Efficacy of coupling gamma irradiation with calcium chloride and lemongrass oil in maintaining guava fruit quality and inhibiting fungal growth during cold storage

This study was performed to explore the efficacy of combining more than one postharvest treatment in maintaining some quality attributes and reducing fungal pathogenicity in cold-stored guava fruits. The investigated postharvest treatments included the control, CaCl₂ (4%), lemongrass oil (2 dm³ kg⁻¹), gamma (γ) irradiation (0.2, 0.4 and 0.6 kGy), 0.4 kGy γ irradiation + CaCl₂ (4%), and 0.4 kGy γ irradiation + lemongrass oil (2 dm³ kg⁻¹). The studied physiochemical attributes included weight loss, decay percentage, fruit firmness, total soluble solids (TSS), titratable acidity (TA), and vitamin C content. Different fungal species were also isolated from decayed fruits and were identified as Alternaria alternata, Alternaria solani, Aspergillus niger, Botrytis cinerea, Fusarium solani and Rhizopus stolonifer. The severity of infection for the different fungi was determined, and an in vitro antifungal assay was conducted for lemongrass oil. All the investigated treatments generally reduced decay and water loss percentages, and controlled TSS, TA and vitamin C decrements that occurred during cold storage. On the other hand, higher irradiation doses generally increased fruit softness, and the 0.4 kGy γ dose did not contribute to the overall fruit quality when coupled with CaCl₂ and lemongrass oil, compared to CaCl₂ and lemongrass oil treatments alone.