Abstract
This study determined the physicochemical properties (apparent viscosity (ηapp), turbidity (A550nm), particle size and molecular mass distribution) of hydrolysates generated from whey protein concentrate (WPC), milk protein concentrate (MPC) and sodium caseinate (NaCN), following incubation with Debitrase HYW20™ and Prolyve™ at 50 °C, pH 7.0 for 1 and 4 h, before and after heat inactivation (80 °C for 10 min). The degree of hydrolysis (DH) increased with incubation time, giving values of 6.56%, 8.17% and 9.48%, following 1 h hydrolysis of WPC, MPC and NaCN with Debitrase HYW20™, and 12.04%, 15.74% and 17.78%, respectively, following 4 h incubation. These DHs were significantly higher compared to those obtained following 4 h incubation with Prolyve™. Hydrolysis with Debitrase HYW20™ gave >40% of peptides with molecular masses < 1 kDa for all substrates, which was higher than the value obtained following hydrolysis with Prolyve™. The effect of hydrolysis on the physicochemical properties was substrate dependent, since ηapp decreased in WPC and NaCN hydrolysates, particle size decreased for all the substrates, with aggregate formation for MPC, and turbidity decreased in WPC and MPC hydrolysates, while it increased in NaCN hydrolysates. The physical properties of the hydrolysates were influenced by the enzyme thermal inactivation step in a DH-dependent manner, with no significant effect on turbidity and viscosity for hydrolysates at higher DHs.
Highlights
Dairy proteins are commonly used as ingredients in complex food systems, either for structuring or for nutritional purposes [1]
Debitrase HYW20TM is an enzyme preparation derived from Aspergillus oryzae and Bacillus spp., which has been shown to produce hydrolysates with reduced bitterness [38,39], while Prolyve 1000TM is a Bacillus licheniformis proteinase, which does not cause gelation [31]
As expected from previous studies [40], there was an effect of incubation time on degree of hydrolysis (DH), with higher DHs being observed after 4 h incubation for all substrates with both enzymes
Summary
Dairy proteins are commonly used as ingredients in complex food systems, either for structuring or for nutritional purposes [1]. Hydrolysis can lead to significant improvements in the foaming, gelling and emulsifying properties of whey protein hydrolysates [19,20,21,22] of casein hydrolysates [23] and milk protein hydrolysates [24,25] in comparison with the intact proteins. This improvement in functional properties may be attributed to changes in the secondary structure and to a decrease in molecular mass following hydrolysis [26]. Whey proteins can give rise to bioactive peptides once the primary structure is hydrolysed; these peptides can display different bioactivities, such as antioxidative activity, be more effective in treating tumours in some cancers and can inhibit ACE activity in vitro [27]
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