bluuebunny/crossref_metadata_2025_split huggingface dataset:
681. The chemical composition and the cell count of milk
Authors: Waite R. , Blackburn P. S. 
Published: June 2009

1. The mixed evening and morning milk from 360 cows, all sampled six times during their lactation, was analysed chemically and for its cell content. A total and a differential cell count were made. Similar analyses were made on 823 samples of farm milk taken at a receiving creamery.2. The total cell counts varied from less than 10,000 to 5,000,000/ml. and there was considerable variation in the chemical composition of samples containing similar numbers and types of cells.3. The proportion of polymorph cells in the total count increased rapidly with increasing total count.4. Stage of lactation had little effect on the number of cells present in the milk, but samples from cows in very early and very late lactation had been avoided. The total cell count was lowest from the 70th to 130th day of lactation with a tendency to rise after the 130th day.5. Both the total and the polymorph cell counts of the milk increased sharply with the lactation number of the cow until the seventh lactation and then remained at a fairly constant level.6. As the total cell count increased to an average value of 500,000/ml. there was a fall in the daily yield of milk per cow and a marked fall (0·25%) in solids-not-fat content. The latter was the result of a steady drop in the lactose content, the casein content being affected only by counts approaching 1,000,000/ml. An increasing cell count was without effect on the fat content. Possible reasons for the relatively small effect on chemical composition of high cell counts in some milks is discussed.7. It is concluded that the presence of subclinical mastitis, as evidenced by the cell count of the milk, leads to a lowering of the solids-not-fat content.The authors wish to thank their assistants in the Technical Chemistry and Veterinary Pathology Departments, who did most of the practical work.
688. Phage-organism relationships among strains ofStreptococcus cremoris: the selection of strains as cheese starters
Authors: Whitehead H. R. , Bush Elizabeth J. 
Published: June 2009

The relationships between nineteen strains ofStr. cremorisand nineteen phage races were investigated. It was found that in addition to clear-cut lytic reactions there were other actions between some phage races and bacterial strains whereby in some cases a phage could show adaptation to a strain and become changed in host range, and in other cases could inhibit growth of a strain without any phage multiplication.There is some evidence to indicate that bacterial strains and phage races fall into family groups within which most of the phages act in one way or another on most of the strains. The suggestion is made that the strains and races in a group may have originated from a parent bacterial strain and parent phage race.The selection of strains ofStr. cremorisfor use as cheese starters is discussed in the light of the findings reported in the present paper. The diffculty of isolating a large number of strains unrelated in every respect is indicated.
715. The relation between the chemical composition of milk and the stability of the caseinate complex: IV. Coagulation by heat
Authors: White J. C. D. , Davies D. T. 
Published: June 2009

1. The variation in the stability of milk protein to heat and the relationship between milk composition and heat stability were examined.2. The coagulation times of the majority of the milk samples decreased by a factor of about 3 with an increase in temperature of 10°C. over the range 130–150°C. Because of the general proportionality of the coagulation times at 130, 140 and 150°C., the coagulation time at 130°C. only were used as a measure of the stability of the samples to heat.3. The coagulation times of herd bulk milks ranged from 17·2 to 59·0 min. at 130°C., whereas the range for samples from individual cows was 0·6–86·2 min.4. Samples of colostrum were very unstable to heat, and milk from cows in late lactation tended to have the longest coagulation times, but otherwise there was little relation between the heat stability of milk and the stage of lactation of the cow.5. Although colostrum samples were comparatively rich in ionized calcium, their marked instability to heat appeared to be caused solely by their high content of lactalbumin plus lactoglobulin.6. The stability to heat of the calcium caseinate-calcium phosphate complex in all samples, other than colostrum, could not be closely related either to the concentration and composition of the complex or to the composition and salt-balance of the aqueous phase.7. When the calcium phosphate content of the caseinate complex was relatively low, the heat stability of the complex tended to be inversely related to the concentration of ionized calcium in the milk, but in general coagulation time was not related to the concentration of ionized calcium.
734. Factors influencing the vitamin content of milk fat: VIII. The influence of various factors on the utilization of carotene
Authors: McGillivray W. A. , Thompson S. Y. , Worker N. A. 
Published: June 2009

