bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of acetaldehyde from threonine by lactic acid bacteria
Authors: Lees G. J. , Jago G. R.
Published: June 2009

Group N streptococci were found to cleave threonine to form acetaldehyde and glycine. Threonine aldolase, the enzyme catalysing this reaction, was found in all strains exceptStreptococcus cremorisZ8, an organism which had been shown previously to have a nutritional requirement for glycine. The enzyme was strongly inhibited by glycine and cysteine. The inhibition showed characteristics of allosteric inhibition and was pH-dependent. Inhibition by glycine, but not by cysteine, was highly specific. Analogues and derivatives of cysteine which contained a thiol group and a free amino group inhibited the activity of threonine aldolase. The presence of a carboxyl group was not necessary for inhibition. The cleavage of threonine by wholecell suspensions was stimulated by either an energy source to aid transport, or by rendering the cells permeable to substrate with oleate. Threonine did not appear to be degraded by enzymes other than threonine aldolase, as threonine dehydratase activity was low and NAD- and NADP-dependent threonine dehydrogenases were absent.
A comparison of microstructures of Cheddar cheese curd manufactured with calf rennet, bovine pepsin, and porcine pepsin
Authors: Eino M. F. , Biggs D. A. , Irvine D. M. , Stanley D. W.
Published: June 2009

Calf rennet, bovine pepsin, and porcine pepsin were used to produce cheese curd, using the same milk and lactic culture for each. Specimens were prepared for scanning electron microscope examination by a modified critical-point drying technique.

From examination of the micrographs, the curd made with bovine and porcine pepsin were similar in structure and in orientation of the coagulated protein, whereas the curd produced with rennet was different, having a more compact and organized structure.
The effect of non-starter bacteria on the chemical composition and the flavour of Cheddar cheese
Authors: Law B. A. , Castañón Marisi , Sharpe M. Elisabeth
Published: June 2009

Differences in flavour scores and in the concentrations of free fatty acids, methyl ketones and H2S were measured in Cheddar cheeses containing various groups of non-starter bacteria or starter streptococci alone, made under controlled bacteriological conditions by the aseptic vat technique. The non-starter bacteria were made up of lactobacilli, leuconostocs, pediococci, micrococci and Gram-negative rods isolated in commercial creameries from raw milk or fresh cheese curd. These were added to the experimental cheese as single groups or as complete floras (reference floras). Several bacterial groups influenced the measured concentrations of the flavour compounds, but flavour differences were not correlated with these chemical differences. Only cheese containing a curd-derived whole reference flora or cheese made in open vats in the N.I.R.D. Experimental Dairy had significantly better flavour than starter-only cheese, but this improvement was not attributable to any particular group of bacteria.
αs0-Casein: its preparation and characterization
Authors: Manson W. , Annan W. D. , Barnes G. K.
Published: June 2009

It has been reported previously (Annan & Manson, 1969) that chromatography of the αs-casein complex of bovine milk on columns of sulphoethyl Sephadex C-50 resulted in fractionation of the complex into a main component, αs1-casein and a number of minor components one of which was designated αs0-casein. The present communication describes the preparation of αs0-casein from unfractionated casein in an amount and state of purity which render possible its further characterization.
Heat-induced changes in sulphydryl and disulphide levels of β-lactoglobulin A and the formation of polymers
Authors: Watanabe K. , Klostermeyer H.
Published: June 2009

The effects of heat and pH on sulphydryl (–SH) and disulphide (–SS–) groups of β-lactoglobulin (β-lg) A have been studied by heating at different temperatures and pH values in air and at pH 6·9 in the absence of air. At pH 6·9 under aerobic conditions a decrease of –SH groups and an increase of –SS– groups was observed with increasing time and temperature. Only small changes were found under anaerobic conditions. At pH from 3·0 to 9·8 the –SH level decreased while the –SS– level increased up to pH 6·9 and then dropped rapidly. In addition to –SH/–SS– interchange there were reactions to other sulphur-containing compounds as seen from the losses in the total amount of –SH plus –SS– sulphur. The results of gelchromatographic investigations suggest that –SH-initiated –SS– exchange-reactions play an important role in the formation of high molecular weight polymers of β-lg A during heat treatment, and that the formation of intermediates depends on the presence of air.
The effect of diet on the γ- and δ-lactone and methyl ketone potentials of caprine butterfat
Authors: Stark William , Urbach Gerda , Cook Leonard J. , Ashes John R.
Published: June 2009

