bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical changes in ultra-heat-treated milk during storage: II. Lactuloselysine and fructoselysine formation by the maillard reaction
Authors: Möller A. B. , Andrews A. T. , Cheeseman G. C.
Published: June 2009

Lactuloselysine (ε-N-deoxylactulosyl-L-lysine) and fructoselysine (ε-N-deoxyfructosyl-L-lysine), formed by Maillard reaction, were identified in enzymic hydrolysates of casein from stored ultra-heat-treated (UHT) milk. Furosine (ε-N-(2-furoylmethyl-L-lysine) and pyridosine (ε-(3-hydroxy-4-oxo-6-methyl-1-pyridinyl)-L-norleucine) were identified in the corresponding acid hydrolysates. Enzymic hydrolysis of the caseins, gel filtration and preparative scale amino acid analysis were used to isolate the compounds which were then identified by reference to synthesized authentic compounds. Lactuloselysine formation was extensive and involved 10–30% of lysine residues in UHT milks stored at 30–37 °C for 6 months to 3 years. Fructoselysine concentration was generally about 10% of the lactuloselysine concentration.
Seasonal variations of copper and iron in Irish milk and butter
Authors: Murphy J. J. , Headon D. R. , Downey W. K.
Published: June 2009

Levels of Cu and Fe in fresh milk and in bulk pasteurized milk were measured. The endogenous levels varied during the lactation period. The level of Cu in bulk pasteurized milk was greater than the endogenous level, suggesting some contamination. This apparent Cu contamination was greater in winter than in summer. No similar contamination was observed with Fe. The levels of Cu and Fe in butter manufactured each month and in retail butter were measured. Higher levels of Cu were detected in ripened cream butter produced in winter compared to that produced in summer. No similar trend was evident for Fe in ripened cream butter. Very low levels of Cu, Fe and lipid oxidation were detected in Irish sweet cream butter and consequently Cu and Fe contamination and resultant oxidation are not a problem in this product.
Proteolysis of αs1-casein by chymosin: influence of pH and urea
Authors: Mulvihill D. M. , Fox P. F.
Published: June 2009

The specificity of chymosin on αs1-casein was shown to be dependent on the reaction pH and on the state of aggregation of the substrate. In aqueous solution αs1-casein was optimally hydrolysed to αs1-I at pH 5·8; if the casein was solubilized in the isoelectric region by the use of 5 M-urea, optimum proteolysis occurred at pH 2·8. Hydrolysis of αs1-I to yield αs1-II, αs1-III and αs1-IV occurred at pH values > 5·8 in the presence or absence of urea. In the isoelectric region αs1-II, αs1-III and αs1-IV were not formed in the absence of urea where the substrate was aggregated: instead a peptide αs1-V was produced; at the same pH and using urea as a solubilizing agent αs1-II, αs1-III and αs1-IV were formed together with a further peptide αs1-VI.
Studies on the motility of smooth muscles of the teats in lactating cows
Authors: Bernabé Jacques , Peeters Georges
Published: June 2009

Rhythmic motility of teats in lactating cows in vivo was studied by an improved plethysmographic technique. Oxytocin was infused intravenously and drugs were injected into the artery of the filled udder. The β-adrenergic agent, isoprenaline, induced relaxation of the teats whereas the α-adrenergic agents phenylephrine and noradrenaline, elicited contraction. In one animal however, noradrenaline always exerted a biphasic effect. Pre-treatment with propranolol, a β-adrenergic blocking agent, changed the biphasic effect into a purely activating response. Adrenaline, which exhibits both a and β effects, induced relaxation, but after propranolol treatment relaxation was abolished and even converted into contraction of the teat. It seems clear that both α and β adrenoceptors are present in longitudinal smooth muscles of the teats.

Milk losses as intermittent spurts were observed in several cows. Spurts occurred synchronously with rhythmical teat motility in the filled udder during oxytocin infusion. The intensity of milk leakage was increased by isoprenaline and inhibited by noradrenaline, indicating the presence of α and β receptors in teat sphincter muscles. Starting and stopping of milk spurts in correlation with rhythmical teat contractions were studied by audiovisual synchronization of video recording tape. The most common type of spurt began near the middle of the teat's relaxation phase and ended either just before or exactly at the beginning of the contraction phase. Interruption of the spurt is primarily due to closure of the streak canal.
Relationship between triglyceride structure and softening point of milk fat
Authors: Parodi Peter W.
Published: June 2009

Eight samples of milk fat were selected for softening point (SP) range. They were separated into high, medium and low molecular weight triglyceride fractions by silicic acid-column chromatography to enable further separation into triglyceride classes by silver ion adsorption thin-layer chromatography. Correlation between triglyceride class content and SP was low. The molecular species composition of the triglyceride classes was determined and correlated with SP. The best correlations were between SP and some low and some high molecular weight triglycerides of the total fat and the trisaturated (SSS) triglyceride class. Correlation coefficients were determined between SP and mole percentage of individual fatty acids and groups of acids. The highest correlations were between SP and individual short chain-length fatty acids (C4–C10) and groupings of short chain-length acids (C4–C10) and groupings of long chain-length acids (C16–C20). The triglyceride class composition of a sample of milk fat was determined before and after interesterification. Interesterification increased the SP from 31·6 to 36·3 °C and produced increased amounts of both low and high and decreased amounts of medium molecular weight triglyceride molecular species in all triglyceride classes. The increases in the amounts of high molecular weight triglycerides were several times greater than the increase in the amounts of low molecular weight triglycerides.
Trypsin-inhibitors in mastitic milk and colostrum: correlation between trypsin-inhibitor capacity, bovine serum albumin and somatic cell contents
Authors: Honkenen-Buzalski Tuula , Sandholm Markus
Published: June 2009

