Differences in flavor characteristics between Chinese traditionally fermented soy sauce and commercial soy sauce

BACKGROUND: Soy sauce produced by the traditional Chinese 'bask in daytime and dewed at night' fermentation method is believed to have a unique flavor profile compared with commercial soy sauces. However, systematic comparative studies on differences in their volatile organic compounds are lacking. This study aimed to characterize and compare the volatile flavor profiles of traditional soy sauce (TSS) and two commercial soy sauces (CSS-H and CSS-C) using an electronic nose (E-nose) and gas chromatography-ion mobility spectrometry. RESULTS: An E-nose combined with principal component analysis clearly separated the three samples, with a cumulative contribution rate exceeding 99%. A total of 88 volatile organic compounds were identified and classified into 12 chemical groups. Traditional soy sauce contained significantly higher levels of key aldehydes such as phenylacetaldehyde and 3-methylsulfanylpropanal, which contributed to roasted and robust soy notes. The CSS-H sauce was dominated by esters, including ethyl 2-hydroxypropanoate and acetic acid ethyl ester, imparting sweet and fruity aromas. The CSS-C sauce was characterized by abundant ketones, such as 2-propanone and terpenes like camphene, yielding sweet and caramel-like notes. CONCLUSION: The fermentation method critically determined the volatile composition of soy sauce. The traditional process yielded a more complex, aldehyde-rich profile, whereas commercial sauces contained a greater proportion of esters and ketones. These findings provide a scientific basis for geographical indication protection of traditional soy sauce and offer potential quality markers for industrial optimization. © 2026 Society of Chemical Industry.