bluuebunny/crossref_metadata_2025 huggingface dataset:
731. Lactobacilli in cheese starter cultures
Authors: Sharpe M. Elisabeth , Perry K. D. , Mattick A. T. R. , Adams R. P. , Druce R. G. , Egdell J. W. , Thomas S. B. , Crawford R. J. M.
Published: June 2009

For a survey of the numbers of lactobacilli present in milk used for cheese-making in creameries, counts were made on an acetate-agar medium (1) selective for lactobacilli. It was observed that the numbers of lactobacilli in the milk in the cheese vat sometimes greatly increased after the addition of the starter to the milk. When these starters were plated on acetate agar growth of lactobacilli, sometimes in large numbers, suggested contamination of the starters with these organisms. The starters in use at sixteen different creameries were then examined on acetate agar, and seven were found to contain lactobacilli. Representative colonies of these organisms were picked from each starter and these strains identified physiologically using the methods of Briggs(2) and Wheater(3,4), and serologically using the group sera of Sharpe(5) and Sharpe & Wheater(6). Table 1 shows the numbers and species of lactobacilli present in the starters. Each starter was sampled several times, usually at monthly intervals.
Factors influencing the lactic acid-producing properties of streptococci used in the manufacture of Cheddar cheese: II. Observations relating susceptibility with insusceptibility
Authors: Jago G. R. , Swinbourne M. F.
Published: June 2009

1. Continuous growth of lactic acid streptococci in autoclaved milk allows strains, originally insusceptible, to become susceptible to inhibition by raw milk.

2. Variants of the original organisms, the growth of which is inhibited in raw milk but not in autoclaved milk, appear to predominate in strains maintained in autoclaved milk.

3. The time required to allow these changes to occur in autoclaved milk varies with the strains used.
The colloidal phosphate of milk: II. Influence of citrate
Authors: Pyne G. T. , McGann T. C. A.
Published: June 2009

A new method for determining the composition of the colloidal phosphate of milk has been developed, based on analysis of milk free from colloidal phosphate. Preparation of this material is described.

The results suggest that the so-called colloidal calcium phosphate of milk should be more properly described as a colloidal phosphate—citrate.

This colloidal phosphate—citrate shows considerable analytical resemblance to the precipitate formed on neutralizing acidified milk serum. Both can be represented approximately by the empirical formula of a hypothetical citrate apatite.
A note on the availability of the calcium of milk submitted to ultra-high-temperature sterilization with or without subsequent in-bottle sterilization
Authors: Henry Kathleen M. , Toothill Joyce
Published: June 2009

The effect of ultra-high-temperature (U.H.T.) sterilization and of subsequent in-bottle sterilization on the availability of milk calcium has been studied in experiments with rats. The heated milks and the raw milk from which they were prepared were freeze-dried and added to a diet low in Ca so that the resulting diets contained some 0·11% Ca and 0·42% P.

Ca retention by groups of six litter-mate male weanling rats was 98·4, 98·4 and 98·5% respectively from diets containing raw milk, U.H.T.-treated milk and milk treated by U.H.T. followed by in-bottle sterilization. It is clear that these processes did not affect the availability of milk Ca.
The use of ultrafiltration and dialysis in isolating the aqueous phase of milk and in determining the partition of milk constituents between the aqueous and disperse phases
Authors: Davies D. T. , White J. C. D.
Published: June 2009

A description is given of various methods for the ultrafiltration and dialysis of milk and of the composition of the sera obtained. Ultrafiltrate prepared by the procedure recommended is reasonably representative of the aqueous phase of milk, but its content of lactose and citric acid, and consequently also of calcium, is determined to a slight degree by the sieving phenomenon known to occur often in ultrafiltration. The composition of diffusate obtained from milk at 20°C is not thought to be controlled to any significant extent by a Donnan effect and is regarded as identical with that of the aqueous phase of milk. The lactose content of diffusate suggests that about 2% of the water in milk is bound to protein, and allowance should be made for this when calculating the concentrations of the soluble constituents in milk from the composition of diffusate. Diffusate prepared from milk at 3°C contains slightly more total calcium, ionized calcium and phosphorus than diffusate prepared at 20°C. These differences are attributed to a change in the partition of calcium and phosphorus between the disperse and aqueous phases at the lower temperature, an explanation that is supported by the reversibility of the change. The composition of diffusate prepared by the procedure recommended indicates that about 5% of the sodium and about 6% of the potassium and citric acid in milk are in the disperse phase.
The oxidation-reduction potential of sterilized milk
Authors: Higginbottom Constance , Taylor Margaret M.
Published: June 2009

For milk sterilized under partial vacuum in closed bottles the oxidation-reduction potential measured under nitrogen was markedly lower (—280 to —300 mV) than that of milk heated in bottles open to the air, measurements being made in air (+10 to —30 mV).

