Formation of a Meat-Like Flavor by Submerged Cultivated Laetiporus montanus.

Basidiomycota are natural sources of aroma compounds. When grown in submerged cultures, the fungus Laetiporus montanus (LMO) forms a spicy and meat-like aroma. It thus represents an interesting candidate for the production of natural savory flavors. To identify the key aroma compounds of LMO grown submerged in malt extract peptone medium, the volatiles were isolated by means of automated solvent assisted flavor evaporation (aSAFE). An aroma extract dilution analysis was performed by means of gas chromatography-olfactometry coupled with a flame ionization detector (GC-FID-O). In the aSAFE extract of LMO, 24 aroma-active compounds were detected. 5-Butyl-2(5H)-furanone (FD 4096), perceived as coconut-like, was determined as the compound with the highest FD factor. (E,E)-2,4-Decadienal, (E,Z)-2,4-decadienal, and sotolon were identified as responsible key compounds for the spicy odor of the submerged cultures. Moreover, supplementation of the cultures of LMO, Laetiporus sulphureus, and Laetiporus persicinus with 13C-labeled thiamine hydrochloride resulted in the formation of 2-methyl-3-(methylthio)furan (MMTF), a compound with a pronounced meaty flavor. The concentrations of MMTF were further increased to 19-27 µg L-1 by additional supplementation of the cultures with ascorbic acid. The results of this study indicate potential for the biotechnological production of a meat-like flavor by Laetiporus species.

Biotechnological Production and Sensory Evaluation of ω1-Unsaturated Aldehydes.

Lipid extracts of the fungus Flammulina velutipes were found to contain various scarce fatty acids including dodec-11-enoic acid and di- and tri-unsaturated C16 isomers. A biotechnological approach using a heterologously expressed carboxylic acid reductase was developed to transform the fatty acids into the respective aldehydes, yielding inter alia dodec-11-enal. Supplementation studies gave insights into the fungal biosynthesis of this rarely occurring acid and suggested a terminal desaturation of lauric acid being responsible for its formation. A systematic structure-odor relationship assessment of terminally unsaturated aldehydes (C7-C13) revealed odor thresholds in the range of 0.24-22 µg/L in aqueous solution and 0.039-29 ng/L in air. In both cases, non-8-enal was identified as the most potent compound. All aldehydes exhibited green odor qualities. Short-chained substances were additionally associated with grassy, melon-, and cucumber-like notes, while longer-chained homologs smelled soapy and coriander leaf-like with partly herbaceous nuances. Dodec-11-enal turned out to be of highly pleasant scent without off-notes.