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A heat-induced change in the ultrastructure of milk and its effect on gel formation in yoghurt

Published online by Cambridge University Press:  01 June 2009

F. L. Davies
Affiliation:
National Institute for Research in Dairying, Shinfield, Beading RG2 9AT
P. A. Shankar
Affiliation:
National Institute for Research in Dairying, Shinfield, Beading RG2 9AT
B. E. Brooker
Affiliation:
National Institute for Research in Dairying, Shinfield, Beading RG2 9AT
D. G. Hobbs
Affiliation:
National Institute for Research in Dairying, Shinfield, Beading RG2 9AT

Summary

Micelles of milk heated at 95 °C for 10 min or autoclaved at 121·7 °C for 15 min were observed by electron microscopy to bear filamentous appendages, whereas micelles from raw milk had relatively smooth contours with no appendages. Experiments suggested that the appendages were composed of denatured β-lactoglobulin and showed that their development was sensitive to sulphydryl blocking agents. Firmness and syneresis of yoghurt were associated with the extent to which micelles coalesced during fermentation; the appendages of micelles in heated milk appeared to inhibit coalescence giving rise to a firmer curd with a lower tendency to syneresis.

Type
Original Articles
Copyright
Copyright © Proprietors of Journal of Dairy Research 1978

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