Incorporating whole soybean pulp into wheat flour for nutrient-enriched steamed bread: Exploring the impact on physical and nutritional characteristics.

ABSTRACT

This research explored the impact of incorporating various levels of whole soybean pulp (WSP) (10%, 20%, 30%, 40%, and 50%) into wheat flour on the physical and nutritional qualities of steamed bread. In comparison with the traditional steamed bread, the substitution of up to 20% WSP did not significantly alter the specific volume, hardness, and chewiness of the steamed bread. Additionally, the crumb texture of the steamed bread with 20% WSP maintained small and uniform pores, with optimal springiness and cohesiveness. Nutritionally, the substitution of 10%-50% WSP enhanced total dietary fiber, total phenolics, and protein by 9.40%-89.79%, 14.96%-116.31%, and 3.45%-34.36%, respectively. Isoflavones in the steamed bread increased markedly from 22.92 µg/g to a range of 140.12-997.12 µg/g. The expected glycemic index showed a decrease from 90.24 to between 85.85 and 70.75, whereas amino acid scores improved from 59.22 to a range of 64.58-65.08, with lysine (Lys) scores notably increasing from 59.22 to between 64.96 and 88.80. In conclusion, partially replacing wheat flour with WSP is an effective method for enhancing the nutritional profile and addressing the essential amino acid imbalance in steamed bread. PRACTICAL APPLICATION This study partially replaced flour with WSP to improve the steamed bread's nutritional quality. The optimal substitution level was determined to be 20% WSP, which improves the bread's nutritional value without significantly impacting its physical qualities. Furthermore, WSP is produced from soaked soybeans through hot water milling. This process simplifies soybean processing, lowers energy consumption and costs, and reduces pollution. It also effectively retains essential nutrients, such as protein, dietary fiber, polyphenols, and soy isoflavones, ensuring the full utilization of soybeans.