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Physicochemical, functional, and nutritional properties of processed purple-fleshed sweet potato (Ipomoea batatas Lam.)
Dissertation Abstract:
The physicochemical, functional and nutritional properties of purple-fleshed sweet potato (PSP) as affected by different pre-drying and drying conditions and its utilization in candies, muffins, and breadswere studied.
Among the four PSP varieties that were screened, Haponita had the highest dry matter (39.14%), iron (19.13 mg/100 g), and zinc (0.80 mg/100 g) contents; and antioxidant activity (74.22%). This was chosen as the best variety.
The different pre-drying treatments and drying temperatures and drying time significantly affected the physicochemical, functional, and nutritional properties of PSP. Steaming process increased the antioxidant activity of raw PSP by 28.56 percent and produced purple sweet potato flour (PSPF) with intense color attributes, higher TSS, WAI, WSI, SWC, and antioxidant activity compared with other pre-drying treatments.
Drying of steamed PSP at 60oC for nine and 11 hours and at 70oC for seven hours produced steamed PSPFs with better physicochemical and functional properties, antioxidant activity, and phytochemical components. A minimum of 40 percent PSPF substitution in candies, 40–50 percent in muffins, and 20–30 percent in bread greatly improved its qualities and its corresponding acceptability to the panelists.
The chemical composition of PSP generally decreased after processing into flour and utilization in candies, muffins, and breads. In terms of nutrient contribution, raw PSP and steamed PSPF are good sources of energy, iron, and zinc. PSPF-substituted candies are good sources of energy while muffins and breads are potential sources of energy, protein, and iron. Wheat flour-based products like muffins and breads can still be considered as high sources of energy, protein, and iron even when substituted with steamed PSPF.