When caprine butterfat was heated in the presence of water vapour and the absence of air, γ- and δ-lactones and methyl ketones were produced which were qualitatively the same as those from bovine butterfat. The saturated δ-lactone and methyl ketone potentials of the caprine butterfat were of the order of one third those of bovine butterfat when the goats and cows received similar rations. γ-Dodecanolactone, γ-dodec-cis-6-enolactone, δ-tetradec-cis-8-enolactone and δ-tetradec-trans-8-enolactone potentials of the caprine butterfat were in the same range as for bovine butterfat when the animals were on similar diets. The γ- and δ-lactone and methyl ketone potentials and the fatty acid composition of caprine butterfat varied with the diet of the goat. Supplementing the diet with polyunsaturated fat, whether or not protected against biohydrogenation in the rumen, lowered the saturated δ-lactone and methyl ketone potentials as well as the proportion of C10,12,14,16fatty acids in the caprine butterfat. Inclusion of crushed oats in the diet increased the γ-dodecanolactone potential. The γ-dodecanolactone and they γ-dodec-cis-6-enolactone potentials were also enhanced by feeding seed oil supplements which were not protected against ruminal hydrogenation. To prevent the development of the sweet off-flavour associated with γ-dodecalactones in heated, ruminant-derived meat and butterfat with elevated levels of linoleic acid, it appears that oats should be excluded from the basal ration of the ruminant and the polyunsaturated oil supplement should have the highest possible degree of protection against biohydrogenation in the rumen.
Metabolism of [14C]bicarbonate byStreptococcus lactis: the synthesis, uptake and excretion of aspartate by resting cells
Authors: Hillier Alan J. , Rice Garry H. , Jago G. Richard
Published: June 2009

Resting cells ofStreptococcus lactisC10 were able to synthesize aspartic acidde novobut could not actively transport aspartic acid into the cell. Intracellular aspartate was excreted from the cell in the presence of glucose but did not exchange with any extracellular amino acids. The results indicated thatStr. lactisC10 obtains the aspartic acid it requires for growth by bicarbonate fixation instead of by the utilization of extracellular aspartic acid.
Natural variations in the average size of bovine casein micelles: II. Milk samples from creamery bulk silos in south west Scotland
Authors: Holt Carl , Muir D. Donald
Published: June 2009

Samples of bulk silo milk from 5 creameries in the south west of Scotland were taken over a 16-month period. The average radii of casein micelles were determined by measuring the wavelength dependence of the turbidity of skim-milk diluted with its own ultrafiltrate. In addition, the concentrations of casein, soluble and colloidal Ca and P1 were measured. The average size of casein micelles followed a pronounced seasonal trend with smaller average sizes in the summer compared to the winter period, confirming earlier observations made on milks from individual cows. The average size of casein micelles correlated positively (r = +0·777, P < 0·001) with the amount of colloidal P1 per unit weight of casein and negatively (r = −0·77, P < 0·001) with casein-bound Ca. Average micelle radius was negatively correlated with heat stability at the natural pH of milk (r = −0·61, P < 0·001), but there did not appear to be any causal relation between these 2 variables.
Storage of lactose-hydrolysed dried milk: effect of water activity on the protein nutritional value
Authors: Burvall Anders , Asp Nils-Georg , Bosson Agneta , José Carmen San , Dahlqvist Arne
Published: June 2009

The retention of the protein nutritional value during storage of lactosehydrolysed dried milk at different water activities (aw) was studied and compared with that of ordinary milk. In the lactose-hydrolysed milk biologically available lysine decreased much more rapidly than in the ordinary milk at all the different aw studied. Thus, at conditions normally accepted for ordinary dried milk (aw ~0·2; moisture ~ 4 %) there was an available lysine loss in the hydrolysed milk of about 25 % after 2 months and about 40 % after 6-months storage at room temperature. This occurred without any visible browning. It is concluded that drying to very low aw (≦ 0·11) is necessary to obtain good stability of the protein nutritional value (PNV) in lactose-hydrolysed milk. The drying, however, must be done so that losses in nutritional value are minimal during that process. It should also be noted that fat oxidation might be a problem at such low aw. A chemical method for available lysine assay (guanidination and assay of homoarginine) gave values in good agreement with the biological evaluations with rats.
A frequency response of the dairy cow's teat
Authors: Reitsma Sybren Y. , Scott Norman R.
Published: June 2009

A frequency response of the cow's teat has been determined by applying sinusoidal changes in vacuum level to the teat. Twelve frequencies were applied ranging from 0.06 to 12 Hz. The responses investigated were the external teat end diameter and the teat milk flow-rate. The measured variables were: (1) frequency of applied pressure and teat end diameter, (2) peak-to-peak pressure and teat end diameter, (3) average vacuum level and teat end diameter, (4) time delay between maxima of vacuum level and teat end diameter, (5) time delay between minima of vacuum level and teat end diameter, and (6) teat milk flow-rate. The results showed that within the range of the investigation milk flow-rates were lower between 0.8 and 2.5 Hz than at frequencies both below and above this range. A statistical analysis of the flow rate and teat end diameter data supports the common practice of applying the same frequency to both front and rear teats during milking. Other findings show good agreement with results reported previously on dynamic responses of the teat to step changes in pressure.
Metabolism of [U-14C; 2, 3-3H]-L-valine by the isolated perfused goat udder
Authors: Roets Eddy , Massart-LeëN Anne-Marie , Verbeke Roger , Peeters Georges
Published: June 2009

Two lactating mammary glands excised from 2 goats were perfused for several hours in the presence of [U-14C; 2,3-3H]-L-valine and received adequate quantities of glucose, acetate and amino acids. In the synthesized milk 96 and 89% respectively of the casein valine was derived from free plasma valine. Valine was extensively catabolized by mammary tissue, resulting in a considerable14CO2production and in the incorporation of14C into milk citric acid and to a lesser extent into casein aspartic acid and glutamic acid. About 30% of the valine molecules which were taken up by the mammary gland were oxidized to CO2and 70% were incorporated in casein as valine residues. About 10% of the plasma valine molecules were reversibly transaminated during one passage through the udder. An important amount of radioactivity of plasma was present in unknown metabolites. Only 7% of this activity was localized in isobutyrate. The radioactivity of total milk fat was very low. Mainly iso-14:0, iso-16:0 and 15:0 were labelled.
Proteolytic activity in UHT-sterilized milk
Authors: Corradini Cesare , Pecis Paola Panini
Published: June 2009

The proteolytic activity in UHT-sterilized milk of a proteinase-containing fraction, prepared from the milk, is reported. The proteinase fraction was isolated from casein micelles as described by Reimerdes & Klostermeyer (1974).

