A study on the use of sorrel seed flour (Hibiscus sabdariffa) for improving functionality of wheat flour bread

Abstract

Bread presents one of the easiest opportunities as a food vehicle for delivery of nutritional and health-promoting benefits to large segments of the world population. However, its low nutritional status due to lack of balance of essential amino acids and inadequate macro- and micronutrients has necessitated recent interest in the development of high-protein hybrid breads (HPHB). Sorrel seed, an underutilized, neglected protein-rich seed holds promising nutritional and antioxidant potentials as source of good quality protein, dietary fibre and bioactive compounds. Furthermore, germination of plant seeds increases the bioavailability of these nutritional and bioactive compounds. Hence, this study has investigated the influence of germination time on nutritional, and functional properties of sorrel seed flour. Further, the amino acid profile, dietary fibre and rheological functionality of wheat-germinated defatted sorrel seed bread were assessed. The sorrel seed was germinated for 24–48 h and defatted. Thereafter, the germinated defatted sorrel seed flours were used to partially replace wheat flour using a linear replacement (w/w) of 95-80% wheat (W) and 5–20% germinated defatted sorrel seed (GS) flours to obtain W95:GS5; W90:GS10, W85:GS15 and W80:GS20. These composite flours and 100% wheat flour (control) were used to produce breads using standard recipe and methods. Results showed significant increase (P < 0.05) in crude protein, dietary fibre and mineral contents after 24 and 48 h germination of sorrel seed. While 24 h germination significantly (P < 0.05) increased WAC from 93.75% to 103.13%, further germination (48 h) caused a reduction of 26.67% (from 93.75 to 68.75%). In vitro protein digestibility of wheat flour decreased significantly (P < 0.05) as supplementation of germinated defatted sorrel seed flour increased. Supplementation of wheat flour with germinated defatted sorrel seed flour in bread production resulted in 51.84–121.42% significant (p < 0.05) increase in the protein content of wheat bread. Similarly, total essential amino acids, dietary fibre, mineral, and ash contents followed the same increasing trend. The in-vivo biological value which ranged from 82.10 to 89.40% was significantly higher (p < 0.05) than 58.30% obtained for the control (100% wheat bread) Thus, inclusion of germinated defatted sorrel seed flour in bread production may serve as a low-cost nutritional supplement for enhancing the nutritional profile and functional benefits of wheat bread.