The trypsin-inhibitor capacity of bovine milk was seen to increase in mastitits. This capacity showed good correlation with the California Mastitis Test score, somatic cell count (Coulter Counter method) and bovine serum albumin (BSA) content (radial immunodiffusion). The elevated antitrypsin level proved to be a safer indicator of mastitis than BSA alone. Using gel-filtration chromatography, the major trypsin-inhibitor activity of mastitic milk and plasma was eluted with BSA, indicating a similar mol. wt (70000). This fraction showed electrophoretic polymorphism. A large molecular weight fraction cross-reacted immunologically with human α2-macroglobulin. The antitrypsin activity in mastitic milk was clearly different from the principal activity in colostrum, which had a mol. wt of about 13000.
Evidence of penetration of the bovine teat duct by Escherichia coli in the interval between milkings
Authors: Bramley A. John , Godinho Kevin S. , Grindal Robert J.
Published: June 2009

In 3 consecutive experiments, each using 20 cows, the application of Escherichia coli to teat ends after milking led to high rates of intramammary infection. These infections were not prevented by disinfection of the teats before milking, by the installation of shields in the short milk tubes of the milking cluster or by the use of an individual quarter milking cluster. Rates of infection were significantly lower when teat contamination was applied 1 h before milking compared to contamination applied immediately after milking.

These data suggest that penetration of the teat duct by the E. coli occurred in the period between contamination and milking. Seventy four percent of infections occurred in hindquarters and there were variations in the susceptibility of cows to infection.
Relationship of somatic cell count and cell volume analysis of goat's milk to intramammary infection with coagulase-negative staphylococci
Authors: Sheldrake Richard F. , Hoare Roderic J. T. , Woodhouse Victoria E.
Published: June 2009

The prevalence of intramammary infection in 4 commercial goat herds was studied in conjunction with electronic somatic cell count and volume analysis, determined using a Coulter Counter and volume analyser.

Neither streptococci nor mycoplasma were isolated from any half and the prevalence of intramammary infection with Staphylococcus aureus ranged from 0 to 3% between herds. For coagulase-negative staphylococci the range for infected halves was 36–71%. There was no significant difference between the mean total microscopic somatic cell count for halves infected with coagulase-negative staphylococci and those free from infection. A similar trend was observed for electronic somatic cell counts although the mean electronic cell count was greater than the mean total microscopic count on the 2 occasions that they were compared. The correlation coefficients between the 2 cell counting methods were 0·86 and 0·94. Between herds there were significant differences in mean electronic somatic cell count, with herd means ranging from 438×103 to 1684×103 cells/ml. In 2 of the 4 herds studied, milk samples from halves infected with coagulase-negative staphylococci had a significantly higher prevalence of cell volume distributions with a modal cell volume between 65 µ3 and 100 µ3. This was attributed to a higher proportion of polymorphonuclear neutrophils.

Use of electronic somatic cell count and cell volume analysis were considered of little value in predicting infection caused by coagulase-negative staphylococci as there was a high proportion of false negative and false positive predictions.
Evaluation of bovine rennets in terms of absolute concentrations of chymosin and pepsin A
Authors: Martin Patrice , Collin Jean-Claude , Garnot Pascaline , Dumas Bruno Ribadeau , Mocquot Germain
Published: June 2009

A method for determining chymosin and bovine pepsin A in commercial extracts of bovine veils, based on the use of the synthetic hexapeptide (Leu-Ser-Phe(NO2)-Nle-Ala-Leu-OMe) as reference substrate, is reported. Chymosin and bovine pepsin A were separated chromatographically from extracts and assayed for clotting activity on a reconstituted skim-milk standardized with reference chymosin and bovine pepsin A, themselves standardized in relation to the hexapeptide. The effect of pH on the absorbance difference between the hexapeptide and the Leu-Ser-Phe(NO2) tripeptide resulting from its hydrolysis was studied. It was found that the ‘optimal’ pH for determining the activities of the reference enzyme solutions was 4·7.

Six chymosin and 3 bovine pepsin A preparations were assayed on the hexapeptide to define the relation between the proteolytic activity and the amount of active enzyme. At pH 4·7 and 30 °C 1 mg chymosin and 1 mg bovine pepsin A hydrolysed 100 and 2700 μm-peptide/s respectively. The clotting activity of these preparations was assayed on a reconstituted skim-milk to standardize it and thus define the relation between the clotting time and the amount of active enzyme. Chymosin had a specific clotting activity twice that of bovine pepsin A. At equal clotting activities, bovine pepsin A was 55 times more active than chymosin on the hexapeptide at pH 4·7.
Assessment of two instruments for continuous measurement of the curd-firming of renneted milk
Authors: Marshall Richard J. , Hatfield David S. , Green Margaret L.
Published: June 2009

