The detection of bruising and ripeness in fruit and vegetables

Tomato fruits (cv. Ailsa Craig) were scanned over the near-infrared wavelength range 850-1300 nm; 4 scans were taken on the surface of each of 10 fruits. The shear elasticity of surface was measured using a puncture test. Principal component analysis showed that reflectance in the range 850-1300 nm was strongly correlated with the tissue structure. The results also indicated that an image of a fruit or vegetable at an appropriate wavelength could be used to determine ripeness or to detect subsurface bruising. Reflectance was also affected by other factors so a single measurement would not itself give a direct indication of surface structure. However, the structure could be observed by taking the ratio of 2 measurements, one at an absorption wavelength and another at a reference wavelength which absorbed less strongly.