TheEh(under nitrogen) of commercial sterilized milk and of ultra-high-temperature short-time heated milk was in the range —200 to —300 mV and of the same order as that obtained in the laboratory for deaerated milk sterilized in closed bottles.
Lactobacilli in milk used for commercial cheesemaking
Authors: Sharpe M. Elisabeth , Mattick A. T. R.
Published: June 2009

The numbers of lactobacilli, including pediococci and some leuconostocs, in raw and heat treated milks at twenty-six cheese factories in different parts of the country were determined over a period of 12 months, by plating on acetate agar. Counts in the raw milks varied from < 1 to > 100000/ml, but were usually within the range 100 to 10000/ml. Widely different times and temperatures of heat treatment were in use at the different creameries, some of which destroyed most of the lactobacilli present, whilst others had less effect. Post heat treatment re-infection of the milk in the vat with lactobacilli usually occurred.
A laboratory method for the investigation of milk deposits on heat exchange surfaces
Authors: Burton H.
Published: June 2009

An apparatus and procedure for the laboratory investigation of some of the factors which control milk deposits on heat exchange surfaces is described. The use of the method has been illustrated by applying it to determine how the amount of deposit varies with the acidity of the heated milk.
Microscopic observations on the dispersibility of milk powder particles in some organic liquids
Authors: King N. , Shimmin P. D.
Published: June 2009

By the application of different water-soluble organic compounds and some protein-denaturing reagents dissolved therein, several stages in the dispersion of milk powder particles can be distinguished. The particles first swell, and agglomeration or coalescence follows. However, no dispersion necessarily takes place at this stage, as indicated by the absence of casein micelles in the surrounding liquid. In the initial stage of self-dispersion, ‘dispersion streams’ emanating from the powder particles may be observed. In certain cases, particularly with spray dried skim-milk, thin membranes may be perceived around the swollen and dispersing powder particles. The dispersibility is dependent upon the fat content of the powder and the method of manufacture.

With propylene glycol and butylene glycol no dispersion of powder particles took place. However, the hydrogen-bond breaking reagents, urea, guanidine hydrochloride and sodium salicylate, as well as an anionic detergent, sodium dodecyl sulphate dissolved in propylene glycol, caused dispersion of powder particles, particularly in spray dried powders. The limited dispersibility of roller dried powders in water could be greatly enhanced by the same reagents.

With water-insoluble liquids enough moisture penetrated through the medium to cause the crystallization of lactose in powder particles.
The reactivation of milk alkaline phosphatase after heat treatment
Authors: Lyster R. L. J. , Aschaffenburg R.
Published: June 2009

A simple system was developed, consisting of a solution of β-glycerophosphate, β-lactoglobulin and magnesium ions, in which alkaline phosphatase isolated from milk became strongly reactivated following heat treatment for 45 sec in boiling water. From 10 to 30% of the original enzyme activity reappeared after incubation at 37°C. Variations in the components of the system, and factors affecting it, were studied. Salts of Hg, Zn and Cd inhibited reactivation at low concentrations.

Milk which, after the same heat treatment, became reactivated to a much smaller extent (about 1%), was found to contain a dialysable, heat labile inhibitor whose presence is thought to be largely responsible for the low level of reactivation, though other factors, e.g. the suboptimal concentration of phosphate esters must be considered as contributory causes.

Milk contains also a non-dialysable, heat stable activator of the reactivation process, capable of replacing β-lactoglobulin in the simple system and active at very low concentration, e.g. 0·2% (v/v).
Note on the action of vegetable rennets on sodium caseinate
Authors: Oosthuizen J. C. , Blair G. W. Scott
Published: June 2009

In an earlier paper, one of us (Oosthuizen, 1962) showed that vegetable rennets produce a fall in the viscosity of sodium caseinate solutions which follows the equation of first-order chemical kinetics; but that the proteolysis involved is stronger than that of calf's rennet since the vegetable rennets attack a greater proportion of the casein ensemble.
A quantitative study of changes in dried skim-milk and lactose-casein in the ‘dry’ state during storage
Authors: Richards E. L.
Published: June 2009

Changes in dried skim-milk and in lactose-casein in the ‘dry’ state during storage at 45 °C and 75% r.h. have been studied by the determination of free amino-N, ε-amino groups of lysine, galactose, lactulose, tagatose and 1-amino-1-deoxy-2-ketoses, and by the measurement of changes in colour, solubility and ferricyanide reducing power.

In both systems there is initially a close relationship between the formation of 1-amino-1-deoxy-2-ketoses and the decrease in free amino-N. This conforms with an Amadori rearrangement of an initially formed lactose-protein complex. Change in colour is rapid only after there has been a rapid formation of 1-amino-1-deoxy-2-ketoses and a corresponding decrease in free amino-N. This conforms with browning being due to a breakdown of the Amadori rearranged complex.

It is postulated that galactose and tagatose may be formed by both the basecatalysed degradation of lactose and also by breakdown of the Amadori rearranged lactose-protein complex. Lactulose is postulated to be formed only by base-catalysed degradation of lactose.
Occurrence of variants sensitive to agglutinins and to lactoperoxidase in a lactenin-resistant strain ofStreptococcus lactis
Authors: Auclair J. , Vassal Yvonne
Published: June 2009

A strain ofStreptococcus lactis, C10, known to be resistant to lactenins, was found to be composed of 47% resistant cells, 10% cells sensitive to lactoperoxidase and 43% cells sensitive to both agglutinins and lactoperoxidase. By subculturing a strain composed of 100% resistant cells in different conditions of medium, temperature and incubation time, it was possible to obtain cultures composed of resistant and sensitive cells in various proportions. These findings help to explain how, after numerous subculturings in autoclaved milk, a resistant strain may become sensitive to the natural inhibitors of milk.
The detection of volatile components of milk by gas-liquid chromatography and its possible application in assessing keeping quality and flavour
Authors: Mabbitt L. A. , McKinnon Gillian
Published: June 2009

The volatile components of milk have been isolated in a form suitable for application to a gas chromatograph, using the simple rapid technique of entraining them in a gas stream and trapping in a syringe barrel cooled in liquid nitrogen.

