The biotechnological generation of natural aroma compounds is rapidly expanding. Aroma chemicals, such as vanillin, benzaldehyde (bitter almond, cherry) and 4-(R)-decanolide (fruity-fatty) are marketed on a scale of several thousand tons per year. Their possible production by single-step biotransformations, bioconversions and de novo synthesis using microorganisms, plant cells or isolated enzymes is shown. The perspectives of bioprocesses for the oxifunctionalisation of lower terpenes by genetically modified organisms and economic aspects are discussed.

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The formation of a green or beany off-flavor during storage of legume protein extracts limits their application in foods. Pea protein extracts were submitted to lactic acid fermentations to improve the flavor by either reducing off-flavor formation or by masking undesirable green notes. The aroma profiles of untreated pea protein extract (PPE) and fermented pea protein extract (PPEF) were compared to each other and to a commercial whey protein as a benchmark. Kinetic measurements of n-hexanal and n-hexanol formation were used as an indicator for progressing lipid oxidation and storage stability. The nonfermented and fermented pea protein extracts showed a shelf-life comparable to the commercial whey protein reference. Volatiles were identified and quantified using dynamic headspace sampling with subsequent coupled TDS-GC-MS and TDS-GC-olfactometry flavor dilution analysis. A total of 18 odorants with dilution factors equal to or higher than 100 were determined in PPE an d 17 in PPEF. Altogether, 23 highly odor-active compounds were identified according to their mass spectra, odor impressions, linear retention indices, and standard substances in PPE and PPEF, among them n-hexanal, 1-pyrroline, dimethyl trisulfide, 1-octen-3-one, 2,5-dimethyl pyrazine, 3-octen-2-one, -damascenone, and guaiacol. The fermentation considerably amended the aroma profile of pea protein preparations resulting in a reduction or a masking of undesirable flavors

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