FOOD SCIENCE ›› 2013, Vol. 34 ›› Issue (1): 150-154.

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Benzoic Acid Formation Mechanism in Traditional Fermented Douchi

  

  • Received:2011-09-27 Revised:2012-11-18 Online:2013-01-15 Published:2013-01-07

Abstract: To explore the mechanism of benzoic acid formation during production of traditional fermented douchi and discover the reason for natural existence of benzoic acid without adding it, changes in the contents of benzoic acid, phenylalanine and β-cinnamic acid and phenylalanine ammonia lyase (PAL) activity were determined by HPLC at different stages of fermentation. After 2 days of incubation, the benzoic acid content of the koji was 2.43 mg/kg and then gradually increased with increasing incubation time, reaching 37.23 mg/kg after 215 days of post-fermentation. Similarly, the phenylalanine content of the starting raw material (soybean) was 4.89 mg/100 g and increased to 272.23 mg/100 g after 215 days of post-fermentation. β-cinnamic acid showed a high level during the koji making stage, resulting in an obvious increase in benzoic acid level, but gradually declined during the post-fermentation stage, without considerably increasing benzoic acid level. Moreover, the PAL activity, which catalyzes the transformation of phenylalanine into β-cinnamic acid, was stronger during the koji making stage, but gradually became weaker during the post-fermentation stage. The contents of benzoic acid and β-cinnamic acid increased and decreased, respectively, due to addition of β-cinnamic acid during the post-fermentation stage. Hence, we conclude that the mechanism of benzoic acid formation during production of traditional fermented douchi may partial hydrolysis of proteins into peptides in the staring raw material, subsequent PAL-catalyzed transformation of phenylalanine into β-cinnamic acid and final oxidization of β-cinnamic acid into benzoic acid under required conditions.

Key words: traditional fermented douchi, benzoic acid, phenylalanine, β-cinnamic acid, phenylalanine ammonia lyase, formation mechanism

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