An effect simulating broken cream in whole milk was produced when Bacillus cereus was grown in washed cream at 22° C. A similar but less marked effect was obtained when a concentrated culture filtrate of B. cereus was added to washed cream.

Microscopic examination of washed cream to which B. cereus or its concentrated filtrate had been added showed that the fat-globule membranes had been broken down. The hydrolysis of lecithin in washed cream in which B. cereus had grown was demonstrated by qualitative estimation of free choline.

Since these results could not be reproduced when a non-lecithinase-producing strain of B. cereus or its concentrated culture filtrate was added to washed cream, it appears that the hydrolysis of the lecithin of the fat-globule membrane is at least partly responsible for the formation of broken cream.

La formation de gaz dans la pâte du fromage fondu, au cours de la conservation, représente un défaut assez fréquent qui entraîne le gonflement ou même l'éclatement des emballages, notamment lorsque ces derniers sont constitués par des boites métalliques.

With 1·0 p.p.m. of added copper, well-defined oxidized flavours described as cardboard, oily and metallic developed in pasteurized whole milk after ·2–3 days' storage at 3° C. With 0°1 p.p.m. copper only slight and irregular off-flavours, usually described as cardboard, appeared. Partial oxidation of the ascorbic acid of the milk with H2O2 did not increase its susceptibility to oxidized flavour development.

Marked off-flavours were always associated with peroxide values in the milk fat of 0·2 and more (m.equiv. oxygen/kg.) determined by the ferric thiocyanate technique. With fat peroxide values of about 0·5, usually obtained after 6–7 days at 3° C. with 1·0 p.p.m. copper, the oxidized flavour was very strong and the milk usually undrinkable.

A method for the determination of lactose in milk based on clarification with dialysed iron and oxidation of the filtrate with alkaline ferricyanide solution, followed by titration with sulphato-ceric acid, is proposed. It is simple, rapid and well adapted to the routine estimation of lactose in milk or to the determination of small quantities of lactose. The conditions of the reactions and comparison of results with other methods are discussed.

1. The coefficient of variation of lactation milk yield was approximately 25% for all age groups. That for lactation milk-fat percentage approximately 10% and that for lactation solids-not-fat percentage only 3%. The last two coefficients tended to increase with the age of the cow.

2. Lactation milk yield was least with first calvers and rose to a maximum for sixth calvers. Milk quality was highest with first calvers.

3. No tendency to vary with the season of calving could be found for any lactation record of any age group.

4. During the first years of the herd's existence there was a small negative correlation between lactation milk yield and lactation milk-fat percentage. This has disappeared in more recent years.

5. There was no correlation between lactation milk yield and lactation solids-not-fat percentage.

6. There was a small (r = +0·40 approximately) positive correlation between lactation milk-fat percentage and lactation solids-not-fat percentage.

1. Hard cheese of Cheddar, Derby and Manfis types was made from cows' milk and from buffaloes' milk. Buffaloes' milk curd of the Derby type was also milled at different acidities.

2. Initial acidity was higher and rate of acid development was greater in cows' milk and curd, whilst loss of fat in the whey was lower.

3. Cows' milk cheese contained more moisture, more total, soluble, and non-protein nitrogen, but less fat than buffaloes' milk cheese.

4. During ripening, the rate of acid development and protein degradation was greater in cows' milk cheese, whilst loss of moisture was usually smaller.

5. Buffaloes' milk cheese was inferior in grading quality to cows' milk cheese.

6. Attempts to improve the quality of buffaloes' milk cheese were made by altering the Derby cheese-making process as follows:

(a) ripening milk longer before renneting;

(b) modification of the milk casein/fat ratio;

(c) combining (a) and (b);

(d) modification of the casein/fat ratio plus scalding of the curd at a lower temperature and for a shorter time.

7. The last treatment (d) proved most effective and yielded cheese of very similar chemical composition and grading quality to that obtained from cows' milk.

The method of assaying rennin described by Berridge(1) requires the formation under reproducible conditions of a thin flowing film of milk. Although the skill needed to keep the film flowing at the optimum rate as the clotting point is approached is readily acquired, an automatic method has the advantage of complete reproducibility. A suitable film can be maintained if 10 ml. of milk are placed in a boiling tube of 2·2 cm. internal diameter and the tube, with its axis inclined at about 30° to the horizontal, rotated at 3·0 r.p.m. In the apparatus now used, the boiling tube is mounted on a rubber bung, which in turn is mounted concentrically on a spindle connected through Meccano gears to a 'Sangamo' electric clock motor. A special mechanical coupling allows the bung to be rotated by hand one revolution forwards, thus allowing 20 sec. for fitting or releasing the boiling tube before the drive is again taken up.