Continuous measurements of curd-firming using a commercial vibratingreed viscometer and a pressure transmission system (PTS) developed at this Institute were compared both in the laboratory and during Cheddar cheesemaking. The coefficient of variation about the mean of the curd-firmness measured in reconstituted skim-milk 40 min after renneting was 3·5% with the viscometer and 2·6% with the PTS. The effects of changes in conditions on the curd-firming rate of raw whole milk were determined. As the rennet concentration was raised the rates increased linearly as measured by the viscometer, but non-linearly as measured by the PTS. Addition of CaCl2 increased the rates measured by both instruments rapidly at first then more slowly at higher levels. Raising the temperature increased the rate exponentially in the case of the viscometer but more slowly with the PTS. With both instruments the curd-firming rates of milk at pH 5·8 were 6·5 times those at pH 6·7 but the rates fell slightly at pH 5·6. In experimental cheesemaking, the mean readings of both instruments at the subjectively determined cutting time of the curd had the same coefficient of variation.

The commercial viscometer is probably more suitable for laboratory investigations of the earlier stages of the coagulation of milk by rennet whilst the PTS may prove the more useful in indicating the optimum cutting time of the curd during cheesemaking.
Accelerated cheese ripening with food grade proteinases
Authors: Law Barry A. , Wigmore Anne
Published: June 2009

The development of typical flavour in Cheddar cheese was accelerated by the addition of bacterial neutral proteinase to the curds, but not by the addition of fungal acid proteinase which produced a bitter defect even at low concentrations. An optimum level of neutral proteinase addition was established at which general proteolysis was increased by about 20% in 2 months and treated cheeses of this age had flavour intensities typical of 4-month-old untreated cheeses. Enzyme-treated cheeses were softer-bodied and more brittle than untreated cheeses of the same age.
Effect of the method of removal of the milking machine cluster on new udder infection
Authors: Griffin Tony K. , Grindal Robert J. , Williams Ray L. , Neave Frank K. , Westgarth David R.
Published: June 2009

A series of short duration experiments show that the way in which the milking machine cluster is removed from the udder influences the rate at which new udder infections occur when bacterial exposure is high at the end of milking. Shields fitted in the base of the liners controlled most of the infections caused by abrupt removal of the cluster.
The roles of native milk proteinase and its zymogen during proteolysis in normal bovine milk
Authors: de Rham Olivier , Andrews Anthony T.
Published: June 2009

Proteolysis was measured quantitatively in normal bulk milk, either raw, pasteurized or heated (95 °C, 15 min). During incubation at 37 °C for 24 h, about 0·7 mM of peptide bonds were split in raw milk, and 1·8 mM after activation of the zymogen with urokinase. The same values were observed in pasteurized milk, and no significant activity was present in heated milk. When compared with a commercial plasmin preparation, these levels correspond to about 1·4 and 3·6μg/ml of plasmin respectively. Most of this activity was separated in the micellar fraction, and it was suppressed by addition of soyabean trypsin inhibitor (SBTI). The remaining activity in the serum phase was not inhibited by SBTI and gave a rather non-specific breakdown with few well-defined casein fragments being produced. Upon further incubation, after the first 24 h, the activity increased, indicating that activation of the zymogen (plasminogen) occurred spontaneously. The rate of this activation was independent of the addition of more plasminogen and was higher in pasteurized than in raw milk. In pasteurized milk, all the native milk proteinase was in the form of the zymogen at the time of secretion. β-Casein was the preferred substrate for the milk proteinase (plasmin) and produced γ-caseins and proteose-peptone components 5 and 8-fast; other fragments were clearly visible on polyacrylamide gel electrophoresis, and included degradation products of αs1-casein. The formation of all these fragments was enhanced by addition of urokinase alone, or of plasminogen and urokinase, or by increasing the incubation time. They were also produced by incubating the micellar fraction alone, but not the serum fraction. Additional fragments were produced when porcine plasmin was added presumably due to differences in specificity between the porcine and bovine enzymes or to contaminating enzymes. Proteolysis induced by additions of plasminogen alone, or of plasminogen plus urokinase, was closer to that observed for the native milk proteinase, and must be recommended for future work in which it is desired to enhance the level of proteinase without altering breakdown patterns, unless a very pure bovine plasmin is available.
Heat stability of milk: influence of cationic detergents on pH sensitivity
Authors: Shalabi Samweul I. , Fox Patrick F.
Published: June 2009

The heat stability–pH profile of milk is shifted to more acidic values by anionic compounds such as SDS, lysolecithin and β-lactoglobulin and to more alkaline values by cationic compounds such as quaternary ammonium compounds. Proline, which reduces the hydrophobicity of proteins, destabilized milk slightly. The results suggest that the heat stability of milk and the shape of the HCT–pH curve may be dependent on micellar charge effects.
Aspects of the formation of lysinoalanine in milk and milk products
Authors: de Koning Petrus J. , van Rooijen Peter J.
Published: June 2009

Treatment of food proteins with heat and/or alkali may convert some of the constituent amino acids into the unnatural amino acid lysinoalanine (LAL), which has been found to cause kidney damage (nephrocytomegaly) when fed to rats. LAL may be produced by β-elimination of a phosphoseryl, of a glycosylated seryl or of a cystyl residue followed by a nucleophilic addition to a lysyl residue. The formation of LAL in αs0-, αsl- and β-casein is discussed in relation to the location of phosphoseryl residues immediately adjacent to lysyl residues. The influence of pH, temperature and exposure time on the formation of LAL in whole casein is described in detail. The formation of LAL can be prevented by the addition of reducing agents, dephosphorylation or chemical modification of the є-amino group of lysine. The LAL content of foodstuffs can be measured accurately by ion-exchange chromatography and a survey is given of the LAL content of commercial milk and milk products.

