Exploring tarhana's prebiotic potential using different flours in an <i>in vitro</i> fermentation model

Tarhana, a traditional fermented food important to Turkish and Central Asian cuisines, is known for its unique composition of yoghurt, flour, vegetables, and herbs, and its potential health benefits through fermentation. The aim of this study was to evaluate tarhana's potential prebiotic and postbiotic properties using an <i>in vitro</i> colonic fermentation model. We explored how ingredient variations, particularly flour types and fermentation methods, influence gut microbial diversity and metabolite production. Tarhana was prepared using wheat, chickpea, einkorn, and purple potato flours, fermented with baker's yeast (<i>Saccharomyces cerevisiae</i>) or chickpea sourdough. Gut microbial composition and levels of short-chain fatty acids (SCFAs) and branched-chain fatty acids (BCFAs) were analysed following <i>in vitro</i> colonic fermentation. Flour type and fermentation method significantly influenced gut microbial composition and metabolite production. Sourdough-fermented tarhana made with purple potato (<i>q</i> = 1.23 × 10^-7), chickpea (<i>q</i> = 1.23 × 10^-7), and einkorn (<i>q</i> = 2.51 × 10^-7) flours reduced <i>Veillonella</i> levels compared to baker's yeast variants. Sourdough purple potato tarhana also decreased <i>Escherichia</i>-<i>Shigella</i> levels in faecal samples, which were higher in baker's yeast-fermented faecal samples (<i>q</i> = 0.003). SCFA levels, particularly acetate and propionate, were higher in chickpea and purple potato tarhana fermented faecal samples, with sourdough variants showing the strongest effects. <i>Bifidobacterium</i> abundance increased in einkorn sourdough tarhana, while chickpea flour tarhana slightly increased isobutyrate levels. This study demonstrates that specific flour types combined with sourdough fermentation enhance tarhana's functional properties by promoting beneficial microbial shifts and increasing SCFA production. These findings suggest tarhana's potential as a personalized functional food to support gut health, warranting further validation through clinical trials.