Multidimensional characterization of red sour soup with different substrates: integrating sensory, physicochemical, bioactive, and safety attributes.

Red sour soup (RSS) is a characteristic Chinese fermented food. This study analyzed tomato-based RSS (T-RSS), tomato-chili-based RSS (M-RSS), and tomato-chili-rice-acid based RSS (R-RSS) for sensory, physicochemical, bioactive, and safety properties. Among the samples, M-RSS exhibited significantly higher levels of polyphenol (161.89 mg GAE/100 g) and total flavonoid (150.85 mg RE/100 g DW). Capsaicinoids were exclusively found in M-RSS and R-RSS, with nordihydrocapsaicin showing the highest level at 1125.61 μg/g. In most samples, lycopene (0.125-3.560 μg/g) was the main carotenoid and lactic acid the primary organic acid (14-54%). Multivariate analysis revealed that capsorubin, zeaxanthin, cryptoxanthin, and lutein were significantly correlated with both RSS redness (a* value, p < 0.05) and specific organic acids, while capsaicin and dihydrocapsaicin were positively associated with polyphenols, vitamin C, tartaric/oxalic acids, and total flavonoids. This study characterized the quality profiles of RSS with different substrates, providing a reference for its quality evaluation and targeted functional improvement.