Evaluation of carbon dioxide elevation on phenolic compounds and antioxidant activity of red onion (Allium cepa L.) during postharvest storage

Abstract

Carbon dioxide (CO₂) is considered one of the eco-related key factors that negatively affect global climatic change. Also, CO₂ can play an important role in the postharvest quality of the agri-products. In this study, the impact of CO₂ on the quality of postharvest onions that were stored at 23 °C for 8 weeks was investigated. The weight loss, phenolic, flavonoid, flavanol, anthocyanin, antioxidant activity, and soluble sugar were analyzed during the study period. The results showed that 20% CO₂ treatment was significantly (P > 0.05) more effective than 15% CO₂ and control in inhibiting weight loss. Additionally, 20% CO₂ treatment significantly retained higher antioxidant enzyme activities such as CAT, APX, and SOD than 15% CO₂ and control. During storage, 20% CO₂ treatment significantly (P < 0.05) improved glucose, fructose, and sucrose levels by more than 15% CO₂ exposure and control groups. Besides the chlorogenic acid, kaempferol and quercetin were significantly (P < 0.05) higher in the 20% CO₂ than in the 15% CO₂ after 2 weeks of storage. In conclusion, this study's novelty comes from the broad prospects of using CO₂ for maximizing the stored onion phytochemical functionality that is usually affected by the room temperature long storage. This will help in the onion shelf-life extension by considering the quality-related attributes.

Keywords: Antioxidant enzymes activities; Carbon dioxide; Phytochemistry; Quality components; Red onion storage; Soluble sugars.