bluuebunny/crossref_metadata_2025 huggingface dataset:
An analysis of the performance of an ultra-high-temperature milk sterilizing plant: IV. Comparison of experimental and calculated sporicidal effects for a strain of Bacillus stearothermophilus
Authors: Burton H. , Franklin J. G. , Williams D. J. , Chapman Helen R. , Jean A. , Harrison W. , Clegg L. F. L.
Published: June 2009

This series of four papers has outlined a method for predicting the bactericidal efficiency of an ultra-high-temperature sterilizing plant. The method has been illustrated with reference to the performance of an A.P.V. 200 gal./hr. plate-type sterilizing plant, treating at different temperatures milk heavily inoculated with suspensions of B. subtilis and B. stearothermophilus spores.

The method involves the determination of the temperature and flow time distributions in the plant, and of the thermal death characteristics of the organism to be considered. The investigations of plant performance are considered in Part I. The determination of the sporicidal effect of the plant from this information is described in Part II. The effect is expressed in terms of the slope of the thermal death line for the organism considered, at the operation temperature of the plant. By expressing the result in this form it becomes general and applicable to any type of organism, at any operating temperature close to that for which the plant is designed.

The thermal death time of any organism at the operating temperature may be obtained by laboratory experiment, by extrapolation if necessary. In Parts III and IV, laboratory data for B. subtilis spores and B. Stearothermophilus spores are used to calculate the performance of the plant, and the calculated results are compared with the results of direct plant experiment. The agreement is satisfactory.

The interpretation of the results with spores of B. stearothermophilus is complicated by their very marked inhibition by u.h.t.-treated milk. Only about one spore per million germinates and grows in such milk. A false impression of the number of truly surviving organisms after the heat treatment may therefore be obtained. It is not known to what extent this effect occurs with spores of other strains of B. stearothermophilus or with other organisms.

It is not suggested that the theoretical method of estimation of performance will give reliable information on the spoilage level to be expected from a plant under practical dairy conditions. The uncertainties as to the number and types of incident organisms are too great. Comparisons can be made between different plants, however, by comparing the results of the theoretical analyses for the plants. No bacteriological data are then required. This may be a less difficult procedure for manufacturers than a direct bacteriological experiment using heavily inoculated milk. The analysis also enables the contribution to the overall lethal effect of the different part of a sterilizing plant to be assessed.
Methods for investigating the bacteria in young Cheddar cheese: inhibition of starter streptococci with bacteriophage and α-bromopropionic acid
Authors: Robertson P. S.
Published: June 2009

The investigation of the non-starter bacterial flora of Cheddar cheese during the first few weeks of the ripening period is rendered difficult by the great preponderance of starter streptococci in the bacterial population. It was found that the starter streptococci could be eliminated from agar plates containing various dilutions of the emulsified cheese by the use of phage specific for the pure culture starters used to make the cheese or alternatively by the use of α-bromopropionic acid.

The successful use of the phage method of eliminating lactic streptococci from bacterial mixtures in poured agar plates depends on the use of single strain starters, and on the absence of phage-resistant forms in the culture used. The latter objective may be achieved by use of starter strains showing a low proportion of resistant cells in a normal culture and by taking precautions to avoid excessive phage development during the cheesemaking process.
Fishy flavour in dairy products: II. The volatile compounds associated with fishy flavour in butterfat
Authors: Forss D. A. , Dunstone E. A. , Stark W.
Published: June 2009

Constituents of a flavour concentrate from fishy butterfat were separated by gas chromatography on silicone oil and ‘Carbowax 400’ columns. Two fractions with distinct flavours were obtained, the one of oily flavour and containing n-hexanal, n-heptanal, hex-2-enal and heptan-2-one, the other of metallic flavour, containing a single carbonyl compound present in relatively small amount. It is considered that these compounds with the exception of heptan-2-one are mainly responsible for the characteristic fish-oil flavour.

Other compounds isolated include propanal, n-pentanal, n-octanal, n-nonanal, n-decanal, acetone, pentan-2-one, nonan-2-one, undecan-2-one, acraldehyde, pent-2-enal, hept-2-enal, oct-2-enal, non-2-enal, hepta-2, 4-dienal, a compound resembling octa-2, 4-dienal, a compound with a mushroom flavour, and a compound that formed the 2, 4-dinitrophenylosazone of methylglyoxal.
The alcohol test applied to sterilized milk
Authors: Higginbottom Constance , Taylor Margaret M.
Published: June 2009

A positive 80% alcohol test was not obtained in sterilized milks containing fewer than 105 bacteria/ml with Bacillus subtilis, B. licheniformis and B. cereus, and usually did not occur until the stationary phase of growth had been maintained for some days. A positive alcohol test with less than 105 bacteria/ml was associated with the lower maximum population density of B. brevis and B. circulans 152.

The alcohol test after 24 h at 37°C was found unreliable as an indicator of the keeping quality of sterilized milk at 22°C. The possibility of using the alcohol test after 3 days at 37°C or a bacterial count after the same incubation period is discussed briefly.
Variations in the rate of milk secretion in milking intervals of 2–24 hours
Authors: Elliott Gillian M. , Dodd F. H. , Brumby P. J.
Published: June 2009

The rates of secretion of milk, fat and solids-not-fat have been measured over milking intervals of 2–24 h in a series of experiments using thirty cows at various stages of lactation. To ensure that the results were not biased by a carryover of residual milk and fat the residual milk was removed after intravenous injections of ‘Pitocin’. The biases that can be caused by previous interval effects and lactation trends were eliminated by the balanced Latin square design used.

