1H NMR Analysis of Peanut-Soaked Solutions
Under various processing conditions, the molecular composition of the peanut is expected to change due to chemical reactions such as the Maillard reaction, macromolecule hydrolysis, protein denaturation and the generation of small molecules such as monosaccharides and free amino acids. Thus, we sought to monitor differences between solutions derived from soaking the peanut under different conditions. In order to track these modifications, we chose 1H Nuclear Magnetic Resonance (NMR) spectroscopy as the most suitable method.1H NMR spectroscopy provides a characteristic spectrum dependent on the chemical environments of individual hydrogen nuclei in the sample. We used this technique to obtain molecular profiles and to identify the chemical changes across different processing conditions. Raw, roasted and autoclaved peanuts were each soaked in distilled water for 48 hours and the resulting solution was analyzed by1H NMR spectroscopy (Figure 1).
The spectra of the raw and roasted peanut-soaked solutions did not differ greatly in peak distribution or intensity (Figure 1A & 1B). However, that of the autoclaved peanut-soaked solution was strikingly different (Figure 1C). Particularly, in the regions between 0.5 ppm and 2.0 ppm as well as between 6.5 ppm and 8.5 ppm, the autoclaved peanut-soaked spectrum had a different peak distribution with a series of broad peaks, indicating the presence of more soluble molecules, likely amino acids and peptides leaching out into solution. The higher-field region in the spectrum (0.5 ppm – 2.0 ppm) corresponds to1H atoms of alkyl groups, while the lower-field region (6.5 ppm – 8.5 ppm) corresponds to 1H atoms of amide bonds and aromatic groups, which likely represent free amino acids and peptide side chains.