Abstract:
This research was aimed at studying the effect of germination period on the chemical composition of mung bean and azuki bean, the optimum concentration of Flavourzyme® for the production of protein hydrolysate from each germinated bean, and the effect of maltodextrin on antioxidant activity of freeze dried protein hydrolysate. The results showed that germination periods (0, 9, 18, 27 and 36 h), at 30 ±2°C, did not significantly affect an increase in crude protein content in mung bean (p>0.05). Total phenolic content (TPC) of the 36-h germinated mung bean was the highest but not significantly different from that of the 27-h germinated mung bean. For azuki bean, it was found that both crude protein and TPC significantly increased with an increase in the germination period (p≤0.05). The 36 h-germinated azuki bean provided the highest content of crude protein but not significantly different compared to that of 27 h-germinated azuki bean (p>0.05). In the production of protein hydrolysate from the germinated beans using Flavourzyme ®, it was found that the highest amount of free amino acid group (FAAG) and TPC was obtained when using 7% (w/w) Flavourzyme® for both 27 h-germinated mung bean and azuki bean. An increase in FAAG and TPC relatively contributed to an increase in antioxidant activity measured using ferric reducing antioxidant power (FRAP). The addition of maltodextrin in the protein hydrolysate before freeze drying caused a significant decrease in TPC, FRAP and ascorbic acid equivalent antioxidant capacity (AEAC) (p≤0.05). The antioxidant activity determined using DPPH radical scavenging activity with electron spin resonance gave the similar result in accordance to that determined with spectrophotometry. However, the addition of maltodextrin resulted in an increase in water activity of the protein hydrolysate powder while surface hydrophobicity and hygroscopicity decreased.