Milk and solids-not-fat secretion appeared to be linear with duration of milking interval up to 16 h, but with longer intervals there was, in some experiments, a decline in the rate of secretion. There was considerable variation between cows in the decline in secretion rate with increasing milking interval and part of this variation was associated with differences in milk yield. In all experiments fat secretion appeared to be almost linear with time over a 24 h period.

After milking intervals of 20 and 24 h the rate of secretion of milk and solids-not-fat, but not of fat, was depressed for at least 16 h.
Microscopic observation of the effect of some reagents on the physical state of casein
Authors: King N.
Published: June 2009

Observations were made by anoptral phase-contrast microscopy of the effect of various reagents on the state of dispersion of casein micelles in skim-milk and in lactic acid and rennet coagula. Among the hydrogen-bond-breaking reagents, urea at higher (4M) concentration dispersed the casein micelles in skim-milk and in acid and rennet coagula. Sodium salicylate was effective at low (M) concentration. Guanidine hydrochloride at low concentration caused aggregation of the micelles in skim-milk but at high concentration caused dispersion, while at both concentrations it dispersed acid and rennet coagula. Lithium iodide and potassium thiocyanate flocculated the casein in skim-milk, but dispersed it in both types of coagula. Flocculation in skim-milk by these reagents was followed by slow coalescence of the casein.

At substantially lower molar concentrations, sodium dodecyl sulphate, an anionic detergent, which attacks either the hydrophobic bonds or the salt linkages in proteins, dispersed micelles and both types of coagula. Sodium thioglycollate, a disulphide-bond-breaking reagent, had no visible effect on the casein.

In rennet coagulum in which the calcium bridges have been destroyed by the sequestering action of EDTA or in lactic acid coagulum, urea at low concentrations caused a quick and almost complete coalescence of casein. Fibres were formed in the rennet coagulum when the coalesced material, which presumably consists of randomly coiled chains of unfolded casein macromolecules, was subjected to stretching or flowing. Similar chemical and physical conditions would appear to prevail when fibre formation takes place in cheddaring cheese curd.
The volatile compounds associated with tallowy and painty flavours in butterfat
Authors: Forss D. A. , Dunstone E. A. , Stark W.
Published: June 2009

From butterfat with tallowy and painty flavours, the same range of carbonyl compounds was obtained as from fishy flavoured butterfat or washed cream. They consisted of the C5–10 n-alkanals, the C5–10 alk-2-enals, hepta-2, 4-dienal and a compound with a metallic flavour. Heptan-2-one, present only in small amounts in washed cream, was also isolated. Three factors distinguished the tallowy and painty from the fish-oil flavoured butterfat. There was a relative increase in n-heptanal, n-octanal, n-nonanal, heptan-2-one, hept-2-enal and non-2-enal in the tallowy butterfat and a relative increase in n-pentanal and the C5–10 alk-2-enals in the painty butterfat. Secondly, the ‘metallic’ compound was present in such small relative amounts in both the tallowy and painty flavoured butterfats as to have no effect on the flavour. Thirdly, the total weight of volatile carbonyl compounds was about 10 times greater in the tallowy and 100 times greater in the painty butterfat than in the fish-oil flavoured butterfat.
Utilization of urea by milking cows
Authors: Balch C. C. , Campling R. C.
Published: June 2009

Friesian cows averaging about 30 lb of milk daily, were used for nitrogen balance experiments of the change-over type, in which 3·0–3·5 lb of two mixtures of molasses and urea were added to basal diets low in protein, but containing a high proportion of starch and lower carbohydrates, and ample energy for the amount of milk produced. The molasses mixtures contained 9–10% urea, about 2% H3PO4 and were added either alone or with 7% ethyl alcohol.

In the first experiment, with three cows, the intake of digestible crude protein from the basal diet was about 90% of the recommended allowance and the utilization of urea nitrogen was poor. In the second experiment, with four cows, the intake of digestible crude protein with the basal diet was about 40% of the recommended allowance and the utilization of the nitrogen of urea and of additional groundnut meal was almost complete.

Owing to the way in which the experiments developed the addition of alcohol to the mixture of molasses and urea could not be expected in the present work to increase the utilization of the nitrogen of urea even if it does have that effect under other circumstances. When added to the basal diet very low in nitrogen, the nitrogen of both urea and groundnut meal was used mainly to prevent the withdrawal of nitrogen from body reserves, but partly for a small increase in milk yield.

