Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometric (GC-MS) analysis of volatile profiles during the stir-frying process of malt

Abstract

The purpose of this study was to analyze the relationship between volatile profile variations of malt and its stir-fried forms, so as to sum up odor changes in the stir-frying process. When the malt was stir-fried, an online-type and non-contact temperature measurement system (ONTMS) was used to monitor the stir-frying temperature. HS-SPME coupled with GC-MS was employed to collected data of the volatile compositions in raw malt and its different stir-fried forms. According to an area normalization method, only compounds with percentage values of more than 1% were investigated. In total, 23 volatile compounds were identified. In raw malt, the major volatile components identified were acetaldehyde (9.51%), acetone (0.05%), 2,6-dimethylpyrazine (0.07%), benzaldehyde (0.00%), furan formaldehyde (16.47%), 5-methyl furan aldehyde (4.08%), 2-acetyl furan (1.05%), diacetone alcohol (0.00%), 2-methyl aldehyde (2.34%) and 3-methyl aldehyde (3.03%). During the stir-frying process of the malt, we collected and analyzed the data of the volatile compositions. The content of acetaldehyde, acetone, two 2,6-methyl pyrazine, benzaldehyde, furan formaldehyde, 5-methyl furan aldehyde, 2-acetyl furan, diacetone alcohol, 2-methyl aldehyde and 3-methyl aldehyde showed regular changes, which might be the leading factors giving rise to the odor changes. The temperature of stir-frying of the malt was monitored by an ONTMS, and this study demonstrated that ONTMS monitoring can be an feasible and effective method. HS-SPME coupled with GC-MS was shown to be a rapid and eco-friendly method with the advantages of high resolution and high sensitivity, and has the potential to qualitatively and quantitatively analyze volatile compounds in raw malt and its different stir-fried forms.