Volatile Organic Compounds in Malt Based on GC-MS and GC-IMS Technology

Abstract

In order to explore the differences of volatile organic compounds (VOCs) in different malts, roasted malt and biscuit malt were detected by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS) respectively. The results showed that more than 90 kinds of VOCs in both roasted and biscuit malt were identified by GC-MS, and 48 kinds of VOCs had relative amounts greater than 0.01%, which mainly included 9 ketones, 14 aldehydes, 4 esters, 4 alcohols, 2 acids, 10 pyrazines and 5 heterocyclic substances. The relative content of aldehydes and acids in roasted malt and biscuit malt were much higher than other compounds, including 2-mmethylbutanal, iso-valeraldehyde and acetic acid. The pyrazines in biscuit malt were richer than roasted malt, especially 2-methylpyrazine, 2,5-dimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine. 135 kinds of VOCs in malt were detected by GC-IMS, and 80 kinds of compound were identified, which concentrated on alcohols, ketones, aldehydes and esters with smaller molecule. The types of pyrazine and heterocyclic substances in malt were not abundant. The results from GC-MS and GC-IMS showed that types of VOCs in roasted malt and biscuit malt were similar, while the contents had significant differences. The esters, alcohols and aldehydes were richer in roasted malt, while the biscuit malt had higher contents of pyrazines and ketones. The principal component analysis (PCA) and fingerprint similarity analysis showed that both GC-MS and GC-IMS technique could distinguish between roasted and biscuit malt effectively. In conclusion, the combination of GC-MS and GC-IMS techniques could provide a comprehensive approach to analyze the composition of VOCs, and offers strong technical support for VOCs researches in malt.

Keywords

• gas chromatography-ion mobility spectrometry
• gas chromatography-mass spectrometer
• malt
• fingerprint
• principal component analysis