Abstract
Chemical analysis of the organic components in beer has applications to quality control, authenticity and improvements to the flavor characteristics and brewing process. This study aims to show the complementary nature of two instrumental techniques which, in combination, can identify and quantify a number of organic components in a beer sample. Nuclear Magnetic Resonance (NMR) was used to provide concentrations of 26 different organic compounds including alcohols, organic acids, carbohydrates, and amino acids. Calorie content was also estimated for the samples. NMR data for ethanol concentrations were validated by comparison to a Fourier Transform Infrared Spectrometry (FTIR) method. Headspace Solid-Phase Microextraction (SPME) Gas Chromatography Mass Spectrometry (GCMS) was used to identify a range of volatile compounds such as alcohols, esters and hop-derived aroma compounds. A simple and inexpensive conversion of a Gas Chromatography Flame Ionization Detector (GC FID) instrument to allow the use of Solid-Phase Microextraction was found to be useful for the quantification of volatile esters.
Highlights
Beer is the most popular alcoholic beverage in America [1]
The analysis of organic chemicals in beer samples has quality control and authenticity applications, and can provide information to the brewer to improve the efficiency of the process, quality of product and discover the source of problems in the system
We demonstrate the complementary nature of Nuclear Magnetic Resonance (NMR) and headspace Solid-Phase Microextraction (SPME) Gas Chromatography (GC)
Summary
Beer is the most popular alcoholic beverage in America [1]. Interest in craft beers in the United States has led to the substantial increase in small scale breweries that typically cannot afford sophisticated analytical techniques. A market potentially exists, for independent entities which have access to laboratories and expensive instrumentation to provide analytical services to breweries. The analysis of organic chemicals in beer samples has quality control and authenticity applications, and can provide information to the brewer to improve the efficiency of the process, quality of product and discover the source of problems in the system. The major aroma and taste influencing compounds are considered to be the esters and alcohols formed during the fermentation process. Esters contribute to a beer’s bouquet, but can result in off-flavors when present at higher concentrations. Higher alcohols are formed in the Ehrlich pathway, which proceeds when amino acids in the wort are taken up by yeast. Information about the amino acids in beer, may be used as indicators for the fermentation performance. Esters are Beverages 2017, 3, 21; doi:10.3390/beverages3020021 www.mdpi.com/journal/beverages
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