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

Carbon dioxide (CO ₂ ) is considered one of the eco-related key factors that negatively affect global climatic change. Also, CO ₂ can play an important role in the postharvest quality of the agri-products. In this study, the impact of CO ₂ 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% CO ₂ treatment was significantly (P > 0.05) more effective than 15% CO ₂ and control in inhibiting weight loss. Additionally, 20% CO ₂ treatment significantly retained higher antioxidant enzyme activities such as CAT, APX, and SOD than 15% CO ₂ and control. During storage, 20% CO ₂ treatment significantly (P < 0.05) improved glucose, fructose, and sucrose levels by more than 15% CO ₂ exposure and control groups. Besides the chlorogenic acid, kaempferol and quercetin were significantly (P < 0.05) higher in the 20% CO ₂ than in the 15% CO ₂ after 2 weeks of storage. In conclusion, this study's novelty comes from the broad prospects of using CO ₂ 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.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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