Valorization of Spent Millet Flour in Composite Bread: Characterization, Predictive Modeling, and Multi-Objective...

Area of Science:

• Food Science and Technology
• Nutritional Biochemistry
• Agricultural By-product Valorization

Background:

• Traditional pito beverage processing generates significant spent millet flour (SMF) by-product.
• Valorization of SMF offers a sustainable approach to reduce food waste and enhance food products.
• Millet proteins and fibers undergo modifications during fermentation, potentially altering their functional properties.

Purpose of the Study:

• To investigate the potential of incorporating SMF into composite bread formulations.
• To determine the optimal SMF substitution level for bread production using Response Surface Methodology (RSM).
• To evaluate the impact of SMF on bread's nutritional composition, quality attributes, and consumer acceptability.

Main Methods:

• SMF preparation involved oven-drying, milling, and sieving to a standardized particle size.
• RSM was used to model and optimize twelve bread quality responses based on SMF substitution levels (10%, 20%, 30%).
• Nutritional analysis, physical dough evaluation, bread quality assessments, and sensory analysis were conducted.

Main Results:

• SMF exhibited higher crude protein, crude fiber, and ash content than wheat flour, with increased water absorption capacity.
• Optimized models showed high predictive accuracy (R²=0.912-0.988) for bread quality responses.
• A 14.2% SMF substitution level was identified as optimal, yielding a 9.8% protein increase and 68.4% fiber increase, with good consumer acceptability (7.21/9.0).
• Increased SMF substitution led to reduced loaf volume, attributed to gluten dilution and physical disruption by bran particles.

Conclusions:

• SMF is a valuable ingredient for enhancing the nutritional profile of composite bread.
• RSM provides an effective framework for optimizing composite bread formulations with by-product ingredients.
• The study demonstrates a trade-off between nutritional enhancement and structural bread quality, with fiber content being a key factor influencing volume reduction.
• The developed RSM optimization methodology is applicable to other fermented cereal by-product systems in sub-Saharan Africa.