FOOD SCIENCE ›› 2021, Vol. 42 ›› Issue (21): 177-185.doi: 10.7506/spkx1002-6630-20201202-030

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Comparison of Phenylpropane Metabolism and Callus in Peel and Pulp of Pumpkin during Wound Healing

LIANG Wei, ZHU Yatong, KONG Rui, CHAI Xiuwei, XIE Pengdong, BI Yang, Dov PRUSKY   

  1. (1. College of Food Science and Engineering, Gansu Agricultural University, Lanzhou 730070, China;2. Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, Rishon LeZion 7505101, Israel)
  • Online:2021-11-15 Published:2021-11-23

Abstract: Objective: To compare the differences in the key enzyme activities and product contents related to phenylpropane metabolism and the accumulation of suberin polyphenolics and lignin in the peel and pulp of pumpkin during wound healing. Methods: Artificially wounded pumpkins were kept at room temperature in darkness for healing. The activities of the key enzymes associated with phenylpropane metabolism and peroxidase and the contents of metabolites and H2O2 in the peel and pulp of pumpkins were determined, and the accumulation of suberin polyphenolicand lignin were observed. Results: During wound healing, higher contents of cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid and total phenolics as well as higher contents of p-coumaroyl alcohol, coniferyl alcohol, sinapyl alcohol and lignin were accumulated in the peel than in the pulp, and the accumulation rates and amounts of suberin polyphenolics and lignin were pronouncedly higher in the peel than in the pulp. The thickness of suberin polyphenolic and lignin cell layers in the peel were 17.55% and 24.37% higher than those in the pulp on the 7th day, respectively. Meanwhile, the activities of phenylalanine ammonia-lyase (PAL), cinnamic acid-4-hydroxylase (C4H), 4-coumaryl coenzyme A ligase (C4L), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) were 24.71%, 42.31%, 21.65%, 13.41% and 37.51% higher in the peel than in the pulp on the 5th day, respectively. Moreover, the H2O2 content in the peel was higher significantly (P < 0.05) than that in the pulp, with a 32.75% increase being observed on the 7th day. Conclusion: The peel of pumpkin showed higher phenylpropanoid metabolism-related key enzymeactivities and products contents and higher H2O2 content and peroxidase activity as well as higher accumulation rates and amounts of suberin polyphenolics and lignin than did the pulp. In summary, epidermis injuries in pumpkin fruit can heal fast, while flesh injuries cannot heal easily but instead aggravate the occurrence of rot. Therefore, deep injuries to pumpkin flesh should be avoided as much as possible during postharvest handling.

Key words: pumpkin; peel; pulp; wound healing; phenylpropanoid metabolism; callus

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