The fraction was added to UHT milks and the proteolysis in the samples, measured as the liberation of non-protein nitrogen, compared with that in control samples without added proteinases. The increase in proteolytic activity and deterioration in samples containing added proteinases indicated that an enzyme process occurred in UHT-sterilized milk which could influence gel formation.
On the size of monomers and polymers of β-casein
Authors: Buchheim Wolfgang , Schmidt Daniël G.
Published: June 2009

The size and number average molecular weight have been determined for β-casein monomers and polymers from electron micrographs using the freeze-etching procedure with spray-frozen specimens. For the spherical β-casein monomers we found a mol. wt of 22600 and a diam. about 10 nm, which compared quite well with data obtained from ultracentrifugation, light scattering and viscosity measurements. Polymer sizes were in agreement with molecular weight determinations from ultracentrifugation and light scattering, assuming that the volume and weight of the particles are proportional.
Structure of β-casein
Authors: Arima Shunrokuro , Niki Ryoya , Takase Kenji
Published: June 2009

The temperature and concentration dependent association of β-casein was studied by means of viscometry, gel filtration chromatography, electron microscopy, analytical ultracentrifugation and UV difference spectrophotometry. Degrees of polymerization of 12, 22 and 49 and free energies of association of –21, –23 and – 25 kJ/mole monomer were found at temperatures of 10, 15 and 20 °C respectively in 0·2 M Na phosphate buffer pH 6·7.

Monomeric β-casein was not a completely random coil but became more compact with increasing temperature, due to hydrophobic interactions.
Application of multiple regression analysis to sedimentation equilibrium data of αs1- and κ-casein interaction for calculation of molecular weight distributions
Authors: Nakai Shuryo , van de Voort Fred
Published: June 2009

Multiple regression analysis was applied to sedimentation equilibrium data for determination of the molecular weight distribution (MWD) of model systems consisting of up to 3 components. Negative weight fractions which were frequently encountered during multiple regression analysis were forced to zero by sequentially eliminating from the regression matrix the corresponding molecular weights in order of the magnitude of negative t-values. The simplex optimization of Morgan & Deming (1974), modified by incorporating a prohibit–range– trespassing routine, was used to search for the best fit values for weight average molecular weights and relative concentrations of the components. This method almost quantitatively reproduced the molecular weights and concentrations of the original model systems. This quantitative information supplemented the multiple regression matrix to improve the resolution of MWD.

A direct comparison using model systems revealed that the multiple regression method in conjunction with the simplex optimization routine was more quantitative than the linear programming method of Scholte (1969). When applied to mixtures of standard proteins (ribonuclease A; ovalbumin; γ-globulin and ovalbumin; γ-globulin; apoferritin), the simplex optimization routine yielded values for average molecular weights and relative concentrations of the component proteins which were in good agreement with the known values in the original mixtures.

The MWD of αs1-k-casein mixtures at an ionic strength of 0.1 suggested that k-casein was readily dissociated to the monomer (or the dimer) and interacted with the monomer (or the dimer) of αs1-casein forming a complex of approximately 400000.
Headspace analysis of hard cheeses
Authors: Manning Donald J. , Moore Carolyn
Published: June 2009

A method is described for the chromatographic analysis of the headspace of hard cheese. Among the cheeses examined were 12 commercial cheeses and 12 Cheddars made in the NIRD experimental dairy. The 12 commercial cheeses were Parmesan, Caerphilly, Stilton, Leicester, Double Gloucester, Cheshire, Gouda, Wensleydale and 4 varieties of Cheddar. It was found that those varieties containing low concentrations of sulphur compounds had little aroma and derived most of their flavour from taste and texture. The concentration of 2-pentanone was found to be a good indicator of maturity of Cheddar cheese.
260. An objective measure of the consistency of cheese curd at the pitching point
Authors: Blair G. W. Scott , Coppen F. M. V.
Published: June 2009

1. A method is described for measuring the consistency of cheese curd during the scalding process which has been found satisfactory with Cheddar, Cheshire, Leicester, Double Gloucester, Caerphilly, Kingston and Derby cheese and is probably applicable to some other varieties.

2. The property (W/h), taken as a criterion of consistency, can be measured within less than 1 min. and is highly correlated with moisture content except when abnormal scalding conditions produce an uneven distribution of moisture in the curd. The size of cut does not affect this correlation within wide limits, though both moisture content and W/h are regularly affected by size of cut until the curd is approximately ready to pitch, at which point both properties show unique values independent of size of cut.

