The influence of heating method and production season of milk on the content and composition of proteolipids in commercial UHT milk

摘要

The objective of this study was to evaluate the influence of the production time and the sterilisation methods on the content and composition of proteolipids of UHT milk. It was shown that there are no statistically significant differences between the proteolipids content and applied sterilisation method from the same production period. However, results indicate the dependence between the amount of proteolipids in UHT milk and production season (summer, winter). Experiments showed that sterilisation methods applied had significant influence on the level of protein in UHT milk proteolipids in these structures. Electrophoretic analysis of the composition of protein fractions of proteolipids showed the presence of alpha(s1)-, a(s2)-, beta- and kappa- casein as well as of beta-lactoglobulin and alpha-lactalbumin. Furthermore, the method of UHT milk manufacture affected the content of fat in the proteolipid complexes. The fatty acid composition of milk fat and proteolipids was comparable. In proteolipid complexes of all tested UHT milk samples the saturated acids were predominant, especially the long chain acids.