Detecting internal breakdown in apples using interactance measurements

A technique using body transmittance in the 450- to 1050-nm region was evaluated as a non-destructive technique for identifying apples with internal breakdown. Apples with internal breakdown absorbed shorter wavelengths of light (<750 nm) more than good apples; however, light at longer wavelengths (>750 nm) was absorbed more by good apples than defective ones. A classifier based on the ratio between the light intensity at 720 and 810 nm was used to segregate apples with internal breakdown from good apples. Only 6.3% of the good apples were incorrectly classified: however, bruises on the apples contributed to the incorrect classification of good apples. None of the apples with severe internal breakdown were incorrectly classified. Apples with very slight internal breakdown contributed to most of the 12.0% error of misclassifying defective fruit as good. The number of misclassified apples was reduced by adjusting the cut-off; however, the number of good fruit that would be discarded increased.