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Product traceability, quantitative analysis and authentication of ancient wheat grains and other commercial grains by ¹³C and ¹H MAS NMR spectroscopy

Wheat has a very complex chemical composition involving carbohydrates, starch, fat, proteins and lignocellulosic materials. Solid-state nuclear magnetic resonance spectroscopy (ssNMR) allows the determination of several metabolites in a single measurement. ssNMR spectroscopy has been demonstrated to be a powerful non-invasive tool for the structural investigation at molecular level and for metabolomics profiling. It provides in-depth information directly on the components without their isolation or fractionation and it is well suited for studying the changes in the chemical structure and composition induced by climate, soil, variety, origin and processing. Studies on the traceability and authenticity of wheat varieties can be conducted by applying ssNMR spectroscopy coupled with multivariate statistical methods.

The baking of bread is a complex process in which water evaporation, volume expansion, starch gelatinization, protein denaturation, and crust formation occur. Despite bread baking’s extensive history, the molecular compositions, structures, and changes that occur as a result of flour hydration remain poorly understood. In part, this has been due to challenges associated with the characterization of such complicated multicomponent, heterogeneous, and non-equilibrium solid-state materials and processes, in which reacting interfaces between different components play large roles. Advanced ssNMR spectroscopic techniques are sensitive to local chemical compositions and structures in solid-state materials, including those without long-range order. ¹³C CPMAS and ¹H MAS NMR can reveal the packing type of starch granules via the characteristic ¹³C (and ¹H) resonances of different crystalline starch polysaccharides and amorphous starch. In addition, the differences in the microstructure of starch/protein matrix in the finished breads as well as the gluten protein conformation and extractability can be revealed by ssNMR spectroscopy.