Optimization of a Solid Phase Dynamic Extraction (SPDE) Method for Beer Volatile Profiling
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Optimization of a Solid Phase Dynamic Extraction (SPDE) Method for Beer Volatile Profiling Luis F. Castro & Carolyn F. Ross & Kevin R. Vixie
Received: 13 November 2014 / Accepted: 20 January 2015 # Springer Science+Business Media New York 2015
Abstract A headspace solid phase dynamic extraction coupled with gas chromatography-mass spectrometry (HSSPDE-GC/MS) method for the analysis of the volatile fraction of beer was optimized using response surface methodology. A preliminary two-level full factorial design was performed, with extraction temperature, extraction strokes, and fill/eject speed as the main factors. The results showed that number of extraction strokes and temperature significantly affected the peak area response of the volatile compounds (p≤0.05). To determine the ideal conditions for extraction, a second optimization of the significant factors was carried out using a Doehlert matrix design. The optimal conditions were identified as an extraction temperature of 60 °C and 55 extraction strokes. The optimized method was applied for the analysis of five commercial beers. A variety of compounds from different chemical classes were extracted from each sample, reflecting the effective application of the SPDE method for volatile compound extraction across different beers.
Keywords Beer . Solid phase dynamic extraction (SPDE) . Doehlert matrix . Optimization . Factorial design . Volatile compounds
L. F. Castro School of Food Science and Nutrition, California Polytechnic State University, San Luis Obispo, CA 93407, USA C. F. Ross (*) School of Food Science, Washington State University, PO Box 646376, Pullman, WA 99164-6376, USA e-mail: [email protected] K. R. Vixie Department of Mathematics, Washington State University, Pullman, WA 99164, USA
Introduction The volatile compound fraction in beer is important as these compounds make a major contribution to the flavor of beer. Beer volatile constituents have been studied since the 1960s. Currently, over 800 compounds have been identified and quantified in the beverage (Jelen et al. 1998; Pinho et al. 2006). The variety of these volatile compounds, with different polarities, volatilities, and wide range of concentrations, makes the analysis of this volatile fraction very challenging (Malherbe et al. 2009). Considering the nature and low concentrations of the volatile compounds in beer, gas chromatography (GC) is the preferred technique for the detection and identification of the volatile components (Da Silva et al. 2008). In recent years, headspace solid phase microextraction (HS-SPME) coupled to GC has become the most widely used headspace sampling technique (Pinho et al. 2006), and has been used in beer analysis (Jelen et al. 1998; Pinho et al. 2006; Saison et al. 2008). Compared to more traditional extraction techniques such as solvent extraction and concentration by steam distillation, SPME presents many advantages. It is fast, easy to automate, and requires low sample volumes. However, SPME does suffer from certain disadvantages such as damage of the coatings
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