Under the special conditions of this experiment, which were very favourable for the utilization of non-protein nitrogen, the allowances of digestible crude protein recommended by Woodman (1957) for maintenance of cows weighing 1250 lb (0·73 lb) and 1340 lb (0·82 lb) and giving about 30 lb of milk daily (0·6 lb/10 lb milk) did not appear to be excessive.
Action of rennet and other proteolytic enzymes on casein in casein-agar gels
Authors: Cheeseman G. C.
Published: June 2009

A series of precipitation zones appears when proteolytic enzymes diffuse through an agar gel containing 1% whole casein and 10–20 mM-calcium chloride. As the enzyme diffuses through the gel the casein stability changes giving first a precipitate which subsequently redissolves followed by a second precipitate which also redissolves. The first or outermost zone of precipitation occurs at the periphery of the area of the diffused enzyme. Using a high enzyme concentration all four zones, two of precipitation and two of subsequent clearing, are visible in about 24 h. The proportion of the total nitrogen which occurs as non-protein nitrogen (N.P.N.) in the first or outermost precipitation zone is similar to that found after the first stage of rennet action on casein solutions.
Studies on the properties of New Zealand butterfat: VIII. The fatty acid composition of the milk fat of cows grazing on ryegrass at two stages of maturity and the composition of the ryegrass lipids
Authors: Hawke J. C.
Published: June 2009

The lipid content of short rotation ryegrass at two stages of growth was followed at weekly intervals for several months in two spring-early summer seasons. Short succulent ryegrass consisting entirely of leaf tissue contained more lipid (mean, 8·1% of the dry weight) than mature ryegrass which contained appreciable stalk (mean, 5·1% of the dry weight). The lipid from the new growth contained fatty acids with appreciably higher proportions of linolenic acid, which was balanced mainly by lower proportions of linoleic and palmitic acids.

When monozygotic twin milking cows were grazed on the short rotation ryegrass grown to two stages of maturity, it was found that the fatty acid composition of the milk fat from the two groups was different. The milk fat of cows grazed on the new growth contained higher proportions of oleic acid and other C18acids, whilst the proportions of myristic and palmitic acids were lower. The total proportions of the short-chain fatty acids were not greatly different, although in the group on new growth butyric acid was present in higher proportions and hexanoic and octanoic acids in lower proportions. The higher unsaturation of the fatty acids in the milk fat of this group of cows may be related to the higher levels of unsaturated fatty acids in the young ryegrass diet and to the extent to which these unsaturated fatty acids are hydrogenated in the rumen.
The preparation ofk-casein
Authors: Hill R. D.
Published: June 2009

A method is described for the preparation ofk-casein and for its purification by chromatography on DEAE cellulose. The conditions of preparation have been chosen so as to avoid drastic alteration of thek-casein and permit the isolation in relatively pure form of one-half to two-thirds of the amount theoretically available.
The determination of citric acid in milk and milk sera
Authors: White J. C. D. , Davies D. T.
Published: June 2009

The accuracy of methods that utilize the colour-forming reaction between pyridine, acetic anhydride and citric acid for the determination of citric acid in milk and milk sera has been examined. A method based on that of Saffran & Denstedt (1948), in which a trichloroacetic acid (TCA) filtrate is used, gave values 3–5% low for the citric acid content of both milk and milk ultrafiltrate. The method of Merier & Boulet (1958), in which aqueous samples are analysed, gave an accurate value for the citric acid content of milk. The same technique but applied to aqueous-NaOH samples (Marier & Boulet, 1960) gave values about 7% high for the citric acid content of milk and about 3% high for the citric acid content of ultrafiltrate. However, a method using the technique of Marier & Boulet and TCA filtrate gave accurate values for the citric acid content of both milk and milk ultrafiltrate.
Preparation of β-casein by a modified urea fractionation method
Authors: Aschaffenburg R.
Published: June 2009

It has been shown by Hipp, Groves, Custer & McMeekin (1952) that the differential solubility in urea of the casein components of cow's milk can be utilized for preparative purposes. Fractionation is achieved by step-wise dilution of a solution of all the casein components in strong (6·6 molar) urea. In connexion with the work on the three genetically distinct β-caseins discussed in the preceding paper, the need arose to prepare the variants A, B and C from the milk of appropriate homozygotes. This led to the development of the modified procedure described in this note, a procedure more sparing in urea and more effective in the initial isolation of the β-casein fraction than the original method of Hipp et al.
Lactic casein whey powder in rations for pigs: II. A comparison of un-neutralized and neutralized lactic casein whey powders with barley meal in all-meal rations for growing pigs
Authors: Dunkin A. C.
Published: June 2009

From 50 to 140 lb liveweight pigs were given mixtures containing 25 or 50% of either un-neutralized or neutralized lactic casein whey powders in partial replacement of barley meal in a control ration.

Those animals that were given rations containing 25 and 50% un-neutralized whey powder and 25% neutralized whey grew significantly faster and more efficiently up to 110 lb liveweight than the controls and those given the rations containing 50% neutralized whey powder. For the overall trial period, only differences between the last-named group and each of the 3 other groups that received whey powder were statistically significant.

Water intake increased with level of whey powder in the diet and was significantly greater at both levels with the mixtures containing the neutralized powder than with the other diets.

Carcass measurements did not indicate any significant difference in treatment.

