Optimisation of wort production from rice malt using enzymes and barley malt

Abstract

Commercially, rice malt has never been successfully used in brewing because of its low free α-amino nitrogen (FAN) content. This study was designed to optimise rice malt replacement for barley malt in wort production and to improve FAN by adding α-amylase and protease. The response surface methodology (RSM) through face central composite design (CCD) was selected to examine the effects of the four independent variables at three levels: germination time (X₁), rice malt ratio (X₂), α-amylase (X₃) addition, and protease (X₄) addition. The rice malt ratio influenced the adjusted wort yield (AWY); 75% rice malt gave the maximum AWY. The addition of protease increased the amount of wort FAN due to the improvement in amino nitrogen liberation. Moreover, the germination time of rice had the most impact on wort FAN. On the 1st and 3rd days of germination of the rice malt, the FAN was 18.76 and 44.70 mg/100 g malt, respectively; on the 5th day, the FAN was 118.45 mg/100 g malt. The optimisation process for wort production using the addition of enzymes and rice malt was successfully accomplished. The rice malt ratio was increased up to 90% (w/w) using the five-day germinated rice malt, α-amylase and protease at 0.40 g/100 g malt.

Key words: Response surface methodology (RSM), rice malt, wort production.