An update on post-harvest losses of onion and employed strategies for remedy

Onions (Allium cepa L.) are widely cultivated staple vegetables in daily cooking while, harvested onions as living entities that undergo various physicochemical changes including respiration, weight loss, rotting, and sprouting at storage. Due to high moisture content fresh onions are prone to rapid spoilage which is aggravated by inappropriate handling. Storage is a complicated issue regulated by numerous pre- and post-harvest features encompasses irrigation, fertilization, bulb maturity, harvesting period, curing techniques, storage environment, packaging materials, and chemical treatments; causing about 30–40 % losses of total yield. Again, the attritional changes at physiological, fructant and hormonal levels of stored onions enhance sprouting and microbial spoilage. Among the onion diseases, only Fusarium causes 50 % of rotting at storage, which is augmented by elevated temperatures and humidity. Such an alteration of onions during storage has a robust effect on both their quality and marketability. Although the storage life of onions is an inherent trait, it could be improved through efficient pre and post-harvest practices such as application of growth regulators, ensuring balanced nutrition, nanofertilizers application, and chemical treatments in addition to curing. Curing largely helps to prevent spoilage at storage and increases the availability of onions around the year. Moreover, issues such as sprouting, drying, and microbial spoilage could be minimized by employing advanced techniques like perfect handling, modified ventilation and controlled storage atmospheres with elevated CO2. Here, we present an overview of the strategies used to minimize post-harvest losses and discuss recent advances in preserving quality and extending the shelf-life of onions at storage.