The modification of volatile and nonvolatile compounds in lupines and faba beans by substrate modulation and lactic acid fermentation to facilitate their use for legume‐based beverages—A review

Abstract

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.

Fermentation Conditions Affect the Synthesis of Volatile Compounds, Dextran, and Organic Acids by Weissella confusa A16 in Faba Bean Protein Concentrate

“…On the other hand, the levels of hexanal, 3-methyl-1-butanol, 2-hexenal, nonanal, 1-pentanol, pentanal, hexane, and octane decreased with increasing fermentation time and temperature. Hexanal, a product of oxidation of linoleic acid, is frequently referred to in the literature as a major contributor to the beany flavor of pulses [ 13 ]. Its levels notably decreased during fermentation, thus confirming previous findings that hexanal is reduced during fermentation by lactic acid bacteria [ 32 ].…”

“…Its levels notably decreased during fermentation, thus confirming previous findings that hexanal is reduced during fermentation by lactic acid bacteria [ 32 ]. The degradation pathway of hexanal by lactic acid bacteria is still unclear [ 13 ]. Our results support the theory that the degradation of hexanal by lactic acid bacteria would yield hexanoic acid ethyl ester as a secondary product [ 13 ].…”

“…The degradation pathway of hexanal by lactic acid bacteria is still unclear [ 13 ]. Our results support the theory that the degradation of hexanal by lactic acid bacteria would yield hexanoic acid ethyl ester as a secondary product [ 13 ]. When studying the effect of germination on the volatile profile of faba bean, the levels of hexanal and nonanal decreased until 48 h, but notably increased afterward [ 44 ].…”

“…This and other compounds (e.g., hexanal, octanal, nonanal, 1-octen-3-ol, octanol) are very common in different protein-rich materials [ 10 ] and are often associated with beany, earthy, and grass odors [ 12 ]. The combination of several volatile compounds is known to result in an overall beany odor [ 13 , 14 ].…”

“…Moreover, alterations to the sensory profile caused by fermentation are dependent on both the substrate and the strain [ 13 ]. Therefore, understanding the metabolism of the selected starter culture on a specific food matrix, as affected by fermentation conditions, is also important.…”