Provitamin A Crops: Acceptability, Bioavailability, Efficacy and Effectiveness

Vitamin A deficiency (VAD) is the world’s commonest cause of childhood blindness. More than half of these cases occur in developing countries. Animal sourced foods though good sources of vitamin A are too expensive for poor rural people. Crops biofortified with provitamin A offer a convenient and accessible source of vitamin A. The other micro-nutrient programs of fortification and supplementation require more expensive inputs. Biofortification programs have developed crops that are rich in provitamin A. These crops include: maize, golden rice, cassava and orange fleshed sweetpotato (OFSP). With exception of golden rice, the rest of the biofortified crops have received considerable acceptance among the communities. Both animal and human studies have shown that provitamin A from biofortified crops is highly bioavailable and have capacity to improve vitamin A status. After several years of research and promotion, it is time to fully commercialize provitamin A crops by encouraging farmers to start their large scale production and consumption.

Potential Use of Selected Sweetpotato (<i>Ipomea batatas</i>Lam) Varieties as Defined by Chemical and Flour Pasting Characteristics

Chemical and functional properties of ten sweetpotato varieties were investigated. The sweetpotato were of various flesh colours which included orange, yellow, cream and white with dry matter content ranging from 30.2% - 39.2%. The sweetpotato varieties varied significantly (p < 0.05) in total amylase activity, total starch and amylose content whose value ranges were 0.256 - 0.570 mg/ml/min 68.4% - 73.6%, 16.2% - 23.4% respectively. The pH of flours from the different sweetpotato varieties ranged from 6.01 - 6.64. The pasting behaviours of the sweetpotato flours also showed significant differences (p < 0.05) in the individual parameters (peak time, pasting temperature, peak viscosity, trough viscosity, final viscosity, breakdown and setback) among the different varieties. The results revealed the influence of variety on the chemical composition of sweetpotato and their pasting properties. Correlations were also revealed among different components of the sweetpotatoes which would be a basis in selection of the varieties for processing into different products.

Amylolytic Activity in Selected Sweetpotato(Ipomoea batatas Lam)Varieties during Development and in Storage

Sweetpotato varieties (five) were investigated for changes in α- and β-amylase activities during root development and on subjection of harvested roots to different postharvest handling and storage conditions. Changes in α- and β-amylase activities in development were monitored from 10 weeks after planting. At physiological maturity, sweetpotato roots were harvested and subjected to various conditions: freshly harvested roots and cured roots (spread under the sun for four days at 29℃ - 31℃ and 63% - 65% relative humidity), stored at ambient conditions (23℃ - 26℃ and 70% - 80% relative humidity) and in a semi-underground pit (19℃ - 21℃ and 90% - 95% relative humidity). Generally α- and β-amylase activities increased during development with NASPOT 9 and 10 consistently registering the highest activities and NASPOT 1 the lowest activity. Generally, maximum α-amylase activities were achieved at week 3 in ambient stores for NASPOT 9 and NASPOT 10 at 0.930 and 0.897 CU/g, respectively. Maximum β-amylase activity was achieved in ambient stores at week 3 and 4 for fresh and cured NASPOT 9 at 806 and 782 BU/g, respectively. Generally, curing and storing sweetpotatoes in ambient conditions registered the highest amylase activity. Maximum α- and β-amylase activities were registered at 67℃ - 68℃ and 58℃ - 60℃, respectively. These findings provide information for controlled modification of amylase activities of these sweetpotato varieties for product development efforts and monitoring the shelf life of the roots during storage.

Effect of Salt on the Sensory and Keeping Quality of Orange Fleshed Sweetpotato Crisps

The study was carried out to determine the effect of salt on the sensory, nutritive and keeping quality of OFSP crisps. Crisps were made by deep frying slices of approximately 3.5 mm thickness treated with, 2% and 4% table salt. A control with no salt treatment was prepared alongside the treated ones. Two varieties of OFSP;Ejumula and Kakamega were used in the study. After deep frying, the crisps were cooled to room temperature, packed in paper-lined high density polythene pouches and stored in a dark cupboard at room temperature for three months. During the storage period, the crisps were analyzed for proteins, fat and carotenoid content. Changes in sensory attributes were analyzed using a semi-trained panel. Results indicated that freshly prepared crisps treated with 2% salt had the highest acceptability mean scores for all attributes while there was no significant difference (p > 0.05) between crisps made from either Ejumula or Kakamega variety. Carotenoid content decreased with increase in salt concentration in both OFSP varieties. Shelf-life studies showed that the decline in sensory attributes started after 2 months of storage. The study shows that OFSP crisps treated with 2% salt are more acceptable and reasonably stable during storage.