Rapid Measurement of 3-Alkyl-2-methoxypyrazine Content of Winegrapes To Predict Levels in Resultant Wines

We describe an optimized protocol for analysis of the herbaceous smelling 3-alkyl-2-methoxypyrazines (MPs) in whole berries that predicts MPs in resultant red wines. Berries are homogenized by bead-milling with a deuterated standard prior to headspace solid phase microextraction (HS-SPME) and quanti...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2009-09, Vol.57 (18), p.8250-8257
Main Authors: Ryona, Imelda, Pan, Bruce S, Sacks, Gavin L
Format: Article
Language:English
Subjects:
3-alkyl-2-methoxypyrazines
Analytical Methods
Biological and medical sciences
Chromatography, Gas
Fermented food industries
food analysis
food composition
Food industries
Fruit - chemistry
Fruit and vegetable industries
Fundamental and applied biological sciences. Psychology
Gas Chromatography-Mass Spectrometry
measurement
Odorants - analysis
prediction
product development
pyrazines
Pyrazines - analysis
rapid methods
Vitis - chemistry
Wine - analysis
wine grapes
wine quality
wines
Wines and vinegars
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Summary:We describe an optimized protocol for analysis of the herbaceous smelling 3-alkyl-2-methoxypyrazines (MPs) in whole berries that predicts MPs in resultant red wines. Berries are homogenized by bead-milling with a deuterated standard prior to headspace solid phase microextraction (HS-SPME) and quantification by two-dimensional gas chromatography time-of-flight-mass-spectrometry (GC×GC−TOF-MS). In the case of 3-isopropyl-2-methoxypyrazine (IPMP), GC×GC−TOF-MS successfully resolved interferences that coeluted with the analyte in the first dimension. HS-SPME parameters (pH, queue time, incubation time, extraction time, extraction temperature) were optimized by a statistical experimental design. Good method accuracy was observed (consistent ratio of unlabeled analyte to labeled standard) at 10 min extraction times when 80 °C extraction temperatures were employed, although increasing sensitivity was observed for longer extraction times (up to 140 min). Standard addition of 3-isobutyl-2-methoxypyrazine (IBMP) and IPMP into preveraison and harvest ripe berry matrices showed good linearity (r 2 >0.99 in all cases), with limits of detection ranging from 0.6 to 1.8 pg/g. The protocol was validated by comparing IBMP in 16 lots of Cabernet Franc berries (range = undetectable to 18.4 pg/g) to the resulting wines (range = undetectable to 14.5 pg/g). Berry and wine MP content were strongly correlated, (r 2 = 0.97, p < 0.0001). Following correction for CO2 loss, the observed concentration of IBMP in wines was 67 ± 13% of the IBMP concentration observed in berries.
ISSN:0021-8561
1520-5118
DOI:10.1021/jf9019695