The souring process in milk which occurred during incubation at 22 °C was followed by observing the differences between chromatograms of samples taken at intervals. Onset of souring was detected with a sensitivity similar to that obtained by measurement of pH, but the chromatographic method had the advantage of being independent of the initial pH and buffering power of the milk.

With suitable chromatographic apparatus the total analysis time including the preparation of the sample could be about 3 min. Modifications are discussed which would increase the speed of analysis, and thus form a basis for the development of a practical method of assessing the odour of milk before processing.
n-Alkan-1-ols in oxidized butter
Authors: Stark W. , Forss D. A.
Published: June 2009

The C1,2,5–8 n-alkan-1-ols were identified from oxidized butter prepared from cream treated with cupric chloride and ascorbic acid. The six n-alkan-1-ols occurred in approximately equimolar amounts and in concentrations of approximately 1 μmole/kg, the same order of magnitude as that of the C6–9 n-alkanals. The amounts increased rapidly during the first 4 weeks of storage, but only slowly during the succeeding 4–20 weeks. Only insignificant amounts of the C3–8 alkanols formed in the untreated samples. It is suggested that C1–8 alkanols are formed by the oxidation of unsaturated fatty acids according to the theory of Farmer, Koch & Sutton (1943) from primary alkoxy radicals resulting from the decomposition of lipid hydroperoxides.
The stability of milk protein to heat: II. Effect on heat stability of ageing milk at different temperatures
Authors: Davies D. T. , White J. C. D.
Published: June 2009

The effect on heat stability as measured by coagulation time, of storing separated milk at 20, 4 and −20 °C has been examined. Milk with a good coagulation (initial clots large) could be stored for at least 30 h at 20 °C, 1 week at 4 °C and 1 month at −20 °C with no significant change in coagulation time. With milks giving a poor coagulation (initial clots small), a common occurrence during storage at 20 °C was a marked progressive increase in coagulation time; the rate of increase was reduced by storage at 4 °C. The increase in coagulation time of these labile milks, which are usually obtained from cows with subclinical mastitis, may occur to the same extent in darkness as in light, may be enhanced by exposure to light or may occur only when the milk is exposed to light. From these results, together with others reported by Davies & White (1966) and White & Davies (1966) it is concluded that, in studying heat stability, milks giving a good coagulation should be regarded as in a different class from milks giving a poor coagulation.
The transfer ofN-acetyl-4-aminoantipyrine and of thiocyanate from blood to milk
Authors: Wheelock J. V. , Rook J. A. F.
Published: June 2009

The entry into milk from blood ofN-acetyl-4-aminoantipyrine (NAAP) and urea, compounds known to be distributed evenly throughout the whole of body water, and thiocyanate and thiosulphate, the distribution of which is confined largely to extracellular fluid, has been investigated. The concentrations of NAAP and urea in blood and in milk were similar, but the concentrations of thiocyanate and thiosulphate in milk were much lower than the concentrations in blood plasma. A progressive increase in the ratio of the thiocyanate concentration in milk to that in blood occurred with advancing lactation and marked variations in the thiocyanate ratio of the milk of the separate quarters were observed in some cows, and these variations in the ratio were closely related to variations in the chloride content of the milk; similar inter-quarter variations in the ratio for NAAP were not observed. With NAAP, there was a continuous equilibrium between blood plasma and milk within the udder, whereas with thiocyanate the content in milk after its secretion into the ducts and cisterns of the udder appeared to be largely independent of later changes in the concentration of thiocyanate in blood plasma. These results are discussed in relation to the secretion of chloride in milk.
Acetaldehyde and diacetyl production by Streptococcus thermophilus and other lactic streptoccocci
Authors: Bottazzi Vittorio , Dellaglio Franco
Published: June 2009

The quantities of acetaldehyde and diacetyl produced in skim-milk and MRS media are reported for strains of Streptococcus lactis, Str. cremoris, Str. diacetilactis, Str. faecalis and Str. thermophilus obtained from culture collections or freshly isolated from natural milk cultures used in cheese manufacture. The diacetyl: acetaldehyde ratio in skim-milk medium was found to be approximately 0·1:1 for Str. lactis and Str. cremoris, 0·5:1 for Str. diacetilactis (5:1 for Str. diacetilactis PIM 13 and K.2 strains) and for Str. thermophilus 0·3:1, in skim-milk medium, and 0·8:1, in MRS medium; in the latter species cultured in MRS medium the ratio varied from 3·5:1 to 0·04:1 and when cultured in milk from 1·2:1 to 0·03:1.

In both media all strains of Str. thermophilus formed more acetaldehyde and diacetyl than other homofermentative lactic streptococci.

The ratio diacetyl: acetaldehyde in 9 strains of Str. diacetilactis was found to be unsuitable for a good culture flavour.
The effect of milking throughout pregnancy on milk secretion in the succeeding lactation
Authors: Smith A. , Wheelock J. V. , Dodd F. H.
Published: June 2009

In each of 5 cows, 2 quarters which had been regularly milked throughout the whole of pregnancy produced less milk in the next lactation than the other 2 quarters which had a normal dry period. The concentrations of the individual constituents in the milk of all 4 quarters of each cow were similar. The effect appears to be due to factors located within the individual quarter of the mammary gland rather than to factors such as the hormonal background or plane of nutrition which affect the whole animal.
Effects of some protein modifying agents on the properties of rennin
Authors: Cheeseman G. C.
Published: June 2009

Loss of milk clotting activity when rennin was treated with urea at several concentrations and at different pH values was compared with the change in UV absorption of the protein. The change in absorption at 287 and 293 nm did not correlate with loss in activity, indicating that the loss of enzymic properties was not related to the extent of unfolding of the molecule but was related to the reaction of susceptible groups to the environmental conditions.

