Structural changes in cell wall of Japanese radish accompanied by release of rhamnogalacturonan during pressure cooker heating.

Changes in the cell wall of Japanese radish due to heating at 100 °C or 117 °C for 3 h were examined. Signals in C cross polarization magic angle spinning solid-state NMR (which detects rigid components) showed no differences between heating temperatures. C pulse saturation transfer magic angle spinning NMR (which detects flexible components) showed clear temperature-dependent changes in the rhamnose side chains of rhamnogalacturonan. Alcohol-insoluble solids isolated from raw samples were heated in water at 100 °C or 117 °C for 3 h. The concentrations of dissolved sugars and metal ions measured after heating in water at 117 °C were greater than in samples heated at 100 °C, indicating that loosening of cell wall structures increased with temperature, likely via degradation and elution of rhamnogalacturonan followed by β-elimination of homogalacturonan, and fewer interactions between cell wall components, including divalent metal ions. Vegetable shape was retained despite fewer interactions.