3. When the curd is nearing the pitching point, W/h measures the extent to which a standard cylinder of curd loses whey, the liquid being replaced in the solid structure by air. At an earlier stage in the scalding process the capacity of the curd to retain its shape under the force of gravity also affects W/h.

4. Although the cheese-maker judges the consistency of curd suitable for pitching by a complex mixture of properties, it is believed that Wjh will serve as an effective single-value criterion of consistency, suitable for judging pitching time if the acidity is also known.
A note on an indirect measure of machine milking rate
Authors: Griffin T. K. , Dodd F. H.
Published: June 2009

From an analysis of the milking rate data of 200 cows it has been shown that for individual cows the yields of milk obtained in the second minute of milking give a good prediction of their maximum milking rates.
Action of rennin on α-, β- and γ-caseins
Authors: Lahav E. , Babad Y.
Published: June 2009

Whole acid casein and α-, β- and γ-caseins were isolated and treated with rennin. Chemical, chromatographical and electrophoretical analyses were done on the caseins and on the products obtained from them after rennin treatment. Three different fractions were obtained which had some specific protective activity for the Ca-sensitive forms of α-, β- and γ-casein, respectively, and which differed in their chemical, chromatographical, and electrophoretical properties.

It is suggested that each casein fraction in milk is associated with its own protective fraction which when released by the action of rennin, allows the casein to clot.
The effect of restricted grazing during a single day upon milk yield, milk composition and butterfat characteristics
Authors: Munford R. E. , Campbell I. L. , McDowall F. H. , Davey A. W. F.
Published: June 2009

The effects of depriving cows of pasture, for part or all of a single interval between the morning and evening milkings, on milk yield and composition have been investigated. The yields of milk and solids-not-fat, but not of fat, were reduced. The characteristics of the butterfat obtained at the first 2 milkings following grazing restriction differed markedly from those of cows allowed to graze normally.

The changes observed suggested that the grazing restriction led to a temporary reduction in the supply of volatile fatty acids from the rumen and an increased utilization of fatty acids from body fat by the mammary gland.
A meter for measuring pulsation ratio in milking machines
Authors: Thiel C. C. , Akam D. N.
Published: June 2009

A portable apparatus is described for indicating continuously as a measure of pulsation ratio the proportion of the cycle during which a liner is more than half open. With the machine set for milking, a probe with an electric switch which opens as the liner collapses is inserted in one liner, the others being closed with rubber bungs. The pulses of current from the switch are fed to a damping circuit so that the proportion of the cycle time during which current flows can be read on a meter. The problem of interpreting the various measures of pulsation ratio are discussed.
The effect of acidity, salt and copper and iron contamination on the keeping quality of butter
Authors: McDowell A. K. R.
Published: June 2009

Butter made from good quality sweet cream is usually free of any major defect in flavour, even after a long period of cold storage. However, butter made from cream ripened with starter, is liable to develop oily and fishy flavours during storage. Thus the manufacture in New Zealand of butter for export has been confined to the sweet cream product.
The nature and cause of seaminess in Cheddar cheese
Authors: Conochie J. , Sutherland B. J.
Published: June 2009

Microscopical and chemical studies of seaminess in Cheddar cheese revealed that the white lines or seams characteristic of the defect are sections through layers of crystals lying between the milled curd particles. The crystals were identified from their X-ray diffraction pattern and by their refractive index as calcium orthophosphate dihydrate, CaHPO4. 2H2O. On each side of the adjoining curd surfaces in affected cheese there is a zone about 20 μm thick of strongly contracted protein which is almost devoid of crystals.

Adding sodium chloride to cheddared curd increased the quantities of calcium, phosphorus and water released. The increases were proportional to the amount of salt applied within the range 0–2·5 g NaCl per 100 g curd.

The solubility of calcium orthophosphate was found to rise from about 0·0025 M in water to a maximum of 0·008M in 2 M sodium chloride solution.

It is postulated that calcium and phosphate ions released from the curd into the seam crystallize in the form of CaHPO4. 2H2O as the solubility of the compound is lowered by diffusion of salt from the surfaces into the curd particles.
The influence of cream-processing methods on the rate of setting and final hardness of sweet cream butter
Authors: Wood F. W. , Dolby R. M.
Published: June 2009

Cream-cooling rates, cream-pre-cooling treatments (Alnarp) and seasonal changes in the chemical composition of butterfat were found to influence the setting rate of butter. Vacreator pasteurization, however, especially at high steam intensity, had the greatest effect. Comparative hardness values of butter made from platepasteurized and Vacreator-pasteurized cream were 1·5 and 2·9 kg and 4·4 and 8·3 kg at the end of ½ and 5 h, respectively, after the completion of working. The highest setting rate, which resulted in a hardness of 6 kg at the end of 30 min, was recorded for butter made from Vacreator-pasteurized cream which was rapidly cooled to 5 deg F below normal churning temperature and churned after holding for 30 min. Abrupt breaks noted in the setting curves of this rapidly setting butter lead to speculation that changes in the butterfat crystal form may be involved

In general, the final hardness values of butter stored at 45 °F for 30–50 days were not greatly influenced by the setting rates observed at 55 °F during the 5-h period immediately after the completion of working. Exceptions to this observation were obtained when the cream was rapidly cooled to or slightly below churning temperature and also when the cooling of plate-pasteurized cream was delayed at 65 °F for 3–4 h before final cooling to the churning temperature.

