222. Bacteriological studies of spraydried milk powder

Abstract

1. Over 400 samples of spray-dried. milk powder from eight factories operating in England and Scotland have been examined. These samples were taken at different stages of the day's run and were obtained from several types of plant situated in widely different districts. Samples were taken in both the summer and winter months. The samples were, therefore, sufficiently representative to enable general conclusions to be drawn regarding the factors affecting bacteriological quality.2. In reconstituting milk powders for bacteriological examination it is necessary to ensure (i) that the sample is sufficiently large to be representative, and (ii) that external contamination is avoided during weighing and handling. The use of a 20 g. sample is advocated. Complete reconstitution of the powder is best obtained by shaking the sample with glass beads in a 180 ml. water blank which is contained in a screw-capped bottle. Details are also given of the methods used in bacteriological examination of the samples and for the isolation of pure cultures from them.