bluuebunny/crossref_metadata_2025 huggingface dataset:
682. Some results on the variability of the clot-on-boiling test
Authors: Hosking Zena D. , Barkworth H.
Published: June 2009

The C.O.B. test has been carried out at 15 min. intervals on raw milk samples stored at 20°C. to examine worker and replicate variability. Within experimental limitations, the differences between workers were not significant (P>0·05) and, in general, good agreement was found between the five replicates examined for each milk sample, coefficients of variation less than 4·0%. The change from absence to presence of a precipitate generally occurred with successive tests, but there were indications that the times to increased intensity of clotting differed with samples.

Captain H. Barkworth was responsible for the plan and design of these experiments which were carried out by members of his staff at Shardlow.
685. Factors influencing the destruction by heat of vitamin B12in milk
Authors: Ford J. E.
Published: June 2009

The processing of liquid milk, particularly sterilization ‘in-bottle’ or ‘in-can’, may cause considerable destruction of its content of vitamin B12. This loss can be greatly reduced by thorough deaeration of the milk before heating.

The author would like to thank Dr S. K. Kon for helpful advice and criticism.
727. The variations in the per capita consumption of milk between towns in Great Britain, and their causes
Authors: Empson J. D.
Published: June 2009

That there are variations in the per capita consumption of milk between families has been amply demonstrated—the reports of the National Food Survey, conducted by the Ministry of Agriculture, Fisheries and Food, record them year by year(1). Some, at least, of the reasons for these variations—such as result from differences in income and in the size and composition of families—are also known. There are, in addition, variations in the per capita consumption of milk between different towns and areas of Britain, and it is the purpose of this paper to consider them.
732. Lactobacilli in Cheddar cheese: II. Duplicate cheeses
Authors: Naylor Jill , Sharpe M. Elisabeth
Published: June 2009

The lactobacillus flora of two pairs of duplicate cheeses, each pair being made under the same conditions and from the same milk, was examined during ripening. A different distribution of serological types of lactobacilli was found not only within a pair of cheeses but in the top and bottom of the same cheese. A third pair of cheeses, to one of which a known Lactobacillus had been added, was found to have a more regular distribution of lactobacilli owing to greater numbers being present in the cheese milk.
Influence of temperature treatment and season on the dilatometric behaviour of butterfat
Authors: De Man J. M. , Wood F. W.
Published: June 2009

The melting dilation of butterfat between 10° and 30° C. has been determined from results obtained for the thermal expansion of solid and liquid butterfat. Measurement of the solid fat percentages obtained with different cooling treatments showed that at higher rates of cooling there was an increase in the solid fat content, which is in accordance with the theory of mixed crystal formation. A cooling rate existed beyond which no further increase in solid fat content took place, since butterfat cooled by immersion in a 5° C. water-bath had practically the same solids content as it had when cooled in a 0° C. water-bath. Differences in cooling rate changed the solid fat content mainly in the region of lower melting-point glycerides. Seasonal variations in solid fat content indicated relatively large differences in the content of higher melting glycerides. There is an indication that not only the quantity of solid fat, but also the composition of the crystals is important as a factor influencing the hardness of butter. It was possible to recrystallize mixed crystals in butterfat at 22·5° C. and thereby lower the solid fat content of the butterfat.
Studies of the secretion of milk of low fat content by cows on diets low in hay and high in concentrates: VII. The effect of administration of volatile fatty acids to cows giving normal milk and milk of low fat content
Authors: Balch C. C. , Rowland S. J.
Published: June 2009

1. The administration of 0·5–1·5 kg. sodium acetate to cows in which the milk fat percentage had been reduced by diets low in hay and high in concentrates usually brought about an appreciable improvement in fat percentage. The extent of the response varied from slight to complete. The Reichert value of the milk fat fell with diets low in hay, but was raised by administration of acetate.

2. The daily administration of 500 g. sodium acetate to cows receiving diets containing normal levels of hay and concentrates according to their milk yields did not affect the milk fat content.

3. The daily administration of 414 g. sodium propionate did not restore fat percentages lowered by the diets low in hay. Butyrate appeared, in a test with one cow, to possess the restorative properties of acetate.

4. With diets containing either 50 lb. silage as the sole roughage or 60 lb. fodder beet and only 6 lb. hay, fat percentages were the same as with a normal diet containing 16 lb. hay.
Viscosity changes in concentrated skim-milk treated with alkali, urea and calcium-complexing agents: II. The influence of concentration, temperature and rate of shear
Authors: Beeby R. , Lee J. W.
Published: June 2009

An essentially exponential relationship between maximum viscosity and concentration of casein was observed for concentrated skim-milk undergoing treatment with calcium hydroxide. Positive temperature coefficients of viscosity were found for samples treated with alkali, while negative coefficients were found with sodium hexametaphosphate. The time of appearance of the maximum viscosity was independent of temperature in concentrated skim-milk treated with sodium or calcium hydroxide; however, when sodium hexametaphosphate was used the maximum appeared earlier at higher temperatures. The viscosity of all systems studied decreased with increasing rate of shear, the deviation from Newtonian being greatest when the viscosity was at its maximum. The effects are explained in terms of a swelling and disintegration of the casein micelles as was postulated in the previous paper.

