The potato and bean sprouts were tested using dynamic mechanical analysis (DMA), in air with 90% humidity between 30 and 90 degrees C. Temperature plots of storage (SM i.e. elastic) and loss (LM i.e. inelastic) moduli were obtained. The SM and LM values were the basis for the calculation of the loss tangent (LT), the parameter expressing the ratio of inelastic to elastic parenchyma toughness. As expected, the tissue toughness decreased with increasing temperature. For both moduli, the characteristic temperature area with temperature slope minimum was observed - it was termed the negative peak on the temperature slope plots or separation point. It was shown that the negative peak was related to an increase in the inelastic part of the tissue toughness. These changes were interpreted as a consequence of pore protein denaturation followed by changes of the internal stresses inside the parenchyma cells. (C) 2013 Elsevier Ltd. All rights reserved.