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Galactomannan-carnauba wax coating improves the antioxidant status and reduces chilling injury of ‘Paluma’ guava

Germano, Thais Andrade, Aguiar, Roseane Pontes, Bastos, Maria Socorro Rocha, Moreira, Renato Azevedo, Ayala-Zavala, Jesus Fernando, de Miranda, Maria Raquel Alcântara
Postharvest biology and technology 2019 v.149 pp. 9-17
carnauba wax, carotenoids, catalase, cell walls, chilling injury, chlorophyll, climacteric fruits, coatings, cold treatment, color, degreening, firmness, galactomannans, guavas, hydrogen peroxide, hydrolysis, lipid peroxidation, physiology, principal component analysis, refrigeration, storage quality, superoxide dismutase
Physiologically mature ‘Paluma’ guava were treated with galactomannan (0.75%) and carnauba wax (0.9%) coating, stored at ambient (25 °C) and refrigerated (11 °C), and evaluated every 3rd day for postharvest quality and physiology. Ambient uncoated fruit were apt for consumption for only nine days; meanwhile, coated guavas were acceptable for 15 d with climacteric respiratory peak of 168.6 mg kg−1 h-1 at day 12, and firmness of 14.3 N attributed to lower lipid peroxidation and cell wall hydrolysis. Coating increased antioxidant enzymes SOD and CAT activities that led to 35% lower hydrogen peroxide content, when compared to uncoated control. Coating prevented guava degreening by inhibiting chlorophyll degradation with content of 45.05 mg kg-1, lower carotenoid content with 27.8 mg kg-1 and PPO activity, under refrigeration for 15 d. Refrigerated uncoated fruit exhibited as symptoms of chilling injury inhibition of softening and respiratory peak. Principal component analysis showed that coating and refrigeration treatment maintains guava quality for 15 d of storage similar to observed for control, at day zero. In conclusion, galactomannan-carnauba wax coating improved guava postharvest quality through maintenance of firmness and color, besides preventing chilling symptoms under refrigeration.