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(j) The Chemistry of Incipient Oxidation Defects in Butter (C. R. Barnicoat).—This study was made at the. University of Minnesota, United States of America. The butters used were made from sweet cream pasteurized for ten minutes at 160° F., churned, worked and salted by hand, and were graded after storage at 40° F. for one day, and then after one and two months. The following conclusions were drawn from an extensive series of experiments. Incipient off-flavours such as " flat," " bitter," " stale storage," and " metallic " may be promoted by oxidation catalysts, including traces of copper and iron ; but ferric iron is inactive. These incipient oxidation changes may occur long before there is any evidence of oxidation in the butterfat, and the addition of oxidized fats or fat-soluble peroxides to butter fails to produce off-flavours of the foregoing types, but tends to promote "oxidized," "oily," or "tallowy" flavours, due to oxidation of the unsaturated fatty acids of the triglycerides. It would appear that oxidation of the lecithoprotein (present in cream as the natural emulsifying " membrane " substance surrounding the fat globules) is responsible for these incipient off-flavours. This oxidation of the lecithoprotein is readily transferred to the fat, with which the lecithoprotein is in intimate contact. The oxidation of the lecithoprotein " membrane " appears to proceed more easily in the presence of catalysts such as metals and also in the absence of certain natural antioxygenic substances which exist in the plasma (or skim-milk) fraction. Most of the antioxygenic effect found in milk plasma would appear to be due to the presence of soluble phosphates and citrates, but the proteins also possess this property to some extent. Of the seven vitamins tested, only vitamins C and E appeared to have antioxygenic properties. Most of the current research is centred around vitamin C, which in this investigation was not found to be consistently antioxygenic even in high concentrations. The results observed with other plasma ingredients, particularly the inorganic salts, were much more striking. (k) Survey of District and Seasonal Variations in Butter (W. J. Wiley, R. M. Dolby, and G. A. Cox). — Samples of butter were obtained at monthly intervals from certain factories, believed to be typical of most, from north to south in the Dominion. On arrival at the Institute these samples were graded, and thereafter were examined analytically, especially for variations in the composition of their fat. Samples showed seasonal variations clearly and also consistent variations in hardness between one factory and another. Differences in the chemical composition of the butterfat were sufficient to account only partially for the variations in hardness of the butters. Investigation of these points is continuing. Mycological Projects. (I) Control of Moulds in Dairy Products (T. R. Yernon). —In order to secure some definite information on the amount of air-borne contamination, a survey has been made throughout the year of the numbers and types of moulds present in the atmosphere in and near dairy factories. Outside the factory the spore load is influenced by many factors, but, generally speaking, it is during the summer months that the spore load is greatest. Inside the factory the spore load depends mainly on the sanitary condition of the factory itself, and it has been demonstrated clearly that simple precautionary measures may materially reduce the amount of contamination. From the commercial point of view it is unfortunate that butter and cheese manufactured when the spore load is greatest tend to be sold when conditions are most favourable for growth. The moulding of paint-work in dairy factories is largely attributable to inadequate ventilation and the use of unsuitable paints on unsuitable surfaces. Work is in hand on a study of the resistance offered to mould attack by different pigments and the effect of various paint vehicles and driers. The use of aluminium paint, particularly on rough surfaces, is meeting with some success. It offers considerable resistance to mould attack, it reflects light well, and in curing-rooms may be of value in reducing the rate of heat transmission. Experiments are being carried out to determine the value of ozone in suppressing mould growths in cheese-curing rooms, and a commercial ozone-producing apparatus is being tested. High humidities encourage moulding ; low humidities increase shrinkage losses. In practice it is necessary to compromise. With the object of mould control in view, a study is being made of conditions in cheese-curing rooms. Data on temperature, humidity, and air movements are being collected which will be of value both in relation to mould control and the problem of shrinkage losses. Dairy Husbandry Projects. (to) Relation between Pasture Plants and Dairy Products (I. L. Campbell).—(l) Experimental Grazing Herd: A long-term study is being made in which the performance of one group of dairy cows grazing on pure perennial rye-grass swards is being contrasted with that of another similar group grazing mixed swards of the dominant perennial rye-grass - white clover type. Hay and silage made from the respective pastures supplement the ration in times of shortage. Records are being kept of the condition and health of the animals, the calcium, phosphorus, and magnesium levels in the blood, milk and fat yields, the flavour of cream, and changes in the composition of the milk and fat followed from analyses. This trial has been in progress since July, 1938, and to date the performance of both groups has been similar and apparently normal. Since, however, the main object of the experiment is to study the effects of these diets continuously fed to the same animals over several lactations, it is too early to draw final conclusions.

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