Quantitative magnetic resonance imaging of satsuma mandarin fruit during growth

Whole-fruit proton magnetic resonance (MR) imaging was performed on satsuma mandarin (Citrus unshiu Markovich cv, Miho Wase) during a 15-week period c ommencing 10 weeks after anthesis and continuing to maturity, and at 6 week s after anthesis the following season. Images with long repetition times (> 1600 ms) and short echo times (20 ms) provided the dearest details of anato mical changes in the peel (flavedo, albedo) and vascular system, while thos e with similar repetition times but longer echo times (120 ms) were best fo r viewing juice sac morphology within pulp segments. At 6 weeks after anthe sis, images of fruits of slightly different physiological ages highlighted rapid changes in the vascular bundles and albedo tissue at this stage of de velopment. Variation in the relaxation measurements, T-1 and T-2, was deter mined from quantitative MR images of the juice sacs in equatorial slices, a nd images of expressed juice from whole fruit. Seasonal measurements of T-1 determined in situ (1760 ms) were significantly greater than those in juic e (1413 ms). By contrast, there was no mean seasonal difference between in situ T-2 measurements (360 ms) and those for juice (332 ms). No association s between trends in the MR data and total soluble solids, pH, titratable ac idity, and sugar and organic acid composition of the juice were established . Cell structure is identified as a hindrance in the use of quantitative MR imaging for probing compositional changes in solution in serial imaging st udies.