Effects of pre-treatments on chemical composition of sweet potato flour using different drying methods

Sweet potato (Ipomoea batatas, Convolvulaceae), a perennial crop grown in tropical and subtropical lowland agro-ecologies, is a high-energy crop with more edible energy per hectare per day than cereals. Despite its high carbohydrate content, sweet potatoes have a low glycemic index, making them suitable for diabetics and obese people. The goal of this study was to see how pre-treatment and drying methods affected the chemical composition of sweet potato flour. Four pre-treatment methods (soaking in water, TR1; blanching, TR2; calcium chloride solution, TR3 and pre-drying at 60 °C for 30 minutes, TR4 along with the control, TR5) and three drying methods (sun drying, DR1 oven drying, DR2 and microwave drying, DR3) were employed in the preparation of flour from three varieties of sweet potato (Dergaon red, Shree Bhadra and ST-14). All the pre-treatment methods and the drying methods were found to affect significantly. Orange fleshed variety; ST-4 was found nutritionally superior over the other two. All the pre-treatments caused significant reduction in the nutritional parameters compared to control with TR4 being the worst. Sun drying was found better in maximum retention of crude protein, crude fat, starch and amylose over the other two. Microwave drying was found better for crude fibre and ash content. Being orange fleshed, ST-14 had the highest β-carotene content and sun drying was found as the best. The interactive effect of variety, pre-treatment and drying method was found to have a significant effect in all the attributes of sweet potato flour.