Nondestructive techniques for quality evaluation of pineapple fruits

Pineapple industry is the largest fruit industry in Thailand. For fresh consumption, fresh fruit is graded based on eating quality of the flesh as the 'First Grade' and 'Second Grade' which is related to the degree of sweetness and percentage of translucency of the flesh. The high flavour score and TSS/acid ratio of the first grade fruit was found to correlate well with sinking-floating characteristic but not with the skin colour. This characteristic of pineapple was also related to its tapping sound which showed 100% accuracy in quality sorting, particularly on a dual purpose 'Smooth Cayenne' pineapple cv. 'Pattavia.' Therefore, electronic acoustic sensing device could be developed as the alternative method for quality grading of pineapple. In northern cultivar such as 'Nang Lae': the correlation of the above parameters was less. Based on the image processing technique, the X-ray computed tomography (CT) has been used to produce a precise internal image of the fruit electronically without having to really cut open the fruit. Our recent research reveals that the intensity of X-ray CT images and CT numbers show significant correlation with the ripeness and translucency of flesh which reflects the taste quality. The technique could identify other internal defects such as bruise damage and porosity as well as identify the inferior fruit with non-symmetrical shape. Thus, the X-ray CT can be an effective nondestructive tool for internal quality evaluation as well as following the internal change of each fruit during storage under a certain treatment.