Faba beans (Vicia faba L.) and whole-grain oats (Avena sativa L.) offer a high protein content, are a source of dietary fibre and they can be sustainably produced in the Nordic countries, yet face sensory limitations that restrict their wider use in food. This study aimed to overcome these sensory limitations by soaking the faba bean and whole-grain oats with Lactiplantibacillus plantarum, followed by solid-state fermentation with Rhizopus microsporus to produce tempeh-like products. Volatile organic compounds in uncooked and cooked tempeh were analysed using Headspace Solid-Phase Micro-Extraction (HS-SPME) with Gas Chromatography-Mass Spectrometry (GC-MS). Sensory profiling was combined with texture and moisture measurements from uncooked and cooked tempeh-like products to explore sensory and physicochemical attributes. A hedonic test evaluated overall acceptability of the selected samples. A total of 65 volatile organic compounds were identified and semi-quantified, including 3-methyl-1-butanol, ethanol, 2-butanone, acetic acid, and acetoin. L. plantarum soaking reduced certain volatile organic compounds typically associated with beany off-flavours, while cooking increased certain compounds such as acids and pyrazines, potentially masking off-flavours. The soaking resulted in increased sourness, umami taste, and chewiness, with notable texture variation when whole-grain oats were included compared to only faba bean tempeh. Texture measurements were significantly influenced by L. plantarum soaking, as shown by the panellist. Hedonic testing (n = 107) indicated a higher degree of liking for tempeh made from the faba beans and whole-grain oats mix compared to only faba bean tempeh. These findings emphasise the need to assess how pre-treatments, such as soaking, impact on tempeh-like production.

Tempeh is a fermented soybean food with high nutritional value, culinary versatility, and palatability. Its popularity is rising because it aligns with the trend towards sustainable and healthy plant-based diets. However, consumers have exhibited a strong preference for local ingredients over soy. Faba bean is a promising raw material in Scandinavia due to its high protein, dietary fiber, and phytochemical content. In this study, we evaluated the effects of soaking media (vinegar, water and sodium bicarbonate with or without lactic acid bacteria (LAB)) on boiling time and physicochemical properties of faba bean-based tempeh. We demonstrated that sodium bicarbonate, with and without LAB, significantly reduces the boiling time of faba beans (7–8 min), while beans soaked in vinegar and water with and without LAB require longer boiling times for tempeh production (>16 min). Texture analysis has revealed notable variations among the samples, with statistically significant differences (p < 0.05) observed across the majority of the measured attributes. Our study has demonstrated that faba beans are suitable for tempeh production and expand the sources of possible raw materials. However, further studies are needed to investigate consumers’ preferences and expectations towards faba bean-based tempeh.

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 is increasingly cultivated in Nordic regions due to its nutritional value and agronomic adaptability, but its use is limited by anti-nutritional factor (ANF) content and functional properties. This study evaluated soaking and boiling as treatments to modulate composition and functional properties. Beans were soaked in water, sodium bicarbonate, Lactiplantibacillus plantarum (LAB), or a combination of both, followed by heat treatment as boiling. Microbiology analysis showed that LAB inoculation during soaking lowered pH and maintained microbial safety, potentially influencing the breakdown of ANFs. Protein content ranged from 28 to 37% dry matter (DM). Resistant starch decreased from 12.8% in raw beans to 3.7–6.0% DM after processing, with a corresponding increase in digestible starch. The highest reduction of vicine, convicine, and phytic acid occurred in samples soaked only with L. plantarum and boiled, with decreases of 45.7%, 47.1%, and 71.3%, respectively. Free amino acids in treated samples ranged from 2.9 to 3.6 mg/g DM, and total phenolic content ranged from 1.0 to 1.7 mg GAE/g. Microscopy confirmed that sodium bicarbonate loosened the plant matrix, while LAB softened the cell wall structure. To evaluate functional implications, an unfiltered plant-based beverage model (12% w/v solids) was prepared. LAB-treated beverages exhibited improved low-shear viscosity, higher water-holding capacity, reduced phase separation, and lighter colour compared with other samples. These findings demonstrate that soaking strategy influences not only compositional and structural properties but also techno-functional performance relevant for plant-based beverage applications.