The causes of the differences observed in the setting and final hardness values of butters made from plate- and Vacreator-pasteurized cream were not determined and warrant further investigation.
The cell count of cow's milk and the micro-organisms cultured from the milk
Authors: Blackburn P. S.
Published: June 2009

Total and differential cell counts were made on a total of 26272 quarter samples of foremilk taken at fortnightly intervals from cows in the Institute herd during the 12 years 1953–1965, and the samples were also examined bacteriologically.

The average cell count in each lactation up to the 7th was calculated.

The average total cell count of samples from which no staphylococci, streptococci or coliform organisms were isolated increased from the 1st to the 7th lactations from 0·19 to 0·60 million cells/ml, and from the 2nd lactation onwards the increase was due entirely to an increase in the number of polymorphs. With infected samples, however, changes in the average total cell count were caused by changes in the numbers both of polymorphs and of cells other than polymorphs.

The average total cell count of samples from which coagulase-negative staphylococci were isolated varied between 0·58 and 1·00 million/ml throughout the 7 lactations. For samples from which coagulase-positive staphylococci were isolated the cell count varied between 0·72 and 4·94 million/ml, the highest average total cell count occurring in the 5th lactation.

The average total cell count of samples from which streptococci were isolated varied between 1·48 and 4·62 million cells/ml, the highest value occurring in the 2nd lactation.
Fat testing of composite Milk samples with the Milko-tester
Authors: McDowell A. K. R.
Published: June 2009

With 10-day composite milk samples the effect has been investigated of various preservatives, of variations in the method of preparing the composites and of the condition of the composites at sampling on Milko-tester results for fat content.

The results for composites preserved with mercuric chloride agreed much more closely with the Werner Schmid results than did those for corresponding composites preserved with potassium dichromate, formaldehyde solution or paraformaldehyde.

In composites preserved with mercuric chloride, prepared and held at ambient temperatures at 2 dairy factories, a small proportion contained destabilized fat when sampled at 98–103 °F and gave very low Milko-tester results in comparison with the Werner Schmid and Gerber results. After high-speed mixing of the composites at 115 °F the Milko-tester results were closer to, but still lower than, the Werner Schmid results.

The average Milko-tester result for 133 composites free from destabilized fat when sampled at 98–103 °F was 0–099 ± 0.055% lower than the average Werner Schmid result. Results for 133 duplicate samples, which were also free of destabilized fat at 98–103 °F but which had not been swirled after the daily addition of fresh milk, were on average — 0.158 ± 0.076% lower than the Werner Schmid result. The Werner Schmid and Gerber results agreed well. The lowering of the Milko-tester result in the ‘swirled daily’ samples was due (a) to the effect produced by dissolving mercuric chloride in milk, (b) to slight fat hydrolysis, and (c) to some other factor, possibly fat oxidation. The further lowering of the Milko-tester result in the ‘non-swirled’ samples was due mainly to greater hydrolysis of the fat with production of higher fat acidities. Other composites, which were swirled daily but which were held at 38–40 °F gave on the average higher fat acidities and lower Milko-tester results than the ‘swirled daily’ composites held at ambient temperatures.

A correction of +0.10% to the Milko-tester readings of all ‘swirled daily’ composites, preserved with mercuric chloride and in suitable condition for sampling at 98–103 °F, brought over 90% of the results to within ± 0.10% of the Werner Schmid results.

The Milko-tester (Foss Electric, Hillerød, Denmark) is already in use in a number of countries for the rapid estimation of fat in milk. The fat content is read directly by a photometric measurement of the turbidity due to the fat globules after heating, homogenizing and diluting the sample with a protein-dissolving versene solution. The instrument has been found satisfactory for the routine testing not only of fresh milks but also of milks to which preservative has been added (Černá & Písecký, 1966; Murphy & McGann, 1967). Grubb (1966), however, reported that Milko-tester readings for samples preserved with potassium dichromate were lower after 14 days' storage.

In the present paper the results are presented of an investigation into the suitability of the Milko-tester for fat testing of 10-day composite milk samples.
Factors affecting vacuum within the teatcup liner during milking
Authors: Thiel C. C. , Clough P. A. , Westgarth D. R. , Akam D. N.
Published: June 2009

Factors associated with the milking cluster and the long milk tube which cause a diminished or a fluctuating vacuum within the liner of the teatcup assembly during simulated milking with an artificial udder fell into 3 groups. 1. Lower milk flow rates and admission of air at the clawpiece greatly decreased vacuum fluctuation within a pulsation cycle and increased the mean level of vacuum in the liner during that part of the cycle in which milk was flowing from the teat. 2. Larger bore of the short milk tube connecting the liner to the clawpiece, pulsation of the teatcup liners in pairs instead of all 4 together, and larger volume of the clawpiece bowl in the main decreased fluctuation in vacuum within the liner. 3. Larger bore and shorter length of the long milk tube connected to the clawpiece and decreased height above the outlet of the clawpiece to which the milk was raised mainly increased the mean vacuum in the liner during that part of the cycle in which milk was flowing from the teat.

