Artit Kongkaew (1), Chokchai Wanapu (1), Neung Teaumroong (1), ULAIWAN USANSA (2)
(1) Suranaree University of Technology, Maung Nakhon Ratchasima, Thailand; (2) Kasetsart University, Bangkok, Thailand
Rice has been used in brewing for a long time, but with limited
content due to the neutral, empty flavor of rice and its low protein
content; therefore, malting of rice grain was proposed as an alternative
method to improve flavor and add enzymes for increasing soluble
nitrogen. The present experiment aims to increase the rice ratio for
lager beer production by using malted rice grain and adding heat-stable
α-amylase and nutrease in the wort production step. The response surface
methodology (RSM) through face center composite design (CCD) was
selected to examine the effects of the four variables: germination time
of rice (X1), ratios of rice malt (X2), α-amylase (X3), and protease
added content (X4) in three levels. Small-scale mashing of 26
experiments was carried out with mashing temperature programmed as
follows: 45°C×10 min, 50°C×60 min, 63°C×40 min, and 95°C×60 min.
Germination time of rice, rice malt ratio, amount of α-amylase, and
protease were expressed as the independent variables. The analysis of
variances indicated that α-amylase was essential for extraction and
improved the filtrate volume due to the saccharification activity,
whereas bacterial protease and germination time of rice malt were not
affected to extract content and filtrate volume when α-amylase was
supplemented. Rice malt ratio influenced filtrate volume; 75% rice malt
mashed with 0.25 g of malt α-amylase supplement per 100 g illustrated
the maximum filtrate volume. Addition of bacterial protease increased
the amount of wort FAN. However, germination time of rice demonstrated
the most impact on wort FAN. Malt from the fifth day of germination
could be mashed at 90% wt/wt with both enzymes at 0.4 g of malt per 100 g
and illustrated the appropriate wort for brewing. High rice ratio wort
was successfully formulated; therefore, an appropriate yeast strain and
fermentation process should be considered in further work.
Ulaiwan Usansa holds a Ph.D. in biotechnology.
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