Off-Odor Compounds Produced in Cork by Isolated Bacteria and Fungi: A Gas Chromatography−Mass Spectrometry and Gas Chromatography−Olfactometry Study

Abstract

The risk of development of specific olfactory profiles in cork was evaluated after inoculation of cork granules and agglomerated and natural cork stoppers with isolated bacteria and fungi. The highest incidence of off-odor development was found in assays when fungi were inoculated. Cork granules with musty-earthy, musty-earthy-TCA, and vegetative deviations were inspected by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Sixteen odor zones were clearly recognized in the GC-O analyses. Among these, octanal, 2-methoxy-3,5-dimethylpyrazine (MDMP), Z-2-nonenal, 2-methylisoborneol, 2,4,6-trichloroanisole (TCA), geosmin, and guaiacol were the most significant odorants and helped in the discrimination of sensory deviations. Only TCA and guaiacol were detected above their respective detection limits by HS-SPME-GC-MS. The fungi Cryptococcus sp. isolate F020, Rhodotorula sp. isolate F025, Penicillium glabrum isolate F001, and Pennicillium variabile F003A and the bacterium Pseudomonas jessenii isolate A1 were found to produce TCA to a greater extent. Additionally, 13 of 38 isolated microorganisms (2 bacteria and 11 fungi) proved able to produce unpleasant musty-earthy or vegetative odors that were not related to a significant TCA accumulation.

Quantification of cork off-flavor compounds in natural cork stoppers and wine by multidimensional gas chromatography mass spectrometry

“…MDMP was chemical background and monitor the responsible compounds during quality control of cork stoppers as well as in rejected wines. Among the most important compounds discussed in previous studies associated with atypical cork off-flavors differing from the typical TCA taint are geosmin (GSM), 2-methylisoborneol (MIB), 3,5-dimethyl-2-methoxypyrazine (MDMP), 3-isopropyl-2-methoxypyrazine (IPMP) and 3-isobutyl-2-methoxypyrazine (IBMP) [2][3][4][5][6][7]. These compounds were also confirmed in a comprehensive study [8] on cork samples that had been considered as conspicuous in sensory trials.…”

“…Microorganisms isolated from cork were able to produce GSM and MIB as well as TCA and MDMP [4]. Sensory properties of MIB are described as "earthy," "musty," "muddy," and in higher concentrations as "camphoraceous."…”

Gas chromatography-olfactometry of alcoholic beverages

“…The list of possible compounds producing unpleasant aromas in cork is relatively large, but many reports showed that the highest incidence of musty, earthy odour are due to 2,4,6-trichloroanisole (TCA), 2-methoxy-3,5-dimethylpirazine (MDMP) responsible for fungal must and 2,4,6-tribromoanisole (TBA). Other compounds, such as 1-octen-3-ol, 1-octen-3-one (mushroom aroma), guaiacol (smoky, phenolic aroma) and geosmin (trans-1,10-dimethyl-trans-9-decanol) and 2-methylisoborneol (earthy aroma) have also been reported (Prat et al , 2009). Disinfectant-like or swimming pool-like taints have been recognized in some wines, and chlorophenols have been associated with this particular taint (Capone et al , 2010).…”

Multivariate analysis of volatile compounds detected by headspace solid-phase microextraction/gas chromatography: A tool for sensory classification of cork stoppers

“…It should be noted that although the sample distribution in the defined canonical space obeys changes in the concentration of defined volatile compounds in the cork macerate, no direct assignation of these compounds to a specific off-odour can be made except for ME-TCA. In fact, ME and ME-VEG off-odours had been previously screened by GC-O analysis both in natural cork samples and in cork granules previously incubated by selected bacteria and fungi with low coincidences in significant odour-active molecules (Prat et al, 2009). Key odourants defined in the sensorial classes were 2-methoxy-3,5-dimethylpyrazine (MDMP), 2-methylisoborneol and geosmin in the case of ME and MDMP combined with octanal for ME-VEG.…”

“…Other methods such as GC-olfactometry are used instead (Culleré, Cacho, & Ferreira, 2009;Culleré, Escudero, Pérez-Trujillo, Cacho, & Ferreira, 2008). In a recent work, we have used GC-O analyses to characterise musty-earthy taints not related with TCA in cork and to relate off-odour formation to the inoculation of selected bacterial and fungal isolates (Prat et al, 2009).…”