Both whey powders were sticky and unpleasant to handle, the neutralized material being worst in this respect.
A simple method for detecting an early stage in coagulation of rennetted milk
Authors: Blair G. W. Scott , Burnett J.
Published: June 2009

An apparatus is described which measures at 10—15 sec intervals the viscosity of rennetted milk taken from a cheese vat. The first signs of an increase in this viscosity mark what is at present the earliest measurable stage in the process of coagulation. Coagulation times so determined agreed fairly closely with the observations of a skilled cheese-maker and, for a given milk, were inversely proportional to rennet concentration over quite a wide range. Clotting times obtained by the method of Berridge (1952) for standardizing rennets came 2 or 3 min after those determined by the new method and were linearly related but not proportional to inverse rennet concentration.
A reduction in milk yield associated with certain half-udder milking techniques
Authors: Morag M.
Published: June 2009

During a series of lactation studies on ewes a half-udder technique was used for comparing twice- with thrice-a-day milking. The treatments were applied to the half-udders of 8 ewes in a Latin square design, in which each period lasted 7 days. Essentially the treatments were as follows: (A) a half-udder milked twice daily whilst the opposite half-udder was milked thrice; (B) a half-udder milked thrice daily whilst the opposite half-udder was also milked thrice; (C) a half-udder milked twice daily whilst the opposite half-udder was also milked twice.
The distribution and characters of coagulase-negative staphylococci of the bovine udder
Authors: Edwards S. J. , Jones G. W.
Published: June 2009

Coagulase-negative staphyloccoci were isolated regularly over a period of 39 weeks from quarter milk samples of 18 cows belonging to one herd. They did not produce a leucocytosis in the milk or high anti-haemolysin titres in the blood of these cows, but such responses occurred in 2 cows infected with pathogenic staphylococci. The coagulase-negative variety was found to colonize the teat duct and surface of the teat in preference to the milk and possessed greater resistance than pathogenic staphylococci to certain long-chain fatty acids. Infection with coagulase-negative staphylococci was thought to antagonize the colonization of the udder by a pathogenic variety present in the herd; 23% of the coagulase-negative strains were found to elaborate an antibiotic substance inhibitory to the growth of a coagulase-positive staphylococcus. Coagulase-negative strains were characterized by the production of ɛ-toxin and could be divided into 3 main groups according to their effect on gelatin, mannitol and phenolphthalein diphosphate as substrates.
The induction of ketosis in the lactating dairy cow
Authors: Hibbitt K. G.
Published: June 2009

Injections of l-thyroxine into normal dairy cows at the beginning of lactation resulted in animals fed on a high protein diet becoming ketotic. Some of the symptoms observed in the induced ketotic cows showed many similarities when compared with those associated with the spontaneous condition.

In most cases the levels of the constituents estimated in the blood of the induced ketotic cows were similar to those measured in blood from spontaneous cases. A histological examination of the liver from an induced ketotic cow showed a considerable increase in the fat content, particularly in the centrilobular regions. The fat content of this tissue amounted to 26% with a concomitant depression of liver glycogen to only 10% of the normal level.

Diet was found to play an important role in the susceptibility of cattle to the induced ketosis, since animals fed on rations containing a lower level of protein were more resistant. Attempts to induce ketosis in cows 6—8 months after calving were completely unsuccessful.

The part played by the thyroxine and the diet in the induction of ketosis is discussed.
Changes in the quantity and composition of mammary gland secretion in the dry period between lactations: I. The beginning of the dry period
Authors: Wheelock J. V. , Smith A. , Dodd F. H. , Lyster R. L. J.
Published: June 2009

The changes in the yield and composition of the mammary gland secretion in the first 16 days of the dry period have been investigated in 6 cows. The quantity of secretion, lactose, potassium, casein, α-lactalbumin, β-lactoglobulin and fat present in the gland decreased rapidly. A decrease was also observed for sodium, chloride, residual albumin and proteose-peptone + globulin but was much less marked. Changes in composition were qualitatively similar to those normally occurring at the end of lactation but they were much more pronounced. Within 8 days after drying-off the concentrations in the secretion of sodium, chloride and potassium were similar to those of blood. There were differences between, animals in the rate at which the changes developed. As the secretory activity of the gland ceased, the constituents of the mammary gland secretion appeared to be resorbed.
Investigations on the use of the Milko-tester for routine estimation of fat content in milk
Authors: Murphy M. F. , McGann T. C. A.
Published: June 2009

Results of studies on the operation of the Milko-tester Mark II for the estimation of fat in both herd and individual milks are presented. Milko-tester readings were compared to the means of duplicate Gerber results.

It was found that, for 894 herd milks, a direct Milko-tester reading (G = M) had a standard error of estimate of ±0·071, whereas regression equation (G = 1·02 M −0·075) derived for the same data gave ±0·070. For 1133 individual milks, the equation (G = 1·03 M − 0·186) also had an accuracy of ±0·070, while the direct Milko-tester reading gave ±0·107. However, a simple subtraction of 0·077 from each Milko-tester value (i.e. G = M−0·077) for individual milks reduced the standard error to ±0·071.

It is concluded that the Milko-tester is satisfactory for herd milks, particularly for milks up to 3.8 % fat. For individual milks a special regression relationship is necessary to achieve comparable accuracy.
Detection of caeruloplasmin in bovine milk and blood serum
Authors: Hanson L. Å. , Samuelsson E.-G. , Holmgren Jan
Published: June 2009

The copper-binding protein, caeruloplasmin, has been detected in bovine blood serum, colostrum and normal milk using immuno-diffusion techniques by comparison with a precipitating oxidase-positive system of human caeruloplasmin and anti-caeruloplasmin. The possible importance of this copper-binding protein of milk in the oxidative deterioration of milk and dairy products is discussed.
Effects of repeated heat treatments on the levels of some vitamins of the B-complex in milk
Authors: Burton H. , Ford J. E. , Franklin J. G. , Porter J. W. G.
Published: June 2009

A study was made of the destructive effects of repeated heat processing of milk on its content of vitamin B6, vitamin B12, thiamine and folic acid. Losses of thiamine and vitamin B6 were cumulative, and increased with frequency and severity of heating.

