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 °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 applications Tenderness 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.

The polyphenol distribution in fresh waxy corns of different color varieties and their functional activities, which may be useful for treating various chronic diseases, were investigated. The in vitro antioxidant activity, and hypoglycemic and hypocholesterolemic effects of the free and bound corn phenolics were determined to evaluate the edible value of fresh waxy corn. The colored varieties contained more phenols than the common varieties (white and/or yellow). The total free phenolic acid content of the six varieties was 6637.73 µg/g DW (dry weight), which was slightly higher (P > 0.05) than that of the total bound form (6276.65 µg/g DW). The total free flavonoid content was 5850.09 µg/g DW, which was higher (P < 0.05) than that of the total bound form (4874.51µg/g DW). No bound anthocyanin was detected in the methanol extracts of the tested varieties. For all the varieties, free polyphenols contributed 86−100 % and 70−78 % of the 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging abilities, respectively, and 100 % of the ferric reducing capacity. The free phenolics in fresh waxy corn showed better (P < 0.05) hypoglycemic effect than the bound form in terms of inhibition of α-amylase activity, whereas the bound phenolics of most varieties showed higher α-glucosidase inhibitory activity than the free forms. The free phenolics showed better (P < 0.05) glycocholesterol binding than the bound form for all varieties. The bound polyphenols showed better sodium cholate and taurocholate binding than the free form for most varieties. In conclusion, the difference between free and bound polyphenol content and functional activities indicates that fresh waxy corn can be potentially used for the development of functional food.

In this study, we investigated the influence of alginate oligosaccharides (AOS) coating on the quality of white shrimp (P. vannamei) at 4 ± 1 °C. We measured shrimp quality by surveying changes in certain properties, such as sensory quality, the microbiota, total volatile basic nitrogen (TVB-N), pH, and sensory characteristics. Compared to control group, AOS coating effectively stopped the growth of bacteria and decreased the formation of TVB-N (from 40% down to 30%). The pH of samples treated with AOS was visibly lower than that of the control group. The sensory quality of the AOS coated shrimp resembled microbial and physicochemical properties, and the acceptability was improved. Furthermore, we found the abundance of spoilage microorganisms, such as Shewanella and Pseudoalteromonas, in AOS coated groups is reduced compared to control groups. All these results suggest that our AOS coating treatment may improve storage and preservation of frozen shrimp.