Bitter pit

Schumacher, R., Fankhauser, F. and Stadler, W. (1980). Influence of shoot growth, average fruit weight and daminozide on bitter pit , in Atkinson D., Jackson J.E., Sharpies R.O. and Waller W.M. Mineral Nutriton of Apple Trees, Butterworth, London, 83-91. 

Bitter pit in apples, caused by calcium deficiency, also common in light, sandy soil. 

Figure 8.7 Bitter pit on a Golden Delicious apple, (a) RGB image (b) NIR image. Illustration courtesy of C. Guizard, Cemagref...

Another, easily detected, example of structural changes in fruit tissue is that of bitter pit, which causes necrosis of the subsurface tissues in apples this in turn creates a localized dehydration such that the bitter pit spot appears white when using a very simple, one-band (1200nm) setting (Figure 8.7). 

Actual defects such as bruises or bitter pit encounter scattering coefficient changes, due to water movements in the tissues. As shown in Section 8.3.1 (see also Figures 8.6 and 8.7), these types of defect (bruise, bitter pit, necrosis) are relatively easily detected, with several research groups having successfully tackled the problem. 

Another defect, which is more difficult to detect than bruises, is bitter pit this appears as a subsurface necrosis of apple tissues, as spots of 2-5 mm diameter. Bitter pit appears as white spots in NIR images, as do old bruises showing dehydration (see Figure 8.7). 

Fig. 12. a) Canonical discriminant functions of LDA for Stark variety b) Canonical discriminant functions of LDA for Golden variety. C=control, B=bitter pit, T=scab and CY=Cydia Pomonella. 

A hyperspectral imaging system was developed by Nicolai et al. to identify a pit lesion on apples. A partial least squares (PLS) calibration model was constructed to discriminate between pixels of unaffected and bitter pit lesions [42]. The obtained calibration model was successfully validated on different apples. The... 

Nicolai, B.M., Lotze, E., Peirs, A., Scheerlinck, N., and Theron, K.I. (2006) Non-destructive measurement of bitter pit in apple fruit using NIR hyperspec-tral imaging. Postharvest Biol Technol, 40 (1), 1-6. 

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