In a milking experiment with 75 cows mean overall fluctuations in milking vacuum within the liner in a pulsation cycle at peak flow were 11·5 and 4·8 inHg and corresponding mean levels of vacuum during that part of the cycle when milk was flowing from the teat were 11·75 and 13·0 inHg. There were no differences in milking performance of practical consequence.
Growth and proteinase production inPseudomonasspp. cultivated under various conditions of temperature and nutrition
Authors: Juffs H. S. , Hayward A. C. , Doelle H. W.
Published: June 2009

A study was made of the formation of the extracellular proteolytic enzymes during the growth cycle of several species ofPseudomonascultivated under different conditions of temperature and nutrition. Proteolytic activity was not proportional to growth. Expressed per unit of cell dry weight, the proteolytic activity showed a peak in the early logarithmic phase which was greater in cultures grown at 3 than at 28°C. Proteolytic enzyme was not formed in the absence of organic nitrogen. Of 16 organisms studied,Pseudomonas aeruginosaATCC 10145 was the most prolific producer of proteolytic enzyme.
The composition of the milk of young and of old cows
Authors: Waite R.
Published: June 2009

The milk produced by old cows frequently contains a lower concentration of solids-not-fat (S.N.F.) than that of young cows, mainly because of a low concentration of lactose. This can result from mastitis or possibly from other factors associated with ageing. The composition of the milk of 2 groups of old cows has been compared with that of substantially disease-free first-lactation cows. A comparison has also been made between the milk from the 4 quarters of each cow.

The first part of the work was done with 8 old cows and 4 first-lactation cows, and the milk was examined bacteriologically, cytologically and chemically at frequent intervals throughout the lactation. There was strong evidence that most of the difference in chemical composition of the milk of the old cows compared with that of the young cows was the result of mastitis, mainly subclinical. The milk from the old cows had a higher incidence of infection, a lower concentration of lactose and casein, higher concentrations of serum albumins, globulins and proteose-peptones and contained more total and polymorph cells. There was also some indication of another effect, not directly associated with disease in the current lactation, that led to a decrease in the lactose concentration of the milk of the old cows after about 80–90 days in lactation.

In the second part of the work, the milk from 23 old and 8 first-lactation cows in 8 commercial herds was examined twice, once after 58 and again after 163 days in lactation. Milk of abnormal composition as a result of disease was produced by 30% of the quarters of the old cows at the first examination and by 62% of the quarters at the second examination.

Some indication is given of the probable loss of milk and milk constituents that can be attributed to disease.
The sterilizing effect againstBacillus subtilisspores of hydrogen peroxide at different temperatures and concentrations
Authors: Swartling P. , Lindgren B.
Published: June 2009

An investigation was made of the death-rate ofBacillus subtilisspores in suspension in hydrogen peroxide concentrations of 10, 15 and 20% at 25, 50, 60, 70 and 80°C. Average logarithmic survival curves were plotted against normal time and death-rate constants andQ10values were calculated from the graphically determined decimal reduction times. This treatment of the experimental findings was found to be warranted in the temperature range 60–80°C. The first-order death-rate constant was ∽ 0·1 s−1for 10% hydrogen peroxide solution at 60°C and theQ10was about 1·6. Increases in the concentration from 10 to 15% and from 15 to 20% each gave an increase of about 50% in the rate constant. The application of these data to commercial practice is discussed.
Growth ofstreptococcus lactisin milk in a continuous fermenter
Authors: Linklater P. M. , Griffin C. J.
Published: June 2009

Milk was added to a continuous fermenter to maintain a selected operating pH in the range 5·4–6·0, a fermentation system controlled in this way being called a pH-stat. Below pH 5·4 casein coagulated in the fermenter and on the pH electrodes. At pH 6·0 stirring inhibited the growth of the test culture,Streptococcus lactisC 10, but the inhibitory effect was reduced and the culture grew satisfactorily when the milk reservoir was sparged with 5% CO2in N2or with N2alone. The dilution rate was highest near pH 6·0, which was close to the optimum pH for the growth of the organism. The rate of production of lactic acid and of bacterial cells in the fermenter was highest at pH 5·4.
Properties of aseptically-packed UHT milk: casein modification during storage and studies with model systems
Authors: Andrews A. T. , Cheeseman G. C.
Published: June 2009

Storage of aseptically packed UHT milk produced changes in the electrophoretic pattern of the milk caseins when the milk was stored at ambient or higher temperatures. Lower temperature storage at 4°C did not give rise to these changes.

The alterations in electrophoretic properties of the caseins appeared to be due to the action of carbonyl compounds, produced by a Maillard type of reaction, which led to changes in the charge of the protein together with some degree of polymerization. These conclusions have been drawn from results obtained on model systems of casein-lactose subjected to various heat treatments, and on casein and milk treated with acetaldehyde.

Changes in the sensitivity to calcium ions of individual caseins, whole casein and milk that had been subjected to various heat treatments or to treatment with acetaldehyde showed that all these different treatments gave rise to modified casein which, in general, became less sensitive to calcium. κ-Casein when treated alone rapidly lost its ability to protect αs1-casein from precipitation by calcium ions, while αs1-casein treated alone only gradually became more soluble in the presence of calcium. Thus, on treating whole casein there was evidence for a stability minimum when the protective ability of the κ-casein has been destroyed without a compensating gain in the stability of the αs1-casein.

