Method and system for determining the quality of a crop

The invention relates to a method for determining the quality of a crop, comprising the determination of at least one characteristic parameter of the photosynthesis process of the crop, which parameter serves as a quality indicator for the crop, wherein the parameter belongs to the photosystem I (PSI), which is known per se, and wherein the determination of the parameter comprises the following steps: (a) bringing at least some of a number of types of molecules which are located on the donor side of PSI into an oxidised state; (b) allowing at least some of the oxidised molecules to be reduced; and (c) determining a relaxation parameter which contains information on the rate of the reduction, wherein step (c) comprises at least the following sub-steps: (1) measurement of absorption of light in a predetermined wavelength region by the oxidised molecules in the crop during the reduction, and (2) calculation of a rate parameter which contains information on the rate of a change in the measured absorption as a function of time, the rate parameter being the relaxation parameter. The invention also relates to a system for determining a quality indicator for a crop on the basis of the relaxation parameter obtained using the said method