Analysis of Physicochemical Quality and Flavor Differences of Five Commercially Available Tiger Nut Oils with Different Processes Based on GC-IMS Technique

In order to evaluate the differences in physicochemical quality and flavor of commercially edible tiger nut oil, gas chromatography-ion mobility spectroscopy (GC-IMS) combined with principal component analysis was used to compare the volatile compounds in tiger nut oil from different extraction methods (physical pressing, hot pressing, subcritical extraction, high-pressure cold pressing and cold pressing). The GC-IMS results showed that 76 volatile compounds including 12 esters, 16 alcohols, 29 aldehydes, 9 ketones, 5 acids, 3 furans, 1 pyrazine and 1 sulfur compound were identified in the oil from different extraction methods. The relative content of aldehydes, esters and furans (53.54%, 13.06%, 5.41%) in the hot-pressing group were higher than others. The flavor differences of tiger nut oil from different processes were mainly derived from four key flavor substances as 1-octen-3-ol, nonanal, (E)-2-octenal and hexanal. The results of principal component analysis (PCA) showed that PC1 and PC2 were 48.7% and 30.1%, respectively, with a cumulative difference contribution of 78.8%, and the differences in volatile compounds between different processes were significant, which could be well distinguished by different extraction methods. The results of pearson correlation analysis showed that there was a significant positive correlation between b^* value and acid value, peroxide value, p-malondialdehyde value and 1-octen-3-ol (0.57<r<0.88, P<0.05). The research could provide some reference value for the production and processing, theoretical research and quality inspection of commercial tiger nut oil.