Heat treatments against the green Mould on sweet orange (citrus sinensis L. Osbeck) fruits at tropical ambient storage
2015
Aborisade, A. T.
Sweet orange fruits are easily injured during harvest and the juice released aids germination of the spores of the green mould resulting in rapid decay of fruits. Heat treatment has been found to control decay in many fruits and vegetables. The protocols adopted in commercial operations depend on the region, cultivar of commodity and the type of natural microflora on the produce. Orange fruits were wound inoculated with Penicillium digitatum (27×10(5) conidia/ml) in the flavedo. At 12 h post inoculation, fruits were subjected to steam (ST) and dry hot air (HA) treatments before storage at 28±2°C and 86±2% RH. Heat treatments controlled decay of fruits to various extents. Treatments with either ST at 50°C for 50 min or HA at 46°C for 90 min totally prevented or significantly reduced disease within 24 days of storage. Other steam treatments at 50°C for 30 min and 55°C for 50 min reduced disease within the same post-treatment storage period. However, there was complete decay on fruits exposed to ST at 55°C for 30 min by day 14 of storage. HA treatment at 75°C for 2, 6 and 22 min also significantly reduced disease severity within 14 days storage and then within the next 10 days compared with control which was completely decayed by day 24. Weight loss from fruits, immediately after treatment, with ST and HA was insignificant (0.06-1.20%) but was high (13.25-17.67% by day 14) during storage, with control fruits losing weight the most. Rind hardening with storage was not correlated with heat treatment but with weight loss. Steam and hot air treatments have potential for extending the shelf-life of fruits during subsequent storage at ambient temperature.
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