Non-Destructive Evaluation of Apple Fruit Maturity on the Tree

The evaluation of apple fruit maturity (Malus domestica Borkh.) is based on destructive analyses, analysing starch conversion, fruit flesh firmness and Brix value. Specific threshold values exist for each cultivar and according to post-harvest treatment and storage. A rapid non-destructive method to evaluate the fruit maturity could be very important to obtain more reliable results. Since miniaturised spectrometer modules were available, visible/near infrared spectroscopy has been used to build up portable spectrometer equipment.

Measurements were carried in weekly intervals on three cultivars in a commercial orchard in 2003 to 2005 during the period from August to October. The fruit maturity stage was described by two non-destructive spectral indices i) the chlorophyll decrease and ii) the anthocyanins increase. Both indices demonstrated the high variability of fruit maturity stage in orchard. The characteristics of several apple cultivars could be used to evaluate the actual differences in maturity stage. The spectral indices pointed out the influence of fruit yield and of temperature on the fruit maturity.