Non-destructive pigment measurement as a monitoring tool for plum fruit (Prunus domestica) ripening

High fruit quality (taste, firmness, and aroma) of European plum (Prunus domestica) has become very important for markets and consumers in recent decades. Determining the correct picking time is a crucial factor affecting fruit quality and storability of the fruits. Hence, the non-destructive tool Multiplex^® (FORCE-A) was used to follow the plum fruit maturation to find out if it can be used for determining the optimal picking time. During the ripening process, the profile and the concentration of secondary metabolites in fruit peel change - flavonols decrease, anthocyanins increase and stay stable until the end. The non-destructive sensor Multiplex^® (FORCE-A) indicates a turning point in anthocyanin signal while the real concentration stays stable (measured by HPLC). The reason for the discrepancy in both measuring systems could be induced by a change in the cellular vacuoles of peel cells. This turning point may be used as a marker for determining the optimal picking time and should be investigated individually for plum fruit cultivars with blue fruit color.