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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.

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

Supelco
SPME LC Tips, PDMS/DVB, pkg of 96 ea
Sigma-Aldrich
2-Isopropyl-3-methoxypyrazine, 99%, FG
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
4-Methyl-2-pentanone, suitable for HPLC, ≥99.5%
Sigma-Aldrich
2-Octanol, 97%
Supelco
IonSense® C18 SPE-it Tips, pkg of 96 ea
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), metal alloy fiber, df 100 μm (PDMS), needle size 23 ga, for use with autosampler
Sigma-Aldrich
1-Octen-3-one, 96%
Sigma-Aldrich
2-Methylisoborneol, ≥98.0% (GC)
Sigma-Aldrich
3-Octanone, ≥98%
Supelco
3-Octanone, analytical standard
Supelco
4-Methyl-2-pentanone, analytical standard
Supelco
Dehydrated Alcohol, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 7 μm (PDMS), needle size 23 ga, for use with autosampler
Supelco
SPME fiber assembly polyacrylate (PA), df 85 μm (PA), for use with autosampler, needle size 23 ga
Supelco
2,4,6-Tribromoanisole, PESTANAL®, analytical standard
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 30 μm (PDMS), needle size 24 ga, for use with autosampler
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 100 μm (PDMS), for use with manual holder, needle size 23 ga
Supelco
SPME fiber assembly polyacrylate (PA), df 85 μm (PA), for use with manual holder, needle size 24 ga
Supelco
SPME fiber assembly polyacrylate (PA), df 85 μm (PA), for use with autosampler, needle size 24 ga
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 7 μm (PDMS), needle size 24 ga, for use with autosampler
Supelco
SPME Portable Field Sampler, coating PDMS
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 manual holder
Supelco
SPME fiber assembly Polydimethylsiloxane (PDMS), df 100 μm (PDMS), for use with autosampler, needle size 24 ga
Supelco
Ethanol solution, certified reference material, 2000 μg/mL in methanol
Supelco
SPME Portable Field Sampler, coating CAR/PDMS