Shumin Hu (1); (1) Tsingtao Brewery Co. Ltd., Qingdao, China
Malt and Grains
Poster
The main objective of this research was to investigate the effect of
L-cysteine (L-Cys) as a food additive on malt quality during
germination. Barley was laboratory-germinated from 0 to 5 days with
different levels of L-Cys (0 mM, 2.5 mM, 5 mM, 10 mM).
First, malts at days 2, 3, 4 and 5 of germination were obtained to
determine the activities of alpha-amylase, beta-amylase, limit
dextrinase (LD) and its inhibitor. The results showed that L-Cys
addition increased the activities of total LD and decreased the
activities of LD inhibitor at all germination times. Unlike total LD and
LD inhibitor, activities of alpha-amylase, beta-amylase and free LD
were increased with the addition of 2.5 and 5 mM L-Cys at germination days 1 to 4, whereas activities were decreased when higher L-Cys (10 mM)
was added or germination time was longer (days 5). These results showed
that L-Cys not only accelerated the synthesis and release of amylase,
but also promoted protease activities, leading to the decrease of
amylase with higher L-Cys addition or at longer germination time. Next,
malts at germination day 4 with the addition of 5 mM L-Cys
or not were mashed. As a result of higher amylase in malt with the
addition of L-Cys during germination, the non-fermentable sugars were
reduced, and the glucose and maltotriose were improved compared to the
control. Furthermore, the effect of L-Cys on protein degradation was
investigated. Low molecular weight protein increased and middle
molecular weight protein decreased obviously in wort from the malt
germinated with L-Cys, demonstrating that L-Cys promotes protein
degradation by activating protease activities. Last, malt filterability
with the addition of L-Cys was better than the control, maybe because
L-Cys promotes the degradation of storage material (starch, protein and
non-starch polysaccharide). In conclusion, L-Cys can react with the
protein and regulate protein form by splitting the disulfide bonds,
leading to better malt quality.
Shumin Hu, born in 1984, received a Ph.D. degree in fermentation
engineering from Shandong University in Jinan, China. She joined in
State Key Laboratory of Biological Fermentation Engineering of Beer, Co.
Ltd. in August 2011 as a postdoctoral researcher. After finishing her
postdoctoral career in 2014, she continues to work in Tsingtao Brewery
Co. Ltd. and focus on the research of starch degradation, including
amylase, malt quality evaluation and process control.
