H.—34.

to cutting by a wire, while giving results in general agreement with those obtained from the Scott-Blair apparatus used previously, has proved more satisfactory in that it gives much more reproducable values and is not affected by a tendency of the butter to crumble. (ii) Relation of Manufacturing-conditions to Hardness of Butter : A continuation of the factory experiments has confirmed the observations previously reported on the effect of rate of cooling of cream after pasteurization and of temperature of wash water on hardness of butter. It has also been shown that the temperature at which the cream is held during the ripening period has a definite effect on butter hardness, a lower holding temperature giving a firmer butter. A comparison of Vacreator with flash-pasteurizer treatment has shown that the method of pasteurization has no effect on the hardness of the butter. (iii) Composition of Butterfat and Hardness of Butter : It has been shown that the iodine value of butterfat has a definite influence on the hardness of butter. It is evident, however, that other factors in the composition also exercise an effect. (d) Variations in the Composition of Butterfat (G. A. Cox).—Samples of butter obtained at monthly intervals from nine factories scattered throughout New Zealand have been analysed in a study of variations in the composition of the fat. The results show clearly a seasonal variation in the properties of the fat common to the butters from all the factories. Determinations of iodine value on samples of butterfat from the different gioups of cows in the Institute experimental herd fed under controlled conditions show that the same seasonal variations occurred —viz., a depression in the November-January period—in spite of alteration in the feeds. Mycological Projects. (T. R. Vernon). During the year mycological work has been directed mainly to the control of " mould " in cheese-factories. The survey work has shown the difficulties of controlling contamination. The amount of contamination varies greatly from factory to factory, and while more or less proportional to the general sanitary condition of the factory itself, many factors lie outside the control of the manager. In spite of this, certain common factors contributing to mould contamination have been noted. These arc avoidable —e.g. (a) the storage of local and export cheese in the same room, (b) the prolonged storage of cheese from slow vats, (c) careless storage of salt and cheese bandage. To prevent mould growth in spite of contamination three methods have been investigated : (a) Controlled temperature and humidity, (b) ozone, (c) ultra-violet radiations. (a) Controlled Temperature and Humidity of Cheese-curing Rooms.—The advantages of controlled temperature in cheese-curing rooms is well known, and the connection between humidity and mould growth has long been appreciated. Although managers have kept daily records of temperature and humidity, no attempt at humidity control has been made. Investigations showed that controlled humidity could control mould in spite of contamination. Once expensive, machinery is now available at a reasonable cost, and three local factories are now equipped with temperature and humidity control apparatus. One of these factories which has been in operation for a whole season has been completely free from, mould troubles. Humidity has been controlled between 80 per cent, to 85 per cent. A study has been made of the effect of controlled temperature and humidity on shrinkage losses and quality. While it has been difficult to assess values to changes in quality, a saving of J per cent, has been observed in the shrinkage of cheese held under controlled conditions compared with that of similar cheese held in an uncontrolled room. Work is now in progress to determine the effect of controlled humidity on cheese stored for long periods. (b) Ozone. There is ample evidence to show the inhibitory effect of low concentrations of ozone on mould growth, and from Australian reports it would appear that it has been tested in cheese-curing rooms with favourable results. In a series of experiments carried out during the season it has not been possible to duplicate these favourable results. It has been found that if the humidity is high enough to encourage " mould " the rate of ozone production is drastically reduced, and although mould growth and spore formation are retarded somewhat they are not entirely controlled in spite of the fact that the apparatus was handling a volume of air less than one-tenth of its capacity. After removal from the ozone chamber, " mould " developed rapidly. T he apparatus tested does not appear to be of any practical value in cheese-curing rooms. (e) Ultra-violet Radiations.—By means of a commercial apparatus for the production of ultraviolet rays the common dairy moulds have been tested. The results show that fungal spores are much more resistant to ultra-violet rays than are bacteria, and that wide variations occur amongst the moulds themselves. Resistance depends largely on the colour of the spore coat. At a distance of 3 in. an exposure of five minutes brings about a reduction in numbers of more than 90 per cent, for most moulds, but species with dark-coloured spores proved more resistant. In one case a complete kill was not obtained after eighty minutes' exposure. In general, the results indicated that the apparatus would not be readily applicable to cheese-curing rooms. Tests have also been carried out on milk-bottles contaminated with bacteria. When direct irradiation was possible the reduction in numbers was high, but the curvature of the bottle produced a blind spot and complete sterilization was not obtained. (d) Casein Paint. With the object of increasing the mould resistance of casein paint, tests are being carried out with a variety of fungicides,

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