Modeling RGB-based estimation of apple fruit maturity in the semi-arid Loess Plateau via starch-iodine staining mapping

In order to accurately determine the appropriate harvest period for new and superior apple varieties in the Loess Plateau region, starch staining charts were created for fruits of 12 apple varieties harvested at different times, and a maturity estimation model was established based on the RGB model. The results showed that Honglu, Gala, and NY543 reached maturity 115–120 days after flowering, Asda 130–135 days, Yanfu No.0, 2001 Fuji, KCo No.8, Yanfu No.3, Chengji No.1, and Ganhong 180–185 days, and Shoufu No.1 and Jingning No.1 at 185–190 days after flowering. A feasible model for estimating the fruit starch index was established based on the RGB model, using linear combination parameters of the R, G, and B color values of fruit slices. This model can accurately determine fruit ripeness, providing a theoretical basis for high-quality apple production and cultivation. • Determining the Maturity and Harvest Periods for Different Apple Varieties • Establishment of a Colored Starch Atlas for Different Apple Varieties. • Based on the RGB Model, a Fruit Ripeness Prediction Model was Established.