With folic acid, the first heat treatment potentiated the destructive effect of subsequent treatments; in contrast, the loss of vitamin B12 during in-bottle sterilization was markedly reduced by preliminary HTST pasteurization. These anomalous effects are possibly related to a specific interaction of ascorbic acid with each of these 2 vitamins.
The effect on milk yield and composition of adding the calcium salts of acetic, propionic, butyric and lactic acids to the diets of dairy cows
Authors: Balch C. C. , Broster W. H. , Johnson V. W. , Line C. , Rook J. A. F. , Sutton J. D. , Tuck Valerie J.
Published: June 2009

The effects, on the yield and composition of the milk of the cow, of additions to the diet of the calcium salts of acetic, propionic, butyric or lactic acids were determined in 3 change-over experiments. In all cases yield of milk was increased slightly and milk fat content was reduced; solids-not-fat (SNF) percentage was depressed by acetate and butyrate. The effects of these treatments differed markedly from those observed previously when dilute solutions of the corresponding acids were infused into the rumen, but the relative effects of the calcium salts were similar to those of the free acids. It was concluded that the specific effects of the acids were overshadowed by a more marked general effect arising from their addition to the diet as calcium salts. This was confirmed in a subsequent experiment with fistulated cows, in which the effect of an infusion of propionic acid into the rumen was compared with that of an infusion of calcium propionate and of calcium propionate given with the diet. The effect of the addition to the diet of calcium in the form of carbonate differed from that of calcium salts of the fatty acids. It was concluded that the salts were not likely to find practical use.
The effect of temperature fluctuations on the bactericidal effectiveness of continuous heat-treatment processes
Authors: Burton H. , Cocks A. M.
Published: June 2009

In correctly operated continuous heat-treatment plant the processing temperature is maintained at a sufficiently elevated level to give the desired thermal death rate for any micro-organisms present before treatment. This paper shows that if through imperfect operation of the plant, the processing temperature fluctuates about the required level, the chances of survival for bacteria and spores will theoretically be increased. Tabulated results show the magnitude of the effect under varying conditions and the compensating increase in processing temperature to counteract it.
The effects of dietary palmitic and stearic acids on milk yield and composition in the cow
Authors: Steele W.
Published: June 2009

The effects of the isocaloric replacement of starch in the concentrate by either 5 or 10% ‘stearic acid’ (85% pure) or by 10% ‘palmitic acid’ (85% pure) on the yield and composition of milk were investigated in a feeding experiment with 12 cows in mid-lactation. The concentrate mixtures were given with a high-roughage diet that supplied 4.4 kg of hay and 2·7kg of sugar-beet pulp/day.

The inclusion of 5% ‘stearic acid’ in the concentrate mixture resulted in increases in the yields of milk, milk fat, solids-not-fat (SNF) and lactose and a reduction in the content of protein in the milk, whereas, when the level of ‘stearic acid’ in the concentrate was increased to 10%, there was an increase in only the yield of milk and a reduction in the contents but not in the yields of SNF and protein in the milk. The inclusion of 10% ‘palmitic acid’ in the concentrate mixture also reduced the contents of SNF and protein in the milk but produced increases in the yields of milk, milk fat and lactose and also in the content of fat in the milk.

None of the dietary treatments resulted in any changes in the concentration of blood glucose.
Dietary fatty acids and the plasma phospholipids of the lactating cow
Authors: Noble R. C. , Steele W. , Moore J. H.
Published: June 2009

Cows were given either a low-fat concentrate mixture or a concentrate mixture that contained 5 or 10% ‘stearic acid’ (85% pure) or 10% ‘palmitic acid’ (85% pure). The concentrate mixtures were given with a high roughage diet that supplied 4·4 kg of hay and 2·7 kg of sugar-beet pulp/day. Blood samples were taken from the cows on each dietary treatment and the plasma phospholipids were analysed.

Phosphatidyl choline accounted for 70% of the plasma phospholipids when the cows were given the low-fat diet and about 86% of the plasma phospholipids when the cows were given the diets supplemented with the fatty acids. The inclusion of the fatty acids in the concentrate mixtures decreased the relative proportions of the plasma phosphatidyl ethanolamine, sphingomyelin and lysophosphatidyl choline but the relative proportion of the plasma phosphatidyl serine remained unchanged.

When the diet was supplemented with stearic acid the concentrations of 18:0 and 16:0 in the phosphatidyl choline were unaltered but the concentration of 18:1 was increased and the concentration of 18:2 was decreased. When the diet was supplemented with palmitic acid the concentrations of 16:0 and 18:1 in the phosphatidyl choline were increased and the concentrations of 18:0 and 18:2 were decreased. In contrast, the inclusion of stearic acid in the diet increased the concentration of 18:0 in the phosphatidyl serine and decreased the concentration of 16:0; the concentrations of 18:1 and 18:2 were unchanged. The fatty acid composition of the plasma phosphatidyl ethanolamine was unaffected by dietary treatment. The effects of diet on the fatty acid compositions of the phosphatidyl choline and lysophosphatidyl choline were similar. Supplementation of the diet with stearic acid increased the concentrations of 18:0 and 18:1 in the plasma sphingomyelin and decreased the concentrations of 16:0 and 18:2. The addition of palmitic acid to the diet increased the concentration of 16:0 in the sphingomyelin but it decreased the concentrations of the other constituent fatty acids.
The denaturation of α-lactalbumin and β-lactoglobulin in heated milk
Authors: Lyster R. L. J.
Published: June 2009

The rates of denaturation by heat of α-lactalbumin and β-lactoglobulin in skim-milk were measured by an immunodiffusion method over a wide range of temperatures. Both reactions showed an unusual temperature dependence.

