Quantitative magnetic resonance imaging of ‘Fuyu’ persimmon fruit during development and ripening

Qualitative and quantitative proton magnetic resonance imaging techniques were applied to persimmon (Diospyros kaki cv ‘Fuyu’) fruit during development and post-harvest ripening. Spin-lattice (T1) relaxation times in mesocarp parenchyma and vascular tissue exhibited a sigmoidal pattern of increase leading to commercial harvest, but declined abruptly during ripening, 2.5 weeks after picking. T1 times in parenchyma tissue were 1000 and 2100 ms in fruitlets, and at commercial harvest, respectively. T1 times in vascular tissue were consistently shorter than those in parenchyma tissue by 300 to 600 ms. In contrast, spin-spin (T2) relaxation varied over a narrow range during development, i.e., 82 to 106 ms, and 59 to 73 ms, for parenchyma and vascular tissue, respectively. During ripening, T2 measurements increased smoothly, commencing one week after harvest. Dry matter, water content, skin color, water-soluble tannins, soluble solids, and mineral and carbohydrate composition was also determined in companion fruit. No obvious associations linking physico-chemical and MR parameters were established, implying that the changes in relaxation measurements observed in ‘simple’ fruit systems can not be rationalised without recourse to more complex investigations involving SEM and different NMR spectroscopic and imaging techniques.