Wheat bread partially replaced with fermented cowpea flour: optimizing the formulation and storage study at 25 °C

Abstract

Incorporating legume flours, like fermented cowpea flour (FCF), into wheat bread presents an opportunity to enhance protein intake. Fermenting cowpea flour through solid-state methods led to 79 % decrease in phytate levels, a 46 % reduction in tannins, and a 160 % increase in free amino acids. This study further aimed to optimize wheat bread by substituting wheat flour with FCF using a d-optimal mixture design. Varied proportions of wheat flour (66.3–93.7 %), FCF (5–30 %), xanthan gum (0.5–3 %), and lecithin (0.3–1 %) were tested to assess bread qualities such as hardness, color changes in crust and crumb, and specific loaf volume. A special cubic model was fitted to each response. The optimized blend comprised 75.2 % wheat flour, 22.9 % FCF, 1.6 % xanthan gum, and 0.3 % lecithin, scoring a desirability value of 0.63. The corresponding bread crumb hardness was 1981.3 N, and the loaf volume was 1.84 cm³/g. Shelf-life evaluation at 25 °C revealed microbial stability (aerobic mesophile count < 5 log₁₀ cfu/g) of 6 days, with a decline in overall acceptability (9-point scale) ratings from 7.1 to 5.3 after this period. Over time, the bread's crumb experienced increased hardness and retrogradation enthalpy while moisture migration from crumb to crust was observed.