Etiology of UV-C-Induced Browning in Var. Superior White Table Grapes
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- 作者：Rocí ; o Gonzá ; lez-Barrio ; Marjatta Salmenkallio-Marttila ; Francisco A. Tomá ; s-Barberá ; n ; Emma Cantos ; and Juan Carlos Espí ; n
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2005
- 出版时间：July 27, 2005
- 年：2005
- 卷：53
- 期：15
- 页码：5990 - 5996
- 全文大小：379K
- 年卷期：v.53,no.15(July 27, 2005)
- ISSN：1520-5118
文摘
White table grapes, var. Superior, were treated with UV-C light after harvest to increase stilbenesconcentration, especially trans-resveratrol (RES), because this may be of relevance to the health-promoting properties assigned to these compounds. However, irradiated grapes also developed somebrowning on the surface on the third day of storage at 22 
C, with the subsequent detriment in thesensorial quality of the fruit. Possible causes for browning development during storage wereinvestigated. 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 grapeswhich could be considered as a general wound response in plant tissues. These results suggest thatthe development of browning in Superior white grapes after UV-C treatment is not closely relatedwith the evolution of oxidative enzymes during storage and may be mainly due to the decrease ofchlorophylls content.Keywords: Browning; chlorophyll; polyphenol; pheophytin; polyphenol oxidase; peroxidase; stilbenes;table grape; UV-C; cell wall; microstructure
C, with the subsequent detriment in thesensorial quality of the fruit. Possible causes for browning development during storage wereinvestigated. 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 grapeswhich could be considered as a general wound response in plant tissues. These results suggest thatthe development of browning in Superior white grapes after UV-C treatment is not closely relatedwith the evolution of oxidative enzymes during storage and may be mainly due to the decrease ofchlorophylls content.Keywords: Browning; chlorophyll; polyphenol; pheophytin; polyphenol oxidase; peroxidase; stilbenes;table grape; UV-C; cell wall; microstructure