Proton relaxation of waxy and non-waxy rice by low field nuclear magnetic resonance (LF-NMR) to their glassy and rubbery states

The proton relaxation of waxy and non-waxy rice was investigated using low field nuclear magnetic resonance (LF-NMR). The relaxation showed 3 types of protons from their relaxation times as strongly-bound (T_2b), moderately-bound (T₂₁) and weakly-bound (T₂₂). These relaxation times were analyzed as a function of temperature. The strongly-bound proton showed three characteristics of critical temperatures. The second critical temperature (i.e. when relaxation time increased after a plateau region) was observed as close to the DSC glass transition. Considering relaxation time as a function of temperature, one maximum peak was observed in the case of T_2b and T₂₁, whereas T₂₁ showed an additional minimum peak. The relaxation time T₂₂ did not show any peak, however non-waxy rice showed a minimum peak while it increased after a plateau region in the case of waxy rice. The characteristic relaxations were relatively similar in the cases of waxy and non-waxy rice, while both rice varieties showed similar diffraction angle (2θ) with different intensities as measured by X-ray diffraction (XRD).