Reactions of modifying agents, for example N-bromoacetamide, 2-hydroxy-5-nitrobenzyl bromide and mercuric ions with tryptophan groups and the relationship of these changes to enzyme activity suggested that tryptophan was not specifically associated with enzyme action but was important in maintaining tertiary structure.

Rennin was not inhibited by the pepsin inhibitors p-bromophenacyl bromide and α-diazo-p-bromoacetophenone which suggested that the active site did not possess a reactive carboxyl group as in pepsin. However, the reversible inhibition with 1-cyclohexyl-3(2morpholinoethyl)-carbodiimide metho p-toluenesulphonate together with the results of oxidation by N-bromoacetamide indicated that a tyrosine group or groups was important in enzyme activity.
The heat stability of milk as affected by variations in pH and milk salts
Authors: Morrissey P. A.
Published: June 2009

The maximum and minimum heat stability exhibited by most milks over a relatively narrow range of pH values is shown also by synthetic colloidal calcium caseinate-calcium phosphate systems and even by simple caseinate systems, provided all possess adequate contents ofβ-lactoglobulin, soluble calcium and phosphate. The phenomenon is not, however, dependent on the presence of the characteristic micellar structure of the casein of milk. The minimum stability observed, usually around pH 6·9, is the most characteristic feature of the phenomenon and arises from heat induced deposition of calcium phosphate on a caseinate/β-lactoglobulin complex. This reaction, which tends to occur to a marked degree at relatively high pH values and calcium ion concentrations, sensitizes the complex to precipitation by calcium ions. The precise pH values at which the maximum and minimum stabilities occur can vary depending on the salt composition of the serum, since the latter can influence the solubility of calcium phosphate.
Fractionation of bovine serum lipoproteins and their characterization by gradient gel electrophoresis
Authors: Brumby P. E. , Welch V. A.
Published: June 2009

Bovine serum lipoproteins were fractionated by precipitation with dextran sulphate followed by ultracentrifugation and were examined by paper electrophoresis and by disk electophoresis in acrylamide gels. Gels containing concentration gradients of both sucrose and acrylamide gave better resolution of lipoproteins than did gels of uniform composition or gels with a concentration gradient of sucrose and a uniform concentration of acrylamide.

The densities of the lipoprotein classes isolated (listed in order of increasing mobility on electrophoresis in acrylamide gels) were as follows:

I,d< 1·019; II, 1·039 <d<1·050;

III, 1·019 <d<1·039; IVa and IVb,d> 1·050.

Lipoproteins of classes I, II and III were precipitated by dextran sulphate. On paper electrophoresis, lipoproteins of class II had β mobility and lipoproteins of classes IVa and IVb had α mobility. Lipoproteins of class I remained at the origin.

The lipoprotein classes of bovine sera resembled those of sheep and goat sera in that class IV predominated. In contrast, the sera of several non-ruminant species showed a predominance of lipoprotein classes of low electrophoretic mobility.
An improved method for canning 3-fold concentrated whole milk
Authors: Board P. W. , Mullett J. T.
Published: June 2009

A method is described for canning and sterilizing concentrated whole milk containing 36·5% total solids. The product had acceptable organoleptic properties and did not form sediment or undergo age-thickening during storage. The method involved initially increasing the pH of the raw milk and forewarming. The product was not homogenized nor were polyphosphates added.
Determination of nitrite in cheese and other dairy products
Authors: Rammell C. G. , Joerin M. M.
Published: June 2009

Details are given of a spectrophotometric method for determining nitrite in cheese and other dairy products at levels down to 0·05 μg NO2-N/g and of a spectrofluorimetric method for levels down to 0·003 μg NO2-N/g. Nitrite-N levels in cheese varied from 0·003 μg/g to 0·021 μg/g. These levels increased up to 4-fold after UV irradiation of the cheese extracts. No nitrite (< 0·003 μg/ml) could be detected in raw milk.
Metabolism of cod-liver oil in relation to milk fat secretion
Authors: Brumby P. E. , Storry J. E. , Sutton J. D.
Published: June 2009

The effects of daily supplements of 300 g native and 2 hydrogenated cod-liver oils (CLO) to the diets of lactating cows have been examined. Native CLO supplements increased the proportion of propionate and decreased the proportion of acetate in the rumen and also decreased the yields in milk of fatty acids synthesized within the mammary gland and those derived from plasma triglycerides. These effects were reduced or eliminated when the hydrogenated oils were given instead of the native CLO. With all 3 supplements about 15% of the dietary C20and C22acids was secreted in milk.

Both native and hydrogenated CLO supplements increased the concentrations of the cholesteryl ester and phospholipid components of the α-lipoproteins in the blood plasma. These components contained most of the C20and C22acids of the CLO supplements that were incorporated into the blood plasma lipids. With the native CLO supplement about half of the C20and C22acids present in the blood plasma were polyunsaturated.