The denaturation of α-lactalbumin is a first-order reaction; between 90 and 155 °C the kinetic constant k1in s−1is given by the equation

whereTis the temperature in °K.

The denaturation of β-actoglobulin in skim-milk is second order with respect to time, and the kinetic constant k2in 1g–1s–1is given by 2 equations, valid for different temperature ranges. Between 68 and 90 °C,

Between 90 and 135 °C

Results obtained by the immunodiffusion method agreed well with those found by salt fractionation of the milk proteins. The denaturation rates decreased when a specific reagent for sulphydryl groups was added, suggesting that such groups are involved in the denaturation of both proteins.
The tertiary phase of rennin action on αs- and β-caseins
Authors: El-Negoumy A. M.
Published: June 2009

Casein, whole αs-casein and β-casein were incubated for 3 and 14 h with crystalline rennin, at pH 6·60 and 36 °C, both in phosphate buffer and in milk dialysate. Products obtained from both systems, comprising 30–83% calciumsensitive (Cas) components, gave similar patterns on starch gel electrophoresis. Whole casein and whole αs-casein were not so soluble in milk dialysate as in phosphate buffer. No significant differences in composition were observed between the Casand the calcium-insensitive (Ca1) products from the same source.

The αs1-component of the Casproduct from rennin-treated whole αs-casein had faster gel mobility in comparison to the αs1-component in the Casproduct from untreated whole αs-casein. Also, αs1-casein yielded one faster-moving degradation product, while αs2,3,4appeared unaltered after 14h. The Casproduct of rennintreated β-casein also had faster mobility than untreated β-casein and yielded one faster degradation product and several minor ones of slower mobility. Arginine was the onlyN-terminal amino acid found in the Casproduct of both rennin-treated and untreated αs- and β-caseins. The arginine content increased from 3·48 and 4·98 moles/105g to 5·12 and 6·38 moles/105g in the Casproducts from rennin-treated β-and αs-caseins, respectively.
The effects of 2 methods of incorporating soybean oil into the diet on milk yield and composition in the cow
Authors: Steele W. , Noble R. C. , Moore J. H.
Published: June 2009

In a feeding experiment with 6 cows in mid-lactation a portion of the starch in the concentrate part of the diet was isocalorically replaced by 8% soybean oil, and the effects on the yield and composition of the milk were studied. The oil was incorporated into the diet either as coarsely ground soybeans or by direct addition of the oil itself. The concentrate mixtures were given with a high-roughage diet that supplied 5·5 kg hay and 2·7kg sugar-beet pulp/day.

When the soybean oil was included in the diet either in the form of soybeans or as the oil itself there was an increase in the yields of milk, solids-not-fat (SNF) and lactose, and an increase also in the percentage of lactose in the milk. The percentage of protein, however, was decreased.

When the oil was included in the form of soybeans there was an increase in the yield of fat but a decrease in the percentage of SNF in the milk.

When soybean oil was included in the diet, the yield of protein was increased but the yield of fat and the percentage of fat in the milk were both decreased.

With both methods of incorporating the oil there was an increase in the relative proportion of propionic acid and a decrease in that of butyric acid in the total volatile fatty acids of the rumen liquor. When the oil was added directly, but not when it was added as soybeans, there was a decrease in the proportion of acetic acid in the total volatile fatty acids. The implications of these findings are discussed.
On the mechanism of milk clotting by rennin
Authors: Green Margaret L.
Published: June 2009

Two possible hypotheses for the mechanism of milk clotting were tested. The results obtained constituted strong evidence against one and suggested that the second is improbable. Milk was separated into a 5-fold-concentrated casein micelle suspension and milk serum. Pre-renneting of the serum did not reduce the rate of clotting on subsequent addition to the micelle suspension whether or not the conditions were such that the para-κ-casein became extensively aggregated. Washing of casein micelles up to 3 times with milk dialysate at 23°C extracted very little casein from the micelles and did not increase the clotting time of micelles resuspended to about the same concentration as in milk. The results appear to constitute decisive evidence against the hypothesis of milk clotting proposed by Parry & Carroll (1969). S-carboxymethyl-κ-casein, S-carboxymethyl-κ-casein containing 2·5 dimethylaminonaphthalene sulphonyl residues per mole, and rennin-treated dimethylaminonaphthalene sulphonated-S-carboxymethyl-κ-casein all bound Ca to the same extent at 30°C and pH 6·5, over the range 0·5–15·3 mM-CaCl2. This adds support to existing evidence that milk clotting does not involve formation of Ca bridges between casein micelles.
A note on the growth of some micro-organisms in stored bovine colostrum
Authors: Palmer G. H. , Mudd A. J.
Published: June 2009

Changes in the microflora and titratable acidity of bovine colostrum stored at 4 and 30 °C were monitored for 21 days. Colostrum did not inhibit the indigenous microflora, and increased titratable acidity may have accounted for the observed decrease in the numbers of Enterobacteriaceae after an initial rapid growth period.
A comparison of various methods for the estimation of solids-not-fat in milk and whey
Authors: McDowell A. K. R.
Published: June 2009

The total solids (TS) content of milk was estimated using freeze-drying followed by a Karl Fischer (KF) titration. The average solids-not-fat (SNF) value for 12 milks calculated from the TS results by this method was 0·003±0·039 % lower than that calculated from the TS results by the British Standard (1963) gravimetric method (BS). The average SNF value calculated from the sum of the contents of lactose anhydride, ‘total’ protein and ash was slightly higher (+0·017±0·068 %) than that obtained from the BS method.

