Stress relaxation in cooked potato tubers expressed by improved rate controlled model

Stress relaxation in two varieties of cooked potato tubers was studied using the sigmoid rate controlled model (RCM). The model parameters C-1, C-2 and K were rationalised in dimensionless form (C-1' and C-2') or as a ratio to the initial stress (K'). The activation volume and some other helpful parameters were calculated from the model parameters. The activation volume behaved similarly as activation volume obtained for raw tubers, but variety differences are very low. Variety differences were observed for the model parameter N: 2.34 +/- 0.42 for 'Nicola' and 3.36 +/- 0.57 for 'Panda'. Other variety differences were observed for i) ratio of activation volumes of the cooked and raw tubers and ii) ratio of f-values obtained at the same test parameters for the varieties to be compared.