The authors wish to thank Miss Audrey K. Morris, Dairy Research Section, C.S.I.R.O., Melbourne, for valuable technical assistance, and to express their appreciation for the helpful advice of other members of this Section during the preparation of the manuscript.
The genus Leuconostoc and its nomenclature
Authors: Garvie Ellen I.
Published: June 2009

A preliminary examination of strains of leuconostocs collected from many different laboratories has resulted in a division into six groups. Some of these groups are heterogeneous. The nameLeuconostoc cremorisis used in preference toLeuconostoc citrovorumfor the non-sucrose fermenting species. Reasons are given. Other arguments lead to the conclusion thatStreptococcus kefir(Evans) should be regarded as a synonym ofLeuconostoc mesenteroides, and the nameLeuconostoc lactisis used in preference toStreptococcus kefir(Abd-el-Malek & Gibson).
Some volatile compounds in New Zealand Cheddar cheese and their possible significance in flavour formation: III. Time of first appearance of volatile carbonyl compounds during ripening
Authors: Harvey R. J. , Walker J. R. L.
Published: June 2009

Two Cheddar cheeses were analysed for aldehydes and methyl ketones at intervals during the ripening period. One-day-old cheese was found to contain acetaldehyde and acetone, together with traces of butan-2-one and pentan-2-one. As the cheese matured heptan-2-one, nonan-2-one and undecan-2-one appeared, and the concentrations of all these compounds progressively increased.
Some volatile compounds in New Zealand Cheddar cheese and their possible significance in flavour formation: IV. The addition of flavour compounds to cheese curd to simulate Cheddar flavour
Authors: Walker J. R. L.
Published: June 2009

On the basis of the experimental data provided by Harvey & Walker (1960) and Peterson, Johnson & Price (1949) various mixtures of methyl ketones (mixture K1) and fatty acids (mixture FA) were made up in proportions corresponding approximately to those found in a mature Cheddar cheese (9–10 months old). Only those carbonyl compounds which showed a significant increase in concentration as the cheese matured were included since it was assumed, for these experiments, that these ketones were the key flavour-producing compounds. It was visualized that there might be differences in the uptake of the various ketones by the curd so three additional ketone mixtures (K2, K3, K4), in which the balance of the various constituents had been altered, were also prepared.
Dye-binding methods for estimation of protein in milk
Authors: Dolby R. M.
Published: June 2009

The amido black and orange G methods for protein estimation in milk were investigated. The quantity of dye required for complete precipitation of a given quantity of milk protein was determined.

Dye samples of various degrees of purity all gave a linear relation between protein and dye precipitation, as determined by optical density, but with the less pure samples slightly less dye was bound per unit weight of protein.

Amido black, though reacting with protein in the same molar ratio as orange G, gave a much more sensitive optical indication of protein content.

In milks of individual cows there was a relatively constant relationship between dye values and Kjeldahl protein from 3 to 4 days after calving until 3 to 4 weeks before the end of lactation. Late lactation milks gave about 5% higher dye values than did normal milks of the same protein content.

The relation of dye precipitation to Kjeldahl nitrogen was the same for casein as for total nitrogen in normal milks.
The effect of the presence of penicillinase producing micrococci on the growth of cheese and yogurt starters in milk contaminated with penicillin
Authors: Reiter B. , Vazquez D. , Newland L. G. M.
Published: June 2009

Coagulase-negative micrococci isolated from the cow's udder, when cultivated together with cheese and yogurt starters in milk containing 0·3 I.U./ml of penicillin, contributed sufficient penicillinase to permit normal rates of acid production by the starters. Subcultures of such ‘mixed’ cultures also grew at normal rates in milk contaminated with penicillin at the same level.

The possibility of using such micrococci to protect the starter organisms in both the preparation of bulk starters and during manufacture of cheese and yogurt is discussed.
Gas packing milk powder with a mixture of nitrogen and hydrogen in the presence of palladium catalyst
Authors: Abbot J. , Waite R. , Hearne J. F.
Published: June 2009

Whole and skimmed milk spray dried powders have been gas packed by two methods, and the chemical and physical changes taking place during storage at 17 and 37 °C for two years have been measured. The conventional method of double gas packing with nitrogen, with an interval of several days for desorption, was used as a control for a new method employing a single gas packing with a mixture of nitrogen (90%) and hydrogen (10%) plus the inclusion within the can of a solid catalyst pellet containing palladium.

The new system was more effective in removing oxygen and in maintaining an almost oxygen free atmosphere within the cans. Used on a commercial scale it would have several important advantages over the conventional method, and both whole and skimmed milk powders packed in this way would probably be usable after storage for 10 years at normal temperatures.

