The effect of treatment methods and storage conditions on postharvest disease and fungal quality of Irvingia gabonensis (Aubry-Lecomte ex O’Rorke) kernels

Abstract

Irvingia gabonensis (Aubry-Lecomte ex O’Rorke) are especially valued for their fat and protein rich kernels but are often contaminated, while in storage, by spoilage fungi that are potentially hazardous to human and animal health. Hence in this research, the postharvest disease and fungal quality of Irvingia kernels was studied. Freshly harvested Irvingia kernels were subjected to three treatment methods (sun-dried, 0.9% NaCl and 3% KHCO₃) and stored in both sealed and open bags for 28 days. Results showed that fungal population and postharvest disease incidence of Irvingia kernels in storage were dependent on treatment methods, storage conditions and storage days. Overall mean log cfu of fungi on Sun-dried Irvingia kernels (5.60) was significantly (P? 0.05) lower than those treated with 0.9% NaCl (5.95) or 3% KHCO₃ (5.99). Incidence and severity of diseased Irvingia kernels stored in sealed bags were significantly (P? 0.05) lower than those stored in open bags. Disease incidence and severity of Irvingia kernels increased significantly (P? 0.05) as storage period increased. Eight species of fungi Aspergillus niger (26.60%), Rhizopus stolonifer (21.28%), Aspergillus flavus (19.15%), Penicillium species (10.64%), Mucor species (8.51%), Candida tropicalis (5.32%), Phytophthora species (4.26%) and Fusarium oxysporum (4.26%) were isolated from the kernels after 28 days of storage. Results further showed that A. flavus, Penicillium and Fusarium species, known to produce mycotoxins were not isolated from kernels treated with NaCl or sun-dried and stored in sealed bags. It is therefore advisable to store Irvingia kernels in sealed bags after drying them under direct sun or treating with 0.9% NaCl.

Keywords: Irvingia gabonensis, Postharvest disease, Postharvest treatment, spoilage fungi, storage.