FL—34.

During the past dairying season the " costed cheese " system of payment has been in use in several cheese-faotories, and apparently has not offered any technical difficulties either in the factory or in the office. Through the kind co-operation of the factory directorates and managers the system has been given a further trial in some thirteen factories, where the composite samples have been tested for both fat and casein. In these factories the system has also given satisfaction from the technical standpoint. The trial has provided an opportunity of meeting any unforeseen difficulties. It became apparent as the season advanced that a closer check was necessary on the strength of the standard alkali prepared by the factory-managers, and during the later portion of the trial standard alkali has been provided by the Institute. It is considered that the difficulty could be overcome most easily by the purchase of more concentrated alkali from a reputable supply house and dilution of this as required in the cheese-factory for casein testing. The trial in the factories during the past season is also being used to provide information on the extent of unfairness existing in those factories under the present system of payment. These results are not yet available. In the report on payment for cheese milk, sections have been included summarizing present knowledge of the effect of various factors on the composition of milk, and also of the effect of factors such as pasteurization on the yield of cheese from milk of constant composition. Figures are given showing the average composition of the milk supplied to the factories concerned in the investigation. The Walker-casein Test: A burette has been designed which will permit the direct reading of the casein value on the burette, without reference to a table. (d) Chemistry of Cheesemaking. —Previous work on cheesemaking has emphasized the importance of the acidity of whey at drying on the quality of the resultant cheese. Small variations in this value in any one type of milk can effect very great changes in the character of the body and flavour of the cheese. Inquiry shows, however, that the practices required to obtain the best-quality cheese at factories in different districts are widely divergent. In some factories —in the Waikato district, for instance —the standard system of cheesemaking necessitates a rapid production of acid and a high drying acidity. Such a procedure at the Institute factory and at many factories in the Manawatu district would mean the production of acid cheese. There is at present no apparent reason for this difference in procedure. By a study of the effects of running the whey at different acidities, an attempt has been made to provide some explanation of these differences. The results have not yet been adequately studied to permit the formation of any conclusions. (e) Renneting difficulties in Cheesemaking. —A report on this subject has been prepared for publication. In New Zealand the main difficulty in obtaining a satisfactory coagulation of milk with rennet is of only spasmodic occurrence. In some cases the firmness of the curd can be increased by use of a longer ripening period, but in the most difficult cases this procedure does not effect an improvement. The addition of some calcium chloride appears to be the only corrective method at present available, and this requires careful application. It has been shown that some cows give milk of this slow renneting type persistently throughout the season. (/) Adulteration of Cheese Milk by addition of Water and Incidence of " Non-acid Milk." —Work done at the Laboratory of the Federation of Taranaki Co-operative Dairy Factories in collaboration with the Institute has included a study of the above subjects. The data obtained will provide an indication of the extent to which improvements could be made in the quality of milk supplied to cheese-factories. BuTTEBMAKING INVESTIGATIONS. (a) Butter Flavour. —The work on the relationship between the diacetyl content of butter and the flavour has been developed considerably. It would appear that while butter made from sweet cream, or from cream ripened without developing any appreciable amount of diacetyl, can have an attractive aroma, the inclusion of a small amount of diacetyl imparts a desirable " bloom " to the product. With larger amounts of diacetyl (up t_o about one part per million) the butter resembles the Danish product. Experiments were designed to follow —(1) The distribution of diacetyl and its flavourless precursor, carbinol, during the manufacturing process ; (2) the fate of the diacetyl in storage ; and (3) the conditions of the factory ripening process which determine the maximum development of diacetyl within the limits of a safe churning acidity. It has been found that a portion of the diacetyl and carbinol are destroyed in the pasteurizing and neutralizing process, and the proportion of the flavouring substances lost is governed by the degree of neutralization. For example, over-neutralized cream (acidity 0-04 per cent.) had only 60 per cent, of the original concentration of these substances. The diacetyl (and carbinol), whether developed naturally or added artificially to the butter, are included in the butter with the buttermilk, and only a trace is removed in the wash water. The diacetyl disappears, even during churning to some slight extent, through the oxidizing action of the air entrapped in the butter. Butters made with starter, particularly when the starter has been in a state of active growth when the cream was churned, lose less diacetyl in the subsequent processing and storage stages. Obviously a butter with a relatively large initial concentration of diacetyl will have a better " bloom " when taken from storage than a butter kept under identical conditions but with a lower initial amount of diacetyl substances. Most authorities consider that the diacetyl is formed from its parent substance, carbinol, by oxidation with air entrapped in the butter. This has been found not to be the case. The oxidation which is evidently a bacterial one, is under further investigation. (b) Vitamin A. —It has been shown that the vitamin A content of butter from a typical New Zealand herd remains practically constant over a season, a finding which is very different from the observations given in the literature for butter from typical herds in Great Britain. In that country the vitamin A values fall off seriously when the cattle are placed under stall-feeding conditions in winter.

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