Enhancing aggregatum onion curing: evaluating a purpose-designed storage structure and moisture sorption isotherms

Abstract

Small onion or multiplier or aggregatum onion (Allium cepa L. var. aggregatum) is widely grown in southern regions of India. The enormous post-harvest losses are the main cause of concern in cultivating small onions, especially during the monsoon period. Curing is an important practice followed after onion harvest to minimize storage loss. In this context, a curing cum storage structure was designed and fabricated. Based on the physiological and physicochemical properties, a comparative analysis between the conventionally cured onions under the sun and those cured artificially by blowing hot air at 38–40 °C. The Physiological Loss in Weight (PLW), Total Soluble Solids (TSS), and Pyruvic acid content increased significantly (p < 0.01) whereas the firmness and moisture content decreased significantly (p < 0.01) with increasing curing time. The sorption isotherms of both conventional and artificially cured onions at ambient and 40 °C followed the characteristic sigmoid shape exhibiting a type II sorption behaviour. The curing time for conventional and artificial curing of onion was found to be 192 and 72 h, respectively. Based on the parameters analyzed it could be concluded that artificial curing would be the best curing method compared to the conventional practice.