EFFECT OF WATER ACTIVITY ON THE STRUCTURE AND CHARACTERISTICS OF RYE AND FIBROUS CRISPBREADS

Abstract

The paper investigates the effect of water activity on the structure and mechanical properties of rye crispbreads and fiber crispbreads containing whole grain rye flour, wheat bran, oat flour and sesame seeds. The crispbreads were stored at water activities in the range of 0-0.75. The mechanical properties were measured using three-point bending tests. Water activity significantly affected the mechanical properties of the crispbreads. An increase in water activity caused an increase in the failure stress at water activities in the range of 0.030 to 0.255 for rye crispbreads and at 0.039-0.319 for fiber crispbreads. An increase in water activity above these values caused softening and a sharp decrease in the deformation modulus and failure stress. Rye crispbreads had lower deformation resistance than fiber crispbreads, probably due to differences in composition, and the added grain ingredients produced a more heterogeneous structure.