Because of the low general level of oxygen in all the cans packed by both methods and because of the low moisture content there was little difference in the keeping quality of the powders. What little there was, however, was in favour of the new method.
A preliminary investigation of the importance of clostridia in the production of rancid flavour in Cheddar cheese
Authors: Goudkov A. V. , Sharpe M. Elisabeth
Published: June 2009

Bacteriological examination of 15 pairs of Cheddar cheeses, of which one of each pair was made aseptically, showed that there was a relationship between the development of rancid flavour and the numbers ofClostridium tyrobutyricumpresent. Other species of clostridia,Cl. beijerinkii, Cl. sporogenesandCl. perfringens, were also present but occurred only as spores. Conditions for the growth ofCl. tyrobutyricumappeared to be more favourable in the aseptically made cheese; it is suggested that the adventitious bacterial flora of the non-aseptically made cheese, which gains access during cheesemaking, has some inhibitory effect on the growth of this organism.
The component fatty acids of the colostral fat and milk fat of the sow
Authors: Duncan W. R. H. , Garton G. A.
Published: June 2009

The fatty acid composition of colostral and milk fat samples representative of the total secretion of the nursing mammae of each of 3 sows was determined by gas-liquid chromatography. In both colostral and milk fats, acids of chain length C16and C18accounted for more than 90% of the total fatty acids present; colostral fat contained a higher proportion of oleic acid and linoleic acid and less palmitic acid and palmitoleic acid than normal milk fat. Structural studies on milk triglycerides showed that, as in pig depot fat, palmitic acid is preferentially esterified to the secondary alcoholic group (2-position) of the glycerol molecules with the C18acids (stearic, oleic and linoleic acids) being present for the most part in the 1- and 3- positions.
A compound responsible for metallic flavour in dairy products: II. Theoretical consideration of the mechanism of formation of oct-1-en-3-one
Authors: Wilkinson R. A. , Stark W.
Published: June 2009

Possible mechanisms are considered for the formation of a metallic flavour component, oct-1-en-3-one, in a vacuum-packed butterfat-antioxidant-synergist mixture, and in washed cream and butter with free access to atmospheric oxygen. The oct-1-en-3-one is likely to be derived from linoleic or arachidonic acids, or both. A complex of reactions linking oxygen, catalysts, substrate, radicals, and antioxidants is discussed. Pathways for the production of intermediates giving rise to oct-1-en-3-one are suggested for systems with free and with limited access to oxygen. These mechanisms would involve secondary oxidations with formation of polyfunctional monomers and would be competing for oxygen with those giving rise to polymers. The reasons why they compete to a significant extent are discussed in relation to the detailed environmental conditions including lipid reactivity, effective oxygen pressurein situ, steric effects at phase boundaries and the role of acidity and of ionic intermediates.
The sensitivity of bovine staphylococci, streptococci and corynebacteria to cloxacillin and various other antibiotics
Authors: Jones A. , Higgs T. M. , Neave F. K. , Smith A.
Published: June 2009

The sensitivities of isolates of bovine staphylococci, corynebacteria and streptococci to various antibiotics were determined. The growth of various strains of Staphylococcus aureus was inhibited by the following range of concentrations of antibiotic: cloxacillin, 0·07 to 0·6 μg/ml; penicillin G, 0·018 to > 250 μg/ml; streptomycin, 1·25 to > 250 µg/ml; novobiocin, 0·15 to 25 μg/ml; chlortetracycline, 0·6 to 10 µg/ml. The concentrations of cloxacillin required to inhibit growth were between 0·15 and 1·25 μg/ml for strains of Streptococcus agalactiae; 0·07 to 0·3 μg/ml for strains of Streptococcus dysgalactiae and 0·15 to 0·6 μg/ml for strains of Streptococcus uberis.

The corynebacteria were generally sensitive to the penicillins (ampicillin, penicillin G, phenethicillin and cloxacillin), but showed least sensitivity to cloxacillin which had a similar activity to that of chlortetracycline, neomycin and oleandomycin. Chloramphenicol and streptomycin were less active than the penicillins and novobiocin showed little activity against Corynebacterium ulcerans.

A clear relationship was confirmed between the sensitivity of staphylococci to cloxacillin and penicillin G. Some indication was found of an association between the sensitivity of staphylococci to cloxacillin and the success of cloxacillin intramammary therapy in the non-lactating udder. There was no evidence of a change in the sensitivity of Staph. aureus following exposure to cloxacillin in the non-lactating udder.
Size distribution of fat globules in cow's milk during milking, measured with a Coulter counter
Authors: Kernohan Elizabeth A. , Lepherd E. E.
Published: June 2009

A Coulter counter was used to measure the diameters and numbers of fat globules in serial samples taken during a single milking of each of 8 cows. Milk fat percentages of samples were estimated by the Babcock method. The average globule diameter, globule number and fat percentage all increased during milking. Regression analyses indicated that fat percentage was a stronger function of fat globule diameter than of globule number. The results are discussed with relation to the rise in fat percentage that occurs during milking.
Impact force as a possible cause of mechanical transfer of bacteria to the interior of the cow's teat
Authors: Thiel C. C. , Thomas Carol L. , Westgarth D. R. , Reiter B.
Published: June 2009

Using bacterial endotoxin as a tracer material, it has been shown that a jet of liquid impinging on the end of the teat for 1 min after milk flow had ceased during machine milking could force material past the barrier of the streak canal. Positive results were obtained when the maximum pressure at the centre of the impact area was about 0·25 bar, with a considerably higher frequency of positives at 0·3–0·5 bar. It seems possible that such impact pressures might occur during milking and cause transfer of infective material to the teat sinus. Impact force could arise when milk returned to the teatcup liner as the result of local or general conditions of instability in the milking machine vacuum.
Influence of aggregation on the susceptibility of casein to proteolysis
Authors: Fox P. F.
Published: June 2009

