1H NMR-Based metabolomics and 13C isotopic ratio evaluation to differentiate conventional and organic soy sauce

Abstract

Organic foods gaining popularity due its connection with the health, high nutritional value, and high quality. Therefore, it is of prime importance to develop the analytical methods to combat with food authentication and protect consumer from the food fraud. Conventional soy sauce (CS) and organic soy sauce (OS) were characterized and differentiate for the first time using 1H NMR-based metabolomics approach. Classification methods like orthogonal partial least squares of discriminant analysis (OPLS-DA) showed a significant (p < 0.01) separation among CS and OS yielding important metabolites contributing towards this separation. OS was characterized by increased levels of leucine, threonine, isoleucine, valine, choline, phenylalanine, tyrosine, lactate, and acetate whereas, CS showed elevated concentrations of glutamate, glucose, and sucrose. The abundance ratio of 13C to 12C was determined by 1H NMR spectroscopy which showed an increased ratio of 13C isotope in OS samples indicating the organically grown wheat and soybean used for the preparation of OS. The results can be helpful to convey the information to the end-user to prevent them from economically motivated adulteration. This information could also pave the way to further trace and authenticate the raw materials used in the production of soy.

Keywords

• 1H NMR spectroscopy
• Metabolomics
• 13C Isotopic ratio
• Food authentication
• Food adulteration
• Soy sauce