There were no differences in the effectiveness of high-density plasma lipoproteins as activators of triglyceride emulsions for lipoprotein lipase hydrolysis whether the lipoproteins were from cows receiving the native or the hydrogenated CLO supplements or the control diets. Significant rates of hydrolysis by lipoprotein lipase could not be demonstrated using as substrates low- or high-density plasma lipoproteins or activated emulsions of their extracted lipids.

Additional in vitro experiments using activated triglyceride emulsions as substrates for mammary lipoprotein lipase showed that replacement of a soybean oil emulsion by an emulsion of native CLO reduced the rate of hydrolysis considerably, whereas an emulsion of hydrogenated CLO was without effect unless it was present at levels in excess of 50%.

It is concluded that the change in rumen fermentation induced by the polyunsaturated fatty acids of CLO is implicated in the decreased intramammary synthesis of fatty acids, but that additional information is required before the reason for the reduced mammary uptake of plasma fatty acids can be established.
Measurement of the protein content of milk from mastitic quarters by the Amido Black method
Authors: Waite R. , Smith G. M.
Published: June 2009

An investigation was made into the effect of subclinical mastitis on the accuracy of the Amido Black method for measuring the crude-protein percentage of the milk of individual cows. Values obtained by the dye-binding and Kjeldahl methods on a sample of milk from each quarter of 46 cows, 11 of which were sampled at regular intervals during lactation, were compared. It was concluded that, even in cases of severe subclinical mastitis, the effect is so small as to constitute no objection to the use of the dye-binding method. The accuracy of the Amido Black method, irrespective of disease, was less in milk produced in the first and last months of lactation.
Casein micelle structure: location of κ-casein
Authors: Fox P. F. , Morrissey P. A.
Published: June 2009

The effect of heat treatment on the rennet coagulation times (RCTs) of various casein–whey protein systems, the effect of pre-renneting centrifugal serum on the RCT of casein subsequently mixed with such serum, the influence of repeated centrifugation and resuspension at constant protein level on the RCT of such suspensions, and the rate and completeness of the hydrolysis of sialic acid in micellar and non-micellar caseins, all lead to the conclusion that κ-casein does not occur in milk in 2 functionally different states, as proposed by Parry & Carroll (1969).
Periodic omission of dairy cow milkings: I. Effect on milk yield and composition and on udder health
Authors: Radcliffe J. C. , Bailey L. F. , Horne M. L.
Published: June 2009

Forty-five Friesian cows were assigned to one of 3 milking management treatments: (1) cows milked 14 times weekly, (2) cows milked 13 times weekly (Wednesday morning milking omitted), and (3) cows milked 12 times weekly (Tuesday evening and Wednesday morning milkings omitted). Cows were removed from the trial at the end of their lactations, and newly calved cows were added as they became available. The trial was continued for 12 months.

When one milking was omitted weekly, the total lactational milk yield was reduced by 3·5%, fat yield by 2% and protein yield by 1·5%. These reductions were not statistically significant. When 2 consecutive milkings were omitted, the yield of milk and of its main components was reduced by 14% (P < 0·001). The effects were greatest for highly productive cows in early lactation.

When one or 2 milkings were omitted the milk yield on the following day was nearly 50% greater than the mean daily yield. No increase in the incidence of subclinioal mastitis was observed in either milking omission treatment.

It is concluded that it is practicable to omit one milking each week though it is suggested that the technique should not be used in highly productive herds unless most of the cows are past the sixth week of lactation.
Seasonal variations in the composition and thermal properties of New Zealand milk fat: II. Thermal properties of milk fat and their relation to composition
Authors: Norris Gillian E. , Gray I. K. , Dolby R. M.
Published: June 2009

Melting curves were determined by differential scanning calorimetry on 17 samples of milk fat obtained at approximately fortnightly intervals through one dairying season. Liquid-fat content at a number of temperatures was calculated from the melting curves.

Correlation between percentage liquid fat at 12 and at 22 °C and weight percentage of short-chain fatty acids (C4–C8) was low (r = 0·45 and 0·58 respectively) as was that with cis-unsaturated acids (r = 0·39 and 0·29). Correlation with the sum of short-chain and cis-unsaturated acids was higher (r = 0·71 and 0·68). With a multiple regression model including short-chain and cis-unsaturated acids the values of the multiple correlation coefficient (R) were 0·75 and 0·78.

The softening point showed a high correlation (r = 0·79) with weight percentage of long-chain saturated acids and also with the temperature at which 94 % of the fat was liquid (r = 0·75).

Possible explanations of these findings are discussed.
Cavitation and separated flow in a simple homogenizing valve and their influence on the break-up of fat globules in milk
Authors: Phipps L. W.
Published: June 2009

Flow separation and cavitation effects in a simple homogenizing valve have been studied visually and recorded photographically. The degree of separation depended upon the profile of the seating inlet boundary, the pressure loading and several other interdependent factors. Cavitation did not occur independently of separation; conditions would be suitable for microscale cavitation to occur within the separated flow itself, but this was not discerned with certainty. The suppression of separation and any cavitation, assessed visually, did not influence the homogenizing characteristics of the valve. It was concluded that hydrodynamic forces of cavitation are not responsible for fat globule disintegration in drop-and-lift or poppet types of high-pressure homogenizing valve.
The influence of lysolecithin on the complex formation between β-lactoglobulin and κ-casein
Authors: Korver O. , Meder H.
Published: June 2009

