Experiments were made to determine the effects on yield and butterfat percentage of three times a day milking and of inefficient milking using cows whose milk secretion rates had been shown to be unaffected by the milk accumulation involved. The milking treatments were applied to half-udders of the same cow to ensure that there was no difference between each pair of experimental units in the amount of oxytocic hormone released by the pituitary gland.

Milking three times a day compared with twice a day over a 39-day period resulted in an increase of 12% in both milk and butterfat yields. Increasing the residual milk by 1 lb in each half-udder for a 39-day period caused a 15% decrease in both milk and butterfat yields. It was concluded that since the cause of these findings could be neither the direct effect of differences in milk accumulation nor the effect of different amounts of oxytocic hormone, some local cell effect was involved, activated either by differences in the amount of residual milk or by long-term effects of differences in milk accumulation.

Comparable cheeses were made using single strains of Streptococcus cremoris and Str. lactis as starters. The three Str. lactis strains imparted a characteristic rather abnormal flavour to the cheese, whereas the three strains of Str. cremoris all gave cheeses of normal flavour. The abnormal flavour caused by the lactis cultures increased in intensity as ripening proceeded, and differed slightly from strain to strain.

Bacteriophage usually developed slightly in the whey and in the curd during the manufacturing process, but never to such a degree as to delay acid production unduly. The extent of phage development did not have a significant influence on cheese flavour.

All the lactis strains survived in much larger numbers in the cheese than the cremoris strains. The simplest explanation of the data is that the ‘lactis’ flavour was a direct effect, due to flavour substances produced by the Str. lactis cells present in the young cheese.

Two levels of steaming-up and two levels of concentrate feeding after calving were compared in a feeding trial extending over a complete lactation using sixteen autumn-calving Ayrshire cows in each of 2 years. On the high and low levels of steaming-up 3·3 and 1·6 cwt of concentrates respectively were fed per cow in the 5 weeks before calving. On the high and low levels of concentrate feeding after calving the concentrates were fed at rates of 4·1 and 2·2 lb per 10 lb of milk respectively from the third day after calving until spring grazing began. The total weight of concentrates fed after calving was 25·8 cwt per cow on the high treatment and 12·1 cwt on the low treatment. All the cows grazed good pasture in the autumn and the following spring and had a ration of 9–11 lb of hay and 50–90 lb of grass silage per day during the winter feeding period. During this period the estimated mean intakes of starch equivalent on the high and low concentrate treatments were 17 and 13 lb/day, which were equivalent to 122 and 103% of Woodman's standards respectively.

Milk yield, milk quality, length of lactation and live weight were not affected by the difference between the steaming-up treatments, and no interaction between steaming-up and post-calving treatments was found. Average milk yields in the first 70 and 140 days after calving and in the complete lactations were all higher on the high post-calving concentrate treatment than on the low treatment, and the response per 1 lb additional starch equivalent fed was 1·05 lb milk. The fat content of the milk was similar on all treatments whereas the S.N.F. content increased from 8·64% on the low treatment to 8·82% on the high treatment, giving a response of 0·045% S.N.F. per 1 lb of additional starch equivalent.

Larger losses in live weight occurred on the low treatment in the first 10 weeks after calving than on the high treatment, but in both groups the weights were almost identical after 45 weeks.

Three strains of micrococci and two of pediococci were individually tested for effect on Cheddar cheese flavour by their addition to cheese milk. Only one of the micrococcal strains had a significant effect on flavour. In twenty-eight of the thirty-three trials with this strain the flavour of the experimental cheeses was appreciably better than that of the corresponding control cheeses; in the other five trials the experimental and control cheeses were similar in flavour.

This micrococcus did not grow appreciably during manufacture or ripening of the cheese, the peak number being present in the curd at the time of pressing. The count fell to less than 30% of the peak number after 1 week, and to less than 0·5% after 5 weeks.

The ways in which the micrococcus may have influenced the flavour of the cheese are discussed and attention is drawn to the possibility that bacterial action in the milk and the young cheese may play an important part in flavour development.

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.

Two experiments concerned with the testing of plant material for oestrogenic activity, utilizing vaginal reactions and uterine weight changes in immature ovariectomized mice are reported.

In the first experiment the effects of varying the feeding period of an oestrogenic diet, containing 20% of freeze-dried red clover, and of varying the interval between the last feeding of this diet and slaughter were investigated. In general, uterine weight increased linearly with increased period of feeding and decreased linearly with delay in slaughtering. A feeding period of 4 days was satisfactory for comparisons based on uterine weight. If vaginal reactions were also to be utilized a feeding period of not less than 6 days was desirable.

In the second experiment the dose-response relationships of diethylstilboestrol, genistein and oestrogenic red clover were investigated. All materials were incorporated in the diet of mice, and the level of plant material was kept at 20% of the mixed feed by adding inactive plant material where necessary. In general, either diethylstilboestrol or genistein could form a satisfactory standard for biological estimation of oestrogenic activity in red clover. Relative potencies based on uterine weight response and occurrence of vaginal opening and oestrus-type vaginal smears are given.

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.

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.

The presence of pyridoxamine phosphate in extracts of freeze-dried raw and evaporated milks has been demonstrated by separation and identification of the vitamin B6 active compounds by chromatography and electrophoresis on paper. Its presence in the milk extracts is the cause of the higher values for vitamin B6 activity measured with Streptococcus faecalis as compared with those obtained with Str. faecium or Saccharomyces carlsbergensis. This is because Str. faecalis can utilize the phosphate for growth as readily as free pyridoxamine, whereas Str. faecium and S. carlsbergensis cannot. The mild acid treatment used for extracting the vitamin B6 active compounds from the milk samples for microbiological assay was found to be insufficient to hydrolyse the pyridoxamine phosphate. Further treatment of the acid extracts with intestinal phosphatase released the pyridoxamine from its phosphate and increased the vitamin B6 activity measured with S. carlsbergensis and Str.faecium so that the total vitamin B6 activities of the freeze-dried raw and evaporated milks measured microbiologiclly, were then in agreement with the values found in previous tests with chicks and rats.

Pyridoxamine phosphate could only be detected in small amounts in a sample of fresh milk. The possibility that more of it was formed during the processing and storage of the freeze-dried samples is discussed.