Abstract
In this paper, we studied the practical usefulness of the NMR-based non-destructive testing method for watermelon. So far, in some experiments, it has been shown that void detection and sugar content measurement are possible in principle using the NMR technique. However, in those experiment, the samples were fixed during measurement. Therefore the practical usefulness of this method has not been proved yet.
In this study, to show the practicability of the NMR method, samples were carried by a conveyer during measurement.
In the void detection experiment, samples were moving at 350mm/s. NMR signal intensity from moving sample was reduced about 30% comparing to fixed sample. However, the same accuracy was obtained for both the fixed measurement and the carrying measurement.
For sugar content measurement, to know the most suitable measurement position, we investigated the distribution of sugar content in some samples before investigating the possibility of measuring sugar content with the conveyer. We obtained a result showing that the center is the most appropriate position. After the investigation, we measured NMR relaxation time of samples. In the measurement we stopped the samples 6 seconds at the magnet center. Then we analyzed the relation between sugar content and NMR relaxation time of the center of samples, and made a calibration equation.
The SEP and the BIAS of the calibration equation was 0.49 Brix% and 0.02 Brix% respectively. This result suggested that the NMR relaxation time a was good parameter to predict the sugar content of watermelon.
In conclusion, we have established the practicability of the NMR method for non-destructive testing of watermelon.
