Abstract
Here we present a method for the accurate quantification of major volatile metabolites found in different food and beverages, including ethanol, acetic acid and other aroma compounds, using gas chromatography coupled to mass spectrometry (GC-MS). The method is combined with a simple sample preparation procedure using sodium chloride and anhydrous ethyl acetate. The GC-MS analysis was accomplished within 4.75 min, and over 80 features were detected, of which 40 were positively identified using an in-house and a commercial mass spectrometry (MS) library. We determined different analytical parameters of these metabolites including the limit of detection (LOD), limit of quantitation (LOQ) and range of quantification. In order to validate the method, we also determined detailed analytical characteristics of five major fermentation end products including ethanol, acetic acid, isoamyl alcohol, ethyl-L-lactate and, acetoin. The method showed very low technical variability for the measurements of these metabolites in different matrices (<3%) with an excellent accuracy (100 ± 5%), recovery (100 ± 10%), reproducibility and repeatability [Coefficient of variation (CV) 1–10%)]. To demonstrate the applicability of the method, we analysed different fermented products including balsamic vinegars, sourdough, distilled (whisky) and non-distilled beverages (wine and beer).
Highlights
Gas chromatography and mass spectrometry (GC-MS) in one of the most mature analytical technologies that provides excellent chromatographic resolution due to the high sensitivity and specificity of mass spectrometry [1]
We present a direct injection GC-MS method for the quantification of different fermentation end products in food products and beverages, which combine the high specificity of electron impact (EI) mass spectrometry with the high reproducibility and high chromatographic resolution of gas chromatography
Our initial aim was to develop a rapid, reproducible and inexpensive GC-MS method to accurately quantify ethanol and acetic acid simultaneously in various fermented food products and beverages using only 100 μL of sample (Figure 2), we were able to detect over 70 features only within 4.75 min while using 1000 μL of sample (Table 1)
Summary
Gas chromatography and mass spectrometry (GC-MS) in one of the most mature analytical technologies that provides excellent chromatographic resolution due to the high sensitivity and specificity of mass spectrometry [1]. GC-MS has always been the most preferred analytical platform for the analysis of volatile metabolites present in different biological samples including food and beverages. Many methods are already available that make use of headspace (HS) and solid-phase micro extraction (SPME) techniques in order to quantify volatile compounds accurately in fermented food and beverage samples [2,3,4,5,6]. HS analysis requires a large sample volume and SPME requires expensive fibres for effective extraction of volatile metabolites. Liquid injection GC-MS offers a cheaper and more straightforward option for the analysis of major fermentation end products (e.g., ethanol, acetic acid, higher alcohols, esters and volatile fatty acids, Figure 1) with an advantage of being able to identify other volatile metabolites that are commonly found in fermented products.
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