Physicochemical properties and radical scavenging activity of whey protein hydrolysate by conjugation with lactose

Whey protein isolate (WPI) was hydrolysed to whey protein hydrolysate (WPH) using alcalase produced by Bacillus licheniformis at 65℃ for 3 hrs with an enzyme-to-substrate ratio of 1:50. The WPI and WPH were then conjugated with lactose via Maillard reaction by heating the solution at 95°C for different heating time which were 0 hr, 1 hr, 2 hrs, 3 hrs and 4 hrs. The objectives of this study were to characterise the physicochemical properties (pH value, browning intensity, degree of glycation and Fourier transform infrared spectroscopy) of conjugation of WPI and WPH with lactose and to analyse the antioxidant activity of WPI and WPH after conjugation with lactose. The pH value and degree of glycation of WPH-Lactose for all different heating times was higher compared to WPI-Lactose. The antioxidant activity of WPH-Lactose conjugate was higher compared to WPI-Lactose conjugate as shown in the analysis of ABTS+ radical scavenging activity which was 2.37% for WPI-Lactose and 12.68% for WPH-Lactose that have been heated for 4 hrs. However, the antioxidant activity of WPH was high even though without the conjugation with lactose. Hence, findings showed that WPH can be used as a potential ingredient for encapsulating bioactive compounds due to its high antioxidant activity.