EN
The aim of his work was to determine the effect of water activity on mechanical properties of wheat grain. The mechanical properties of wheat varieties Bogatka and Kobra Plus were measured during uniaxial compression of grain. Water activity and the selected mechanical parameters were determined. The increase of water activity to 0.320for variety Bogatka and 0.430for wheat v. Kobra Plus caused an increase of force and displacement at rapture point as well as modulus of elasticity. It was shown that hardening of wheat grain was observed at those water activities. At water activities higher than 0.430, water plasticized the material and the increase of unit compression work and the decrease of force at rapture point were observed. The grain wheat v. Bogatka characterized the higher mechanical resistance and lower elasticity than observed for variety Kobra Plus.