H. 34;

It was with the object of facilitating the commercial use of lactobacilli that the experiments outlined below were carried out. During the whole season dry powdered cultures of suitable lactobacilli were prepared and used in practical cheesemaking trials in the Institute experimental factory. Powder preparations were made by centrifuging yeast-milk cultures of the organisms and vacuum drying the curd in admixture with precipitated calcium carbonate. The resulting dry powders were usually found to have a count of approximately 100 million organisms per gram. The use of lactose in place of calcium carbonate, as commonly employed in the preparation of powdered starter cultures, was found to lower considerably the numbers of viable lactobacilli. Two vats (80 gallons) were used in the manufacture of the cheese. Vat No. 1 served for the manufacture of control cheeses ; vat No. '2 in a separate room and run under closely similar conditions was inoculated with the powdered cultures. The percentage inoculation, calculated on the weight of milk, ranged from 0-005 to 0-04. While most of the cheeses manufactured have not yet been examined at maturity, results so far to hand show that inoculation of the milk led, in general, to an improvement in the flavour of the cheese. The simplicity of the method suggests that an adaption of this procedure would be practicable under commercial conditions. Bxjttbrmaking Projects. (a) Land Cress Taint in Cream (P. H. McDowall).—The previous work on the treatment of cream for the removal of land-cress taint had been carried out during November and December. An attempt to repeat the experiment during the months of September and October did not meet with success. It appears that during the early spring, when the plant is in the less mature growth stages, the cream becomes more strongly tainted than in the later months when the plant is mature. By an indirect process, an oil has been obtained from the plant material consisting of almost pure benzyl isothiocyanate, and therefore differing from the oil obtained by direct distillation—viz., benzyl cyanide. Addition of benzyl isothiocyanate to cream, however, did not give the true cress taint in the cream or butter. Benzyl isothiocyanate is obtainable from the mature plant, and when added in quantity to the diet of a cow does not cause cress taint in the milk or cream. It is proposed to continue the study of the chemistry of the plant during the early spring months when the taint causes most trouble m the factories: In co-operation with Mr. A. V. Alio, of the Fields Division, Department of Agriculture,; some grazing trials were made at Tauranga. Tt, was found that removal of cows from land-cress-tamted pastures at 12 noon have a considerable reduction in intensity of cress taint in the cream, hut was not completely effective in preventing the delivery of tainted cream. With badly-infested pastures, grazing for one hour between 9 a.m. and 10 a.m. only was sufficient to give a taint in the evening's cream. In the case of badly-infested pastures, therefore, there seems to be no alternative to grazing by dry stock or mowing the herbage until the cress disappears with progress of the season. lb) Hardness of Butter (R. M. Dolby).—Determinations of hardness of butter have been made again this year in conjunction with the studies on butterfat composition carried out by Mr. G. A Cox, on monthly'samples from nine New Zealand factories. A statistical analysis has been made of the results for one season. For convenience in calculation " softness ' (reciprocal of hardness) was used instead of hardness. It has been shown that the iodine value and the softening-point, of the butterfat each have independently a highly-significant effect on the softness of the butter. The Reichert-Meissl value of the butterfat has no significant efiect. The iodine value and softening-point together account for nearly half the variance in softness. The remaining variance is accounted for by — (a) Seasonal effects due to variation in manufacturing conditions or in composition other than that shown by iodine value and softening-point. (b) District variations in manufacturing conditions or composition independent of iodine value and softening-point. (c) Random variations and experimental error. Factors (a) and lb) are of approximately equal importance, while factor (c) is of rather less importance. The exceptional softness of spring butter is only partly accounted for by the analytical figures obtained for the butterfat. There is a general tendency, independent of composition as shown by the analyses, for butter from the southern factories to be softer than that from the northern lactones. (c) Variations in the Composition of Butterfat (G. A. Cox).— Samples of butter from nine representative factories are being analysed for a third season in a study of seasonal and district variations m the composition of the fat. The chief differences noted have been due to seasonal variations. lodine values were highest in winter, with a marked drop during October and November to low levels, lollowed by a gradual rise from February till winter. Hardness determinations showed that the butter was softest from June to September, corresponding with the high iodine values, and then markedly increased in hardness during October and November, the months in which the iodine values fell very decidedly. The high iodine values obtained in mid-winter, when feed is scarce, may be related to the plane of nutrition as it is known that the iodine values rise when the animals are on subnormal rations. Opposite'seasonal trends in iodine values have been recorded in European trials, where the cows are fed indoors in winter. Colour intensities of the butter were lowest in autumn and early winter, and rose to a maximum about November, and then gradually decreased to low autumn values. The increase in the colours would probably be due to the fresh spring pasture grass, and possibly to the lactational factor. Kingcountry values were lower than those of Manawatu and Waikato. Butters from Canterbury and Otago were very low in colour values.

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