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

The extent of fat separation occurring during storage of UHT milk homogenis ed using conventional valve homogenisers was compared to milk emulsified us ing a microfluidiser. High-pressure microfluidisation of milk reduced the e xtent of fat separation during storage of UHT milk samples. Only slight fat separation was found in microfluidised UHT milk samples after 9 months sto rage at 25 degrees C, compared to moderate fat separation after 2-3 months storage for milk subjected to conventional valve homogenisation. Samples ho mogenised before UHT processing with a conventional homogeniser developed m oderate fat separation after 2 months storage, while a similar extent of fa t separation was not evident until after 4 months storage with samples homo genised after UHT processing. High-pressure microfluidisation resulted in a fat globule particle size about 25% smaller than that found with homogenis ed milk. There was no major change in fat globule size over the storage per iod.