Only optimally picked apples meet the high standards of taste, color, appearance and fruit firmness, which are a prerequisite for a good sale of bearing apples, even after several months of storage. According to the method of Dr. Streif starch breakdown, flesh firmness and sugar content to be determined and calculated to the so-called Streif Index. In storage trials crop values for the Streif index already have been developed for many varieties of apples.
The determination of starch degradation is carried out by staining the sliced apples with Lugol's solution. So far the starch index was determined by visual comparison with a 10-step template. The result picture varied with the subjective judgment of the person performing and the surrounding light conditions. UP developed an image-analysis method to overcome this problems and to offer an objective determination of the starch degradation.