Characteristics of Commercial Nonfat Dry Milk for Cottage Cheese

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Abstract
A number of bacteriological, chemical, and physical characteristics of 30 samples of commercial low-heat nonfat dry milk, intended for use in cottage cheese manufacture, were determined. The tests included: standard plate, direct microscopic, psychrophilic, and coliform counts, titratable acidity, lactic acid, ash, Ca, N, whey protein N, dispersibility and rennet curd tension. Selected powders were used for the manufacture of cottage cheese. Samples obtained from different plants varied considerably in most of the characteristics whereas those received from the same plant over a 4-month period were relatively uniform. Approximately 90% of the samples contained sweet-curdling organisms which were resistant to 80[degree]C for 10 min. The cottage cheese-making properties (curd quality and cooking time) of the reconstituted milks could not be related to any of the bacteriological, cnemical or physical characteristics of the powders. A direct relationship between cutting acidity and the time required for cooking the curd was demonstrated. Cutting at below normal acidities reduced the time required for cooking without impairment to the quality of curd made from powders having low whey protein N and rennent curd tension values.