry casein, other methods (microscopy, sediment volume) about 2·2. Roughly half of the discrepancy can be explained by the micelles being not perfectly spherical. To explain the remaining difference, it is assumed that the micelles are hairy, i.e. they have molecular chains protruding into the milk serum. The hairyness would increase with decreasing temperature and be largely removed by the action of rennet. It would cause some entropic repulsion between micelles at close approach.
A new laboratory method for preventing bacteriophage attack on cheese starter streptococci
Authors: Erskine J. M.
Published: June 2009

A method of preventing the action of bacteriophages on starters in cheese milk is described. Direct intramuscular injection of high titre phage preparation into a cow resulted in the appearance in the blood serum and milk of a high concentration of antibody. Even after considerable dilution this antibody is capable of neutralizing the homologous phage and serologically related phages. Methods of concentrating the antibody-containing milk were examined with a view to commercial application of the method in the protection of starter bacteria from phage attack.
Some bound forms of pantothenic acid in the milk of normal dairy cows
Authors: Hibbitt K. G.
Published: June 2009

The levels of coenzyme A were measured in the milk of normal dairy cows during the first 20 weeks of lactation. Estimations were made on milk samples obtained from some cows in their first lactation and from older cows. The microbiological method described by Brown (1959) for the estimation of bound forms of pantothenic acid was used, but considerable modification of this method was necessary to avoid elevated results due to the stimulatory action of free pantothenic acid on the response of the assay organism. Appreciable amounts of coenzyme A were excreted in the milk of cows in their second or subsequent lactations during the first 12–16 weeks after parturition, peak levels being reached after the end of the 1st week. In comparison, only small amounts of coenzyme A were excreted in the milk of cows in their first lactation. Attempts to detect the presence of phosphopantetheine in milk were unsuccessful.
A new method for the preparation of an immunologically homogeneous β-casein
Authors: Garnier J. , Ribadeau-Dumas B. , Mocquot G.
Published: June 2009

The preparation of an immunologically homogeneous β-casein is described, involving several separations by chromatography on diethylaminoethyl cellulose with urea-imidazole buffer at pH 7, followed by Tris buffer at pH 8·2. 30% of the β-casein present in the skim-milk is obtained by this method. β-casein gives a single band in urea-starch gel electrophoresis when it is obtained from the milk of cows homozygous for this character.
Teneur en caséine κ de la caséine de colostrum de vache
Authors: Ribadeau-Dumas B. , Veaux Monique
Published: June 2009

Casein derived from cow's colostrum contains 0·85%N-acetyl neuraminic acid and liberates 2·95% nitrogen soluble in 12% trichloroacetic acid (NPN) under the action of rennin. It therefore appears to contain a large proportion of κ-casein (calculated to be approximately 35%).

The smaller the micelles of casein in colostrum the larger is the amount ofN-acetyl neuraminic acid they contain. Soluble casein, i.e. 25% of the casein in colostrum, contains 1·52% of this acid and gives 6·24% NPN under the action of rennin.

Casein and particularly the soluble casein of colostrum appear to be important sources of κ-casein and caseino-glycopeptide.
Factors affecting the multiplication and survival of coagulase positive staphylococci in Cheddar cheese
Authors: Reiter B. , Fewins B. Gillian , Fryer T. F. , Sharpe M. Elisabeth
Published: June 2009

The presence of a thermolabile inhibitor of coagulase-positive staphylococci in milk was confirmed. Starter streptococci significantly suppressed the multiplication of staphylococci in milk not only by their acid production but also by some other competitive effect.

Cheesemaking trials showed that staphylococci multiplied considerably more rapidly in ‘slow’ or ‘sweet’ cheese, where the starter was inhibited by phage, than in normal cheese. Little decrease in numbers occurred in ‘sweet’ cheese even after 18 months, in contrast to the rapid decline in the normal cheese.

Staphylococci subjected in the laboratory to sublethal heat treatments had a prolonged lag phase on all media and their % recovery on selective media was significantly lower than on optimal non-selective media. It is suggested that the low survival rate of the staphylococci in cheese made from milks heated at sublethal temperatures is due to the lag in recovery of heat-shocked cells and their inability to multiply in the unfavourable cheese curd.
A comparison of media for counting and isolating the bacteria from Cheddar cheese
Authors: Robertson P. S.
Published: June 2009

In an endeavour to find an ideal medium for the isolation of the bacteria from Cheddar cheese 10 media were compared. The initial criterion was of ability to yield maximal counts with each of 23 representatives of species common in Cheddar cheese. Subsequently the more promising media were compared for ability to give the highest counts for cheese emulsions without obvious distortion of the proportions of the various species present.