The importance of these changes in relation to the stability of UHT milks has not yet been elucidated but the results indicate that cross linking between protein chains and changes in calcium sensitivity occur during long-term storage.
Reproducibility of the electronic cell-count procedure for counting somatic cells in milk
Authors: Pearson J. K. L. , Greer D. O. , Stewart D. A.
Published: June 2009

A series of experiments is described, outlining a study of 5 factors likely to influence the efficiency and reproducibility of a standardized method used for the electronic counting of somatic cells in milk. Samples containing cells covering 5 ranges from 250000 cells/ml to 1500000 cells/ml were used and the results analysed statistically.

The residual error was given special consideration, and was found not to contribute to any significant degree to the accuracy of the method. Sample volumes of 0·5 ml and 0·1 ml used for counting were compared, and there was a decrease in accuracy using the smaller volume. The influence of individual technician skill was studied with 4 workers having differing degrees of experience, and no significant addition to the overall error was observed. The effect of agitating bulk tank milk for between 0 and 2 min before sampling was examined. Variations were considerable for agitation times of less than 1 min, but the recommended mixing time of 2 min was found to be adequate with milk quantities between 450 l and 2250 l (100 and 500 gal), and at the 5 cell-count levels chosen.

The distributions of the cell counts at the 5 levels were found to be normal with the marginal exception of samples tested at 250000 cells/ml.

All aspects of the technique, sample preparation, use and calibration of the Coulter Counter, etc, should be closely followed to ensure that no inaccuracies will result from inadequate maintenance of the machine or other equipment employed in the test.
Comparative micelle structure: II. Structure and composition of casein micelles in ovine and caprine milk as compared with those in bovine milk
Authors: Richardson B. C. , Creamer L. K. , Pearce K. N. , Munford R. E.
Published: June 2009

The casein micelles of sheep (Ovis aries), goat (Capra hircus) and cow (Bos taurus) milks have been examined by electron microscopy. The ovine micelles were smaller than bovine micelles, most being below 80 nm diam. The caprine micelles were either large (c. 200 nm diam.), easily sedimented and electron-dense, or small (below 80 nm) and similar to the ovine micelles. Examination of the micelles using the freeze-etch technique showed, however, that they were all composed of subunits of similar dimensions (10–15 nm diam.).

Electrophoresis of the caseins showed that there were differences between them, with the caprine casein containing a smaller proportion of its protein in the more mobile components. The mineral contents of the milks were also different, but these were apparently related to the different pH and casein contents of the milks. It is likely that the diiferences in micelle size distribution are determined by the physical and chemical properties of the casein components.
Thermal conductivity of creams
Authors: Fernández-Martín F. , Montes F.
Published: June 2009

Thermal conductivities of creams of about 20, 30 and 40 % fat were measured at several temperatures between 5 and 75 °C. Because of the meagre data on cream, special attention was given to the prediction of conductivity using different mathematical models. An equation was derived for the thermal conductivity of cream as a function of temperature and volume fraction of the fat phase.
Effect of thiocyanate on mammary gland growth in rats
Authors: Pyska H.
Published: June 2009

In growing rats from 3 weeks to 3 months old, 0·1 % potassium thiocyanate (KSCN) decreased the plasma protein-bound iodine level by 47 % and the total DNA in the mammary gland by 11 %, but had no effect on the total KNA. Administration of thiocyanate in the form of 0·1, 0·3 and 0·5 % KSCN during pregnancy and 14 d of lactation lowered the protein-bound iodine level by 48–66 %, the total DNA by 11–47 % and the total RNA by 14–63 %, depending on the KSCN dosage. The 14-d-old litters of rats receiving thiocyanate weighed 4–41 % less than those in the control group.
Localization of glycosylated κ-casein in bovine casein micelles by lectin-labelled gold granules
Authors: Horisberger Marc , Vonlanthen Monique
Published: June 2009

The localization of glycosylated k-casein in isolated bovine casein micelles was investigated at the ultrastructural level with gold granules labelled with the Ricinus communis lectin specific for galactose. No evidence was obtained for the presence of glycosylated k-casein on the surface of glutaraldehyde-fixed micelles whether or not they had been treated with neuraminidase. Glycosylated k-casein was mainly located in the bridging network interconnecting the micelles and appeared to be loosely associated with the micelles. When thin sections of micelles were marked, no clear-cut evidence was observed for the presence of intramicellar glycosylated k-casein.
Preparation and properties of rennets from lamb's and kid's abomasa
Authors: Anifantakis Emmanuel , Green Margaret L.
Published: June 2009

Lamb and kid rennets were prepared by extraction of dried abomasa with 6% (w/v) NaCl-2% (w/v) H3BO3 and activation of the proenzymes at pH 2·0. Each gave one zone of precipitation on casein-agar gel diffusion, enabling them to be differentiated from calf rennet and pig pepsin. After agarose gel electrophoresis, the proteinase activity of lamb rennet occurred in chymosin and pepsin bands only, whereas kid rennet contained an additional proteinase of intermediate mobility. Relative to their milk-clotting activities, lamb and kid rennets contained less pepsin and were less proteolytic on both haemoglobin at pH 1·8 and casein at pH 5·3 than calf rennet. The milk-clotting activities of lamb and kid rennets increased less with decrease in pH and were more stable to storage at both the pH value of maximum stability and lower pH values than that of calf rennet. Neither cathepsin activity nor lipolytic activity on milk fat was detected in any of the 3 rennets, but lamb rennet caused slight hydrolysis of tributyrin.
Multiple modification/restriction systems in lactic streptococci and their significance in defining a phage-typing system
Authors: Boussemaer Jean Pierre , Schrauwen Peter P. , Sourrouille Jean Louis , Guy Philippe
Published: June 2009

