Tracing the change of the volatile compounds of soy sauce at different fermentation times by PTR-TOF-MS, -nose and GC-MS.

Proton-transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS), combined with electronic nose (-nose), was first used to track the change of volatile organic compounds (VOCs) in soy sauce in this study. The results showed that 163 VOCs with different mass numbers were identified. Based on the differences in VOCs, the entire fermentation cycle was divided into four stages (0D and 15D; 30D-75D; 90D; 105D-120D).