Since no one medium gave maximal counts with all strains, two complementary media of quite different composition are suggested for the bacteriological examination of cheese.
A note on the effect of a commercial drying process on the long chain fatty acids of milk
Authors: Moore J. H. , Williams D. L.
Published: June 2009

The role of the essential fatty acids, linoleic and arachidonic acids, in human nutrition has been widely studied, particularly with respect to their possible action in preventing arterial disease in adults, e.g. Kinsell (1963). In addition, Hansen, Haggard, Boelsche, Adam & Wiese (1958) have emphasized the importance of linoleic acid in the nutrition of infants. Although milk fat contains only relatively small amounts of linoleic and arachidonic acids, the part played by milk and milk products in contributing essential fatty acids to the human diet has received considerable attention (Combes, Pratt & Wiese, 1962; Kon, 1962; Hansenet al.1963; Garton, 1964). However, despite the initial dependence of many infants on dried milk as an exogenous source of essential fatty acids the effects of commercial drying processes on the constituents of milk fat have not been much investigated. A comparative study of the fatty acid compositions of raw and dried milk was therefore undertaken.
Studies on the к-casein complex: II. The isolation of a sialic acid-containing fraction by disrupting the complex at low pH in the presence of sodium chloride
Authors: Beeby R.
Published: June 2009

When crude к-casein was precipitated at pH 3 in the presence of 0·4m-NaCl the supernatant contained up to 80% of the total sialic acid but no detectable cystine or cysteine. Two fractions were obtained from this supernatant by chromatography on DEAE cellulose; one containing 4–6% sialic acid and the other only onetenth of this amount.

Most of the sialic acid of the sialic acid-rich fraction was soluble in 12% trichloracetic acid following treatment with rennin. It is suggested that the glycopeptide released by the action of the enzyme on casein originates from this fraction.
A method of maintaining a reference flora of constant bacteriological composition
Authors: Reiter B. , Fryer T. F. , Sharpe M. Elisabeth
Published: June 2009

A method is described by which the microbial flora of a raw milk sample was reconstituted on different occasions. After segregation on selective media into groups consisting of lactic acid bacteria, Gram-negative rods including coli-aerogenes, staphylococci, streptococci, and microbacteria, and propagation by replica plate techniques on optimal media, suspensions of these groups of organisms were then added in approximately the original proportions to 40 gal batches of heated milk of low bacterial count. When this was repeated on 18 different occasions over a period of 11 weeks, the milk flora was found to be almost identical with the original one.
The effect of inoculating the bovine teat duct with small numbers of Staphylococcus aureus
Authors: Newbould F. H. S. , Neave F. K.
Published: June 2009

Fifty-seven inoculations of a strain of Staphylococcus aureus were made into the outer 4 mm of the teat ducts of 8 cows. The inocula ranged from 10 to 600 colony-forming units (CFU) and were made with a stainless steel instrument designed to overcome the disadvantages of glass rods and cotton swabs hitherto used.

A single inoculation resulted in either no colonization of the duct, in temporary colonization for up to 7 days, or in colonization followed by intramammary infection.

The recovery of the organisms depended on the size of the inoculum. When 70–100 CFU were placed in the teat duct no organisms were recovered from 12 of 24 quarters after the 1st post-inoculation milking. When 500–600 CFU were used, organisms were recovered from all of 31 quarters for at least 3 milkings, and from 61% for 6 milkings or more, in spite of dipping the teats in a strong disinfectant twice daily.

Intramammary infection developed in 1 of 12 quarters (8%) inoculated in the teat duct with about 600 CFU when the animals were milked twice daily, and in 5 of 19 (23%) quarters if the 1st post-inoculation milking was omitted.

