Lupines and faba beans are promising ingredients for the beverage industry. They contain high amounts of protein and can be grown in different climate zones and agricultural areas. Therefore, these legumes appear as ideal raw material for vegan, functional, and sustainable beverages. Nevertheless, the sensory characteristic of legumes is generally not accepted in beverages. Therefore, the market contribution of legume-based beverages is currently only marginal. This review highlights known major flavor aspects of lupines and faba beans and the possibilities to improve these by germination, heat treatment, enzymatic treatment, and subsequent lactic acid fermentation. First, the main aroma and taste compounds are described. Thereby, the "beany" aroma is identified as the most relevant offflavor. Second, the nutrients and antinutrients of these legumes regarding to their use as food and as substrate for lactic acid fermentation are reviewed, and possibilities to modulate the substrate are summarized. Finally, the modification of the sensory profile by lactic acid fermentation is outlined. To conclude, it seems likely that the nutritional and flavor attributes in legume-based beverages can be improved by a combined process of substrate modulation and fermentation. In a first step, antinutrients should be decomposed and proteins solubilized while transforming the solid grains into a liquid substrate. Due to such substrate modulation, a broader variety of strains could be employed and the fermentation could be based exclusively on their impact on the flavor. By applying the concept of combining a substrate modulation with a subsequent fermentation, the use of legumes in beverages could be facilitated and new products like vegan, protein-rich, refreshing beverages could be marketed.

Lupines and faba beans are protein-rich legumes, which can be utilized as a plant-based substitute for animal proteins in human nutrition in general and in the beverage industry in particular. However, their application is hampered by low protein solubility in the acidic pH range and by antinutrients such as flatulence-causing "raffinose family oligosaccharides" (RFOs). Germination is known in the brewing industry for increasing enzymatic activities and mobilizing storage compounds. Therefore, germinations of lupines and faba beans were performed at different temperatures, and their impact on protein solubility, the concentration of free amino acids, and degradation of RFOs, alkaloids, and phytic acid was evaluated. In general, changes were comparable for both legumes but less pronounced in faba beans. Germination depleted the RFOs entirely in both legumes. The protein size distribution was found to be shifted toward smaller fractions, the concentrations of free amino acids multiplied, and protein solubility increased. No substantial reductions in the binding capacity of phytic acid toward iron ions were observed, but a release of free phosphate in lupines was detected. The results prove that germination is an applicable process for refining lupines and faba beans for use not only in refreshing beverages or milk alternatives but also in other food applications.

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