Certain modifications of the BS method for TS gave erroneous results. Heating 1 or 2 g milk at an oven temperature of 100 °C for 5 h, however, gave results agreeing fairly closely with the BS values.

For lactic (starter) casein whey the average SNF content from freeze-drying and KF titration was 0·075 % higher than that obtained by following the BS procedure (for TS in milk). Average values for the sum of the SNF constituents (including lactic acid) were 0·08–0·11 % lower than those obtained from BS method.

In many of the values recorded in the literature there is an unexplained discrepancy between the SNF content calculated from the sum of the constituents and that calculated from the TS content estimated gravimetrically by an alternative British Standard (1951) method. The need for a uniform method for estimating TS is stressed.
Properties of aseptically packed ultra-high-temperature milk: II. Molecular weight changes of the casein components during storage
Authors: Andrews A. T. , Cheeseman G. C.
Published: June 2009

Storage of aseptically packed ultra-high-temperature (UHT) milk has been shown to be accompanied by pronounced changes in the molecular weight distribution of the pH 4·6 insoluble casein. These changes were both time-dependent and temperature-dependent, proceeding much more rapidly at 37 °C than at 30 °C, but even at 4 °C the changes were considerable. The proportions of high molecular weight material present before and after storage have been studied by gel filtration in dissociating solvents using Sephadex G-200. Measurements have also been made on casein material isolated from in-bottle sterilized milks and canned evaporated milk for comparison. The results of gel filtration have been compared with sedimentation coefficients recorded by ultracentrifugation and with changes in the content of amino groups titratable with trinitrobenzene-sulphonic acid. The results are compatible with the suggestion that the Maillard reaction occurred at ambient temperatures, and over a period of several months led to browning and sediment formation due to covalent cross-linking of polypeptide chains. The implications of this are discussed with reference to spoilage of UHT milk on storage and the phenomenon of gelation.
Volatile compounds in butter oil: III. Recovery of added fatty acids and δ-lactones From volatile-free butter oil by cold-finger molecular distillation
Authors: Stark W. , Urbach Gerda , Hamilton Janet S. , Forss D. A.
Published: June 2009

More than 90% of the C2,4,6,8,10fatty acids and C8,10, δ-lactones added at quantities between 0·5 and 40 ppm were recovered from volatile-free butter oil by cold-finger molecular distillation at 35°C, while approximately 65% of the C12fatty acid and of the C12δ-lactone was recovered. Cold-finger molecular distillation at 50°C increased the recovery of the C12compounds to more than 90%. The acids and lactones were estimated quantitatively as the free compounds by gas chromatography on a mixture of Carbowax 20 M and isophthalic acid as the stationary phase.
Some properties of frozen concentrated starters produced by continuous culture
Authors: Lloyd G. T. , Pont E. G.
Published: June 2009

Frozen concentrated cheese starters were prepared from 7Streptococcus cremorisand 2Str. lactisstrains by continuous culture. pH control with NH4OH and Ca(OH)2increased the yield ofStr. cremorisstrains as compared with NaOH, but the resultant cells were smaller and less active. Maximum yields for both species were obtained at a dilution rate of 0·6 and pH 6·3, but withStr. cremoriscell activity was reduced above pH 6·0.

Degeneration in continuous culture was observed in the 2Str. lactisstrains, due apparently in one case to the action of a bacteriophage and in the other possibly to selection or to loss of adaptive enzymes.

Concentrated starters retained full viability and activity when stored for 10–12 weeks at −110°C, and 94% activity after storage for 4 weeks at −40°C.

Cheese made with the concentrated starters ripened normally and was comparable in quality with control cheese made with normal bulk starter.
Metabolite levels and enzyme activities in the bovine mammary gland in different stages of lactation: II. Some metabolite levels and enzyme activities of the citric acid cycle
Authors: Waldschmidt Marianne , Rilling S.
Published: June 2009

Samples of the mammary gland were obtained by the freeze-clamping technique from heifers, lactating and dry cows. Levels of acetyl CoA, citrate, isocitrate and α-oxoglutarate were determined in extracts of the samples and calculated per g fresh gland and per mg DNA. All mammary metabolite levels were significantly higher in lactating cows than in heifers or dry cows. The accumulation in the lactating gland increased in the sequence acetyl CoA–α-oxoglutarate–isocitrate–citrate. NADP/NADPH ratios in cytoplasm, as calculated from the equilibrium of isocitrate dehydrogenase, were lowest in lactating glands. The activities of some enzymes were also determined in the cytoplasm and calculated per g fresh gland, per mg protein and per mg DNA. Mammary citrate synthase activity did not vary significantly between different groups of cattle, whereas mammary isocitrate dehydrogenase activity was higher in lactating cows than in heifers or dry cows. No activity of ATP citrate lyase was detected.
Further studies on the estimation of diacetyl by the methods of Prill and Hammer and Owades and Jakovac
Authors: Walsh B. , Cogan T. M.
Published: June 2009

