**Table 2.** PLSR findings for SSC of mixed apple size groups.


As can be seen from Table 2, the SSC model built with mixed apple fruit diameter has a poor prediction performance with an Rp of 0.722 and an RMSEP of 1.086. When there is a large difference in apple fruit diameter in the model, it will cause the problem of poor prediction performance of the established model, so size correction of apple fruit diameter is needed to improve the prediction performance of its SSC model.
