Type II sourdough fermentation as a strategy to improve the nutritional profile of kale-enriched wheat flour wheat flour and semolina flatbreads

This study aimed at investigating the incorporation of freeze-dried kale powder (KP) into wheat and semolina flatbreads and evaluating the impact of Type II sourdough fermentation on their nutritional, sensory, and functional properties. Flatbreads were prepared with 0 %, 5 %, and 10 % KP and subjected to either lactic acid bacteria (LAB) fermentation with Lactiplantibacillus plantarum or baker's leavening yeast used as control. The results show that sourdough fermentation decreased the pH in the doughs, while leading to a significant increase in organic acids and a reduction in free sugars. Exacerbated by sourdough technology, flatbread total phenolic content (TPC) and antioxidant activity were increased because of KP incorporation, while further changes in sulphur compounds metabolites were also promoted. Textural analysis showed decreasing hardness in KP-containing flatbreads when sourdough fermentation was applied. Sensory evaluation highlighted the effect of sourdough fermentation in balancing the bitterness and acidity imparted by KP, which results in an improved overall acceptability. Furthermore, in vitro digestion and fecal fermentation tests demonstrated the positive impact of fermented flatbreads on gut microbiota taxa presence and its relative Short Chain Fatty Acids (SCFA) production. Additionally, we monitored how the combined use of KP and sourdough fermentation improved the shelf-life of flatbreads by preserving texture and limiting moulds growth during 7 days extended storage. In exploring the valorisation of underutilized leafy greens, these findings suggest that KP addition to flatbreads, combined with Type II sourdough fermentation, is a promising strategy to enhance the nutritional profile, sensory attributes, and potential health benefits of traditional flatbreads.