Journal of Bioscience and Biotechnology Discovery

Integrated control of postharvest decay on sweet orange fruits by hot water and sodium carbonate (Na₂CO₃) applications during subsequent storage at 28°C was investigated and the effect of such treatment on internal quality attributes of orange fruits determined. Mature sweet orange fruits without bruises were selected and washed in 2% sodium hypochlorite solution for 5 minutes before treatment. For ordinary sodium carbonate treatment (without hot water), selected fruits were separately immersed for 150 seconds in a water bath containing 2% (w/v) and 4% (w/v) sodium carbonate (Na₂CO₃) solutions. In another experiment, selected fruits were immersed for 150 seconds in a water bath containing hot water and sodium carbonate solution. Sodium carbonate concentrations at 2% (w/v) and 4% (w/v) in 45°C hot water temperature were tested. After treatment, the fruits were rinsed, allowed to air dry and then placed inside plastic buckets and stored at 25°C and 88% relative humidity and assessed weekly for mould infection. Result showed that fruits treated with 4% ordinary Na₂CO₃ concentration had no incidence of decay during the first week of storage. However, untreated fruits and fruits treated with ordinary 2% Na₂CO₃ concentration recorded 20.00% disease incidence in the first week of storage. The percentage decay of fruits later increased to 44.16±10.83 in all the fruits treated with 2% Na₂Co₃ concentration by week two and continued till third week when they were completely diseased, having 100% decay incidence. The causal organisms in the decaying fruits were Penicillium digitatum and Phytophthora palmivora. However, fruits treated with 2% Na₂CO₃ concentration in 45ºC hot water recorded 0% decay incidence throughout storage duration which lasted for 6 weeks and as such implied that all the treated fruits were diseased free.