Lignin accumulation and biosynthetic enzyme activities in relation to postharvest firmness of fresh waxy corn

Lignification and changes in the enzymes involved in lignin biosynthesis were investigated in relation to the reduced tenderness occurring during the postharvest storage of fresh waxy corn at 20 degrees C. The firmness of the corn and its lignin and polyphenol contents increased as storage time increased. The lignin content was significantly correlated (p < .05) with the polyphenol content and firmness. Phenylalanine ammonia-lyase was not the rate-limiting enzyme in polyphenol biosynthesis, whereas the cinnamate 4-hydroxylase activity was significantly correlated (p < .05) with the polyphenol content. The activity of coenzyme A ligase (4CL) had a limited effect on the polyphenol content. Peroxidase was significantly correlated (p<.05) with the lignin content, while no significant (p>.05) effect of polyphenol oxidase or cinnamyl alcohol dehydrogenase (CAD) on the lignin content was observed. Practical applicationsTenderness is a main factor in sensory quality of fresh waxy corn. Secondary cell wall lignifications induced by phenylpropanoid pathway is the main reason of tenderness decline for postharvest fresh waxy corn. But little information of lignin accumulation of fresh waxy corn is obtained from the present studies. Analyzing the changes of lignin and related precursor materials, enzyme activities will help to comprehensively understand the regulatory mechanism of postharvest lignification of fresh waxy corn, which can provide suitable methods to delay postharvest lignin accumulation, and maintain the eating quality of fresh waxy corn.