Smoke taint volatile compounds are analysed by gas chromatography mass spectrometry (GCMS) using stable isotope dilution analysis (Pollnitz et al. 2004, Hayasaka 2010).
Smoke taint phenolic glycoside compounds are analysed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) using stable isotope dilution analysis (Hayasaka et al. 2013). Samples are prepared according to the method described by Hayasaka et al. (2010), except using d3-Syringol glucosyl glucoside (gentiobioside) as the internal standard instead of d3-guaiacol monoglucoside.
Smoke taint phenolic glycoside compounds can also be analysed by a direct acid hydrolysis technique based on the glycosyl-glucose (GG) assay (Williams et al. 1995) and an adaption of this assay incorporating solid phase extraction (SPE), for the quantification of glycosylated guaiacol and 4-methylguaiacol (Singh et al. 2011).
Wilkinson et al. (2011) detail a comparison of the glycoside methods.
Analytical glycoside results produced using a hydrolysis/GCMS method are not comparable to results using the HPLC-MS/MS method, as demonstrated during a cross-validation of analytical data between Vintessential Laboratories and Affinity Labs.
For free volatile phenols, analytical results from different laboratories can generally be compared to the AWRI’s volatile phenol background data; however, it is not possible to compare glycoside results from a hydrolysis/GCMS method to the AWRI’s background database for glycosides, as these have been analysed using the HPLC-MS/MS method.
References
Pollnitz, A.P., Pardon, K.H., Sykes, M. and Sefton, M.A. 2004. The effects of sample preparation and gas chromatograph injection techniques on the accuracy of measuring guaiacol, 4-methylguaiacol and other volatile oak compounds in oak extracts by stable isotope dilution analyses. J. Agric. Food Chem. 52: 3244–3252.
Hayasaka, Y., Parker, M., Baldock, G.A., Pardon, K.H., Black, C.A., Jeffery, D.W., Herderich, M.J. 2013. Assessing the impact of smoke exposure in grapes: development and validation of a HPLC-MS/MS method for the quantitative analysis of smoke-derived phenolic glycosides in grapes and wine. J. Agric. Food Chem. 61(1): 25-33.
Hayasaka, Y., Baldock, G. A., Parker, M., Pardon, K. H., Black, C. A., Herderich, M. J., Jeffery, D. W. 2010. Glycosylation of smoke-derived volatile phenols in grapes as a consequence of grapevine exposure to bushfire smoke. J. Agric. Food Chem. 58(20): 10989−10998.
Singh, D.P., Chong, H.H., Pitt, K.M., Cleary, M., Dokoozlian, N.K. and Downey, M.O. 2011. Guaiacol and 4-methylguaiacol accumulate in wines made from smoke-affected fruit because of hydrolysis of their conjugates. Aust. J. Grape Wine Res. 17: S13–S21.
Wilkinson, K., Ristic, R., Pinchbeck, K., Fudge, A., Singh, D., Pitt, K., Downey, M., Baldock, G., Hayasaka, Y., Parker, M., Herderich, M. 2011. Comparison of methods for the analysis of smoke related phenols and their conjugates in grapes and wine. Aust. J. Grape Wine Res. 17(2): S22-S28.
Williams, P.J., Cynkar, W., Francis, I.L., Gray, J.D., Iland, P.G. and Coombe, B.G. 1995. Quantification of glycosides in grapes, juices, and wines through a determination of glycosyl glucose. J. Agric. Food Chem. 43: 121–128.