There was no evidence of sensitization resulting from previous infection.
A survey of the incidence of coagulase-positive staphylococci in market milk and cheese in England and Wales
Authors: Sharpe M. Elisabeth , Fewins B. Gillian , Reiter B. , Cuthbert W. A.
Published: June 2009

The occurrence of coagulase-positive staphylococci in 954 samples of raw or heat-treated market milk and in 910 samples of cheese of different varieties, taken at 40 cheese factories or farms in England and Wales was determined. Only 9% of the cheeses contained more than 500 000 staphylococci/g, and these were all made from raw milk. All but the mildest of the heat treatments used were effective in greatly reducing the numbers of staphylococci present in milk and usually resulted in cheese virtually free from staphylococci. The effect of sublethal heat treatment on multiplication of these organisms in cheese curd is discussed.
A simple laboratory-scale HTST milk pasteurizer
Authors: Franklin J. G.
Published: June 2009

A simple, quick, batch-type method for the laboratory-scale HTST pasteurization of milk is described and details of construction, operation, cleaning and sterilization of the apparatus are given. The heating and cooling curves approximate closely to those of commercial HTST milk-pasteurizing plants and the end-product, as measured by residual phosphatase, is similar. The method has a relatively high sample throughput and is suitable for the routine pasteurization of large numbers of milk samples of up to 300 ml in volume. Other possible applications of the method are discussed.
The detection of abnormal milk by electrical means
Authors: Greatrix G. R. , Quayle J. C. , Coombe R. A.
Published: June 2009

A preliminary study has been made of some relationships between the relative conductivity of milk and its cellular content and 3 basic relationships subjected to an extensive computer analysis. The results suggest that relative conductivity can be used to detect about 3 out of every 4 cows yielding milk samples from one or more quarters with a cellular content greater than 500000/ml, and about 4 out of every 5 cows with a cellular content greater than 1000000/ml. Less than 1 in 20 cows would be incorrectly detected as having cell counts greater than 500000/ml in milk from any one quarter.
The effects of a series of saturated fatty acids in the diet on milk-fat secretion in the cow
Authors: Steele W. , Moore J. H.
Published: June 2009

The effects of the isocaloric replacement of part of the dietary concentrate mixture by 5% lauric acid (99% pure) or by 10% of myristic (95% pure), palmitic (96% pure) or stearic (94% pure) on the yield and composition of milk fat was investigated in 2 feeding experiments with a total of 10 cows in mid-lactation. The concentrate mixtures were given with a high-roughage diet that supplied 9·1 or 7·7 kg hay/day in expts 1 and 2, respectively.

In expt 1 the inclusion of myristic acid in the diet decreased the yields of milk and solids-not-fat (SNF), but increased the percentage of fat in the milk without altering the fat yield. When stearic or palmitic acid was included in the diet there was an increase in milk fat yield; palmitic acid caused the greater increase. In expt 2 the inclusion of lauric acid in the diet did not appear to affect the yields of milk or SNF but it caused large reductions in the percentage of fat in the milk and in the yield of fat.

In expt 1 the inclusion of myristic acid increased the yields and percentages of 14:0, 14:1 and 16:1 in the milk fat and decreased the yields and percentages of the short-chain fatty acids (4:0–8:0), 16:0, 18:0 and 18:1. When palmitic acid was included in the diet there were increases in the yields and percentages of 16:0 and 16:1 in the milk fat and decreases in the yields and percentages of 10:0, 12:0, 14:0, 18:0 and 18:1. The inclusion of stearic acid in the diet increased the yields and percentages of 18:0 and 18:1 in the milk fat and decreased the yields and percentages of 12:0 and 16:0. In expt 2 the inclusion of lauric acid in the diet increased the yield and percentage of 12:0, and in 1 cow the content of 14:0 in the milk fat; there were reductions in the yields and percentages of all the other fatty acids in the milk fat. There was no evidence of any marked elongation of the carbon chains of 12:0 and 14:0 in the mammary gland to form 16:0 or 18:0.

In expt 1 the incorporation of myristic acid in the diet decreased the concentration of total steam-volatile fatty acids in rumen liquor. The inclusion of either myristic, palmitic or stearic acid in the diet had little effect on the relative proportions of the individual volatile acids in the rumen liquor. In expt 2 the addition of lauric acid to the diet reduced the acetic acid:propionic acid ratio in the rumen liquor.
Chemical methods for assessing lipid oxidation in ultra-high-temperature creams
Authors: Downey W. K.
Published: June 2009

