Effect of processing methods on the food value of sweet potato variety ‘Blesbok’

The white fleshed sweet potato cultivar Blesbok is a top selling cultivar, accounting for 80% of national production with yields averaging 45 t/ha when grown commercially. Blesbok is rich in beta carotene (BC), vitamin C, minerals, carbohydrates and proteins. However, preparation and processing methods can denature protein and destroy BC and vitamin C due to temperature variation during processing. The objective of the study was to investigate the effect of preparation and processing methods on the vitamin C of Blesbok sweet potato (BSP) cultivar. Raw Blesbok tubers were divided into unpeeled and peeled samples prior to processing. The experiment was a factorial conducted in triplicates, where factor A were the two preparation methods (unpeeled and peeled) and factor B were the four processing methods (raw, boiling, baking and frying). The raw unpeeled and peeled sweet potatoes served as standards. After processing, vitamin C was determined prior to analysis of variance through SAS software. Relative to the standards, vitamin C increased by 360% in unpeeled baked tubers. However, in the unpeeled boiled and fried tubers, the vitamin C was reduced by 20 and 40%, respectively. In contrast, the peeled tubers when boiled, baked and fried, reduced vitamin C by 98, 97 and 99%, respectively, when compared to standard. Notably, vitamin C was reserved in unpeeled baked tubers. In conclusion, results indicated that interaction of preparation x processing method increased vitamin C in unpeeled baked BSP.