Main content area

Low-speed magic-angle-spinning carbon-13 NMR of fruit tissue

Ni, Q.W., Eads, T.M.
Journal of agricultural and food chemistry 1992 v.40 no.9 pp. 1507-1513
apples, grapes, bananas, persimmons, peaches, plant tissues, spectral analysis, glucose, fructose, ripening, senescence
High-resolution carbon-13 NMR spectra of intact fruit tissues (grape, peach, persimmon, banana, and apple) were obtained while spinning the sample at the 'magic angle' (MAS) to improve resolution. Only low speeds were required (a few hundred hertz) to reduce susceptibility broadening, which decreased as apple > banana > grape. Fructose, glucose, and sucrose resonances appeared with correct chemical shifts, thus permitting their identification and quantitation. The most abundant anomers of fructose and glucose were observed. Scalar 1H-13C couplings were observable as multiplets in spectra taken without proton decoupling, providing an aid to assignment. Measured values of nuclear Ovrhauser effect (NOE) and longitudinal relaxation time T1 were consistent with rapid, effectively isotropic tumbling of sugar molecules,at rates very close to those observed in solutions of pure sugars. Potential applications of MAS NMR to fruit include quality assessment, analysis of chemical change accompanying ripening and senescence, and measuring the in situ physical state of dissolved components.