The flavour quality and stability of 3 different UHT creams are described. The rate of oxidation was measured by the thiobarbituric acid (TBA) and peroxide methods as well as by organoleptic assessment. Lipid oxidation developed in some UHT creams on prolonged storage, particularly in creams manufactured during the winter months and stored at 18°C, while little or no oxidation occurred at 4 °C. Creams manufactured during the summer months were most resistant to oxidation. Creams with no detectable oxidized flavour had TBA values ≤ 0·08; values ≥ 0·16 and peroxide ≥ 2·0 were associated with pronounced oxidized flavour. These relationships between the chemical and organoleptic assessments were highly significant (P < 0·01). Low peroxide levels (< 2·0) were not necessarily indicative of good flavour quality.
A method for the quantitative analysis of the enzyme complement of commercial rennets
Authors: O'Leary P. A. , Fox P. F.
Published: June 2009

A method by which it is possible to quantify with very high accuracy the levels of rennin, bovine pepsin, porcine pepsin and proteases from Mucor miehei (fromase) or M. pusillus (emporase) in a ‘commercial rennet’ containing some or all of these enzymes is described. The method employs chromatography on DEAE cellulose in piperazine buffer (0·02M, pH 5·3) to fractionate the enzymes into 2 groups: (peak A) rennin, emporase, and fromase, eluted at ∼0·2 m-NaCl and (peak B) bovine and porcine pepsins eluted at ∼0·4 m-NaCl. The rennin in peak A is selectively denatured at pH 9·0, 20°C for 60 min and the rennin plus emporase at pH 6·0, 60°C for 20 min, permitting the quantification of emporase and fromase (and rennin by difference) and fromase, respectively. The porcine pepsin content of peak B is quantified by selective denaturation at pH 7·0, 30°C for 3 min. A number of commercial rennet preparations were analysed using this method: full rennet contained 45–60% bovine pepsin and ‘half and half’ contained 20–25% rennin, 25–30% bovine pepsin and 50% porcine pepsin.
Properties of aseptically packed ultra-heat-treated milk: Electron microscopic examination of changes occurring during storage
Authors: Andrews A. T. , Brooker B. E. , Hobbs D. G.
Published: June 2009

Changes in the appearance of casein micelles and fat globules in ultra-heat-treated (UHT) milk were comparatively slight within a 14-month storage period although closer inspection often revealed the beginnings of some of the changes observed after even longer storage. Within this period the milks remained liquid and no evidence for any proteolytic breakdown was seen on electrophoretio examination. After 34 months the milks had all gelled and there was evidence of a small amount of proteolytic breakdown. Electron microscopic changes were striking and depended on storage temperature. At 4 °C the casein micelles in the gel phase had become very ‘spiky’ and long tendrils often bridged micelles, forming extensive networks. At room temperature and at 30 °C this tendril formation was less marked and the average micelle size was considerably greater than in freshly processed milk. There was also clear evidence for the coalescence of micelles. After storage at 37 °C the micelles were much larger than in the other samples, often exceeding 0·4 mμ in diam.
Hydrolysis of lactose in milk and whey with minute amounts of lactase
Authors: Dahlqvist A. , Asp N.-G. , Burvall A. , Rausing H.
Published: June 2009

A method for lactose hydrolysis in sterile milk or whey with Saccharomyces lactis lactase is described. The properties and stability of this enzyme are very favourable for use in milk and neutral whey. The long shelf life of sterilized milk and whey products is utilized for a prolonged incubation time – one to several weeks – at room temperature. Thus, minimal amounts of enzyme are needed which makes enzyme costs very low.
Nutritional value of lactose-hydrolysed milk: protein quality after some industrial processes
Authors: Burvall A. , Asp N.-G. , Dahlqvist A. , Öste R.
Published: June 2009

The nutritional protein quality of lactose-hydrolysed milk after some industrial processes was studied with N balance experiments on growing rats.

Ultra-high-temperature sterilization and evaporation at 25 °C did not influence the nutritional value significantly, whereas spray-drying under conditions usually used for ordinary milk gave a considerable reduction in protein quality. This was caused mainly or entirely by loss of biologically availabe lysine.
Some factors involved in milk lipase activation by agitation
Authors: Deeth H. C. , Fitz-Gerald C. H.
Published: June 2009

Several factors which influence the shape of activation curves relating the degree of agitation-induced lipolysis in raw milk to the temperature of agitation were investigated. Curves of the type previously reported (Fitz-Gerald, 1974) containing a maximum at 12–15 °C resulted from low speed agitation with incorporation of air, with fresh (< 12-h old) milk, with milk of fat content ≥ 3·0 % approx. and by low temperature incubation of activated milks. Activation curves containing no distinct maximum at 12–15 °C were obtained from high speed agitation and homogenization, with milks of low fat contents and with aged (≥ 24-h old) milk. Agitation at low temperatures resulted in a maximum degree of activation in fresh milk after 2–4 h cold storage.