The susceptibility of the casein in milk to proteolysis was shown to be greatly influenced by its state of aggregation. In normal milk, where the casein is largely in micellar form, the αs1- and β-caseins are almost inaccessible to proteolysis. On removal of the colloidal phosphate, the casein micelles disintegrate, rendering the components, especially the αs1-casein, accessible to proteolysis. The role of colloidal calcium phosphate in the casein micelle is believed to be that of a non-specific aggregating agent which can be effectively replaced by calcium. Dissolved colloidal phosphate can be effectively reformed by elevation of the pH of colloidal phosphate-free (CPF) milk before equilibrium dialysis. Addition of κ-casein to CPF milk also causes aggregation of the component caseins but the micelles formed are smaller than those of normal milk.

The behaviour of micellar β-casein differs considerably from that of micellar αs1-casein. The evidence suggests that part of the β-casein freely dissociates either outside or within the micelle when the temperature is reduced. The temperature dependence of the susceptibility of β-casein to proteolysis was similar in skim-milk and in solutions of sodium caseinate, and increased as the temperature was reduced. αs1-Casein was quite resistant to proteolysis in normal milk but became susceptible when the micelle structure was disrupted on removal of colloidal phosphate.

It is concluded that limited proteolysis may prove a valuable technique in the study of casein micelle structure.
Extraction of the 260 nm-absorbing material from Group N streptococci as a method for estimating cell growth
Authors: Hogg D. McC. , Jago G. R.
Published: June 2009

A method is described for estimating the growth of Group N streptococci in milk and other media by measuring the 260 nm-absorbing material extracted from the cells with 0·1 M-NaOH at 100°C. A good correlation between the absorbance at 260 nm of the hot alkali extracts and the dry weight of the cells was obtained for cultures of Streptococcus lactis during the logarithmic and early stationary phases of growth.
Comparison of milks processed by the direct and indirect methods of ultra-high-temperature sterilization. III. A note on the results for spore destruction obtained with an experimental ultra-high-temperature milk sterilizer
Authors: Burto H.
Published: June 2009

The bacteriological results of Franklin, Underwood, Perkin & Burton (1970) are analysed to show that colony counts of Bacillus stearothermophilus spores in UHT-treated milk are influenced by the inhibitory action of the milk, so that the sporicidal effects of the UHT process as calculated from the results are too high. Only the elimination of the inhibitory factor will allow true sporicidal effects to be determined.
The interaction of bovine milk caseins with the detergent sodium dodecyl sulphate. II. The effect of detergent binding on spectral properties of caseins
Authors: Cheeseman G. C. , Knight Dorothy J.
Published: June 2009

The dissociation of casein aggregates by the detergent sodium dodecyl sulphate (SDS) gave rise to difference spectra and these spectra were characteristic for each of the different types of casein. Increase in absorption by the chromophore groups, tyrosine and tryptophan, when αs1- and β-casein aggregates were dissociated indicated binding of the detergent at regions of the molecule containing these residues. A decrease in absorption when κ-casein was dissociated indicated that the tyrosine and tryptophan residues were not in the region of the molecule to which the detergent was bound and that in the κ-casein aggregate these residues were in a more hydrophobic environment. Peaks on the difference spectra were obtained at 280 and 288 nm for αs1-casein and 284 and 291 nm for β-casein and troughs at 278 and 286 nm for κ-casein. The difference spectrum reached a maximum value when the αsl- and β-casein aggregates were dissociated and the further binding of SDS did not alter this value. The large negative change in the difference spectrum of κ-casein did not occur until after most of the aggregates were dissociated and did not reach a maximum until binding with SDS was complete. The value obtained for ΔOD was found to be temperature-dependent for β-casein-SDS interaction, but not for αs1- and κ-casein. Changes in spectra were also observed when αs1- and κ-casein interacted to form aggregates. The data obtained confirmed the importance of hydrophobic binding in casein aggregate formation and indicated the possible involvement of tyrosine and tryptophan residues in this binding.
The associative effect of level of energy and protein intake in the dairy cow
Authors: Gordon F. J. , Forbes T. J.
Published: June 2009

Eight lactating cows were used in a Latin square experiment, to study the associative effects of level of energy and protein intake on milk yield and composition. Four diets were used, supplying 80 and 120% of estimated energy requirements and 80 and 120% of estimated protein requirements. The level of energy intake significantly affected milk yield, milk energy output, percentage butterfat, ash and non-protein nitrogen. The level of protein intake only significantly affected milk energy output and the non-protein nitrogen content of the milk. Although only the interaction of the effects of energy and protein intake on the milk content of solidsnot-fat (SNF) and ash was significant, it was evident that the effect of each of these factors on milk yield or composition was related to the level of the other in the diet.

Input-output relationships within each protein level were used to compute the response in milk energy output and bodyweight change to a change in energy intake. These showed a greater partitioning of additional energy toward milk energy output with the high than with the low protein level. Multiple regression analysis within each level of protein intake was used to partition energy intake between that used for maintenance, milk energy output and liveweight change. The results showed efficiencies of utilization of metabolizable energy for milk output of 63 and 50% on the high- and low-protein diets, respectively.

