TEXTURE OF CHINESE WATER CHESTNUT - INVOLVEMENT OF CELL-WALL PHENOLICS

Chinese water chestnuts (CWC) fail to soften during cooking. This is due to thermal stability of cell wall polymers involved in cell-cell adhesion. Information concerning these polymers was obtained by subjecting CWC tissues to a range of chemical and biochemical treatments designed to cleave selectively cell wall chemical bonds. Neither chelating agents nor weak base (Na2CO3, 0.05 M) facilitated vortex-induced cell separation (VICS) in fresh or canned tissues. However, VICS could be induced after extraction in dilute, cold alkali (0.1 M KOH), dilute hot acid, or a purified, specific endoxylanase. The CWC cell walls also exhibited considerable pH-dependent autofluorescence which originated mainly from ferulic acid and its derivatives. This disappeared during alkali-induced VICS. The results are consistent with the involvement of ferulic acid-containing cell wall hemicelluloses in the thermal stability of cell-cell adhesion and therefore texture in CWC tissues.