Comprehensive profiling of amino and carbonyl compounds in the Hong Yao sour soup, a type of fermented sour soup, in Huangluo Yao Village of Guangxi, China

Fermented sour soup is a traditional condiment in daily southwestern Chinese cuisine. Compounds found in Hong Yao sour soup were fractionated using size-exclusion chromatography. Amino compounds were identified through derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate and liquid chromatography tandem mass-spectrometry (LC-MS/MS) with precursor scan, followed by identification using product ion scan. Other compounds lacking amino groups were isolated using solid-phase extraction with a strong cation exchanger and detected through LC-MS in full scan mode. Carbonyl compounds, including carboxylic acids, were detected and identified by derivatization with 2-nitrophenylhydrazine and LC-MS/MS. Besides amino acids and carboxylic acids including lactic and acetic acid, amino acid metabolites such as monoamines (tyramine, pyrrolidine, tryptamine), polyamines (cadaverine, putrescine), N-acetyl- and N-lacoyl-amino acids, and α-keto acids from Val, Ile, and Leu were also detected. However, unlike Japanese rice wine, only a few dipeptides were detected. This information aids in understanding the unique characteristics of Hong Yao sour soup.