The biological effects of free and protein-bound LAL are discussed. It seems that renal changes due to the presence of LAL in the diet are species-specific to the rat although recent findings have shown that no effect is observed in rats fed a mixed diet containing proteins with and without protein-bound LAL. When LAL is removed from the diet, nephrocytomegaly disappears. From these results it may be concluded that the health risks for man, connected with the eating of proteins which have been subjected to treatment with heat and/or alkali, are small.

The decrease in lysine content of milk and milk products due to formation of LAL is small (0–1 or 2%) in comparison with the decrease in available lysine possibly caused by the Maillard reaction (0–24%) and so the decrease in nutritive value of food products due to LAL formation may be neglected.
Effect of milking machine factors on the somatic cell count of milk from cows free of intramammary infection: I. Vacuum fluctuations
Authors: Olney George R. , Scott George W. , Mitchell Robert K.
Published: June 2009

The effect of vacuum fluctuations during milking on the somatic cell count of milk from cows free of intramammary infections was determined. Four vacuum fluctuation treatments were compared using a Latin square design with 20 cows being milked at each of the 4 treatments for a continuous period of 12 d. The vacuum fluctuations were designed to simulate the depressions in vacuum that occur when applying teatcups during milking. In the most severe treatment the vacuum level fell from 50 to 14 kPa. The somatic cell count was not affected by vacuum fluctuation treatment and it is concluded that vacuum fluctuations will not cause an increase in the somatic cell count of milk in the absence of mastitis infections.
Surface tension of whole and skim-milk between 18 and 135 °C
Authors: Bertsch Antonio J.
Published: June 2009

The surface tension (γ) of whole milk (4% fat) and skim-milk was determined in the temperature range 18–135 °C by the drop number method. Measurements were carried out in a temperature-controlled chamber under pressure. Above 90 °C, the mean residence time of the milk at the test temperature was 15 s. Surface tension values were calculated by the Harkins and Brown method, corrections being made to account for the kinetic energy of the drops. The results for whole and skim-milk were not significantly different and the combined data (66 values) could be represented by the equation:

γ =1·8 10-4θ2–0·163θ+55·6,

(where γ is in mN. m-1 and θ is the temperature in °C) with a residual s.d. of 2·1 mN. m-1 (mean relative error 9·6 % at the 5 % level of significance).
Effect of homogenization on the heat stability of milk
Authors: Sweetsur A. W. Maurice , Muir D. Donald
Published: June 2009

The effect of homogenization on the heat stability characteristics of milk was examined. The heat stability of homogenized milk, as determined by the time taken for protein clots to form when heated at 140 °C, was reduced with increasing pressure in the range 3·5–34·5 MPa. The heat stability of homogenized milks was greater for samples obtained in the summer months than for those obtained in the winter. The general destabilizing effect of homogenization could be partly offset by 2-stage homogenization (20·7 MPa followed by 3·5 MPa), addition of phosphate stabilizers (0·08% w/v) or homogenization at a high temperature (65 °C). Whilst homogenized and unhomogenized milks reacted similarly to the addition of Ca, phosphate stabilizers, sulphydryl-blocking and oxidizing agents, the effects of season, addition of urea or formaldehyde were different for homogenized milk.
Stimulation of Streptococcus thermophilus growth in mastitic milk
Authors: Marshall Valerie M. , Bramley A. John
Published: June 2009

Growth of Streptococcus thermophilus was faster in mastitic milk, aseptically collected following intramammary infusion of Escherichia coli endotoxin, than in normal aseptically collected milk. The contribution of polymorphonuclear leucocytes (PMN), of plasma and plasmin to this stimulation has been investigated. Addition of plasmin to low cell count milk stimulated growth of the streptococcus to the same degree as mastitic milk. However, addition of plasma or PMN from blood or from milk were less stimulatory. The part played by these components in providing casein breakdown products for the weakly proteolytic Str. thermophilus in mastitic milk is discussed.
Nutrient content of liquid milk
Authors: Scott K. John , Bishop Dinah R. , Zechalko Alicja , Edwards-Webb John D.
Published: June 2009

Concentrations were measured of different vitamins in milk as delivered to the home and after storage in the domestic refrigerator, during summer and winter periods. Vitamin C concentrations varied greatly, ranging from 0·1 to 18·4 εg/ml. Most of the lower vitamin C values were associated with known exposure of the milk to daylight and there was a clear tendency for the concentrations to fall with increased time of refrigerated storage especially when associated with prior exposure of the milk to daylight. Riboflavin values were mostly in the range 1·35–1·92εg/ml, but occasional lower values were associated with low content of vitamin C and in some instances with prolonged exposure to daylight on the doorstep. Concentrations of the other vitamins (εg/m1) were: folic acid 0·041–0·074, thiamin 0·38–0·48, vitamin B12 0·0032–0·0044 and vitamin B6 0·56–0·71. All fell within the normal ranges and were not significantly influenced by exposure of the milk to daylight or subsequent storage in the refrigerator.
Studies on micellar calcium phosphate: composition and apparent solubility product in milk over a wide pH range
Authors: Chaplin Lesley C.
Published: June 2009

