Particle sizes and stability of UHT bovine, cereal and grain milks

Commercial ultra high temperature (UHT) processed bovine, oat, rice and soy milks were analysed for stability and particle size. Product stability was determined using a turbidity analyser to follow particle migration over time. Changes in the level of backscattering produced by the sample as a function of time were related to the stability of the sample. The results indicated that the level of stability of the milks varied and the type of destabilisation phenomenon (sedimentation or creaming) also varied between the milks. The relative stability of the samples studied was determined to be: rice much less than oat < soy < bovine. The milks generally had bi-modal particle size distributions. Particles less than about 3 mum were mainly fat or oil globules, while particles greater than about 3 mum were dense non-fat milk solids. The size and relative amount of fat globules and solid particles varied with milk type. The size of the particles in the milks was highly correlated to the stability of the milks, with the most stable milk having the smallest particles. (C) 2003 Elsevier Science Ltd. All rights reserved.