Heat-induced destabilization of oil-in-water emulsions formed from hydrolyzed whey protein.
The emulsifying ability, heat stability, and coalescence stability of oil-in-water emulsions prepared with whey protein of varied degrees of hydrolysis (DH), and at varied protein contents, was studied. Whey protein hydrolysates (WPH) with a DH of 4% and 10% had poorer emulsifying ability than non-hydrolyzed whey protein concentrate (WPC), but were more heat stable. Increasing DH between 10 and 27% improved emulsifying ability and further improved the heat stability of the emulsion droplets. Increasing DH from 27 to 35% led to a big decrease in both emulsifying ability and heat stability. The quiescent coalescence stability of WPH emulsions was relatively good up to a DH of 27%. Above DH 27% emulsions become highly unstable. It appears that two mechanisms of instability are at work here. At low DH heat-induced denaturation and aggregation occur. In the DH range of 4-20% heat stability increases as protein globular structure is disrupted. At a DH greater than 27% we see a change from a hydrolysis-induced increase in heat-stability to coalescence instability, with a resultant large increase in emulsion breakdown during heating.
Euston
S R
SR
Food Science Section, New Zealand Dairy Research Institute, Private Bag 11029, Palmerston North, New Zealand. S.R.Euston@hw.ac.uk
Finnigan
S R
SR
Hirst
R L
RL
D004655:Emulsions; D006358:Hot Temperature; D006868:Hydrolysis; D007700:Kinetics; D008894:Milk Proteins / Q000737:chemistry*; D009821:Oils; D014867:Water; D000067816:Whey Proteins
D004655:Emulsions; D008894:Milk Proteins; D009821:Oils; D000067816:Whey Proteins; D014867:Water