Effect of homogenisation and microfluidisation on the extent of fat separation during storage of UHT milk.

Abstract

The extent of fat separation occurring during storage of UHT milk homogenised using conventional valve homogenisers was compared to milk emulsified using a microfluidiser. High-pressure microfluidisation of milk reduced the extent of fat separation during storage of UHT milk samples. Only slight fat separation was found in microfluidised UHT milk samples after 9 months storage at 25°C, compared to moderate fat separation after 2-3 months storage for milk subjected to conventional valve homogenisation. Samples homogenised before UHT processing with a conventional homogeniser developed moderate fat separation after 2 months storage, while a similar extent of fat separation was not evident until after 4 months storage with samples homogenised after UHT processing. High-pressure microfluidisation resulted in a fat globule particle size about 25% smaller than that found with homogenised milk. There was no major change in fat globule size over the storage period.