A single injection of 100 i.u. ACTH given to milking cows had no statistically significant effect on the yield or composition of the milk. A long-acting preparation of ACTH, when given to cows in single doses of 200 and 400 i.u., depressed milk yield and raised the butterfat content of the milk. There was no significant change in the SNF content of the milk but the SNF content of the milk serum was increased. Three injections of 300 i.u. of long-acting ACTH given at 24-h intervals reduced yields of milk, fat and SNF and increased the fat and SNF contents of the milk.

Small but generally consistent changes occurred in the butterfat characteristics of the milk of all groups treated with ACTH. There was a decrease in the iodine number and refractive index and a rise in the softening point of the fat in all the experiments. The Reichert value of the butterfat was lowered by single or multiple injections of the long-acting preparation. The carotene content of the butterfat was lowered by injections of the long-acting ACTH preparation but the vitamin A content was unaffected.

The early loss of viability of Streptococcus cremoris strain C 13 in Cheddar cheese was investigated. The growth of this strain was markedly inhibited by cheese extracts containing unesterified fatty acids of which oleic acid was the major inhibitory constituent active against the coccus. This acid was found to accumulate in cheese early in the ripening process and may be responsible for the early loss of viability of strain C 13 in cheese.

Early loss of viability of a starter organism in cheese could result in a low peptidase activity by limiting the number of bacterial cells present. The subsequent accumulation of unhydrolysed bitter peptides would produce a bitter flavour.

The homogenization of milk and cream with a piston-type homogenizer has been studied. An examination has been made of the influences upon the mean fat globule diameters of changes in milk fat content, flow rate and homogenization temperature. The results are discussed in terms of the variations in the parameters q and P0 of the empirical equation d = (P0/P)q relating the globule diameter d to applied pressure P.

Following enzymic digestion with pronase, masked SH groups in micellar casein became available for titration in disaggregating media with mercurial reagents. The content of cystine and cysteine was also estimated after reduction with (a) sulphite, and (b) borohydride, and also by reaction in alkaline conditions with Cd(OH)2. The results show that the micelles contain mainly cysteine, and that it is likely that cystine is not present.

A method was devised for separating proteins of skim-milk on Sephadex G 100 dextran gel. Four fractions were obtained, the first 3 corresponding to casein micelle, lactoglobulin, and lactalbumin fractions while the last contained no protein. The fractions were examined using starch gel electrophoresis, and results are also given for the average composition of the fractions. Differences between the composition of the casein micelle fraction and that of sodium caseinate made from the same milks are reported.

It was previously found that low concentrations of oleic acid in the growth medium inhibited the growth of Streptococcus cremoris strain C 13. However, a variant of this strain has now been isolated which is capable of growth in relatively high concentrations of oleic acid. This was achieved by the extended incubation of inocula of strain C 13 in milk containing various concentrations of oleic acid.

In an endeavour to find an ideal medium for the isolation of the bacteria from Cheddar cheese 10 media were compared. The initial criterion was of ability to yield maximal counts with each of 23 representatives of species common in Cheddar cheese. Subsequently the more promising media were compared for ability to give the highest counts for cheese emulsions without obvious distortion of the proportions of the various species present.

Since no one medium gave maximal counts with all strains, two complementary media of quite different composition are suggested for the bacteriological examination of cheese.

A method of preventing the action of bacteriophages on starters in cheese milk is described. Direct intramuscular injection of high titre phage preparation into a cow resulted in the appearance in the blood serum and milk of a high concentration of antibody. Even after considerable dilution this antibody is capable of neutralizing the homologous phage and serologically related phages. Methods of concentrating the antibody-containing milk were examined with a view to commercial application of the method in the protection of starter bacteria from phage attack.

The levels of coenzyme A were measured in the milk of normal dairy cows during the first 20 weeks of lactation. Estimations were made on milk samples obtained from some cows in their first lactation and from older cows. The microbiological method described by Brown (1959) for the estimation of bound forms of pantothenic acid was used, but considerable modification of this method was necessary to avoid elevated results due to the stimulatory action of free pantothenic acid on the response of the assay organism. Appreciable amounts of coenzyme A were excreted in the milk of cows in their second or subsequent lactations during the first 12–16 weeks after parturition, peak levels being reached after the end of the 1st week. In comparison, only small amounts of coenzyme A were excreted in the milk of cows in their first lactation. Attempts to detect the presence of phosphopantetheine in milk were unsuccessful.

A method is described of measuring pressures in a teatcup assembly using strain gauge transducers and simultaneously following movement of the liner wall by means of a cine camera. In preliminary experiments with a narrow bore type liner it was found that pressures below the teat could vary during a single pulsation cycle from a few inches of mercury below atmospheric pressure (inHg vacuum) to as high as 25 inHg vacuum in the absence of an airbleed. Bleeding air into the barrel of the liner or into the clawpiece considerably reduced fluctuation in pressure, and the vacuum barely rose above the nominal milking vacuum of 15 inHg. Reducing the rate of change of pressure in the pulsation chamber did not greatly affect the maximum vacuum obtained. Opening and closing of the liner by pressure change in the pulsation chamber was under some conditions considerably delayed by the pressure conditions existing inside the liner.

It is suggested that inertia effects of milk in the cluster and the natural frequency of the system are largely responsible for the observed pressure changes under the teat.

From a batch of raw milk, evaporated milk was prepared commercially by 3 procedures: A, a normal commercial procedure involving holding the filled cans at a maximum temperature of 113 °C for 15 min; B, with nisin added and holding at a maximum temperature of 105 °C for 15 min; C, with nisin added and holding at a maximum temperature of 113 °C for 3 min. The content of B vitamins in the raw and evaporated milks was measured microbiologically; the nutritive value of the proteins was determined in rat tests.

In milk A, 83% of the vitamin B12, 38% of the vitamin B6 and 20% of the thiamine were destroyed during processing. In milk B, the losses were 67, 30 and 19%, respectively, only the loss of vitamin B12 being significantly lower than in milk A. In milk C, the losses were 67, 23 and 14%, respectively, each of them being significantly lower than in milk A. There was no further loss of thiamine on storage of the milks for 12 months at 4 °C, but at room temperature and at 37 °C further losses occurred in all the milks. Similarly, the vitamin B6 activity of the milks decreased on storage, the loss being greatest at 37 °C, but also detectable at 4 °C. No change in the vitamin B12 content occurred on storage, and no losses of biotin, nicotinic acid, pantothenic acid or riboflavin were detected during manufacture or storage of the evaporated milks.

The biological value and true digestibility of the proteins of the evaporated milks were slightly lower than for the raw milk. Neither nisin treatment nor storage at room temperature for a year affected these characteristics.

A study of casein micelles was made with the electron microscope, using very thin sections cut from micelles embedded in Araldite. The micelles appear to be built up of units that are approximately spherical, about 100 Å in diameter and of about 300000 molecular weight.

The serological identity of group N streptococci was established by Shattock & Mattick (1943), who discovered that Streptococcus lactis and Str. cremoris had a common antigen, which differentiated them from the rest of the Lancefield groups of streptococci. Although phage typing of these organisms has met with some success (Nichols & Hoyle, 1949; Whitehead & Bush, 1957) attempts to type these organisms with rabbit antisera so far have failed (Briggs & Newland, 1953).