title: Screening of whey protein isolate hydrolysates for their dual functionality: influence of heat pre-treatment and enzyme specificity.
abstract: Heat pre-treated and non heat pre-treated whey protein isolate (WPI) were hydrolysed using α-chymotrypsin (chymotrypsin), pepsin and trypsin. The in vitro antioxidant activity, ACE-inhibition activity and surface hydrophobicities of the hydrolysates were measured in order to determine if peptides with dual functionalities were present. Dual functional peptides have both biological (e.g. antioxidant, ACE-inhibition, opioid activities) and technological (e.g. nanoemulsification abilities) functions in food systems. Heat pre-treatment marginally enhanced the hydrolysis of WPI by pepsin and trypsin but had no effect on WPI hydrolysis with chymotrypsin. With the exception of the hydrolysis by trypsin, heat pre-treatment did not affect the peptide profile of the hydrolysates as analysed using size exclusion chromatography, or the antioxidant activity (P>0.05). Heat pre-treatment significantly affected the ACE-inhibition activities and the surface hydrophobicities of the hydrolysates (P<0.05), which was a function of the specificity of the hydrolysing enzyme. Extended hydrolysis (up to 24 h) had no significant effect on the DH and the molecular weight profiles (P>0.05) but in some instances caused a reduction in the antioxidant activity of WPI hydrolysates. The chymotrypsin hydrolysate showed a broad MW size range, and was followed by pepsin and then trypsin. The bioactivities of the hydrolysates generally decreased in the order; chymotrypsin>trypsin>pepsin. This study showed that by manipulating protein conformation with pre-hydrolysis heat treatment, combined with careful enzyme selection, peptides with dual functionalities can be produced from WPI for use as functional ingredients in the manufacture of functional foods.
authors.affiliation: EH Graham Centre for Agricultural Innovation, Charles Sturt University, Private Bag 588, Wagga Wagga, NSW 2678, Australia.
authors.forename: Randy
authors.initials: R
authors.lastname: Adjonu
authors.forename: Gregory
authors.initials: G
authors.lastname: Doran
authors.forename: Peter
authors.initials: P
authors.lastname: Torley
authors.forename: Samson
authors.initials: S
authors.lastname: Agboola
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000737:chemistry; D000975:Antioxidants / Q000737:chemistry*; D002918:Chymotrypsin / Q000737:chemistry; D006358:Hot Temperature; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D008894:Milk Proteins / Q000737:chemistry*; D010434:Pepsin A / Q000737:chemistry; D011492:Protein Hydrolysates / Q000737:chemistry*; D014357:Trypsin / Q000737:chemistry; D000067816:Whey Proteins
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D000975:Antioxidants; D008894:Milk Proteins; D011492:Protein Hydrolysates; D000067816:Whey Proteins; D002918:Chymotrypsin; C117608:alpha-chymotrypsin; D014357:Trypsin; D010434:Pepsin A