Nutritional Value and Antioxidant Capacity of Mexican Varieties of Sweet Potato (Ipomoea batatas L.) and Physicochemical and Sensory Properties of Extrudates

The objective of the study was to perform a nutritional analysis and antioxidant capacity of three varieties of sweet potatoes, Ipomoea batatas L., from Mexico, classified by color as: purple, yellow and white. In addition, sweet potato extrudates were produced and evaluated for their nutritional, antioxidant, sensory and texture properties. The average content of macronutrients for the three varieties was 77.92 g of carbohydrate, 10.51 g of dietary fiber, 8.25 g of protein, and 0.53 g of lipid per 100 g tuber on a dry matter (DM) basis. The purple variety exhibited the highest content of fiber as well as zinc and sodium, and the white one displayed the highest content of protein. In turn, contents of calcium, iron, and magnesium were the highest in yellow potatoes. Ascorbic acid content ranged from 60.6 to 106.0 mg/100 g DM, being higher in the yellow potatoes, and the total phenolic content ranged from 216 to 581 mg GAE/100 g DM, being higher in the purple potatoes. The average antioxidant capacity was 40.7 and 23.4 μmol TE/g DM in DPPH and ABTS assays. A lower total phenolic content and antioxidant capacity of extruded sweet potatoes were found with respect to the fresh ones. Among the extrudates, the purple ones had the highest total phenolic content (307 mg GAE/100 g DM) and exhibited the highest antiradical activity in the ABTS assay (15.5 µmol TE/g DM). They were also scored the highest in the sensory analysis, although the instrumental texture analysis showed their greater hardness (64.4 N) compared to the yellow and white extrudates (46.9 and 30.5 N, respectively). Extrudates of the three potato varieties exhibited a sweet taste and, thus, can be considered as sweetener substitutes in snacks with increased nutritional and bioactive potential.