Brettanomyces bruxellensis Aroma-Active Compounds Determined by SPME GC-MS Olfactory Analysis

Abstract

A survey of 95 Brettanomyces strains was undertaken to identify strains that consistently give positive aroma characteristics (e.g., spicy, fruity, and floral). These strains were grown in a defined medium, and five human evaluators rated each strain according to aroma quality, and their ratings were coupled with a solid phase micro-extraction with gas chromatography (SPME GC-MS) analysis. None of the strains yielded universally positive aromas for the evaluators. A further characterization of nine of these strains grown with both aromatic amino acids (phenylalanine, tryptophan, and tyrosine) and hydroxycinnamic acids (caffeic, p-coumaric, and ferulic acids) indicated that low levels of compounds that were most important in differentiating the strains may contribute to a positive sensorial perception of Brettanomyces strain aromas under these conditions. To define the components associated with positive Brettanomyces character, the volatile aroma compounds produced by five Brettanomyces bruxellensis strains were analyzed. Compound detecting in SPME GC-MS was coupled with olfactory analysis (SPME GC-MS-O), using nine individual evaluators to identify compounds most associated with Brettanomyces character and to assess the breadth of descriptive terms used by different individuals for the same compound. Twenty-two compounds were identified as having an impact on aroma, including the well-known ethylphenols and vinylphenols, as well as several fatty acids, alcohols, esters, terpenes, and an aldehyde.