Effects of roasting and boiling on the physical and mechanical properties of 11 Portuguese chestnut cultivars (Castanea sativa Mill.)

In order to characterise the changes produced by boiling and roasting on the mechanical properties of 11 Portuguese chestnut cultivars (cvs.), the moisture, mass, force and energy required as well as shell and kernel stiffness of raw, boiled and roasted chestnuts were evaluated. In comparison to raw chestnuts, boiling increased the moisture content about 4% and roasting decreased the moisture content about 20%. Lamela and Judia cvs. required more energy to rupture the shell, while Negra and Boaventura kernels offered higher resistance to penetration. Colour was also evaluated because it is a parameter that influences the consumers' choice. Thus, processed chestnuts showed lower brightness than the raw fruits. After boiling, the most attractive chestnuts with higher brightness were cvs. Judia and Lamela, and after roasting, cvs. Lada and Lamela. These results provide important information about the cultivars most suitable for processing, resistant to mechanical harvest and most attractive to consumers.