Ultraviolet difference spectral measurements and some circular dichroism data are reported on the systems (β-lactoglobulin (BLG)/soya-lysolecithin (sll)), (κ-casein (KC)/sll) and (BLG/KC/sll). Sll destabilizes the native conformation of BLG and KC and promotes the interaction between BLG and KC. The influence of sll: protein ratio and time of heating on the complex formation has been investigated.
Studies on the heat stability of milk protein: II. Effect of exposing milk to light
Authors: Sweetsur A. W. M. , White J. C. D.
Published: June 2009

It was found that the increase in heat stability (coagulation time) that occurs when some milks are stored in light was not caused by changes in pH. These labile milks invariably gave a type A heat-stability curve, had a pH in the range corresponding to the coagulation-time minimum of the curve, and showed the expected abnormal 2-stage type of coagulation. The increase in coagulation time following exposure to light resulted from a delay in the occurrence of the first coagulation, the second coagulation time remaining unaltered. The presence of riboflavin in milk and of O2 in the headspace atmosphere during storage were necessary conditions for milk to be labile. Since light, headspace O2 and riboflavin had similar influences on rennet coagulation time it is suggested that in both instances the causative reaction, as proposed by others to account for the increase in rennet coagulation time of H2O2-treated milk, is stabilization of the heat- and rennin-sensitive methionine-phenylalaninebond in κ-casein by photo-oxidation of the methionine to methionine sulphoxide.
Studies on the heat stability of milk protein: III. Effect of heat-induced acidity in milk
Authors: Sweetsur A. W. M. , White J. C. D.
Published: June 2009

An examination was made of the effect of varying the protein, lactose and total serum ion content of milk on the rate of production of heat-induced acidity (as measured by pH decrease), on heat stability (as measured by coagulation time), on the relationship between coagulation time and initial pH of milk (as measured by coagulation time-pH curves) and on the interrelationship of these parameters. In addition, the effect on these parameters and their interrelationship of varying the composition and volume of the headspace atmosphere in contact with the milk was investigated. Explanations are proposed for the observed effects on heat stability of varying the composition of milk and the heating conditions, with special reference to the influence of heat-induced acidity.
Preparation and properties of β-casein from buffalo's milk
Authors: El-Salam M. H. Abd , El-Shibiny Safinaz
Published: June 2009

β-Casein from individual buffalo's milk was found to be homogeneous by starch-gel electrophoresis. β-Casein was separated from buffalo's milk by the method of Warner (1944) and purified by DEAE-cellulose chromatography.

Buffalo β-casein possesses identical end-groups to those of cow β-casein; namelyN-terminal arginine and assuming a single polypeptide chain a possibleC-terminal sequence of Ile-Ile-Val. However, the amino-acid composition and the tryptic peptide patterns of the 2 proteins are not the same.
The preparation and assessment of a suitableMucor pusillusLindt proteinase–swine pepsin mixture for Cheddar cheese-making
Authors: Green Margaret L. , Stackpoole A.
Published: June 2009

A simple test procedure was used to predict the most suitable mixture of Noury rennet (Mucor pusillusLindt proteinase) and swine pepsin for Cheddar cheesemaking. Duplicate cheeses were made with 6 Noury rennet–swine pepsin mixtures and with each enzyme alone, with calf rennet as the control. There were slight differences in the course of the cheese-making process and in the yields of the cheeses. Sensory evaluation showed that the most acceptable cheeses were those made by coagulant mixtures closely similar to the predicted mixture and these were as acceptable as cheeses made with calf rennet. The survival rates of different groups of bacteria were similar in all cheeses. There were differences in the products of proteolysis in the various cheeses throughout ripening, particularly with respect to products derived from αs1-casein. The Noury rennet was characterized for the proportion of milk clotting activity associated with each of 4 components and its stability in solution was determined.
A comparison between the amino acid compositions of 2 chymosin-sensitive polypeptides and C-terminal segments of κ-casein
Authors: Beeby R.
Published: June 2009

Two distinct types of chymosin-sensitive polypeptide were found in the soluble fraction obtained when a solution of crude κ-casein in 0·4 m-NaCl was adjusted to pH 3. One corresponded to a segment of κ-casein comprising residues 94–169. The other was very similar to the section Gln77-Val169 in the protein, but contained a phosphate group plus isoleucine and glycine in the region between the N-terminus and the chymosin-sensitive bond. If these polypeptides form as a result of a specific cleavage of κ-casein, the data indicate that there is a variant of this protein with a number of amino acid replacements on the N-terminal side of the chymosin-sensitive bond. The shorter polypeptide and κ-casein are both rapidly cleaved by chymosin at pH 6·7 which suggests that the contribution of residues 1–93 to the sensitivity of the Phe-Met bond in κ-casein is a minor one.
Cytochemical observations on the extracellular carbohydrate produced byStreptococcus cremoris
Authors: Brooker B. E.
Published: June 2009

