Identification and Profiling of Volatiles Using Headspace-Solid-Phase Microextraction/Gas Chromatography–Mass Spectrometry and Headspace Gas Chromatography–Ion Mobility Spectrometry to Reveal Early Contamination Progress of Sour Rot in Citrus

Sour rot, a devastating postharvest fungal disease induced by<i>G. citri-aurantii</i>, causes substantial losses and flavor deterioration of citrus. Headspace-solid phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) and HS-GC-ion mobility spectrometry (IMS), available tools for accurate detection of multifarious VOCs, identified 149 and 120 VOCs during <i>G. citri-aurantii</i> invasion of citrus from 0 to 48 h. Different infection stages were classified successfully based on the VOC variation by PLS-DA analysis, and 22 differential VOCs were screened as characteristic VOCs for understanding the contamination progress and early monitoring in sour rot citrus. Among them, 14 VOCs, such as ethyl propanoate, ethyl butanoate, <i>α</i>-pinene, etc., were not found in the early infection stage but subsequently accumulated, and 9 VOCs, such as 2-hexanol and 2-hexenal, were present in the early infection stage and subsequently disappeared. These findings could distinguish the contamination severity of citrus sour rot and offer application potential of odor profiling for monitoring <i>G. citri-aurantii</i> infestation of postharvest citrus.