ONIONS - Liable to a natural loss in weight. If subjected to warm and humid atmosphere, will decay readily through natural process. Onions exude carbon dioxide, and ventilation must be sufficient to carry away this gas and to supply oxygen. Shipment in close mesh bags, not allowing adequate ventilation, will cause deterioration.
Principal causes of damage are lack of ventilation or contact with fresh or seawater. Protracted contact with water will result in rotting. When subjected to heat and moisture onions will eventually sprout; shrinkage then takes place, resulting in depreciation in value. Onions damaged by freezing may not be a total loss. The freezing may have affected certain of the scales, leaving others unaffected. Onions so affected can be restored by drying.
Egyptian onions, if shipped after the middle of April, are nearly ready to germinate, and this may occur during the voyage. Incipient germination can be detected by a small green sprig just showing at the top of the onion.
The edible onion belongs to the lily family (Liliaceae) and comes originally from Central Asia.
The onion (bulb) is composed of a highly compressed basal plate, which gives rise to the roots, and the main shoot apex, around which the thickened onion scale leaves are arranged. These end in the onion neck, from which the above-ground shoot or peduncle emerges. The outermost scale leaves are dry and protect the onion from external influences.
The ripening process starts when the onion bulb proper forms. Bulb formation is determined by day length and varies with the variety of onion.
Postharvest, the onion undergoes a post-ripening process. This post-ripening does not consist merely of the purely physical process of drying of the onions but also of the attainment of a certain physiological stage known as sprout or growth dormancy. During this process, the roots, peduncle and outermost scale leaves dry; the latter change color and lie tightly around the onion neck, providing protection against evaporation and attack from microorganisms. This process is further assisted by subsequent post-drying.
- Commodity Name:
VEGETABLES AND FRUIT (Fresh)