Electron microscopy showed that a varying proportion of cells ofStreptococcus cremorisNCDO 924 grown in autoclaved skim-milk possessed a layer of extracellular material attached to the cell wall. Occasional filamentous extensions of this layer made contact with neighbouring casein micelles. The same surfacestaining material persisted during the production of cheese-curd, but after maximum scald it was predominantly filamentous in appearance. These filaments made frequent contact with the adjacent curd matrix and with milk-fat globules.Str. cremorisNCDO 1986 produced similar surface material when in curd, but not when grown in skim-milk. In all situations, the extracellular material stained with colloidal iron hydroxide, ruthenium red and periodic acid–thiosemicarbazide–silver proteinate, indicating that it was largely composed of an acidic carbohydrate. It is suggested that this carbohydrate facilitates the adhesion of starter bacteria to the cheese-curd matrix and that during the initial stages of syneresis this serves to prevent their expulsion from the curd with the whey.
Amino acid nutrition of some commercial cheese starters in relation to their growth in peptone-supplemented whey media
Authors: Law B. A. , Sezgin Emel , Sharpe M. Elisabeth
Published: June 2009

Some strains of commercial cheese starters were obtained in higher yield after batch culture in whey-based media supplemented with soy peptones than in those supplemented with papain digested skim-milk. The soy peptones contained a greater proportion of small peptides than did the skim-milk digest. Also the average size of peptides was lower (3·4–3·9 residues) in soy preparations than in the milk digest (6·8). Small peptides isolated from the soy peptones were utilized by growing starters more completely than the equivalent peptides isolated from the papain digested milk. These observations may account for the difference in cell yields with soy and milk-digest peptones.
Kinematic viscosities of New Zealand skim-milk
Authors: Buckingham J. H.
Published: June 2009

The variation in kinematic viscosity (ν) with solids concentration and temperature has been determined for native skim-milk concentrates and reconstituted New Zealand skim-milk. Below 40% (w/v) total solids, samples reconstituted from a single batch of skim-milk powder model the behaviour of native concentrates obtained from an evaporation plant at all times of the year. Above 40% (w/v) agethickening and seasonal variations in the viscosity of native concentrates become significant. Age-thickening can be reduced by cooling the concentrate. These results are discussed in relation to milk powder manufacture.
The uptake of amino acids and peptides byStreptococcus lactis
Authors: Rice G. H. , Stewart F. H. C. , Hillier A. J. , Jago G. R.
Published: June 2009

Peptide and amino acid transport inStreptococcus lactiswas both energy-and temperature-dependent. Separate systems were present for the transport of amino acids, dipeptides and oligopeptides as well as for individual amino acids. Both tri- and tetra-peptides were readily transported while an apparent size restriction at the point of uptake resulted in a relatively low rate of uptake of the pentapeptide. The effects of pH, temperature and salt concentration on the uptake of amino acids and peptides were studied. Exchange reactions played a significant role in the uptake of both peptides and amino acids.
Antibacterial effect of the lactoperoxidase system on psychrotrophic bacteria in milk
Authors: Björck L.
Published: June 2009

Activation of the antibacterial lactoperoxidase system in milk, i.e. increasing the thiocyanate concentration to 0·25 mM and adding an equimolar amount of H2O2, results in a substantial reduction of the bacterial flora and prevents the multiplication of psychrotrophic bacteria for up to 5 d. This treatment has no effect on the physico-chemical properties of milk and does not lead to the accumulation of resistant bacteria. The practical application of the lactoperoxidase system in prolonging the storage period of raw milk at low temperatures is discussed.
Heat stability of milk: influence of denaturable proteins and detergents on pH sensitivity
Authors: Fox Patrick F. , Hearn Catherine M.
Published: June 2009

α-Lactalbumin and SDS in addition to β-lactoglobulin introduced pH sensitivity to the heat stability–pH curve of serum protein free casein micelles particularly by increasing stability in the pH range 6·4–6·7. Bovine serum albumin, ovalbumin and lysozyme caused marked destabilization of milk and casein micelle suspensions throughout the pH range 6·4–7·4. Tetramethyl ammonium bromide caused destabilization of milk at pH values > 7·0, but had no effect in the region of maximum stability while the non-ionic detergents Triton X-100 and Tween 80 had no effect on heat stability.
Heat stability of milk: influence of κ-casein hydrolysis
Authors: Fox Patrick F. , Hearn Catherine M.
Published: June 2009

The release of 12% (w/v) TCA-solubleN-acetylneuraminic acid from casein at 5 temperatures between 110 and 150°C was determined and showed aQ10°C about 3; coagulation occurred when about 20% of the κ-casein was hydrolysed. Renneting of milk or colloidal calcium phosphate-free milk rendered the caseinate very heat-labile at its normal pH when more than about 20% of the κ-casein had been hydrolysed. Heat stability at the pH of maximum stability was not significantly decreased until after very prolonged renneting, but stability at pH values alkaline to the minimum was very sensitive to such hydrolysis suggesting that κ-casein is the principal factor responsible for heat stability in that region. Systems which do not have a maximum or minimum in the heat coagulation time–pH profile, i.e. serum protein-free casein micelles in milk diffusate, or milk which had been dialysed against water, were destabilized by renneting throughout the pH range 6·4–7·4.
Effects of mechanical agitation of raw milk on the milk-fat globule in relation to the level of induced lipolysis
Authors: Deeth Hilton C. , Fitz-Gerald Carolyn H.
Published: June 2009

The amount of damage caused to the milk-fat globule by mechanical agitation of raw milk was assessed by several methods and related to the level of induced lipolysis resulting from the agitation. The results obtained by measuring the amount of ‘free’ fat formed, the percentage of fat in the skim-milk phase after separation, and the increase in the proportion of alkaline phosphatase associated with the skim-milk phase, showed little correlation with the level of lipolysis induced by agitation over a range of conditions. However, the level of induced lipolysis showed good correlation with the amount of lipolysis caused by addition of an exogenous lipase (from Candida cylindraceae) to the agitated milk. It is concluded that classical methods of assessing milk-fat globule damage are unsuitable for predicting the amount of fat available for lipase action and the lipolytic potential of raw milk subjected to mechanical agitation.
The metabolism of [14C]bicarbonate byStreptococcus lactis: the synthesis of succinic acid
Authors: Hillier Alan J. , Jago G. Richard
Published: June 2009