Calcium and phosphate concentrations in milk ultrafiltrate prepared at 37 °C over the pH range 4.0–8.0 have been measured and used to calculate the apparent solubility products for various calcium phosphates in milk. Micellar calcium phosphate had a constant Ca/Pi= 1·58·10·03 at all pH values and a near-invariant ion activity product for CaHP04. Apparent solubility products have also been obtained for brushite, hydroxyapatite and amorphous tricalcium phosphate in milk salt solution over a similar pH range. No evidence was found for a hydroxyapatite or amorphous tricalcium phosphate phase in milk.
Factors affecting the volume of milk delivered by a standard loop in the plate loop method for bacterial count
Authors: King Joseph S. , Mabbit Leonard A.
Published: June 2009

Of the various factors influencing the volume transferred by the loop in the automated plate loop technique for enumerating bacteria in milk, the speed of the loop as it emerged from the milk sample was the most important. Increasing this speed from 3 to 6 cm/s resulted in a 23% increase in volume transferred by a standard loop of internal diam. 1·45 mm. The depth of dip was also important, but changes in temperature of the sample from 5 to 20 °C caused no significant change in volume transferred. The results indicate that if the transfer of 1 µl milk is required at speeds commonly used in the automated plate loop technique, the internal diam. of the loop should be reduced from the present standard 1·45 to 1·3 mm.
Assessment of the suitability for Cheddar cheesemaking of purified and commercial chicken pepsin preparations
Authors: Green Margaret L. , Valler Martin J. , Kay John
Published: June 2009

Commercial and pure chicken pepsin preparations were compared with rennet as cheesemaking coagulants. From the milk clotting and caseinolytic activities and enzymic stabilities, predictions were made of the relative activities of the chicken pepsins and rennet during cheese ripening. By this means mixtures of chicken and pig pepsins for cheesemaking trials were formulated. These and mixtures of chicken pepsins with rennet were approximately additive in coagulating activity provided they were used immediately. The amounts of chicken pepsins used in laboratory scale Cheddar cheesemaking trials were minimized by acidification and calcification of the milk. The nature of the coagulant did not affect the cheesemaking conditions, yields or cheese composition. Cheeses made with chicken pepsins alone showed faster proteolysis, more intense flavour, off-flavours and bitterness and were softer than those made with rennet. Cheeses made with chicken pepsin/rennet mixtures were intermediate and those made with chicken pepsin/pig pepsin mixtures were similar to those made with rennet. It was concluded that neither of the chicken pepsin preparations was suitable for Cheddar cheesemaking and that the predictive tests had led to correct assessments.
Changes in milk yield and composition at oestrus in dairy cows
Authors: Horrell R. Ian , Macmillan Keith L. , Kilgour Ron , Bremner Kaye
Published: June 2009

A New Zealand dairy herd of 73 cows was observed at pasture during the breeding season. Individual cow milk yields and composition analyses were obtained before, during and after oestrus. There was an overall reduction in yield at the first, and a rebound enhancement at the second milking after onset of oestrus. Changes in fat content followed the same time course and there was a slight increase in lactose content. Protein and somatic cell content were unaffected. There were considerable individual differences in both the duration and intensity of oestrous behaviour on the one hand, and the extent and timing of the effects on milk production on the other. However no relationship was found between the degree of behavioural excitement shown by a cow in oestrus and its change in milk production.
Preservation of West African soft cheese by chemical treatment
Authors: Aworh Ogugua C. , Egounlety Moutairou
Published: June 2009

The effects of sorbic and propionic acids on shelf life and organoleptic characteristics of West African soft cheese stored at 7–9 °C were investigated. In cheeses treated with 0·1% sorbic acid spoilage was delayed and microbial growth, especially mesophilic bacteria, yeasts and moulds, was suppressed compared with untreated controls. Treatment with 0·05% sorbic acid or up to 10% propionic acid was less effective. An objectionable bitter flavour was reported for sorbate-treated cheese but other qualities were not adversely affected.
Effect of stage of lactation on transport of colloidal carbon orStaphylococcus aureusfrom the mammary gland lumen to lymph nodes in guinea pigs
Authors: Schenkman Daniel I. , Berman David T. , Yandell Brian S.
Published: June 2009

Guinea pig mammary glands which were either lactating, involuting or dry were infused with colloidal carbon or killed staphylococci. At different time intervals following infusion, animals were killed and the superficial inguinal lymph nodes examined for the presence of carbon. Sides which had nodes with visible carbon were designated ‘positive’. The time intervals from infusion to positive for the three groups were compared using logistic regression. The times required for 50 % of the sides to be positive were estimated to be ˜4 h for lactating glands, 32 h for those in involution, and 13 min for dry glands. Histological differences in distribution of carbon in the mammary tissue suggest that differences in transit time may have been due to different mechanisms of transport through the glands in the three different physiological states. The distribution of bacteria was similar to that of the carbon in the corresponding tissues.
Effect of ripening cream with Streptococcus lactis subsp. diacetilactis on the flavour of ghee (clarified butterfat)
Authors: Yadav Jagjit S. , Srinivasan R. Appachar
Published: June 2009

