CURING AND HOUSEHOLD-LEVEL STORAGE METHODS AND THEIR EFFECT ON THE SHELF LIFE OF TWO ORANGE-FLESHED SWEETPOTATO [Ipomoea batatas (L) Lam] CULTIVARS

Abstract

Orange-fleshed sweetpotato (OFSP) is an important root crop capable of ameliorating vitamin A deficiency that is a public health concern in Sub Saharan Africa. However, most of the OFSP cultivars have relatively short shelf life largely due to improper pre-and post-harvest management. This study investigated the effect of two curing (field-piled and in-ground) and two household-level storage (sand box and heap) methods on the shelf life of two OFSP cultivars (Apomuden and Nane) in two successive years. The indicators for shelf life were: wound healing ability, physical and compositional root quality indices, sensory attributes and length of storage. The OFSP cultivars were either cured in-ground/dehaulming; by removing part of vines and leaving 30 cm of it from the base and allowing to cure in-ground for seven days prior to harvest or field-piled cured for seven days by covering harvested roots with fresh sweetpotato vines on the field. To create wounds, 21 roots from the two cultivar either in-ground or field-piled cured were deliberately given three wounds each using a potato peeler. The wound healing ability score was given based on the scale: 0=no lignification, 0.5=patchy lignification and 1=complete lignification. Freshly harvested roots (uncured) together with roots that were cured for seven days from the two curing treatments were stored in either sand box or under moistened straw heap. A hedonic scale ranging 1=extremely dislike to 5=extremely like was used for the sensory evaluation of the boiled roots after storage in either sand box or heap. General appearance, finger-feel firmness, sweetness and overall acceptability were the sensory qualities assessed. Generally, wound healing ability of cultivars increased as curing progressed until the fifth day and levelled off. Apomuden consistently recorded significantly higher (p < 0.05) weight loss and rots than Nane. Roots stored in the sand box were significantly lower (p < 0.05) in all physical root qualities except for sprouts. The β-carotene content of Apomuden and Nane respectively ranged from 13.80 to 28.29 mg/100 g and 11.33 to 17.20 mg/100 g in both years. Curing did not have a significant (p = 0.352) influence on the β-carotene content of roots except for the second year where field –piled cured and stored roots had a significantly high (24.96 mg/100 g; p = 0.007) β-carotene content compared with stored roots from the dehaulmed (22.26 mg/100 g) and uncured (21.01 mg/100 g) treatments. The sand box and the heap storage methods respectively resulted in 10% and 19% decline in β-carotene after 2 months of storage. This indicates that, β-carotene retention is better in the sand box relative to the heap storage. All sensory attributes investigated in both years, had scores ranging from 3.20 to 3.93 indicating a good consumer preference for both cultivars. Storage type showed no significant difference (p > 0.05) in all sensory attributes in both years. Both cultivars showed good wound healing ability and could store well. Field-piled or in-ground curing could be done for a minimum of 5 days as wound healing would have been completed. The sand box storage method showed better retention of β-carotene and consumer acceptability after 2 months of storage. Sand box storage improved the storage properties of up to 2 months and should be encouraged for adoption by farmers in Ghana and the sub region.