Mechanical Modeling of Grape Destemming in a Horizontal Centrifugal Destemmer

Destemming is a critical operation in winemaking, determining the proportion of stems, skins, and vegetal fragments that enter the must and influencing both the mechanical integrity of berries and the extraction kinetics during fermentation. Horizontal centrifugal destemmers, which rely on a rotating beater and a stationary perforated cage, represent the most widely adopted technology in modern wineries. Despite their prevalence, the mechanical basis of berry detachment remains poorly quantified, with operational guidelines grounded largely in empirical practices rather than mechanistic understanding. This study develops an extended theoretical–numerical framework describing the forces acting on grape berries during destemming, focusing on the contributions of centrifugal force, tangential shear, and impact loading. Using realistic machine geometry and published distributions of pedicel detachment strength, the governing equations for each force regime are derived, and their interaction is evaluated through Monte Carlo simulations (n = 10,000). Results demonstrate that tangential shear is the dominant mechanism of detachment, particularly at lower rotational speeds where torque is maximized according to mechanical transmission principles. Centrifugal forces contribute modestly, while impact forces are largely ineffective for detachment and are instead associated with berry damage. The work provides a comprehensive reinterpretation of destemming mechanics and offers new guidance for machine design and operational strategies aimed at improving detachment efficiency while reducing berry damage.