Nitrogen balance data are presented.
A comparison of the milking characteristics of transparent and conventional teatcup liners
Authors: Mein G. A. , Clough P. A. , Westgarth D. R. , Thiel C. C.
Published: June 2009

The milking characteristics of 4 transparent and 8 conventional rubber teatcup liners in new condition were compared for peak flow rate, machine time and strip yield, using 30 cows in two 15×15 Latin squares. The milking characteristics of transparent liners were similar to those of normal liners at the same cluster weight. The 4 transparent liners were then compared with 4 of the conventional liners using 16 cows in two 8×8 Latin squares, to observe the movement of teats within the liners throughout milking. The various analyses indicated significant differences between liners but the ranked liner mean values showed the transparent liners widely distributed in the range. It was concluded that findings from studies of teatcup action using transparent liners could be expected to apply also to conventional liners.

The conventional liners were selected to form groups differing mainly in one physical characteristic only (stiffness of the mouthpiece, wall thickness, bore and rubber hardness). Within groups, there were no significant differences in milking properties of practical importance, but between groups there were small differences in machine time and strip yield. Two properties of the liners which appeared important in controlling movement of the teat into the liner were bore of the barrel and friction, bore having the greater influence at the beginning and friction being the dominant influence at the end of milking. With the transparent liners it could be seen that the end of the teat was frequently bathed in milk. Both with transparent and with conventional liners it was surprising how often the teat penetrated so deeply that complete collapse of the liner in each pulsation cycle was prevented.
The effects of increasing amounts of dietary coconut oil on milk-fat secretion in the cow
Authors: Storry J. E. , Hall A. J. , Johnson V. W.
Published: June 2009

(1). A study is reported on the effects of 4 levels of coconut oil, added to a basal diet low in fat, on the secretion in cow's milk of fat and its component fatty acids. (2) A significant reduction in the yield of milk fat occurred at the highest level of supplementation. In terms of individual fatty acids the yields of lauric and myristic acids increased progressively with increased intake, maximum yields being obtained with the 7% level of coconut oil. Conversely the yields of caproic, caprylic, capric and palmitic acids progressively decreased with increased coconut oil intake. The yields of C18 acids were unchanged.
Seasonal variations in the total nitrogen, non-protein nitrogen and urea nitrogen contents of Friesian and Jersey milk
Authors: McDowell A. K. R.
Published: June 2009

A large number of samples (433) from the milk of Friesian herds was taken during the period November 1968 – September 1969, and a smaller number (159) from Jersey herds during the dairy ‘season’ September 1969 – April 1970, and analysed for total nitrogen (TN) and for non-protein nitrogen (NPN). The Friesian milk sample varied in TN from 0·456 to 0·624% (average 0·531 ± 0·021%) and in NPN from 0·024 to 0·054% (average 0·035 ± 0·004%). The Jersey samples varied in TN from 0·467 to 0·718% (average 0·584 ± 0·036%) and in NPN from 0·022 to 0·051% (average 0·033 ± 0·006%).The average NPN value for all the milks was 0·034 ± 0·005%.

There was a seasonal trend in NPN and TN for the Jersey and in TN but not in NPN for the Friesian milks. The proportion of NPN as a percentage of TN varied widely – for the Friesian samples from 4·9 to 10·2% (average 6·46%) and for the Jersey samples from 3·7 to 8·7% (average 5·74%).

Urea N also was estimated in 125 of the Friesian and in all the Jersey milk samples. It varied from 0·012 to 0·029% (average 0·020 ± 0·004%) in the Friesian and from 0·009 to 0·031% (average 0·020 ± 0·004%) in the Jersey samples. For all the milks the urea N as a percentage of NPN varied from 33 to 79 (average 56·5%).

It is suggested that values for ‘protein content’ of milk should refer only to ‘true’ protein ((TN – NPN) × 6·38) and that in the absence of an analytical result for NPN the use of an average value such as that above would be justified.
An in-line milk sampler for determining the numbers of bacteria derived from teat surfaces and udder infections of cows milked in recorder machines
Authors: McKinnon C. H. , Cousins Christina M. , Fulford Rosemary J.
Published: June 2009

A simple in-line milk sampler is described for determining the bacterial contamination from the udders of cows milked in recorder machines. When sterilized, and used with a sterile cluster, it collects a milk sample bacteriologically representative of the cow's total yield and it can be used with minimum disruption of the milking routine.
Mechanics of the teat and teatcup liner during milking: information from radiographs
Authors: Mein G. A. , Thiel C. C. , Akam D. N.
Published: June 2009

For radiographic studies of the teat and teatcup liner during milking, quarters were infused with a suspension of propyliodone in milk. Simultaneous recordings of vacuum within the liner, in the mouthpiece chamber and in the pulsation chamber, and recordings of liner-wall movement, were made in conjunction with the radiographs.

The studies indicated that the sudden decline in milk flow-rate at the end of the period of peak flow-rate from each quarter, and the concurrent changes in the appearance and position of the teat in the liner, result from a fall in teat sinus pressure. This fall in pressure follows the partial closing of the milk passageway between the teat and udder sinuses. The changes initiating the closing of this connexion seem to occur above the teatcup and are associated with the declining amount of milk in the udder.

