Analysis of volatile compounds of Mesona Blumes gum/rice extrudates via GC–MS and electronic nose

Samples containing 0–20% (w/w) Mesona Blumes gum (MBG) mixed with hybrid indica rice (type 9718) were extruded in a PTW-24/25D laboratory co-rotating fully intermeshing twin-screw extruder under the same condition. Firstly, a portable electronic nose with 10 metal oxide sensor arrays was used to study the volatiles from the headspace of the samples with various MBG contents. The direct electronic nose response recording combined with principal component analysis (PCA) enabled a rapid differentiation of the rice extrudates formulas with various MBG contents. It was clearly shown that odour of rice extrudates with 0% MBG was significantly different from odours of those with 5–20% MBG. Secondly, GC–MS was utilized to identify uncertain volatile compounds resulting in the odour differentiation. The obtained results suggested that these volatile compounds mainly consist of ketones (camphor, 2-butanone), aldehydes (acetaldehyde, 3-methyl-butanal, nonanal and benzaldehyde), pyrrole (1-methyl-1H-pyrrole), piperazine (piperazine), furan (2-pentyl-furan) and some herbal flavor compounds (benzaldehyde, nonanal, dl-limonene). In addition, the herbal flavor compounds mainly resulted in the fine differentiation between these rice extrudates. By multivariate analysis on GC–MS data of 5 different rice extrudates, it was indicated that the formulas without MBG group were distant from formulas with MBG, but formula with 20% MBG was pronouncedly distant from other formulas with MBG, and the chemical compounds representing herbal flavor were concentrated around the point of formula with 20% MBG. Furthermore, the dendrogram of these 5 groups showed the identical trend with PCA (principal component analysis) biplot. In conclusion, an electronic nose combining with GC–MS analysis could distinguish the formulas of rice extrudates with known different MBG content.