Spatial and temporal variability of coffee fruit detachment force in relation to maturity aiming at smart harvesting

The implementation of smart harvesting, guided by variability in fruit detachment force, has the potential to facilitate and expand selective coffee harvesting, thereby strengthening the specialty coffee market. This study aimed to evaluate the variation in coffee fruit detachment force throughout the day, considering ripening stage and solar exposure. Evaluations were conducted over two harvest seasons (2018/2019 and 2019/2020) in an East-West-oriented Catuaí Vermelho IAC 144 coffee plantation located in Presidente Olegário, MG, Brazil. Following the principles of Statistical Quality Control (SQC), we analyzed the detachment force of fruits at different ripening stages across various times of the day and on the North- and South-facing sides of the plants, which receive higher and lower solar exposure, respectively. A portable digital dynamometer was used for measurements. The results indicate that both the time of day and solar exposure influence the coffee fruit detachment force, with increased solar exposure reducing the force required for fruit detachment. Fruits at the cherry stage exhibited the lowest detachment force and least variation in the afternoon, suggesting that this period is optimal for selective mechanized harvesting from a process quality standpoint.