Mealiness assessment in apples using MRI techniques

Small samples of Top Red apples stored 6 months under controlled atmosphere (expected to be non-mealy) and 2 degrees C (expected to be mealy) have bee n used for MRI imaging. Multi-slice-multi-echo magnetic resonance images (6 4*64 pixels) have been recorded with a 8 ms echo time. Three out of four ap ples corresponding to the sample maintained under controlled atmosphere did not developed mealiness while three out of four fruits corresponding to th e sample stored at 2 degrees C became mealy after 6 months of storage. The minimum T-2 values obtained for the mealy apples show to be significantly l ower (F = 13.21) when compared with non-mealy apples pointing that a more d esegregated structure and a lower juiciness content leads to lower T-2 sign al. Also, there is a significant linear correlation (r = -0.76) between the :number of pixels with a T-2 value below 35 ms within a fruit image and th e deformation parameter registered during the Magness-Taylor firmness test. Finally, all T-2 maps of mealy apples show a regional variation of contras t which is not shown for non-mealy apples. Significant differences (F = 19. 43) between mealy and non-mealy apples are found in the histograms of the T -2 maps as mealy apples show a skew histogram combined with a "tail" in the ir high T-2 extreme which is not shown in the histograms of non-mealy apple s. These histogram features are also shown for an apple showing internal br eakdown indicating that in mealy apples there is a differential water movem ent that may precede internal breakdown. (C) 1999 Elsevier Science Inc.