Similarity recognition approach to identify zero-added MSG soy sauce using stable isotopes and amino acid profiles.

Seasonings such as naturally fermented soy sauce without added monosodium glutamate (MSG), are currently a growth market in China. However, fraudulent and mislabeled zero-added MSG soy sauce may cause a risk of excessive MSG intake, increasing food safety issues for consumers. This study investigates stable carbon and nitrogen isotopes and 16 amino acids in typical Chinese in-market soy sauces and uses a similarity method to establish criteria to authenticate MSG addition claims. Results reveal most zero-added MSG soy sauces had lower δ 13C values (−25.2 ‰ to −17.7 ‰) and glutamic acid concentrations (8.97 mg mL−1 to 34.76 mg mL−1), and higher δ 15N values (−0.27 ‰ +0.95 ‰) and other amino acid concentrations than added-MSG labeled samples. A combined approach, using isotopes, amino acids, similarity coefficients and uncertainty values, was evaluated to rapidly and accurately identify zero-added MSG soy sauces from MSG containing counterparts. [Display omitted] • Isotopes and amino acids profiles were characterized for in-market soy sauces. • Strong correlations were found between isotopes and amino acids. • A new approach is proposed using similarity analysis to classify soy sauce. • A decision tree is established to identify zero-added MSG soy sauce. [ABSTRACT FROM AUTHOR]