The teat is elongated by 33–50% as it enters the liner and further stretching of the skin of the teat throughout milking is negligible. Thus, increase in the depth of penetration of the teat into the liner is due to more of the teat entering the top of the liner.

The force exerted on the teat by the closed liner, which is greatest near the end of the teat, usually appears to increase near the end of milking. The force acting against the inner surface of the open liner barrel is greatest during the peak flow-rate period and it appears to be fairly uniform over most of the area of contact.
Residual milk yield as affected by dose and time of injection of oxytocin
Authors: Thompson P. D. , Paape M. J. , Smith J. W.
Published: June 2009

A study was made, using Holstein cows, of the relationship between (1) the dose of oxytocin administered; (2) the time between milking and intravenous (i.v.) injection and (3) the time between injection and withdrawal of residual milk. Effectiveness of each dose for removal of residual milk was expressed as the percentage of residual milk in the quarter which was withdrawn by a test milking. The total amount of milk in the quarter was determined by giving a large dose of oxytocin and a second test milking, which then indicated the volume of milk missed by each combination of dose and delay times. It was found that delay before injection had no consistent influence on the effectiveness of the test dose; however, an increased delay after injection required an increase in the test dose for removal of a constant percentage of residual milk. The mean dose required for 75% removal increased from 6·3 mu/kg bodyweight to 57 mu/kg bodyweight as the time from injection to removal of residual milk increased from 5 to 30 min. The doses which produced removal of 75% of the residual milk in at least 50% of the quarters tested were 5, 10 and 40 i.u. for delays between injection and removal of residual milk of 5, 15 and 30 min respectively.
Adsorption, latent period and burst size of phages of some strains of lactic streptococci
Authors: Keogh Barbara P.
Published: June 2009

The host–phage reactions of 20 strains of lactic streptococci currently used in cheese manufacture, and the phages active on them, were studied under a variety of conditions. The phages of the lactic streptococci conformed in their behaviour with the general behaviour of phages for other bacterial species. The burst size of phages which attack one strain of starter culture varied widely and also varied when one phage attacked different host strains. The burst size of a phage was also influenced by the host on which it was previously propagated. An increase of temperature from 30 to 37 °C the latent period, but it increased, decreased, or had no effect on the burst size. This increase in temperature also usually decreased the percentage adsorption of phage. Rennet at a concentration of 0·02 % significantly reduced the percentage adsorption of phage in sterile reconstituted milk and also in tryptone yeast-extract broth.
Proteolysis detection in milk: II. The effect of preincubation of raw and laboratory pasteurized bulk milk samples on tyrosine value and its relationship with bacterial populations
Authors: Juffs H. S.
Published: June 2009

A study is reported of the effect of preincubation of raw and laboratory pasteurized bulk milk samples on the tyrosine value (TV) of milk and its relationship with bacterial populations. For raw samples, mean TVs before and after preincubation for 20±2 h at both 25 and 30 °C differed (P < 0·001). After preincubation at 30 °C, the TV of 47 % of raw samples exceeded that considered to represent the upper limit of variation in the TV of a normal bulk milk supply. At this temperature, however, there was no indication that proteolytic psychrotrophs were a major contributor to increased TV. With preincubation of raw samples at 25 °C, an increase to above the upper limit of variation occurred in only 20 % of samples; however, proteolytic psychrotrophs appeared more active at this temperature. In similar samples preincubated after laboratory pasteurization, large increases occurred in TV after 20 ±2 h at 30 °C, while at 25 °C the increases were much smaller and of the order found for preincubated raw samples. The results showed, however, that nonpsychrotrophic bacteria were also the principal source of proteinase giving rise to increased TVs in laboratory pasteurized samples.
Influence of dietary proteins on rennin and pepsin content of preruminant calf vell
Authors: Garnot Pascaline , Valles E. , Thapon J.-L. , Toullec R. , Tomassone R. , Ribadeau-Dumas B.
Published: June 2009

Studies were undertaken to determine the influence of dietary proteins on the rennin and pepsin contents of preruminant calf vell. Three groups of 12 Friesian calves were each fed either milk proteins, whey proteins or a 50:50 mixture of these 2 diets. They were slaughtered at a constant weight of 150kg and their vells collected and dried. Another group of vells was obtained from 8 animals that had been fed milk proteins in a separate experiment. The extraction of the abomasal enzymes was carried out at acid pH, and the extracts were quantitatively analysed for rennin and pepsin by DEAE-cellulose column chromatography. Qualitative analyses were also performed by agarose-acrylamide gel electrophoresis. The only enzymes observed using this last method were rennin and bovine pepsin II. Statistical analysis of the quantitative enzyme determinations indicated a trend for the vells from calves fed diets containing casein to be richer in total activity and in rennin, while the level of pepsin remained approximately constant. It seems that casein may induce the secretion of rennin. However, further experiments will be necessary to confirm this. Important differences were observed between the 2 groups of veils from calves given the same diet, but grown in slightly different conditions.
Effects of intramammary arterial infusion of non-essential amino acids and glucose in the lactating goat
Authors: Mepham T. B. , Linzell J. L.
Published: June 2009