Bovine milk cream (40% fat) was ripened under different time/temperature/inoculum conditions with Streptococcus lactis subsp. diacetilactis DRC-1 before converting by heat treatment into ghee (Indian clarified butterfat). Biochemical changes in cream, in terms of titratable acidity, volatile acids, diacetyl and acetaldehyde and flavour changes in the ghee made from it in terms of free fatty acids (FFA), total carbonyls (TC) and flavour score, were studied. Of the different combinations of ripening conditions, 30 °C, 18 hand 3% inoculum produced optimum changes in the cream which resulted in the development of the most desirable flavour in the ghee, being comparable to that of desi ghee (made by the indigenous method). The flavour characteristics as determined by FFA (% oleic acid), TC (μmol/g fat) and flavour score (out of 10) of the best ripened cream ghee were found to be 0·54, 6·756 and 8·83 respectively. The flavour of ghee became impaired after a particular level of acidity developed in cream after 18 h incubation. The optimum conditions of ripening standardized under laboratory conditions were also extended to a semi-industrial scale.
Effect of milk pretreatment and making conditions on the properties of Cheddar cheese from milk concentrated by ultrafiltration
Authors: Green Margaret L.
Published: June 2009

Cheddar cheeses were made from milks concentrated 3- to 6-fold by ultrafiltration. Modifications to the conventional cheesemaking process were designed to obtain the correct composition and pH value in the final curd, improve the fat and moisture retention and cheese texture, and increase the ripening rate. The compositions of all cheeses were similar to those of controls made with unconcentrated pasteurized milk. The curd and cheese structures and the textural properties of the cheeses were closer to those of the controls when made from milk concentrated 5-fold than when made from milk concentrated 3-fold. Light homogenization of the milk before concentration led to improved fat recovery and decreased graininess and crumbliness in the cheese. Lowering the coagulation temperature of concentrated milks gave improved curd structure and less grainy and more sticky cheeses. Addition of the bacterial proteinase, Neutrase, with the salt, stimulated proteolysis and flavour production in the cheeses and made them more sticky. Neither reduction of the mineral levels in the milk by acidification before concentration nor reduction of the lactose concentration by diafiltration had any significant effect on the composition or textural properties of the cheeses.
Analysis by fast protein liquid chromatography of variants of κ-casein and their relevance to micellar structure and renneting
Authors: Dalgleish Douglas G.
Published: June 2009

Fast protein liquid chromatography was used to study the κ-casein fraction of casein micelles from bulk milk and from milk from individual animals homozygous for κ-caseins A and B. The extent of glycosylation of the κ-casein appeared to have no effect on its distribution in casein micelles of different sizes, nor did it affect the rate at which κ-casein was destroyed during renneting. The rate of breakdown of κ-casein during renneting was also almost independent of micellar size. The results may indicate a difference between methods which analyse for intact κ-casein or for the product macropeptide during renneting.
Determinants of bacterial replication rates in mastitic whey
Authors: Mattila Tuna , Syväjärvi Jouko , Jensen Niels-Einar , Sandholm Markus
Published: June 2009

Bacterial growth was measured by a turbidimetric microtechnique in the whey of milk samples from quarters of cows with subclinical mastitis. Samples were grouped according to bacterial isolates recovered and the effects of bacterial species and whey on bacterial growth rates were analysed. Different strains of bacteria and different whey samples gave highly significant differences in bacterial replication rates. Except for penicillin-resistantStaphylococcus aureus, bacteria grew better in whey from mastitic milk where the inflammation was caused by the same bacterial species than in other mastitic milk samples. Inflammation caused by major pathogens generally enhanced the growth in whey of any type of major pathogen. Since mastitis pathogens showed enhanced growth in whey prepared from the same milk from which they were isolated, specific antibacterial factors in the whey did not appear to restrict bacterial growth in whey. The nutritional quality of the medium seems to be the important determinant of bacterial growth.
Interaction of factors which influence the extent of lipolysis during milking and storage of raw milk
Authors: Needs Eric C. , Anderson Malcolm , Morant Steven V.
Published: June 2009

The effect of aeration and agitation during milking on free fatty acid (FFA) levels in raw milk was investigated by comparing (a) a dual vacuum system with a ‘round the barn’ installation and (b) a claw piece requiring high air bleed with conventional claw pieces. Reduced milk transfer pressure resulted in a reduction in lipolysis of 54%, while high air bleed led to a 21% increase. FFA values were related to milk yield, stage of lactation and to a lesser extent the incidence of mastitis. These relationships were largely independent of the type of milking equipment. Fat content and somatic cell count did not affect the level of lipolysis. Increases in FFA due to activation by added blood serum were strongly related to the initial FFA concentrations.
Chemical composition of milk from a herd of Norwegian goats
Authors: Brendehaug Johanne , Abrahamsen Roger K.
Published: June 2009

