Determination of Reductones, Furans and Organic Acids in Aqueous Model Matrices Using Solid-Phase Extraction and Gas Chromatography/Mass Spectrometry

Abstract

A method using solid-phase extraction (SPE) and GC-MS was developed for the determination of a series of polar and unstable flavor compounds: reductones, furans and volatile organic acids, in aqueous model matrices. The SPE procedures were optimized mainly on the pH-dependency of the analytes with regard to their adsorption characteristics. Good recovery of the reductones except DDMP was obtained at pH 2 and 4.5. Furan derivatives were generally recovered in high yields under the acidic to neutral pH conditions examined. All organic acids were recovered almost quantitatively at pH 2. An essentially comparable result was obtained in a model Maillard reaction mixture. In order to apply this method to alcoholic beverages, effect of the ethanol concentration on the SPE adsorption of the analytes was also investigated.Keywords: solid-phase extraction (SPE), gas chromatography/mass spectrometry (GC-MS), reductone, furan, organic acid Reductones, furans (Ledl & Schleicher, 1990) and organic acids (Hofmann et al., 2000) are commonly found in foods and beverages. Most reductones and volatile acids exhibit important sensory properties with low threshold values, and some of them are utilized as food flavors. Furan derivatives generated from sugars by non-enzymatic browning are closely related to the chemical changes in foods and beverages during their processing and storage (Lee & Nagy, 1990).Such types of compounds have relatively high polarity and ionic characters, so that their high water solubility results in low recovery in conventional solvent-extraction methods. Headspace sampling and solid-phase microextraction (SPME) are frequently used for the selective extraction of volatile flavors from a complex matrix. Unfortunately, the main disadvantage of these methods is low recovery of polar analytes (Pan et al., 1995).In addition, reductones and furans tend to be decomposed during the analytical procedures, particularly at the elevated temperature used in GC analysis (Blank et al., 1992). To compensate for losses during the workup procedure for GC analysis, stable isotope dilution assays (Sen et al., 1991) were developed. However, this technique requires the corresponding isotope-labeled derivative of each analyte as the internal standard.Column adsorption (Shimoda et al., 1987) and solid phase extraction (SPE) (Coulibaly & Jeon, 1996) are now widely used for the extraction and clean up of flavor compounds in foods and beverages. Even though some efficient methods had been developed for the analysis of reductones, most of them were optimized to one or a few analytes on high performance liquid chromatography (HPLC) (Walsh et al., 1997). The HPLC methods are not suitable to trace level multiple analytes.To our knowledge, there were only a few reports concerning the GC-quantitation of such polar and unstable volatiles from aqueous matrices using SPE treatments (Wada & Shibamoto, 1997;Adahchour et al., 1999). Recently, Thum and Back (1999) applied their SPE procedure for a selective concentration of a series of aroma compou...

Effects of pH on the Formation of Volatile Products in Non-Enzymatic Browning of Maltose

“…In our preceding paper (Mori & Ito, 2004), we reported a preliminary study on the volatile products generated upon heating a mixture of maltose and proline (each 1 M conc.) at 100˚C for 8 h in 0.2 M phosphate buffer (pH 6.5).…”

“…Analyses of volatile products Analysis of the target compounds was carried out by the procedure described in our preceding report (Mori & Ito, 2004) with minor modification. Two aliquots of the reaction mixture (2 ml) were diluted to 20 ml with water, and the pH of each solution was adjusted to 2 (for the analysis of furoic acid) or 4.5 (for the other reductones and furans) with aq.…”

“…Because of their trace amounts and unstable properties, analysis of these compounds proved to be more difficult than that of the major products. In our preceding work (Mori & Ito, 2004), a method of quantitative analysis for such type of compounds in aqueous solution using solid-phase extraction (SPE) and gas chromatography-mass spectrometry (GC-MS) has been developed, and good recovery was achieved for most of the analytes.…”

Formation of Pyrazines in Aqueous Maltose/Glucose/Fructose-Glutamine Model Systems upon Heating at below 100.DEG.C.

“…Quantitative analysis oj'pyr'azine and pyrrole de/~ivatives by SPE-GCMS In our preceding paper, we demonstrated the efficiency of SPE-GCMS for the quantitation of trace levels of furan, reductone and organic acids in aqueous solution (Mori & Ito, 2004a). This technique was modified for pyrazines.…”

“…SPE procedure The SPE procedure described in our previous paper (Mori & Ito, 2004a) was used for pyrazine derivatives with some modification. Two ml of the sample solution and 50 u1 of I.S.…”