Impact of kilning on the fermentability of oat wholemeal flour and related bioconversion of starch, protein, dietary fibre, and phytate

Considering the nutritional profile of whole oats and the potential health-enhancing effect of fermentation, oat fermentation offers significant potential for developing nutritious foods. However, fermenting oat wholemeal flour, in particular with lactic acid bacteria, proves challenging. We hypothesise this to be related to the kilning step, a heat-treatment typically applied to intact oat groats, which inactivates oat endogenous enzymes, enhancing stability against lipid oxidation and rancidity. However, kilning may also limit enzyme-induced biochemical changes of the food matrix and the enzymatic release of fermentable substrates during fermentation, thereby potentially impeding microbial growth and acidification. To investigate this, oat wholemeal flour suspensions derived from kilned and non-kilned oat groats were fermented for maximum 24h using a strain of Lactiplantibacillus plantarum as a starter culture. The ferments were comparatively evaluated microbiologically ( i.e. , microbial growth and starter culture prevalence) and biochemically ( i.e., acidification, metabolite content, soluble fibre content, soluble protein content, and phytate reduction) over time. Fermentation proceeded faster in non-kilned oat wholemeal flour suspensions, resulting in more rapid acidification and more pronounced biochemical changes than in kilned suspensions. These results highlight the importance of active oat endogenous enzymes to provide nutrients for the fermenting lactic acid bacteria and to achieve desired biochemical changes of the matrix during oat fermentation. • Lactiplantibacillus plantarum Vega Boost LP acidifies and grows much faster in non-kilned than in kilned oat wholemeal flour suspensions. • Kilning reduces oat enzyme activities, limiting molecular changes in oat constituents during fermentation. • Activity of oat enzymes is crucial for generating nutrients for the fermenting bacteria.