Computed tomography imaging-based bitter pit evaluation in apples

Bitter pit is an economically important physiological disorder in apples resulting in serious economic losses. Current visual assessment techniques are not completely useful in evaluating the extent of bitter pit development as they are limited to external symptoms. An X-ray computer tomography (CT) based imaging and associated image processing algorithm was used to assess the number of bitter pits inside the fruit and on the surface of apples. Samples of 40 healthy and 40 bitter pit affected 'Honeycrisp' apples were selected from two different field sites, and scanned with CT equipment on 0, 21 and 63 days after harvest. The results showed that the average number of bitter pits increased both on the surface and inside the fruits with increasing storage period. An average of 42-66% pits was present inside the apple fruits in bitter pit-affected apples. In addition, most of the newly developed bitter pits in healthy apples appeared within the fruit. Therefore, the usefulness of X-ray CT imaging as an effective phenotyping tool in identifying internal bitter pit and on the surface in the automated manner was demonstrated in this study.