Effect of Curing and Storage Temperature on Shelf Life of Onion (Allium cepa L.) Bulbs

Simple and low cost farm technologies are required for small-scale farmers in developing countries to improve marketability and reduce postharvest losses of onion (Allium cepa L.) bulbs. Two experiments were conducted to evaluate the effect of curing and storage temperature on shelf life of onion bulbs. In the first experiment, the cured bulbs of yellow onion ‘Shippo’ were stored at five different temperature levels: 15 °C, 20 °C, 25 °C and 30 °C, and room condition (Rc) for 11 weeks from May to August 2015. It was arranged in a completely randomized design with twelve replications. In the second experiment, cured and non-cured red onion bulbs ‘Shonan Red’ were stored at four different temperature levels: 15 °C, 20 °C, 25 °C and 30 °C, for eight weeks from June to August 2015. It was arranged as a two factorial experiment with 10 replications. Onion shelf life was measured by recording weight loss, sprouted, rotten, and mould infected bulbs, as well as general appearance. The results indicated that curing treatment significantly reduced weight loss and rotting percentage, while maintaining high score of the general appearance. The non-cured bulbs stored at 30 °C showed higher percentage of rotten bulbs (40%) after eight weeks of storage. On the other hand, in case of the cured onion bulbs, rotting and mould infection (%) were recorded only at 15 °C. Sprouting of 8.3% bulb was observed only when stored at 20 °C in the first experiment after nine weeks of storage. The obtained results suggest that onion bulbs should be cured and stored at 25−30 °C for better marketability and longer shelf life. Further experiments can be conducted to evaluate the performance of cured bulbs for different onion cultivars stored in ambient conditions of Rwanda.