Full Length Research Paper

Biochemical changes in low-salt fermentation of solid-state soy sauce

Zhang Yanfang, Wang lijuan and Tao Wenyi*

Key laboratory of Industrial biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122 Jiangsu Province, PR China.

*Corresponding author. E-mail: jean2008373@yahoo.com.cn or wytao1946@163.com Tel.: +86 510 8591 6839. Fax: +86 510 8591 8516.

Accepted 22 January, 2009

   Abstract

Low-salt solid-state fermentation soy sauce was prepared with defatted soy bean and wheat bran. Biochemical changes during the aging of the soy sauce mash were investigated. Results show that after a 15-day aging period, the contents of total nitrogen, formol titration nitrogen, free amino acids, reducing sugar, total sugar and the brown color were increased. However pH was decreased during the fermentation period. Furthermore contents of free amino acids in low-salt solid-state fermentation soy sauce fluctuated during the fermentation period with most of the free amino acids increased. The analysis of free amino acid composition shows that the contents of glutamic acid, aspartic acid, alanine and leucine were higher than other amino acids. Therefore it means that these amino acids may contribute to the taste and flavor of low-salt solid-state fermentation soy sauce. Analyzing the biochemical change in the fermented process of soy sauce is helpful to find out the shortcoming of low-salt solid-state fermented soy sauce. It is of benefit in improving the quality of low-salt solid-state fermented soy sauce.

Key words: Chemical composition, fermentation processing, free amino acid, low-salt solid-state fermentation soy sauce.