Phenolics, lignin, peroxidase activity and increased firmness of damaged pericarp of mangosteen fruit after impact

Firmness, phenolics and lignin content, and peroxidase activity were studied in damaged pericarp of mangosteen (Garcinia mangostana L.) fruits after impact. Firmness of damaged pericarp increased rapidly after impact in air. Under nitrogen however, damaged pericarp was less firm and had lower lignin contents, with more total phenolics than in air. Pel-oxidase activity in damaged pericarp was greater than that in undamaged pericarp after impact. Damaged pericarp infiltrated with cycloheximide was less firm and had lower lignin and higher total phenolic contents than those of damaged pericarp without cycloheximide. Total phenolics in undamaged and damaged pericarp separated by thin layer chromatography showed no difference in patterns of distribution in R-f values. Five R-f values (0.00, 0.03, 0.06, 0.30 and 0.46) of phenolics in damaged pericarp had lower absorbance at 190-400 nm, while three R-f values (0.63, 0.77 and 0.88) did not change. These results suggest that impact enhances incorporation of phenolics into lignin and that there is involvement of peroxidase activity in increased firmness of damaged pericarp. (C) 1998 Elsevier Science B.V. All rights reserved.