Physico-chemical properties of sandwich bread formulated with sweet potato–yeast blends

Abstract

Consumer demand for nutritious and healthy goods made from plant-based functional foods is expanding. This study replaced a portion of the wheat flour in sandwich bread recipes with a mixture of white-fleshed sweet potato (WFSP) and orange-fleshed sweet potato (OFSP), ranging from 10% to 25%, based on five sandwich bread recipes. A Box-Behnken Design model was created with three factors: WFSP (5-10%), OFSP (10-15%), and instant dry yeast (0.3-0.5%). Response Surface Methodology was used to optimize input variables for the optimal expansion volume and β-carotene content in sandwich bread processing. Among the five developed formulations, formula A3, replacing 20% of the sweet potato flour mixture (7.5% WFSP, 12.5% OFSP, 80% wheat flour), was selected due to its favorable textural features and higher levels of fiber, resistant starch, total polyphenol content, and β-carotene content (3.56%, 3.59%, 12.87 mg GAE/g, and 17.21 μg/g, respectively) compared to the control sample A0. Furthermore, the optimal conditions for producing sandwich bread with WFSP, OFSP, and instant dry yeast were identified as 10%, 15%, and 0.5%, respectively. Under these conditions, the bread expanded by 5.63 times and contained 24.13 μg/g of β-carotene. The findings demonstrate the potential for incorporating WFSP and OFSP in sandwich bread manufacturing. The effective utilization of low-cost sweet potato raw materials not only enhances the nutritional and functional value of the product by adding natural colors but also reduces reliance on imported raw materials, thereby supporting the long-term development of the country's sweet potato value chain.