Bacteriological studies on frozen concentrated milk
Harke, Cyril James
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Freezing has long been regarded as a dependable and economical method of preserving perishable foods. Particularly within the last two or three decades many advances have been made in this field. There is no doubt today that the art and science of freezing technology have advanced to a point where one can obtain many high quality, nutritious and economical frozen foods. The dairy industry is continually being faced with the problem of seasonal surpluses and shortages. Any technique which would allow surpluses to be carried over into shortage periods would be highly desirable to this industry. Frozen milks may be one such answer. Milk can be produced at lower cost during the spring and summer than during the fall and winter, therefore, it would be an advantage to process milk into such forms that will be suitable for future use. Storage of frozen concentrated milk appears to have possibilities in aiding the needs of the industry and to supply the fluid milk trade with high-quality milk. Furthermore, concentrated milk may have a place in non-milk-producing areas, particularly where transportation is an important cost factor. Though frozen cream has been a standard product in the manufacture of ice cream mixes, the freezing of fluid and concentrated milks for direct consumption has not been practised on any large scale. A frozen three-to-one concentrated milk is not a new product since experimental work goes back to the early 1930's. However, technical advances, as compared with other industries, were slow, probably due to the unique physical and chemical properties of milk. Protein instability and flavor deterioration have been the main obstacles, either of which limits the storage period. As the storage period is extended this product will undoubtedly develop greater potentials. Since frozen concentrated milk is a food product, attention must be given to the bacterial flora. Further, to add to the knowledge of a comparatively new product and in hope of obtaining information applicable to the industry, studies have been undertaken to determine the effects of processing and storage on the numbers and types of bacteria in frozen concentrated milk.