Three experiments were carried out on 2 lactating goats, in which mammary arterial plasma amino-acid concentrations were elevated by the infusion of a solution of non-essential amino acids into a carotid artery supplying a transplanted mammary gland. In a fourth experiment a solution of glucose was similarly infused. In some cases the increased arterial concentrations of amino acids resulted in their increased mammary uptake, and in a depression of glucose uptake. However, infusions of neither amino acids nor glucose resulted in increased milk protein yield. Infusion of [U-14C]glutamic acid in one experiment demonstrated gluconeogenesis from glutamate carbon within the mammary gland. The results are discussed in relation to data obtained in another laboratory, from which it has been claimed that non-essential amino acid supply may limit milk protein synthesis. The present results provide no confirmation for the claim.
The effect of phosphates in lowering the amount of deposit formation during the heat treatment of milk
Authors: Burdett Marion
Published: June 2009

The addition of small amounts of phosphate salts reduced the amount of deposit formed from heated milk, both in laboratory experiments and during the operation of a practical ultra-high-temperature heat-exchanger. Sodium pyrophosphate was much more effective than the other phosphates tested. Reasons are suggested for these observed effects.
Properties of aseptically packed ultra-high-temperature milk: III. Formation of polymerized protein during storage at various temperatures
Authors: Andrews A. T.
Published: June 2009

The formation of protein polymers in ultra-high-temperature (UHT)-treated milk during storage at various temperatures was examined by gel filtration. The extent of polymer formation was found to depend on both storage time and temperature. After some months of storage at the higher temperatures of 30 and 37°C, the extent of polymerization of the caseins and whey proteins due to reactions of the Maillard type was several times greater than the heat-induced changes resulting from the UHT processing itself. After storage for 6 months the following proportions of milk proteins were found to exist in the form of covalently bound polymers: 50% at 37°C, 40% at 30°C, 26% at 20°C and 21% at 4°C. In addition, further amounts of polymer were formed by disulphide bonding, the contribution of such polymers diminishing gradually in a temperature-dependent manner during storage due to continuing polymerization reactions. It appeared that αs1-casein may be preferentially involved in these polymerizations with β-casein reacting at a somewhat slower rate. Polymerization and associated reactions modifying molecular charge led to the expected alterations in electrophoretic mobility and a loss of definition in the bands due to the various protein components. Measurements of proteolytic breakdown indicated only very small increases in trichloroacetic acidsoluble fragments, suggesting that proteolysis was of minor significance.
Accelerated cheese ripening: a method for increasing the number of lactic starter bacteria in cheese without detrimental effect to the cheese-making process, and its effect on the cheese ripening
Authors: Pettersson H.-E. , Sjöström G.
Published: June 2009

A method is outlined for accelerating ripening in Swedish semihard cheese by increasing the number of lactic starter bacteria present in the cheese without impairing characteristic texture and flavour. In addition to the normal starter inoculum, suitable lactic starter bacteria whose lactic-acid-producing activity had been greatly reduced by previous sublethal heat treatment, were added to the cheesemilk. When suspensions of streptococci and lactobacilli cultivated at a constant pH were heated at 59 and 69°C respectively acid production was retarded by 5–10 h, which was found to be sufficient for the cheese-making. Proteolysis was lowered only 10–30% by these heating temperatures. Bacterial cell suspensions, prepared by the methods outlined and added to the cheesemilk, were incorporated in cheese curd to extents depending on the amount added and the type of starter. The number in the final cheese could be increased to a maximum of 4–5 times that of control cheese. No adverse effect of the extra starter bacteria on pH, fat content and water content of cheeses 24-h old was observed. Proteolysis, measured as the increase in trichloroacetic acid and phosphotungstic acid (PTA)-soluble N, increased with increasing number of cells in the cheese. Organoleptic judgements showed a positive correlation (r= 0·81) between taste and PTA-soluble N, which in turn was influenced by the number of cells in the final cheeses.
Observations on the microscopic crystalline inclusions in Cheddar cheese
Authors: Brooker B. E. , Hobbs D. G. , Turvey A.
Published: June 2009

In ripening and mature Cheddar cheese, 2 distinct types of birefringent microscopic crystalline inclusions are found. One of these is an irregularly shaped large aggregate of needle-like crystals (LAC). The histochemical demonstration of Ca in the LAC together with their total absence from cheese made with δ-gluconic acid lactone (GAL) instead of starter bacteria suggests that they are composed of Ca lactate.

The other type of inclusion is a smaller aggregate of crystals (SAC). They are more numerous than the LAC and are concentrated in areas which probably correspond to the lines of curd particle fusion. The SAC appear in cheese immediately after pressing and increase in number until the cheese is about 1 month old. They can be detected in unsalted, milled curd after 1 d and are present in large numbers in cheese made with GAL. These observations together with histochemical evidence that they may contain phosphate groups suggest that the SAC are probably composed of Ca phosphate. Their location in spaces between the fat and casein phases of the cheese indicates that they crystallize from pockets of residual whey. Each SAC is composed of a large number of very long (maximum length 4·5 μm), thin (maximum diam. 25 nm) crystals each of which is covered by a thin layer of electron-dense material tentatively identified as casein.
Selection and some properties of phage-resistant starters for cheese-making
Authors: Marshall R. J. , Berridge N. J.
Published: June 2009

