Abstract
The effects of pressure and heat treatments on the hardening of Japanese radish were compared. Cubic samples of 1 cm3 were pressurized at 400 MPa and room temperature for 2 h or were heated at 60°C and atmospheric pressure for 2 h. Heat treatment increased the fracture load and fracture strain of Japanese radish more than pressure treatment. The rate constant for softening at 99.5°C was decreased to 52 and 24% by pressure and heat treatments, respectively. Both treatments decreased the degree of pectin esterification, and the amounts of water-soluble pectin and water-soluble calcium ions. Both treatments increased hexametaphosphate-soluble pectin, while sodium chloride-soluble calcium ions were slightly increased by the pressure treatment, and significantly by preheating.