Curves are presented showing the trends in the solids-not-fat fractions of milk during the course of normal lactation periods.

The trends may vary with pregnancy, age of the cow, and the mean level of the solids-not-fat.

The milk from ten sows has been studied over one lactation. The density, viscosity, electrical conductivity and pH have been recorded tbroughout the lactation, and in two cases the study extended to the colostrum.

1. It has been shown that the biological value of undeteriorated dried skim milk is depressed to the same extent by the addition of 1·25% L-lysine as by the addition of 1·25% D-lysine. The latter is not used by the rat. It is therefore concluded that the added L-lysine is surplus to the animal's needs and that the apparent lowering of the biological value is due to excretion of the lysine in the urine.

2. The slightly greater loss in the biological value of milk stored in air-pack compared with gas-pack was eliminated by the addition of 0·5% L-histidine to the former. Histidine is not a limiting amino-acid in the control or stored gas-pack milks for either young or adult rats.

3. A lower biological value was found for the control milk with adult than with young rats at 4 and 8% levels of intake. No further lowering in the biological value of the stored milk, deficient in lysine, was observed with adult rats, the value obtained for this milk being independent of the age of the rat. These results are in keeping with the known lowered requirements of the adult rat for lysine.

4. The significance of these findings in relation to the known amino-acid requirements of young and adult rats is discussed.

Seasonal changes in the solids-not-fat content of milk occur only from April to May when the level rises, from May to July when the level falls and from August to September when the level rises again.

These changes are thought to be due to changes in feeding practice.

The fat-globule size distribution patterns have been determined throughout lactation for ten sows and through the colostrum phase for two.

1. Three samples of spray-dried whole milk were made from milk pre-heated at 190, 230° and 230° F. with regenerative cooling to 190° F., in an A.P.V. H.M. Paraflow Heat Exchanger and dried in a Kestner plant. The powders were packed in plain tin-plate cans and stored at 17, 37 and 47° C. The keeping quality of the powders was determined by examination at intervals for palatability, absorption of oxygen and peroxide value of the fat. The biological value and true digestibility of the protein of the powders were estimated in rat-feeding experiments initially and after 6 months' storage. The breadmaking properties of the powders were also examined.

2. The keeping quality, biological and baking tests showed that the three milk powders were very much alike, and that no advantage was gained by raising the preheating temperature of the liquid milk from 190 to 230° F.

It has been shown that a statistically significant decline in the level of solids-not-fat in milk from Dairy Shorthorn first calvers occurred in the months of January, February, March, April and August. The period of the survey was the 12 years from 1935 to 1946.

1. Reasons for the seasonal variations in the vitamin A potency of New Zealand butterfat have been investigated. Adequate carotene for the production of butterfat of maximum potency has been shown to be present in New Zealand pasture throughout the year, but during the summer period this carotene is relatively non-available to dairy cows.

2. In experiments with monozygotic twins grazing average summer pasture it has been shown that a supplement of 1 g. of tocopherol per day increased both carotene and vitamin A levels in the milk fat, the total vitamin A potency being raised from a typical midsummer minimum of 34 i.u./g. fat to a value approaching the maximum late winterspring level of about 50 i.u./g. This maximum level was unaffected by increasing the tocopherol supplement to 3 g. per day or by supplying 300 mg. of carotene in a readily available form in addition to the 3 g. tocopherol.

3. Supplementing the summer pasture with 300 mg. of carotene in oil without tocopherol was without effect on the potency of the fat, supporting the conclusion that the carotene intake was already adequate.

4. A significant correlation was found to exist between vitamin A potency and tocopherol content of New Zealand butterfat.

5. It is suggested that the low vitamin A potencies may be associated with the high percentage of clover in the summer pastures.

1. Ratings for firmness which were carried out on 150 Cheshire cheese at 2 weeks old, by three judges, were examined so as to extract the expected psychophysical errors.

2. It was found that the value for firmness given to any particular cheese tended to be a function of the average firmness of the group of cheese in which it was judged, so that a cheese of a given objective value would be given a different rating according to its position in the series being judged.

3. A cheese of a given value presented after a firm one is judged softer than if it had been presented after a soft one. This contrast effect was masked by the influence of the group as described in (2). Nevertheless, it seems probable that contrast effects influence the judgements.

4. The frequency distributions of the subjective judgements were examined, and it was noted that the ‘semi-expert’ judge gave subjective values which approximated very closely to a normal distribution, more nearly so than the judgements of the other two judges.

5. Reasons are suggested for the differences in the values allotted to the cheese as judged by the different judges.

6. Some suggestions are made for eliminating the effects described.