Solid-state NMR investigation on the presence of adulterants in coffee samples
Wilma C Josefa1, Daniel F Cipriano1, Aline T Toci2
1Laboratory of Carbon and Ceramic Materials, Department of Physics, Federal University of Espírito Santo (UFES), Av. Fernando Ferrari, 514, 29075-910 Vitória, ES, Brazil.
Abstract:
The presence of impurities / adulterants in coffee and other food materials is one of the most serious problems faced by the food industry and public health authorities dealing with food safety nowadays. In an effort to contribute to the development of new approaches in this field, this work illustrates the potential of a suite of solid-state nuclear magnetic resonance (NMR) methods towards the detection of different types of adulterants (e.g., rice, barley, corn, and soybean) added to roasted and ground coffee samples. Samples containing variable amounts of these adulterants were studied, using 1H and 13C as probe nuclei and employing different pulse sequences, such as 1H13C cross polarization, 1H / 13C single pulse excitation and 1H spin-echo detection. Principal component analysis was used as an exploratory chemometric tool to help in the interpretation of the information available in the solid-state NMR spectra. The results showed that different approaches can be selected as the most suitable ones depending on the chemical characteristics of each adulterant, such as the presence of mobile lipid components or rigid carbohydrates, which give rise to specific features to each type of recorded spectra.
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