Optimization of proteolytic activities in malting sorghum |
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Affiliation: | 1. Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement & Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Xingke Road 723, Tianhe District, Guangzhou 510650, China;2. University of Chinese Academy of Sciences, No.19A Yuquan Road, Beijing 100049, China;3. College of Food, South China Agricultural University, Wushan Road, Tianhe District, Guangzhou 510642, China;4. Juxiangyuan Health Food (Zhongshan) Co., Ltd., No. 13, Yandong Second Road, Torch Development Zone, Zhongshan 528400, China;5. Department of Tea Science, Zhejiang University, 388 Yuhangtang Road, Hangzhou 310058, China |
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Abstract: | The effects of malting conditions on proteolytic activities in three improved sorghum varieties: ICSV400, SK5912 and KSV8 were studied. Grains were steeped for 45 h using 6 h wet and 3 h dry cycles and germinated for 8 days. Moisture contents and their effects on proteolytic activity were monitored at various intervals using standard methods. Significant positive correlations existed between moisture content and carboxypeptidase and proteinase activities during steeping. Optimum carboxypeptidase and proteinase enzyme activities were consistently recorded in both ICSV400 and SK5912 at the 40th h of steeping while those of KSV8 occurred on the 45th h. This suggests that protein hydrolysis of KSV8 is different from that of ICSV400 and SK5912. Similarly, optimum proteolytic activities occurred in all the sorghum varieties on the 5th day of germination suggesting optimum germination time for optimum protein modification. Variety and steeping time affected both carboxypeptidase and proteinase activities significantly (P<0.001) during germination. Significant positive correlations existed in the sorghum varieties ICSV400 and SK5912 between free amino nitrogen (FAN) contents and carboxypeptidase activities during both steeping and germination. In contrast, variety KSV8 showed no significant correlation between FAN contents and carboxypeptidase activities during either steeping or germination. On the other hand, while there was a highly significant positive correlation between CWS-P development and proteinase activities in all the sorghum varieties during steeping, no such relationship existed during germination. |
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