Carrageenan coatings enhance guava shelf life by modulating oxidative stress, antioxidant defenses, and cell wall integrity

The coating based on carrageenan gum (CRG) was applied on guava ( Psidium guajava ) fruits to improve their postharvest quality. The coated fruits were stored for 15 days at 20 ± 1 °C and 85 to 90% RH. CRG-based coating markedly reduced fresh weight loss and incidence of decay. On 15 th day, 1% CRG-coated fruits had 32.6% lower moisture loss and 16–35% lower decay in comparison with uncoated fruits. The rates of respiration and ethylene synthesis were similarly suppressed, with 1% CRG-coated fruits showing 32.9% lower respiration and ethylene rates of 11.73 μl kg -1 h -1 vs. 17.57 μl kg -1 h -1 in controls. CRG treatments moderated ripening, evidenced by slower increases in TSS (9.2% vs. 10% in controls) and sugar-acid ratio (16.04 vs. 25.75), and better retention of titratable acidity (0.57% vs. 0.39%). Oxidative stress markers were reduced in 1% CRG fruits, including malondialdehyde (0.053 mM kg -1 ) and H 2 O 2 (20.74 μM kg -1 ). Antioxidants (ascorbic acid 111.86 mg·100 g -1 , phenolics 297.61 mg kg -1 ) and structural components (protopectin 14.50 g kg -1 ) were better preserved, alongside higher antioxidant enzyme activities. Activities of the enzymes related to cell wall degradation were also suppressed. Overall, 1% CRG coatings effectively maintained fruit quality, delayed ripening, and enhanced shelf life, as supported by physiological, biochemical, and organoleptic evaluations. • Carrageenan coating doubled guava shelf life (from 5 to 12 days). • Weight loss reduced by ∼42% in coated fruits. • Firmness retention improved by ∼38% with coating. • Ascorbic acid preserved ∼28% more than control. • Antioxidant activity enhanced by ∼35% at day 12.