Identification of Malus toringoides (Rehd.) Hughes Teas with Different Processes Based on E-nose and GC-MS

The volatile substances among Malus toringoides (Rehd.) Hughes black tea, green tea and Kang brick tea were detected by electronic nose (E-nose), trap head space-gas chromatography-mass spectrometry (HS Trap GC-MS) and the differences of the volatile substances were analyzed by orthogonal partial least squares discriminant analysis (OPLS-DA), relative odor activity value (ROAV) and differential thermography in order to explore the odor differences of Malus toringoides (Rehd.) Hughes teas with three different processes. Result showed that E-nose could effectively distinguish three kinds of Malus toringoides (Rehd.) Hughes teas, and the prediction ability of the model established by E-nose combined with OPLS-DA was 95.70%. GC-MS analysis showed that aldehydes, esters and hydrocarbons were the main volatile substances, while alcohols were the main common volatile substances of black tea and green tea. The differences in the contents of aldehydes, esters, hydrocarbons and alcohols account for the variations in the aroma of Malus toringoides (Rehd.) Hughes teas produced by different processes. ROAV value combined with aroma type analysis showed that the volatile components of fruit aroma had a relatively large contribution to the formation of the odor of Malus toringoides (Rehd.). Isovaleraldehyde might be the key aroma substance to Malus toringoides (Rehd.) Hughes teas. Differential thermogram analysis showed that trimethoxyester, isovaleraldehyde and 2-ethylfuran were the main common volatile substances in Malus toringoides (Rehd.) Hughes teas.