CHANGES IN HYDROPHOBICITY AND SH CONTENT ON SALT-INDUCED GELATION OF WHEY-PROTEIN

Changes in hydrophobicity and SH content related to salt-induced gelat ion of partially heat-denatured whey protein isolate (WPI) at neutral pHs have been investigated. Soluble aggregates were formed when a 10% WPI solution was heated at 70 degrees C or more for 10 min. During hea t treatment, the hydrophobicity of WPI solution increased considerably with increasing temperature while the SH content decreased. In the fi rst stage of salt-induced gelling process, the hydrophobicity increase d immediately after the addition of NaCl, while the SH content decreas ed gradually. Salt-induced gelation was strongly inhibited by the addi tion of N-ethylmaleimide to the WPI solution preliminarily heated at 8 0 degrees C for 30 min. Major forces for the formation of soluble aggr egates and salt-induced gel network were indicated to be non-covalent bonds, such as hydrophobic interaction and intermolecular disulfide bo nding.