Mechanistic insights into the impact of ferulic acid on starch digestibility and structural properties.

This study investigated how phenolic acids modulate starch hydrolysis and functionality. Feruloyl esterase-producing Lactiplantibacillus plantarum and Saccharomyces cerevisiae Ah4 were applied in rye sourdough fermentation, enhancing total phenolic content (+57.3%), antioxidant capacity, and resistant starch (+16.2%), while reducing starch digestibility and predicted glycemic index (-21.2%), compared with commercial yeast fermentation. The ferulic acid (FA) content in sourdough reached up to 165.00 μg/g (dry basis). To elucidate the underlying mechanism, a rye starch-lactic acid bacteria fermentation model supplemented with FA was employed. Moderate FA (2-5%) promoted resistant starch formation (up to 75%) and increased crystallinity, whereas 10% FA induced antimicrobial stress and disrupted granule structure. Pasting analysis showed that FA addition, particularly at supraphysiological concentrations (5-10%), significantly decreased peak viscosities, indicating restricted granule swelling. Overall, these findings demonstrate that fermentation modulated starch structure and improved its nutritional functionality by introduction of phenolic acids.