639. Some bacteriological aspects of commercially sterilized milk: I. Incidence and nature of spoilage

Abstract

Samples of sterilized milk from fifteen dairies in the Midlands have been examined, and seasonal variations were detected in the incidence of mesophilic and thermophilic sporeformer contamination. Seasonal variation in the rate of spoilage at 30° C. was also apparent.The lower incidence of contamination in summer was considered to be due to (a) less sporeformer contamination during milk production at the farm in the period when the cattle are not housed, and (b) increased processing times and temperatures in warm weather.Cleansed milk bottles were examined and found to be an important source of contamination by mesophilic sporeformers, but the incidence of thermophiles of the type commonly found in sterilized milk was low.Methods of reducing contamination in sterilized milk were discussed.

640. Some bacteriological aspects of commercially sterilized milk: II. Type of sporeforming bacteria isolated

“…'Summer' has been regarded as the 6 months from 1 May to 31 October. It has been shown by Nichols & Candy (6) and by Eidgway (9), that in winter there is a greater incidence of contamination in commercial sterilized milk and more rapid spoilage in samples stored under conditions favourable to bacterial growth. It is suggested that the more rapid spoilage in winter is due to contamination by higher numbers of sporeformers, of which a greater proportion are the B. subtilisjB.…”