The objective of the paper was to determine changes in the texture of “Wasa” rye crispbread and ,,Three cereals” crispbread generated by changes in water activity. The investigations were performed using a method of analyzing the acoustic signals generated. Crispbread samples were broken in a strength testing machine “Zwick 1445”. While breaking the bread samples, an acoustic emission was recorded. The work involved in the breaking process and descriptors of acoustic emission were determined; the latter ones were: acoustic spectra, number of events during the acoustic emission, and crispness index of crispbread showing water activity from 0.038 to 0.650. The spectrum characteristics were presented in the range of frequencies from 0.1 kHz to 15 kHz using a WIDMOŚREDNI software. Spectrum characteristics of products investigated were analyzed very thoroughly, and it was stated that, irrespective of an aw value, the products emitted acoustic signals (sounds) in the range of frequencies from 2 to 8 kHz, and from 13 to 14 kHZ. Moreover, a gradually fading acoustic emission proved that changes were occurring within the texture of crispbreads. The crispness index of crispbread was calculated as a quotient of the number of acoustic emission (AE) events by the value of work involved in breaking. Within the range of water activity from 0.2 to 0.4, the two kinds of crispbread remained crispy, and this fact was evidenced by the crispness index. The number of acoustic emission events and the crispness index decreased exponentially with the increase in activity of water contained in crispbreads.
acoustic emission, crispbread, water activity, mechanical properties