市田柿の品質管理への小型MRIの応用  [in Japanese] Magnetic Resonance Imaging Applied to Quality Control of "Ichidagaki" Dried Persimmon Fruit  [in Japanese]

市田柿の水分分布が関係するカビ発生について新たな知見を得る目的で，予め試験品として選別した健全品とカビ発生品の水分分布を磁気共鳴画像（MRI）法を用いて検討した．1個のカビ発生品を1個または3個の健全品と一緒にスピンエコー法を用いて，0.2テスラの永久磁石と1辺12 cmの開口部をもつソレノイド型検出器を備えた小型MRIで測定した．水分および水分活性に有意差が認められない（<I>p</I> > 0.05）健全品とカビ発生品のMR画像では，NMR信号の強さをMR画像の明るさで表現した場合，両者の明るさに明瞭な違いが認められた．カビ発生品は健全品よりも中果皮，内果皮ともに明るくなるが，内果皮が特に明るくなった．T<SUB>1</SUB>およびT<SUB>2</SUB>緩和時間測定の結果，MR画像の明るい部分では運動性の高い水が増えていた．この明るさの違いは，市田柿のへた側から尻側までのどの横断面でも見られたので，2次元MRIで任意の一断面を測定すれば健全品とカビ発生品の水分分布の違いをとらえることができた．MRIは水分や水分活性ではとらえられなかった市田柿の健全品とカビ発生品の水分分布の違いを，水の運動性の違いからとらえることができたため，品質管理の手段として実用化の進展が期待される．

Moisture distribution in "Ichidagaki" dried persimmon fruit was examined to clarify the water-related differences between sound and moldy samples by using magnetic resonance imaging (MRI). One moldy product was measured together with one or three sound samples by the spin-echo (SE) method with a small MRI system equipped with a 0.2-Tesla permanent magnet and a solenoid-type detector with a 12-cm<SUP>2</SUP> opening. Differences in the moisture content and water activity values of the sound and moldy samples were not significant (<I>p</I> > 0.05). With NMR signal intensity expressed as brightness in the images, the mesocarp and endocarp tissues of the moldy samples were brighter than those of the sound samples. Endocarp tissues of the moldy samples produced especially bright images. This difference in brightness was found in all 2-D images horizontally sliced from 3-D images. The brighter the area in an MRI image, the higher the amount of water present. The T<SUB>1</SUB> and T<SUB>2</SUB> relaxation time-weighted imaging methods revealed that water mobility distributions of the moldy samples shifted upward and endocarp tissues of the moldy samples had higher water mobility. We found that MRI can be used to detect moisture distribution differences between sound and moldy samples of "Ichidagaki" dried persimmon fruit, and expect this practical application of MRI in the quality control of the fruit to be useful.