Effect of Standing After Preheating on the Softening Rate of Root Vegetables

Japanese radish and potato samples were preheated at 60 - 70 degrees C for 10 min and maintained at 20 degrees C for 0 - 7 h to control the changes in hardness. The slopes of the first order plots for softening and the Arrhenius plots of the softening rate constant were linear. The softening rate constants of Japanese radish and potato were reduced to 18 - 49% and 23 - 50%, respectively, compared to the fresh vegetables. The optimum cooking times of Japanese radish and potato samples with respect to hardness, calculated based on the softening rate constants, were 1.9 - 6.7 and 1.5 - 4.0 times longer, respectively, compared to fresh samples. To prevent browning and the elution of soluble components, samples were vacuum-packed, then pretreated, heated and subjected to sensory evaluation. All samples were evaluated for optimum hardness.