Carrageenan based edible coating modulates oxidative stress and delays cell wall polysaccharides disassembly in harvested grapefruit

The cell wall degradation results in firmness loss thus negatively affecting the overall eating quality. So, in this work, the influence of carrageenan [0, 0.5, 1.0 and 1.5% (w/v)] coating was studied on 'Shamber' grapefruit during storage at 20 +/- 1 degrees C for 42 days (d). The 1.5% carrageenan concentration suppressed metabolic activities and reduced disease rate (about 41%), weight loss (around 46%), malondialdehyde, electrolytes leakage, superoxide anion and hydrogen peroxide. The higher antioxidant enzyme activity as well as total flavonoids, ascorbic acid and total phenolic contents were noted in 1.5% treatment. The 1.5% coating delayed the increase in water-soluble pectin (WSP) and suppressed the reduction of sodium carbonate soluble pectin (NCSP), protopectin, chelate soluble pectin (CSP), hemicellulose and cellulose content. The grapefruit coated with 1.5% carrageenan had lower activities of cellulase (CEL), polygalacturonase (PG), R-galactosidase (R-gal) and pectin methylesterase (PME) enzyme along with higher firmness. The 1.5% carrageenan preserved higher titratable acidity and reduced increase in total soluble solids and ripening index in coated grapefruit. In conclusion, 1.5% carrageenan coating could be considered appropriate for delaying the quality deterioration in grapefruit.