Carbon dioxide sensitization delays the postharvest ripening and fatty acids composition of Capsicum fruit by regulating ethylene biosynthesis, malic acid and reactive oxygen species metabolism

Present study would be significant in the sustenance of quality characters for postharvest storage of Capsicum fruit with CO₂-sensitization in biocompatible manner. The present experiment describes effects of CO₂ sensitization on delaying postharvest ripening through physiological attributes in Capsicum fruit. The experiment was conducted with acidified bicarbonate-derived CO₂ exposure for 2 h on Capsicum fruit, kept under white light at 25 °C through 7 days postharvest storage. Initially, fruits responded well to CO₂ as recorded sustenance of greenness and integrity of fruit coat resolved through scanning electron micrograph. Loss of water and accumulation of total soluble solids were marginally increased on CO₂-sensitized fruit as compared to non-sensitized (control) fruit. The ethylene metabolism biosynthetic genes like CaACC synthase, CaACC oxidase were downregulated on CO₂-sensitization. Accompanying ethylene metabolism cellular respiration was downregulated on CO₂ induction as compared to control through 7 days of storage. Fruit coat photosynthesis decarboxylating reaction by NADP malic enzyme was upregulated to maintain the reduced carbon accumulation as recorded on 7 days of storage under the same condition. CO₂-sensitization effectively reduced the lipid peroxides as oxidative stress products on ripening throughout the storage. Anti-oxidation reaction essentially downregulates the ROS-induced damages of biomolecules that otherwise are highly required for food preservation during postharvest storage. Thus, the major finding is that CO_2-sensitization maintains a higher ratio of unsaturated to saturated fatty acids in fruit coat during storage. Tissue-specific downregulation of ROS also maintained the nuclear stability under CO₂ exposure. These findings provide basic as well as applied insights for sustaining Capsicum fruit quality with CO₂ exposure under postharvest storage.