Effect of orange-fleshed sweet potato flour particle size and degree of wheat flour substitution on physical, nutritional, textural and sensory properties of cookies

Abstract

Orange-fleshed sweet potato (OFSP) flour is rich in health-promoting compounds that can improve the nutritional benefits of baked products when blended with wheat flour. However, the flour particle size and blend proportion may affect the quality properties and consumer acceptability of bakery products. This study investigated the effect of flour particle sizes and blend proportions on the physical, nutritional, textural and sensory properties of peeled and unpeeled OFSP composite flour cookies. Peeled and unpeeled OFSP flours (≤ 250 μm and ≤ 500 μm particle size) were produced, and each was used to replace soft wheat flour at the rate of 0 to 100% for cookies formulation. The results obtained showed that substitution of wheat flour with OFSP flours significantly (p < 0.05) decreased cookies baking loss, thickness, volume, crust lightness (L*) but increased diameter, spread ratio, crust redness, yellowness, contents of ß-carotene, vitamin A, ascorbic acid, total phenolics and flavonoids, and the antioxidant capacity. The hardness and fracturability of the OFSP-based cookies ranged between 1.389 and 10.142 kg and 0.873 and 9.431 kg, respectively, whereas the values of the control cookies were 1.281 ± 0.003 kg and 1.274 ± 0.003 kg, respectively. The effect of flour particle size on the physical and nutritional properties of cookies was insignificant (p > 0.05). However, the ≤ 250 μm particle size flour cookies had higher overall acceptability than the ≤ 500 μm particle size flour cookies. The unpeeled OFSP composite cookies had higher bioactive compounds concentrations except for ascorbic acid but had lower overall acceptability than the peeled OFSP cookies. Generally, the 30% peeled OFSP composite flour cookies had the highest consumer acceptability.