During agitation of raw milk redistribution of lipase activity between the cream and skim-milk phases occurred. The extent of redistribution depended on the time and temperature of agitation. Cream prepared from milk agitated at low temperatures contained lipase activity several times greater than cream from unactivated milk. The practical significance of this effect is discussed.
Influence of milk protein concentration on the gelling activity of chymosin and bovine pepsin
Authors: Garnot Pascaline , Corre Christian
Published: June 2009

Two stages of gelling by the milk-clotting enzymes chymosin and pepsin were studied at different milk protein concentrations, using milk retentates. In each case, enzymic velocity versus protein concentration described a standard hyperbola. According to the experimental conditions such as pH and type of enzyme, which changed the enzyme concentration used, either the quasi-linear part of the hyperbola was observed, or the velocity hardly increased and tended to a limiting value. Gelling occurred with a lower degree of proteolysis of κ-casein when the protein concentration increased but a minimum proteolysis (1% of total nitrogenous matter content) was required for aggregation to take place. Gelling time varied with the protein concentration, the pH and the enzyme concentration. The final degree of proteolysis of κ-casein was the same whatever the substrate concentration used.
The effect of lα-hydroxycholecalciferol on the concentrations of calcium, magnesium and inorganic phosphate in the plasma of parturient cows
Authors: Wittwer Fernando , Ford Edwin J. H.
Published: June 2009

135 Cows which were expected to produce a second or subsequent calf within 4–11 d received an intramuscular injection of 500 μg lα-hydroxycholecalciferol (lα-OHD3). In those animals in which the interval between injection and calving was at least 7 d there was, at 7 d after injection of lα-OHD3, a significant increase (P < 0.001) in the blood plasma concentrations of Ca and Pi and a significant reduction (P < 0.05) in that of Mg, compared with those in control animals. Within 24 h of calving there was a significant increase (P < 0.001) in the concentration of Pi but no change in Ca or Mg compared with pre-injection levels, whilst the control animals showed a significant fall (P < 0.001) in the concentration of Ca and a rise in those of Pi (P < 0.001) and Mg (P < 0.05). There was a significant reduction (P < 0.001) in the number of animals with hypocalcaemia (defined as a plasma Ca concentration <1.9 mmol/1) in all animals injected with lα-OHD3; this reduction was particularly marked when the interval between injection and calving was between 1 and 8 d. The previously reported reduction in the incidence of clinical milk fever is considered to be a consequence of the effect of lα-OHD3 on the concentration of Ca in plasma.
Detection of carbonyl sulphide in Cheddar cheese headspace
Authors: Aston John W. , Douglas Keith
Published: June 2009

Carbonyl sulphide (COS) was detected in the headspace of Cheddar cheeses in concentrations ranging from 0·01 ng ml-1 to 0.3 ng ml-1. It was also found in the headspace above certain packaging materials and sealing materials used in the analytical procedures. Evidence that COS was produced within the cheese was given by the findings that experimental cheese containing added cysteine had consistently higher COS levels (up to 1·0 ng ml-1) and that COS could be produced chemically from mixtures of cysteine or methionine with riboflavin and ascorbic acid in laboratory trials.
Heat stability of milk: synergic action of urea and carbonyl compounds
Authors: Shalabi Samweul I. , Fox Patrick F.
Published: June 2009

Urea stabilizes milk to heat only in the presence of a carbonyl compound, such as a reducing sugar. Low molecular weight carbonyl compounds can increase stability in the absence of urea whereas larger molecules, e.g. hexoses and reducing disaccharides, cannot. However, the efficacy of all carbonyl compounds is increased considerably in the presence of urea. Aldehydes and ketones of similar molecular weights appear to be equally effective stabilizers. The optimum concentration of lactose in milk for stability was approximately 1% irrespective of urea concentration within the range 5–20 mM. However, modifying the lactose content of concentrated milks (approximately 8.5% protein) had little effect on heat stability.