Applying HS-SPME-GC-MS combined with PTR-TOF-MS to analyze the volatile compounds in coffee husks of Coffea arabica with different primary processing treatments in Yunnan

Primary processing treatments are crucial to the flavor profile of coffee beans, which create the flavor precursors basis in coffee husks and diffuse into the beans, with satisfying outcomes. In this study, eleven coffee husks of Coffea arabica with different primary processing treatments (sun exposure, washing and honey treatment) from three latitudes of Yunnan were investigated by the combination of HS-SPME-GC-MS and PTR-TOF-MS. A total of 114 volatile organic compounds (VOCs) and 77 masses were identified. The characteristic compounds octanoic acid (S1) and methyl linoleate (S11) in sun-exposed, phenethyl alcohol (F4), methyl salicylate (F7), 3,5-dimethylbenzaldehyde (F9) and phytone (T9) in washed and n-hexadecanoic acid (S9) of honey-treated husks were recognized by the ions at m/z 33.032, m/z 68.049, m/z 83.049, m/z 67.054, m/z 57.034, m/z 41.030 and m/z 49.010, respectively. This study demonstrated the feasibility and complementarity of HS-SPME-GC-MS and PTR-TOF-MS in the rapid identification of VOCs in coffee husks. Meanwhile, the antioxidant capacities of the 11 husks were evaluated in vitro, and the sun-exposed samples exhibited most promising potency, in which methyl salicylate (F7), methyl linoleate (S11), methyl linolenate (S13), ethyl linoleate (S14), ethyl linolenate (S16), linalool (T1), citronellol (T2) and caffeine (J3) contributed mainly to the antioxidant capacities.