The reactions between 6 strains of mesophilic lactic streptococci and their respective phages were studied quantitatively. Of 30 nonhomologous reactions, the bacteria were fully sensitive in 4 and restricted the phages in 23. A mathematical model was developed that was used to identify at least 4 and probably 5 modification restriction (M/R) systems of which up to 3 were found in the same strain. The model was based on 24 measured values and correctly predicted the values of 5 others. One of the 3 negative reactions was shown to be due to a restriction beyond the limit of detection, a second was due to lysogeny or lack of adsorption, but was shown to have the predicted value when the homologous phage was modified on the host of the challenging phage. In the last reaction a measurable restriction was predicted, but could not be proven by means of a modified phage. These results suggest M/R to be one of the main defenses of the lactic streptococci against their phages. They explain why host range is not a useful criterion in the classification of phages and suggest a rational approach to the definition of a starter rotation.
Effect of teat skin disinfection on the rate of infection and interval to infection in cows exposed to high levels of Staphylococcus aureus
Authors: Sheldrake Richard F. , Hoare Roderic J. T.
Published: June 2009

All teats of a herd of lactating cows were contaminated after each milking with Staphylococcus aureus. Two teats of each cow were subsequently dipped in an iodine solution, while the remaining 2 teats were not dipped. For cows with a single infection the interval to infection in dipped and undipped quarters was 64 and 60 d respectively, while for the first infected quarter of cows with multiple infections the interval to infection in dipped and undipped quarters was 50 and 39 d respectively. For the second quarter infected in cows with multiple infections, the period between the first and second infection was 21 and 12 d for dipped and undipped quarters respectively. It is suggested that while teat skin disinfection was effective in reducing the rate of new infection, it had little effect on the process of infection in those quarters becoming infected. The occurrence of an infection in one quarter doubled the rate of infection in the other quarters.
Effect of milk concentration on the nature of curd formed during renneting – a theoretical discussion
Authors: Dalgleish Douglas G.
Published: June 2009

Use of a model of the renneting reaction has led to the definition of the amounts of soluble casein present in milks of different concentrations, at the time of clotting. It is shown that, although the clotting time (RCT) is relatively little affected by the concentration of milk by ultrafiltration, the proportion of casein which is soluble at the RCT is highly dependent upon the concentrations of both milk and rennet. This may affect the structure of the curd.
A differential scanning calorimetric study of the thermal behaviour of bovine β-lactoglobulin at temperatures up to 160 °C
Authors: de Wit Jacob N. , Klarenbeek Gijsbert
Published: June 2009

The thermal behaviour of β-lactoglobulin was studied by differential scanning calorimetry (DSC) in the temperature range 40–160 °C. The DSC curves revealed, in addition to the usually observed denaturation peak near 80 °C, a distinct endothermal peak between 130 and 150 °C. When the pH was increased from 6·5, the area under the peak near 80 °C (denaturation heat) decreased significantly, whereas the peak area near 140 °C increased. The temperature of maximum heat absorption in the peaks near both 80 and 140 °C gradually increased as the pH decreased. Addition of sugars and variation of the heating rate both caused a temperature shift of the endothermal heat effect at 140 °C, similar to that at 80 °C. No peak near 140 °C was observed when β-mercapto-ethanol was added to the β-lactoglobulin solution before scanning. The origin and nature of the high temperature denaturation peak is discussed in terms of conformational changes of the protein.
Development of structure and texture in Cheddar cheese
Authors: Green Margaret L. , Turvey Alan , Hobbs David G.
Published: June 2009

Samples of curd and cheese, taken throughout cheese-making with milks concentrated to different extents, were examined by light microscopy and by scanning and transmission electron microscopy. The mature cheeses were analysed for textural parameters by instrumental and sensory means. The protein was packed in larger, more compact areas and the fat was more segregated in the curds and cheeses from the more concentrated milks. The protein network increased in coarseness in proportion to the concentration factor of the milk, the relative differences being the same throughout cheese-making into the mature cheese. Thus, the basic structure of the protein network was laid down during the curd firming process and was not fundamentally altered later in cheese-making. The fat/protein interfaeial area in the cheese and the changes in structure during maturation decreased as the concentration factor of the milk increased. The instrumental firmness, cohesiveness and force and compression required to cause fracture, and the sensory firmness, crumbliness, granularity and dryness of the cheese all increased as the concentration factor of the milk increased. The adhesiveness declined and there was little change in elasticity, with increase in milk concentration factor. The textural differences were related to the smaller fat content, lower level of proteolysis, stronger links in the protein matrix and reduced capacity of the fat and protein phases to move relative to each other in the cheeses from the more concentrated milks.