1. The influence of a number of factors on the utilization of carotene by rats has been investigated. A high dose level equivalent to that derived from pasture by cows has been employed and liver storage of vitamin A has been used as a measure of the efficiency of carotene utilization.2. Utilization was influenced by level of carotene intake, by concentration of carotene in the oil used as vehicle, by the degree of unsaturation of the vehicle and by the presence of non-digestible wax.3. Carotene was better utilized from the rye grass and ‘low cyanide’ white clover than from ‘high cyanide’ clover, but added cyanide had little or no effect on the uptake of carotene from cyanide-free pasture or from a solution in oil.4. In so far as the results of the investigation can be applied to cows grazing typical New Zealand dairy pasture, it seems that factors which may throw some light on the poor utilization of carotene at certain times of the year are (a) small day-to-day variation in the carotene content of the pasture, (b) variations in the ‘ether extract’ fraction of the pasture, and (c) variations in the degree of hydrogenation of the fat in the rumen.5. Insulin and adrenalin appear to have no influence on the levels of vitamin A alcohol in the blood plasma of rats.The results of this investigation form a section of a thesis submitted by one of us (N.A.W.) in partial fulfilment of the requirements for the degree of Ph.D. of the University of New Zealand. The authors are indebted to the Department of Scientific and Industrial Research for a Grant towards this investigation and to Miss Fay Frecklington for technical assistance; one of us (S. Y. T.) is indebted to the Royal Society, the Nuffield Foundation, and the Board of the Dairy Research Institute (N.Z.) for a travelling fellowship during the tenure of which the work reported here was carried out.
736. Physical changes in milk caused by the action of rennet: III. Effects of separation, homogenization and pasteurization and of varying calcium content on the rigidity moduli and viscosities of curd
Authors: Blair G. W. Scott , Burnett J. 
Published: June 2009

1. Preliminary experiments show that homogenization, separation and pasteurization all tended to delay the onset of rigidity in renneted milk, though it must be borne in mind that the first two of these treatments were accompanied by some heating of the milk.2. Once setting had started, homogenized and separated samples set more quickly, and pasteurized (especially over-heated) milk more slowly, than did raw milk.3. Homogenization would seem to increase, and separation perhaps to decrease the proportion of elastic recovery of the gel which is immediate. The torsiometer, which gives an over-all measure of general consistency, agrees well with the -tube gelometer but when the latter shows an unusual ratio of immediate to slow recovery, the torsiometer follows the former modulus.4. Increasing quantities of CaCl2 added to reconstituted dried fat-free milk progressively reduce the time needed for rigidity to make its appearance but do not greatly alter the final setting rates. All setting curves approximate to the law that, once rigidity is well established, rate of setting is proportional to the percentage of casein still unset. When the amount of added lactic acid is adjusted so as to prevent the addition of various quantities of CaCl2 from altering the pH appreciably, no great difference is found in the setting curves.5. The relaxation times, retardation times and their ratio, called ‘the springiness number’, are not greatly affected by the treatments to which the milk samples, either whole or dried, were subjected.6. Appreciably syneresis usually occurs in the -tube gelometer only when the curd has been strained, though very small strains are sufficient to produce it. The site of its occurrence depends on the hydrodynamic distribution of the larger fat globules. In fat-free or homogenized milk, such syneretic phenomena are either absent or very slight.
Steam distillation of taints from cream: IV. Vapour/liquid equilibrium relationships for mesityl oxide and some α-diketones as possible reference substances
Authors: McDowall F. H. 
Published: June 2009

1. Measurements, by means of a continuous vaporization equilibrium still, of vapour/liquid equilibrium relationships in the steam distillation of dilute aqueous solutions showed that for mesityl oxide the relationship was linear, equilibrium coefficient (CV/CL)= 74.2. For acetylpropionyl it was linear over the concentration range l–10 p.p.m. in the liquid, CV/CL=51, and above a concentration of 20 p.p.m. it was again approximately linear. At 20 and 50 p.p.m. in the liquid the values found for CV/CL were 34 and 21·5 respectively.3. For acetyl-iso-butyryl it was not linear even at very low concentrations, of the order of 1–3 p.p.m. in the liquid, but there was an approach to linearity at concentrations 0–1 p.p.m., CV/CL=240. At concentrations above 1 p.p.m. in the liquid there was a steady fall in the value for the equilibrium coefficient.4. For acetylvaleryl it was curvilinear even over the concentration range 0·1–4·0 p.p.m. in the liquid. At 0·5–1·0 p.p.m. in the liquid the equilibrium coefficient was of the order of 240. Above a concentration of 4 p.p.m. in the liquid the relationship was linear.5. For acetylcaproyl it was approximately linear only over the concentration 0·1–0·4 p.p.m. in the liquid, CV/CL=180. At 4 and 8 p.p.m. in the liquid the coefficients were 90 and 70 respectively.6. For acetylbenzoyl it was curvilinear at low concentrations, i.e. 0·1–0·5 p.p.m. in the liquid, CV/CL=30 decreasing to 16. Above this concentration there was a gradual fall in the equilibrium coefficient to 11·5 at 70 p.p.m. in the liquid.7. Of the substances investigated only diacetyl and acetylpropionyl and, within limits, acetylbenzoyl were considered to be of suitable properties for use as reference substances in detailed investigations on cream deodorization equipment.
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

SummaryThe 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

SummaryConstituents 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

SummaryA 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

SummaryThe 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

SummaryObservations 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

SummaryFrom 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

SummaryFriesian 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

SummaryA 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.