Whole cells ofStreptococcus lactisC10, when incubated with an energy source, converted fumarate to succinate and malate to lactate. Cell-free extracts ofStr. lactisC10 contained fumarate reductase, but no aspartase, adenylosuccinate synthetase and lyase or argininosuccinate synthetase and lyase activity could be detected. Cells grown in the presence of [14C]bicarbonate produced labelled succinate during the synthesis of purine bases. However, the amount of succinate produced by this pathway only accounted for approximately one-sixth of the succinate produced by the cells.
Comparative aspects of milk proteins
Authors: Jenness Robert
Published: June 2009

The current status of knowlege of the major proteins of milks of various species is evaluated. Most of the non-bovine milk proteins are homologous with the recognized families of those ofBos taurus, αs1-caseins, αs2-caseins, β-caseins, K-caseins, β-lactoglobulins, and α-lactalbumins, each family representing a separate genetic locus specific to the mammary gland. No prominent milk protein not homologous to one of these families has yet been discovered in milk of any species. Genetic polymorphism resulting from substitutions in the polypeptide chains and various degrees of post-translational phosphorylation, glycosylation, and proteolysis have been identified in milk proteins of several species. Total protein production ranges among species from about 0.5 to 10 g/d per kg0.75maternal weight. Proportions of the several proteins vary greatly among species, but few accurate analytical data are available except for total casein and total whey protein contents.
The association of bovine SH-κ-casein at pH 7·0
Authors: Vreeman Henk J.
Published: June 2009

The self-association of SH-κ-casein at pH 7·0 in 0·01 m-EDTA, 0·001 m-dithiothreitol buffer, containing 0·1, 0·2, 0·5 or 1·0 m-NaCl is of a monomer–polymer type. The polymer is a spherical particle, diam. 23 nm and mol. wt 570000 (30 monomers). These parameters are not greatly influenced by variations in ionic strength above 0·1. The critical micelle concentration, which is a property of a monomer–polymer equilibrium, decreases with increasing ionic strength. The standard free energy of association is about – 36 kJ/mol. monomer at 20 °C.
The synergic effect of urea and aldehydes on the heat stability of concentrated skim-milk
Authors: Muir D. Donald , Sweetsur A. W. Maurice , Holt Carl
Published: June 2009

When urea is added to concentrated skim-milk (22·5% total solids) no increase in heat stability is observed. However, a similar addition of urea to concentrate stabilized with aldehyde brought about a significant further increase in heat stability. Urea can further stabilize concentrated skim-milk only when aldehyde addition has brought about a change in coagulation mechanism from the normal 2-stage process to a single-stage coagulation. These results can be related to the 2 coagulation mechanisms observed in unconcentrated milks.
Milk yield and fertility of high-yielding dairy cows in a sub-tropical climate during summer and winter
Authors: Folman Yeshayahu , Berman Amiel , Herz Zeev , Kaim Moshe , Rosenberg Miriam , Mamen Meir , Gordin Sali
Published: June 2009

The effect of season on milk yield, milk composition, oestrus manifestation, oestrus cycle characteristics and conception rate was studied in high-yielding Israeli-Friesian cows. ‘Summer’ cows were allotted to control (SC) and forced ventilation (SV) groups. ‘Winter’ cows (W) were kept in one group. During July-September mean rectal temperatures at 16.00 h in primiparous and multiparous cows were 39·6 and 39·8°C, respectively in cows of the SC group, and 39·4 and 39·3°C, respectively in cows of the SV group. Mean rectal temperatures at 16.00 h of the animals in the W group during December-March were 38·9°C in both primiparous and multiparous cows. The mean 122-d milk yields in primiparous cows were 3508, 3251 and 3571 kg/cow in the SC, SV and W groups respectively (not significant (NS)). In the multiparous cows the respective yields were 4183, 4416 and 4538 kg/cow (P < 0·05). Differences in milk composition were small and statistically NS.

Observations on oestrus manifestation, performed 4 times daily, indicated that standing oestrus lasted 9·2 and 10·6 h in primiparous and multiparous cows respectively (P < 0·05); differences between groups were statistically not significant. Oestrous cycle lengths of primiparous and multiparous cows were 21·1 and 22·5 d respectively (P < 0·05) between ovulations and 23·0 and 28·05 d respectively (P < 0·01) between standing heats. Cows were inseminated following standing heat only. Conception rates (on all services within experimental periods) in primiparous cows were 50, 35 and 72% in the SC, SV and W groups respectively (NS). In the multiparous cows, the respective rates were 22, 52 and 80% (P < 0·05).

It is concluded that in the present experiment hyperthermy decreased milk production to a very small extent, in spite of very high milk yields, but fertility was severely affected. It is also suggested that primiparous cows are less affected by heat stress than multiparous cows.
Histochemical detection of alkaline phosphatase in cheese
Authors: Bolcato V.
Published: June 2009

Details are given of a histochemical technique suitable for the detection of alkaline phosphatase in cheese.