Changes in the nutritional profile, anti-nutrients, microstructure, and in vitro digestibility of faba bean–oat tempeh during pre-treatment and fermentation

We explored how fermentation can enhance the nutritional value of faba bean and oats from Sweden. The effects of pre-treatments (soaking with Lactiplantibacillus plantarum and boiling) and subsequent solid-state fermentation (SSF) with Rhizopus oryzae on the nutritional and anti-nutritional profiles of tempeh produced from faba bean and oats were studied. Raw materials, pre-treated, and fermented products, were analysed for macronutrients, dietary fiber, anti-nutrients, and in vitro digestibility (INFOGEST) to explore the degree of protein and starch hydrolysis. Tempeh products significantly increased crude protein content and dietary fiber and resulted in a significant high increase in free amino acids compared to raw and pre-treated samples, while reducing anti-nutritional factors compared to raw materials. Fermentation enhanced in vitro protein digestibility and decreased starch degradation, as reflected by the reduced glucose and maltose release compared to pre-treated samples. Microstructural analysis revealed that the disruption of individual cell structures was pivotal to improving macronutrient bioaccessibility. • Faba bean-oat tempeh has the highest degree of protein hydrolysis. • Phytic acid, vicine and convicine were reduced by over 80% due to fermentation. • Micrographs show cell wall disruption and nutrient release in tempeh-like samples. • Rhizopus oryzae hyphae remained intact post in vitro digestion. • LAB soaking pre-treatment in combination with fermentation improve the faba-oat profile.