Light irradiation affects the total antioxidant capacity, total phenolic compounds, phenolic acids, and related enzyme activities of minimally processed spinach (Spinacia oleraceaL.)

Abstract

This study investigated the effects of continuous light irradiation (30 μmol m2 s−1) on the total antioxidant capacity (TAC), total phenolic compounds (TPC), phenolic acids, and their related enzyme activities in minimally processed spinach during 7 days of storage at 7°C. Compared with darkness, light irradiation induced a 68.57% increase in TPC by activating phenylalanine ammonia lyase (PAL) activity by 68.07% and inhibiting polyphenol oxidase (PPO) and peroxidase (POD) activities by 36.69% and 10.77%, respectively, after 7 days of storage. The increase in TPC might be attributed to the de novo synthesis of eight phenolic acids, because they were positively correlated (R = 0.895, p < .01). Both TPC and phenolic acids significantly contributed to TAC values that were notably improved by light irradiation during storage. In addition, light irradiation alleviated spinach chlorophyll deterioration, however it accelerated fresh weight loss by increasing stomatal conductance during storage. Practical applications Spinach is a leafy vegetable favored by consumers for its attractive sensory quality and health-promoting compounds. The quality and shelf life of fresh spinach are influenced by not only initial quality at harvest but also postharvest factors during the subsequent supply chain. Light irradiation, an unavoidable factor during the supply chain, significantly regulates the postharvest quality and senescence of fresh products. This study clearly demonstrated that continuous light irradiation could improve minimally processed spinach nutritional quality by inducing increases in total antioxidant capacity, total phenolic compounds, and de novo synthesis of phenolic acids after 7 days of storage. In addition, light irradiation alleviated spinach chlorophyll deterioration. These original and innovative findings are expected to provide valuable information to processors and sellers to capture a larger market share and earn maximum profit.