The chemical composition of Norwegian bulk collected goats' milk from the University herd was analysed during one lactation period (30 weeks, 20 samples during 1983). There was considerable variation in chemical composition during the year. Fat content decreased over the first 4 months of lactation and increased during the mountain pasture period. Protein concentration decreased during the first 4 months, and then increased until the end of lactation. Lactose concentration decreased throughout lactation. Casein nitrogen (casein N) was highest at mid lactation and lowest at the beginning and end of lactation. β-Lactoglobulin N showed the opposite trend. Citrate content showed a significantly quadratic decrease and total ash content an increase with advancing lactation. Mutual significant correlations between total P, K, Na, Ca and Mg were calculated, and all increased throughout lactation. There was significant positive correlation between concentrations of individual medium-chain fatty acids and stage of lactation. They remained more or less constant during the first part of the lactation, decreased to minima when the goats were on pasture, and increased during the last phase of lactation. Concentration of C16fatty acid was negatively correlated with C18and C18:1. Goat flavour intensity score and quality flavour score were highest at mid lactation, and positively correlated with the acid degree value.
Determination of the extracellular lipases ofPseudomonas fluorescensspp. in skim milk with the β-naphthyl caprylate assay
Authors: McKellar Robin C. , Cholette Hilaire
Published: June 2009

A method based on the hydrolysis of β-naphthyl caprylate (β-NC) has been developed for quantitating extracellular lipase fromPseudomonas fluorescens. The assay was extremely sensitive to skim milk (SM); as little as 0·02 ml raw SM in a 2·0 ml reaction mixture resulted in an apparent loss of 50% of the lipase activity. Activity improved 3-fold when trypsin (50 μg/ml) was included in the reaction mixture. When super-simplex optimization was used to determine the optimum levels of β-NC, Na taurocholate (NaTC), SM/lipase mixture and trypsin for maximum activity, NaTC was found to be unnecessary for activity. Subsequent addition of 15 mM-NaTC resulted in 80% loss of activity. On the other hand, NaTC was required for native lipase activity in the presence of SM. Native lipase was completely inhibited by heating at 70 °C for 2 min, while B52 lipase retained 75% of its activity under the same conditions. The assay was able to detect lipase produced byPs. fluorescensB52 in SM at 5 °C when the cell density exceeded 108colony forming units/ml. The presence of butterfat (3°5%) in the SM assay inhibited B52 lipase by 97%. The β-NC assay gave results comparable to the tributyrin agar diffusion assay using cell-free extracts of ten strains of common dairy psychrotrophs. The results suggest that the β-NC assay may be useful for determining lipase activity in raw SM.
Effect of casein micelle composition and casein dephosphorylation on coagulation and syneresis
Authors: Pearse Martin J. , Linklater Peter M. , Hall Robert J. , Mackinlay Antony G.
Published: June 2009

The effect of varying the casein composition of artificial micelle milk on rennet coagulation time and syneresis was examined in order to determine whether either of these processes is dependent on the concentration of particular casein components. It was found that the levels of κ-and β-caseins had a significant effect on coagulation, whereas syneresis was only affected by the level of β-casein. Partial dephosphorylation of preformed micelles or the incorporation of dephosphorylated or partly dephosphorylated β-casein into artificial micelle milk was found to have an adverse effect on both coagulation and syneresis. It was concluded that the phosphate groups of casein, particularly those of β-casein, are directly involved in the micelle-micelle interactions which occur during coagulation and syneresis.
Identification of cheese-smear coryneform bacteria
Authors: Seiler Herbert
Published: June 2009

Three groups of coryneform bacteria isolated from the rind of nine soft and semi-hard cheese varieties, i.e. the orange, white and yellow strains, were studied with regard to morphological and physiological features. The 115 orange isolates of the Brevibacterium linens type formed only one homogeneous phenon. The 96 white and 161 yellow pigmented strains were grouped into 15 phena. Five phena (58% of the strains) belong to the species ‘B. ammoniagenes’, Arthrobacter variabilis and A. nicotianae. The other strains were arranged into five Arthrobacter spp. and four Corynebacterium spp. groups as well as a Rhodococcus sp. group. Usually specific forms for the individual cheese varieties were involved. In cheeses of poor surface-smear quality B. linens was found in reduced numbers.
A glyco-phosphoprotein in human milk
Authors: Azuma Norihiro , Yamauchi Kunio
Published: June 2009

A highly glycosylated phosphoprotein (HGPP) was isolated from a human casein fraction by reversed-phase high-performance liquid chromatography. This component contained carbohydrates to ∼ 38·2% (w/w) and phosphorus to ∼ 1·6% (w/w). The molecular weight of this HGPP as estimated by sodium dodecyl sulphate–polyacrylamide gel electrophoresis ∼ 41000. Ultracentrifugal analysis revealed that the sedimentation coefficient of the HGPP was 2·6S in a 10 mM-imidazole-HCl buffer at pH 7·0 and 27 °C, but this component interacted with human κ-casein and formed a complex with s = 10·4S.
Effect of the protein, citrate and phosphate content of milk on formation of lactulose during heat treatment
Authors: Andrews Geoffrey R. , Prasad S. Krishna
Published: June 2009

