Enhancing the functional qualities of soy flour cookies through solid-state fermentation with <i>Streptococcus thermophilus</i>

In the present study, Streptococcus thermophilus was utilized as a starter culture for the solid-state fermentation of soybeans. The fermentation was conducted on soybeans (with and without hull) at 5, 10, and 15 h intervals. The results indicate that the 15 h fermentation significantly reduced antinutritional factors and enhanced nutritional components. Fermented soy flour from both hull (HSF) and dehulled soybeans (DSF) was then used to develop cookies with varying concentrations. The formulations included: control (100% wheat flour), DSF-25 (soy flour 25%; wheat flour 75%), DSF-50 (soy flour 50%, wheat flour 50%), DSF-75 (soy flour 75%, wheat flour 25%), and DSF-100 (soy flour 100%). Blends of fermented soy flour and wheat flour were analyzed for functional properties, which were influenced by increasing soy flour concentration. Key findings included a decrease in moisture content with higher soy flour concentrations, the highest water and oil absorption capacities in DSF-100 (239.6%), and the lowest in DSF-50 (123.63%). The weight and thickness of the cookies decreased as soy flour concentration increased. Textural analysis revealed increased hardness in DSF-25, DSF-50, and DSF-75, but decreased hardness in DSF-100 due to the high soy flour concentration. Sensory analysis showed the highest acceptability for DSF-25 and DSF-50 cookies, while DSF-100 cookies were less preferred. This study demonstrated the potential of using Streptococcus thermophilus for solid-state fermentation of soybeans to enhance their nutritional profile and reduce antinutritional factors. It provides insights into developing nutritionally and phenolic-enriched baked products, catering to consumer demand for functional foods with added health benefits.