Nutrient Retention Capacity of White and Red Varieties of Onion (Allium Cepa) Bulbs as Influenced by Storage Conditions

The influence of different storage conditions (ambient temperature, refrigeration temperature, and hot air wooden cabinet storage) on nutrient retention capacity of onion bulbs was investigated. The fresh onions varieties (red and white) were obtained from a private farm (Modibbo Isah Farms, Bichi, Kano State, Nigeria). The experiment followed a completely randomized design in a factorial 3 × 2 × 8, with a total of 48 treatments, corresponding to three storage temperature conditions, two onion varieties and eight-week storage duration. The storage temperature conditions were ambient temperature (30±2°C), refrigeration storage (5-7°C) and hot air wooden cabinet storage (45-50°C) while the two onion varieties were white and red types. The prevailing relative humidity during the storage period ranged between 70 and 95%. The result showed that some constituents of the stored onions decreased with increase in the storage period and this particularly occurred in moisture content (86.89-63.76%). Some parameters showed increased values with increase in the storage period and these include ash content (0.98-1.60%), fat content (1.28-1.76%), protein content (1.45-4.75%), crude fibre content (0.96-1.74%), and carbohydrate content (9.05-28.82%). The onion types essentially exhibited diverse responses to these different storage conditions which might be linked to botanical diversity. However, the red onions seem to show greater stability in terms of nutrient retention than the white type while ambient temperature storage conditions may be regarded as the best of the three storage conditions investigated