Milk ultrafiltrate and milks of varying protein, citrate and phosphate concentrations were heated in sealed containers. Protein was found not to be involved in the mechanism of formation of lactulose, but increasing the protein content of milk reduced the concentration of lactulose after heating. This was considered to be due to increased condensation of lactose and lactulose with amino groups of the protein, Less lactulose was formed in milk ultrafiltrate than in skimmed milk accorded the same heat treatment, which was attributed to the buffering capacity of the milk protein in skimmed milk. Activation energies for lactulose formation in skimmed milk and in ultrafiltrate were 128 and 131 kJ/mol respectively. Citrate and phosphate catalysed the formation of lactulose. It is proposed that the formation of free lactulose in heated milk and ultrafiltrate proceeds exclusively by the Lobry de Bruyn-Alberda van Ekenstein transformation with the naturally occurring phosphate and citrate acting as base catalysts.
Improvement in the quality of the dried fermented milk product, oggtt
Authors: Al-Ruqaie Ibrahim M. , El-Nakhal Hamza M. , Wahdan Ahmed N.
Published: June 2009

Oggtt is a dried fermented milk product made and marketed primitively under uncontrolled conditions in the Arabian peninsula. By applying controlled conditions for production, the keeping quality of oggtt was greatly improved. The two types (cooked and salted) were produced from fresh pasteurized goats' or cows' milk or from skim milk powder. Oggtts flavoured with chocolate, date, mint or different fruits were also produced. Chemical composition and organoleptic properties of the final products were evaluated. Taste panel results indicated that the plain products, including those made from reconstituted milk, were acceptable, but flavoured oggtts, with the exception of date flavour, were not popular.
Lactulose content, colour and the organoleptic assessment of ultra heat treated and sterilized milks
Authors: Andrews Geoffrey R. , Morant Steven V.
Published: June 2009

24 ultra heat treated (UHT) and 17 in-bottle sterilized milks prepared in commercial plants and of a similar age were presented to taste panels for assessment of flavour and colour. The colour was also analysed instrumentally and the lactulose content of the milks measured by an enzymic method. Flavour defects, other than the cooked flavour, were scored very low. The lactulose content of the milks was negatively correlated with the acceptability of the milks and positively correlated with the cooked flavour. Correlations were also found between the visual and instrumental assessments of milk colour and between some of the instrumental colour parameters and the lactulose content of the milks. UHT and in-container sterilized milks could not always be distinguished on the basis of their organoleptic qualities. The best distinction was observed in the scores for cooked smell and acceptability of taste. The usefulness of the lactulose content and/or the colour of the milks in discriminating between UHT and in-bottle sterilized milks was calculated. Using all the data, sterilized milk could be correctly identified in 96·7% of decisions. The lactulose content of a milk was considered to give a good indication of the organoleptic quality of the milk.
Heat stability of milk: role of β-lactoglobulin in the pH-dependent dissociation of micellar κ-casein
Authors: Singh Harjinder , Fox Patrick F.
Published: June 2009

On heating casein micelle systems containing β-lactoglobulin (β-lg) at 90°C for 10 min, β-lg complexed with casein micelles at pH < 6·9, probably as a result of interaction with κ-casein via sulphydryl-disulphide interchange, and co-sedimented with the micelles on ultracentrifugation. Complex formation with β-lg appeared to prevent the dissociation of micellar κ-casein on heating. However, at pH ≥ 6·9, κ-casein/β-lg complexes dissociated from the micelles on heating, thus enhancing the release of micellar κ-casein. High concentrations of β-lg (≥0·8%) induced coagulation at pH 7·3, essentially by promoting the dissociation of micellar κ-casein. It appeared that αs1-, αs2-, β- and κ-caseins dissociated from serum protein-free casein micelles to equal extents, but the presence of β-lg specifically enhanced the dissociation of κ-casein at pH values ≥ 6·9. Micelle hydration increased slightly when casein micelles were heated in the presence of β-lg at pH 6·7, while at pH 7·3 β-lg decreased the degree of hydration of casein micelles. Formation of a complex between β-lg and κ-casein appeared to stabilize the micelles in the pH range 6·5–6·7, possibly via increased micellar charge or degree of hydration or by preventing the dissociation of κ-casein.
Cardiovascular responses and mammary substrate uptake in Jersey cows treated with pituitary-derived growth hormone during late lactation
Authors: Fullerton Frances M. , Fleet Ivan R. , Heap R. Brian , Hart Ian C. , Mepham T. Ben
Published: June 2009

Pituitary-derived bovine growth hormone (bGH) was administered to Jersey cows during late lactation for 7 d. Milk yield increased significantly during treatment and by a maximum of 49·6% on d 7. The magnitude of the increase was similar to that of mammary plasma flow (47·8±18·3%) over the same period. By 15–21 d after treatment, both variables had returned to pretreatment values. With respect to milk composition, bGH had negligible effect on lactose and fat concentrations but there were significant decreases in protein, sodium and chloride. Arterial plasma concentrations of bGH increased substantially during treatment, but the associated rise in insulin was not statistically significant. Haematocrit decreased significantly, the lowest value being recorded 3 d after bGH treatment ceased. Mammary respiratory quotient fell progressively after the start of bGH treatment and reached the lowest recorded value 3 d after treatment ceased (62·2 ± 7·3% of pretreatment value). Glucose and acetate uptake by the mammary gland increased significantly during treatment, increase in glucose uptake being due both to a greater arterio-venous difference and to mammary plasma flow. There was strong evidence that the acute response in increased milk yield was associated with multiple effects in terms of mammary plasma flow and metabolism, as well as haematocrit changes indicative of increased plasma volume.