Clones ofStreptococcus lactisand ofStr. cremorisresistant to some bacteriophages that could virtually annihilate the parent strains were selected by plating very large numbers of the bacteria in the presence of the phage. Some of the resistant strains were shown to form acid rapidly in milk and to be satisfactory for cheese-making. They were not lysogenic. Adsorption of the phage to which the parent culture had been sensitive still occurred with 3 strains but not with 4 others. Rates of mutation from phage sensitivity to phage resistance were determined for 2 original strains ofStr. lactisand were found to be of the same order as the rates quoted in the literature for other mutations. The mutation rates of phages to forms which could attack the resistant strains were too low to be measured.
The effect of lipolytic Gram-negative psychrotrophs in stored milk on the development of rancidity in Cheddar cheese
Authors: Law B. A. , Sharpe M. Elisabeth , Chapman Helen R.
Published: June 2009

The highest incidence of lipolytic activity among the psychrotrophic Gram-negative flora of commercial raw milks was found in strains ofPseudomonas fluorescensandPs. fragi.The lipases of all of the lipolytic strains remained wholly or partly active after heat treatment at 63°C for 30 min. Two of the strains tested further had lipases which retained 20–25% of their activity even when heated at 100 °C for 10 min. Cheeses made from milks in which strains or a single strain of lipolytic Gram-negative rods (GNR) had been allowed to multiply to > 107colony forming units/ml became rancid after 4 months even though the GNR had been killed by pasteurization. The rancidity was characterized by a soapy off-flavour in cheeses containing free fatty acid concentrations from 3 to 10 times higher than those in control cheeses made from stored milks with low counts of GNR. Strong rancidity could be reproduced by adding the culture supernatant of a pre-grown lipolytic strain, but not the washed cells, to milk and pasteurizing it immediately before cheese-making, demonstrating the extracellular nature of the rancidity-inducing lipases.
The effect of concentration on the heat stability of skim-milk
Authors: Muir D. D. , Sweetsur A. W. M.
Published: June 2009

A progressive change takes place in the heat stability of skim-milk during concentration. At the maximum in the coagulation time (CT)–pH profile of milk concentrated to over 20% of total solids (TS) the total N depletion curve changed from single- to 2-stage and CT became insensitive to the addition of urea. Furthermore, addition of β-lactoglobulin to skim-milk concentrates destabilized the heated milk whilst the opposite effect was observed in the presence of sulphydryl-group blocking agents. As a result of these observations, it has been suggested that the mechanism of coagulation in concentrated milk is similar to that which occurs within the minimum of the CT–pH profile of skim-milk at normal levels of TS.
Reductive methylation of lysine residues in casein
Authors: Olson N. F. , Richardson T. , Zadow J. G.
Published: June 2009

The effect of reductive methylation on the properties of αs-, β- and κ-caseins was studied using preparations of these proteins in which 20 or 60% of the lysyl residues had been reductively methylated. This modification appeared to affect the physicochemical properties of the protein to an insignificant extent and in particular, electrophoretic mobility, sensitivity to precipitation by Ca2+and solubility of Ca salts of individual proteins were only slightly altered. The use of caseins which had been subjected to methylation with radioactive formaldehyde is suggested as a potentially valuable method for the study of protein interactions.
Formation of methanethiol by bacteria isolated from raw milk and Cheddar cheese
Authors: Law Barry A. , Sharpe M. Elisabeth
Published: June 2009

Strains of coryneform bacteria which produce methanethiol from L-methionine in laboratory culture have been isolated from Cheddar cheese and raw milk Many Gram-negative raw milk isolates includingPseudomonas fluorescens, Ps. putida, Ps. fragi, Ps. aureofaciens, Acinetobacter, AeromonasandSerratia marcescensalso produced methanethiol. Representative strains of coryneforms and pseudomonads produced methanethiol only from free L-methionine; glycyl-L-methionine and D-methionine were not degraded. The aerobic nature of the methanethiolproducing bacteria and the instability and alkaline pH-dependence of their thiol producing enzymes explained their failure to increase methanethiol concentrations in experimental cheese, even when large numbers (5 × 107/g milled curd) of pregrown cells were added. Other commonly occurring cheese bacteria such as starter streptococci, micrococci or lactobacilli either did not produce methanethiol or produced only traces. It is concluded that the methanethiol normally present in Cheddar cheese is unlikely to be the product of bacteria or their enzymes.
An improved method for the preparation of crystalline β-lactose and observations on the melting point
Authors: Itoh Takatoshi , Katoh Mineo , Adachi Susumu
Published: June 2009

An improved method for preparing β-lactose crystals was developed by heating a supersaturated solution of lactose under reflux. The product obtained by this method yielded large well-defined crystals.

Differential thermal analysis was used for the characterization of β-lactose. The thermograms of β-lactose obtained when heating conditions were similar to those used in the conventional measurement of the melting point gave an endothermic peak at 229·5–230 °C. A marked difference was observed between the peak temperature on the thermogram and the melting point (m.p.) of β-lactose (252–252·2 °C) given in the literature. The method for determining the m.p. of β-lactose was reexamined in detail and previously reported values could not be confirmed. By application of the conventional method for determining m.p. of organic substances, 229·5 °C (dec.) is proposed as the m.p. of β-lactose.