24 May / June 2016
The Benefits of GC/MS Coupled with a Headspace Trap to Monitor Volatile Organic Compounds in the Production of Beer
by Lee Marotta1 1
2 and Robert Thomas2
GC and GC–MS Senior Application Scientist, PerkinElmer Inc., Shelton, Connecticut. Principal Consultant at Scientific Solutions, Gaithersburg, Maryland.
Beer is a very popular beverage consumed all over the world. It is estimated that in 2015, the total sales of beer worldwide were approximately $522 billion [1]. There are many variations in the types, styles and flavours of beer, but the production process is very similar involving the fermentation of malted extracts from barley, and other grains together with the addition of various flavouring agents such as hops, fruits, honey, herbs and spices. However, even though the end products are very different, they are all highly complex mixtures of many compounds including sugars, proteins, alcohols, esters, acids, ketones, and terpenes. For anyone who really appreciates beer, flavour and aroma are two extremely important qualities, which are directly impacted by its chemical content. For that reason, there is a strong interest by brewers in quantifying the volatile organic compounds (VOCs) in a beer that gives rise to its unique flavour and aroma. In the brewing industry, it is well recognised that some VOCs have a positive effect (known as attributes) on the taste and smell of a beer, while others (known as defects) have a negative effect. Therefore, the ability to characterise these components in beer products before, during and after fermentation is critically important in the product development, process control, and quality control of the entire brewing process.
The traditional approach for the characterisation of VOCs in beer has been to use classical headspace coupled with gas chromatography using multiple detection devices such as electron capture (ECD), flame ionisation (FID) or thermal conductivity (TCD) detectors, depending on the analytes of interest [2]. These detectors work very well, but analysis using this kind of configuration is limiting because it lacks identifying capability, and also may require more than one analytical system and sample preparation [3]. Also, if low-level sulphur compounds are suspected, it would necessitate the use of a highly specific sulphur chemiluminescence detector which is expensive and limiting in its flexibility and range. Additionally, these specific analyte detectors will not fully characterise the beer, compare competitive beer products or identify other flavour components in the brew. The purpose of this research was to determine if a single system consisting of a headspace trap (HST), gas chromatograph (GC) and mass spectrometer (MS) detector can serve the needs of the brewing industry, by generating more useful information about the beer as well as offering time and cost savings when compared to the established detection principles mentioned.
This study will therefore describe- the use of the TurboMatrixTM
HSTrap, and Clarus SQ 8 GC/MS system, (both PerkinElmer, Shelton,
Figure 1: SIM chromatogram of Diacetyl peak at 5.0 ppb
CT) to extract and concentrate volatile species from a beer sample for the purpose of separating, identifying and quantifying the VOCs. In addition, the investigation will demonstrate that the compounds responsible for both the attributes and defects can all be accomplished in a single injection using one system and one detector, which results in a faster analysis time, enhanced productivity, more cost effective,
and a quicker return on investment. Additionally, this analytical approach reveals important information which can be used for fermentation and production troubleshooting purposes.
Investigation
Several experiments were performed that were considered important to the brewing
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
