Characterization of cheesy odor formed during fermentation of soy drink with Agrocybe aegerita.

The market for plant protein-based substitutes for cheeses is growing, but the sensory properties are distinctively different from the original products. Hence, natural and vegan cheesy flavors are needed to aromatize the products. A cheesy, sweaty and parmesan-like aroma was produced by fermentation of soy drink with Agrocybe aegerita. Aroma dilution analysis revealed short-chain fatty acids (SCFAs) as main influencing cheesy odorants analyzed by gas chromatography-mass spectrometry-olfactometry. In comparison to the five cheese varieties, the SCFA profile of the fermented soy drink revealed similarities with Parmesan and Emmental cheese. Meanwhile, principal component analysis showed an approximation of the aroma profile after fermentation with A. aegerita to those of cheeses. 3-Methylbutanoic acid was synthesized from the protein fraction, while the oil fraction contributed to the formation of unbranched SCFAs like butanoic acid. Accordingly, the production of these compounds can be increased by addition of the fractions.

Reduction of aldehydes with green odor in soy products during fermentation with Lycoperdon pyriforme and analysis of their degradation products.

Soy products are rejected by Western consumers because of their green and beany off-aroma. The off-aroma profiles of typical soy products (soy drink and soy protein isolate) were analyzed and forty-five regions imparting green and beany odor impressions were perceived after application of direct immersion-stir bar sorptive extraction coupled with gas chromatography-mass spectrometry-olfactometry. After a fermentation of 28 h with Lycoperdon pyriforme the intensity of the off-aroma was reduced. Accordingly, thirteen and fourteen of the thirty-five quantified compounds were significantly decreased after fermentation of soy drink and soy protein isolate, respectively. The major off-aroma contributors, aldehydes, were reduced during fermentation and their degradation products were analyzed. The following bio-pathways were suggested (i) saturated aldehydes were reduced to the corresponding alcohols with increased odor threshold, leading to less intense sensorial perception, and (ii) di-unsaturated aldehydes did not form any odor-active substance in the volatile spectrum. Both of the phenomena explained the decreased sensorial perception of the off-aroma.