Etiology of UV-C-induced browning in var. Superior white table grapes

Rocío González-Barrio, Marjatta Salmenkallio-Marttila, Francisco A. Tómas-Barberán, Emma Cantos, Juan Carlos Espín (Corresponding Author)

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Abstract

White table grapes, var. Superior, were treated with UV-C light after harvest to increase stilbenes concentration, especially trans-resveratrol (RES), because this may be of relevance to the health-promoting properties assigned to these compounds. However, irradiated grapes also developed some browning on the surface on the third day of storage at 22 °C, with the subsequent detriment in the sensorial quality of the fruit. Possible causes for browning development during storage were investigated. The phenolic-related oxidative enzymes, polyphenol oxidase (PPO) and peroxidase (POD), were not specifically activated, and no new isoforms appeared upon UV-C treatment. UV-treated grapes had lower content of chlorophyll b than control grapes on the fourth day of storage, concomitant with the increase of pheophytins (chlorophyll degradation derived compounds). Microscopy data showed lower fluorescence emission in chloroplasts from the UV-treated samples, which may explain the decrease of chlorophylls content in the corresponding grape berries extracts. In addition, microscopy images showed cell wall thickening in the skin tissue of UV-treated grapes which could be considered as a general wound response in plant tissues. These results suggest that the development of browning in Superior white grapes after UV-C treatment is not closely related with the evolution of oxidative enzymes during storage and may be mainly due to the decrease of chlorophylls content.
Original languageEnglish
Pages (from-to)5990-5996
JournalJournal of Agricultural and Food Chemistry
Volume53
Issue number15
DOIs
Publication statusPublished - 2005
MoE publication typeA1 Journal article-refereed

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Keywords

  • Browning
  • chlorophyll
  • polyphenol
  • pheophytin
  • polyphenol oxidase
  • peroxidase
  • stilbenes
  • table grape
  • UV-C
  • cell wall
  • microstructure

Cite this

González-Barrio, R., Salmenkallio-Marttila, M., Tómas-Barberán, F. A., Cantos, E., & Espín, J. C. (2005). Etiology of UV-C-induced browning in var. Superior white table grapes. Journal of Agricultural and Food Chemistry, 53(15), 5990-5996. https://doi.org/10.1021/jf0504115