NMR Spectroscopy Combined With Multivariate Statistical Analysis For The Differentiation Of Types And Origins Of Soy Sauce

Due to current situation of food borne health hazards there is a highly increasing trend among consumers to authenticate and validate the food products under their consumption.Soy sauce,a well-known seasoning all over the world especially in Asia,is available in global market in a wide range of types based on its purpose and the processing methods.Its composition varies with respect to the raw materials,fermentation processes and addition of additives,preservatives and flavour enhancers.There are many issues linked with the quality and authentication of fermented foods including soy sauce due to the problems associated with their complex composition,processing,raw materials and additives etc.Many techniques have been applied for the authentication and validation of soy sauce and other fermented foods but most of them are targeted,destructive and time consuming.NMR-based metabolomics provides an unbiased,non-destructive,fast and one step approach for this purpose.In the present study,NMR spectroscopy coupled with multivariate statistical data analysis was applied to investigate metabolomic variations among different types of soy sauce,soy sauce from different geographical locations and soy sauce prepared from organic and conventional raw materials.The main additives in soy sauce like glutamate,sucrose and glucose in Chinese dark type soy sauce were easily distinguished and quantified using 13C NMR spectroscopy which were otherwise difficult to be assigned and quantified due to serious signal overlaps in 1H NMR spectra.The significantly higher concentration of sucrose in dark soy sauce,including red cooking and mushroom flavoured soy sauce can directly be linked to the addition of caramel in soy sauce.Similarly,higher level of glutamate in super light as compared to super dark and mushroom flavoured soy sauce may come from the addition of monosodium glutamate(MSG).Soy sauce samples from different Asian regions(China(mainland),Japan,Singapore and Taiwan(China))were also analyzed in terms of 13C NMR spectroscopy.Significantly higher concentration of glutamate in Chinese red cooking(CR)soy sauce could be the result of manual addition of monosodium glutamate(MSG)in final soy sauce product.Whereas,different concentrations of amino acids and the other fermentation cycle metabolites such as acetate and sucrose were observed in soy sauces from different Asian regions.There were some similar trends in variation of fermentation cycle metabolites in Japanese Shoyu(JS)and Taiwan(China)light(TL),and similarly between Singapore Kikkoman(SK)and Chinese red cooking(CR)which depict the influence of climatic conditions,different raw materials and traditional ways f fermentation followed.1H NMR-based metabolomics and evaluation of 13C abundance ratio showed a clear separation among organic and conventional soy sauce samples.13C abundance ratio of metabolites in organic and conventional soy sauce samples was evaluated by 1H NMR spectroscopy.It was found that the 13C isotopic ratio of the organic samples was higher than the conventional soy sauce samples which indicated the different types of wheat and soybean have might been used for the preparation of organic soy sauce.The study highlights the potentiality of NMR spectroscopy coupled with multivariate statistical data analysis in differentiating between the types of soy sauce on the basis of level of additives,raw materials,climatic conditions and fermentation procedures.The results can be helpful to convey the information to the end user about the soy sauce types and the information about the raw materials used and geographical origin of the products.The findings in the current study can also provide guidelines to further advancement of the methodology to establish protocols for the authentication of fermented foods specially the soy sauce.