Determination of the optimal ripeness stage of apples for juice production.

The optimal degree of ripeness for juice production differs from the recommended ripeness level for storage. In order to find the right point in time for processing, clear juices were produced from freshly harvested apples, and after different durations of storage. 'Jonagold' apples were studied in three consecutive years; 'Golden Delicious', 'Ilzer Rosenapfel', 'Pinova' and 'Red Topaz' were analysed in one year each. Apples for juice production should have reached the maximum value of the climacteric peak in respiration before processing since those juices are ranked higher in tastings. In order to meet this point for 'Jonagold' apples Streif-Index should be <= 0,05 and firmness <= 6,5 kg/cm(2). C*-value in base colour >= 37 and C*-value in cover colour >= 43 also seems to be advantageous. Colour values could also indicate the maximum storage duration before juice quality worsens. Further studies are required to find recommendations for the remaining varieties.