Physical Properties of Upper Midwest U.S.-Grown Hybrid Hazelnuts

Abstract

Abstract. Nuts from F1 hybrid hazelnuts grown in Wisconsin were harvested and dried to eight different moisture contents. Nut dimensions and mass were recorded. Nuts were then subjected to uniaxial compression to determine total deformation required for rupture, rupture force, and rupture energy for each of the three major nut axes. Kernel dimensions, shell thickness, shell mass, and kernel mass of each nut were recorded after rupture. Hybrid hazelnuts and kernels were found to be smaller than European varieties. Nut geometry was found to change with nut size. When a nut is loaded, an initial crack forms along a longitudinal line parallel to the direction of applied load and then rapidly propagates until it has extended along two longitudinal lines (both parallel to the applied load), causing the shell to split into two pieces. Under lateral (Y-axis and Z-axis) loadings, the shell is split into nearly identical halves. Loading along the X-axis required the lowest rupture force, rupture energy, and rupture strain of all loading axes. Rupture force, rupture energy, and stiffness were shown to be highly correlated with moisture content. At lower moisture contents, shells fractured into more pieces. Keywords: Hazelnut, Nut cracking, Nut geometry, Nut rupture force, Shelling, Shell thickness.