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  • Gas chromatography-mass spectrometry method optimized using response surface modeling for the quantitation of fungal off-flavors in grapes and wine.

Gas chromatography-mass spectrometry method optimized using response surface modeling for the quantitation of fungal off-flavors in grapes and wine.

Journal of agricultural and food chemistry (2015-02-24)
Navideh Sadoughi, Leigh M Schmidtke, Guillaume Antalick, John W Blackman, Christopher C Steel
ABSTRACT

An optimized method for the quantitation of volatile compounds responsible for off-aromas, such as earthy odors, found in wine and grapes was developed. The method involved a fast and simple headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) for simultaneous determination of 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 3-octanone, fenchone, 1-octen-3-one, trans-2-octen-1-ol, fenchol, 1-octen-3-ol, 2-methylisoborneol, 2,4,6-trichloroanisole, geosmin, 2,4,6-tribromoanisole, and pentachloroanisole. The extraction of the temperature and time were optimized using response surface methodology in both wine base (WB) and grape base (GB). Low limits of detection (0.1-5 ng/L in WB and 0.05-1.6 in GB) and quantitation (0.3-17 in WB and 0.2-6.2 in GB) with good recoveries (83-131%) and repeatability [4.3-9.8% coefficient of variation (CV) in WB and 5.1-11.1% CV in GB] and reproducibility (3.6-10.2 in WB and 1.9-10.9 in GB) indicate that the method has excellent sensitivity and is suitable for the analysis of these off-flavor compounds in wine and grape juice samples.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
1-Octen-3-one, 96%
USP
Dehydrated Alcohol, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
2-Isopropyl-3-methoxypyrazine, 99%, FG
Sigma-Aldrich
4-Methyl-2-pentanone, suitable for HPLC, ≥99.5%
Sigma-Aldrich
Ethyl alcohol, Pure 190 proof, for molecular biology
Sigma-Aldrich
2-Octanol, 97%
Sigma-Aldrich
4-Methyl-2-pentanone, ACS reagent, ≥98.5%
Sigma-Aldrich
4-Methyl-2-pentanone, ≥99%
Supelco
SPME-OC Fiber Assembly, Polydimethylsiloxane/Divinylbenzene (PDMS/DVB), df 75 μm(Coating thickness includes 65 μm coating + 10 μm OC (overcoating), needle size 23 ga, pkg of 3 ea, fiber L 1 cm
Sigma-Aldrich
Ethanol Fixative 80% v/v, suitable for fixing solution (blood films)
Supelco
3-Octanone, analytical standard
Sigma-Aldrich
3-Octanone, ≥98%, FG
Sigma-Aldrich
2-Octanol, ≥97%, FG
Sigma-Aldrich
2,4,6-Tribromoanisole, 99%
Sigma-Aldrich
trans-2-Octen-1-ol, 97%
Sigma-Aldrich
4-Methyl-2-pentanone, ≥99%, FCC
Sigma-Aldrich
3-Octanone, ≥98%
Sigma-Aldrich
Isoborneol, 95%
Sigma-Aldrich
2-Isopropyl-3-methoxypyrazine, 97%
Supelco
SPME Fiber Assembly Polydimethylsiloxane/Divinylbenzene (PDMS/DVB), df 65 μm(PDMS/DVB, needle size 24 ga, StableFlex, for use with autosampler
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 100 μm(PDMS, needle size 24 ga, for use with manual holder
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 7 μm(PDMS, needle size 24 ga, for use with autosampler
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 7 μm(PDMS, needle size 24 ga, for use with manual holder
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 100 μm(PDMS, for use with autosampler, needle size 24 ga
Supelco
SPME fiber assembly polyacrylate (PA), df 85 μm(PA, for use with manual holder, needle size 24 ga
Supelco
SPME Sampling Stand, for use with 4 mL vials
Supelco
SPME Portable Field Sampler, coating PDMS/DVB
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 30 μm(PDMS, needle size 24 ga, for use with manual holder
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 100 μm(PDMS, for use with autosampler, needle size 23 ga
Supelco
SPME Fiber Assembly Polydimethylsiloxane/Divinylbenzene (PDMS/DVB), df 65 μm(PDMS/DVB, for use with autosampler, needle size 23 ga