Both the rate of formation and the total amount of dimethylglyoxime formed from diacetyl in the presence of hydroxylamine were increased on omission of phosphate from the Owades & Jakovac (1963) hydroxylamine reagent. Sodium acetate was also unnecessary and slightly decreased the rate of dimethylglyoxime formation. The optimum concentration of hydroxylamine lay between 0·5 and 0·75 M. The heating time necessary for formation of dimethylglyoxime can be reduced from 60 to 20min at 75°C. Based on these findings a shortened and more sensitive method for the estimation of diacetyl is recommended.
Formation of methyl ketones during ripening of Cheddar cheese
Authors: Walker N. J. , Keen A. R.
Published: June 2009

Cheddar cheeses made using single strains AM2 and HP of Streptococcus cremoris as starter were analysed for methyl ketones during ripening at 7°C. The level of odd-numbered C3–C15 methyl ketones increased very slowly in all cheeses and at maturity represented only 15–20% of the level potentially available from the degradation of esterified β-ketoalkanoic acids of milk fat in cheese. The potential for formation of the methyl ketones in unripened cheese curd was similar to the sum of free and potentially available ketones in mature cheese which suggests that the oddnumbered ketones once formed are not reduced or otherwise degraded by the normal cheese microflora. Significant variations were observed in the level of 2-butanone, which, in some cases, far exceeded the quantity which could be formed by breakdown of β-ketovaleric acid. Organoleptic evaluations and comparison of the levels of methyl ketones present in mature cheese with published threshold data suggest that while the methyl ketones may contribute to flavour they do not in their own right impart a typical mature Cheddar flavour to cheese.
Some physico-chemical properties of porcine milk
Authors: Hoynes M. C. T. , Fox P. F.
Published: June 2009

The principal results of an investigation of the major physico-chemical properties of porcine milk were:

Heat stability: all individual porcine milks examined had poor heat stability and some coagulated in 2 min at 95°C; the Q10°Cwas high and variable and was 40 for some samples. Dialysis of porcine milk against bulk bovine milk did not influence its heat stability; removal of colloidal calcium phosphate (CCP) from porcine milk increased its heat stability 4-fold, but it was still very unstable. Unlike bovine milk, porcine milk did not exhibit a maximum-minimum in the heat stability-pH curve, but rather resembled bovine casein micelles suspended in milk dialysate. Addition of isolated bovine β-lactoglobulin to porcine milk did not influence its heat stability-pH curve.

Rennet coagulation: under similar conditions, porcine milk coagulated about 4 times faster than bovine milk and the resultant curd was about twice as soft. Dialysis of porcine milk against a large excess of bulk bovine milk did not influence its rennet coagulability nor did removal of 50% of its CCP, but complete removal of the CCP rendered porcine milk non-coagulable by rennin. Porcine milk was readily coagulated by rennin down to 5°C; its second-stage coagulation was independent of temperature – a characteristic due mainly to its high level of CCP.

Alcohol stability: porcine milk was coagulated by 66–68% (v/v) ethanol, as compared with 74% (v/v) for bovine milk.

Calcium stability: porcine milk was stable to at least 300 mM-CaCl2at both 2 and 37°C.

Solvation: porcine milk contained significantly less water of hydration than bovine milk, 1·7g H2O/g casein compared with 2·0g H2O/g casein.
The use of marker enzymes to assay the churning of milk
Authors: Stannard D. J.
Published: June 2009

The release of the enzymes xanthine oxidase and alkaline phosphatase from the milk fat globule membrane is shown to be an index of milk churning. The factors affecting globule breakdown in relation to this assay procedure are discussed.
Acid phosphatase activity in cheese and starters
Authors: Andrews A. T. , Alichanidis E.
Published: June 2009

The acid phosphatase activity levels in a number of Greek cheeses and in Cheddar cheeses were found to be unaffected by storage for up to 18 months and 12 months respectively. In Cheddar cheese, starter organisms made an insignificant contribution to this activity. Studies of acid phosphatase prepared fromStreptococcus cremoris-lactisNCDO 762 starter cultures showed that the enzyme was of high molecular weight and largely particle-bound. The pH of optimum activity was 5·2 and the enzyme was inhibited by F−, Al3+, a number of heavy metals, oxidizing agents and sulphydryl-modifying reagents. Kinetic measurements at pH 5·2 gave aKmvalue for p-nitrophenyl phosphate of 1·2 mM. Orthophosphate, pyrophosphate and isoelectrically precipitated casein behaved as competitive inhibitors to the hydrolysis of p-nitrophenyl phosphate withK1values of 1·2 mM, 1·0 mM and 1·1 mM respectively. In spite of this binding to the enzyme, casein provided a very poor substrate for the starter acid phosphatase. The properties of acid phosphatase present in Cheddar cheese made withStr. cremorisNCDO 924 starter were consistent with the enzyme being exclusively of milk origin and small differences between this and the acid phosphatase previously isolated from bovine milk were attributable to the binding of peptides produced during the cheese maturation to the enzyme molecules. It was concluded that in cheese, phosphatase action was due largely to the enzyme of milk origin, with that provided by the starter being of minor importance.