Abstract:
This research aimed to investigate optimal enzymatic hydrolysis condition and suitable drying process for high antioxidant activityblack bean hydrolysate processing. Enzymatic hydrolysis conditions, Flavourzyme® concentration of 1 - 7% by dried weigh of steamed beans and hydrolysis time of 60 - 1200 min, were optimized using response surface methodology with central composite design. The results showed that hydrolysis conditions with increasing enzyme concentration and hydrolysis time resulted in increasing in degree of hydrolysis (DH) value (p<0.05). Increasing DH also resulted in increasing antioxidant activity due to the higher amount of free amino groups and released phenolic compounds in hydrolysate (p<0.05). The multiple regression analysis of response models showed that p-value of Lack of fit and r2 values were in the range of 0.102 - 0.359 and 0.8717 - 0.9557, respectively. Hydrolysis condition with Flavourzyme® concentration of 6.09% and hydrolysis time of 360 min was the optimal condition to yield high antioxidant activityblack bean hydrolysate at DH of 75%. Validation of response models showed that predicted values were different from observed values in the range of 0.54 - 27.46%. Three different drying methods (tray, foam-mat and vacuum drying) at 60๐C were applied to dry black bean hydrolysate. Moisture ratio rate and drying rate in foam-mat drying was higher than those in tray drying. Six mathematic models were applied to describe the drying characteristic of tray and foam-mat dried bean hydrolysate. Model of Weibull was selected due to the highest r and lowest MRS and RMSE values comparing with the values from other drying models. The validation of model showed that the difference between predicted and observed values of moisture content (MC) was in the range of 0.44 - 6.05%. Vacuum drying took 380 - 450 min to dry hydrolysate to 18 - 21% MC. Dried black bean hydrolysate sample, MC~18 and 21%, obtained from different drying methods were analyzed. The results showed that dried hydrolysate obtained from tray drying, at 21% MC, contained higher amount of total phenolic compounds, flavonoids, TCA-soluble peptides and higher antioxidant activity (DPPH radical scavenging, FRAP, Metal-chelating and Oxygen Radical Absorbance Capacity) compared to dried hydrolysate obtained from vacuum and foam-mat drying, respectively (p<0.05).