Involvement of chlorophyllase on chlorophyll degradation in stored broccoli florets and its control by UV treatment
Conference proceedings article
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Author list: Kaosamphan A., Yamauchi N., Srilaong V., Aiamla-Or S., Wongs-Aree C., Uthairatanakij A.
Publisher: International Society for Horticultural Science (ISHS)
Publication year: 2010
Volume number: 875
Start page: 111
End page: 118
Number of pages: 8
ISBN: 9789066055636
ISSN: 0567-7572
eISSN: 2406-6168
Languages: English-Great Britain (EN-GB)
Abstract
Yellowing is the most visible deterioration in broccoli (Brassica oleracea L. Italica Group) that usually occurs with the progress of chlorophyll (Chl) degradation. This study deals with the control of floret yellowing in stored broccoli by using UV-B irradiation at 0 (control) and 8.8 kJ.m-2. The application of UV-B at 8.8 kJ.m-2 effectively delayed yellowing of broccoli florets. Chl a derivatives including chlorophyllide (Chlide) a, C132-hydroxychlorophyll (C132-OHChl) a and pheophytin (Phy) a levels in broccoli florets were decreased concomitantly with the enhancement of pheophorbide (Pheide) a and pyropheophorbide (Pyropheide) a levels especially in the control treatment. On the other hand, Chlide a, C132-OHChl a and Phy a levels were increased in 8.8 kJ.m-2 UV-B treated broccoli during storage at 15ฐC. Two types of chlorophyllase (Chlase) were identified by molecular exclusion chromatography. Type I was suppressed in UV-B treated broccoli on day 4, and the Km value of Type I was lower than that of Type II. Thus, the Chlase activity, especially Type I, was effectively suppressed by UV-B treatment, whereas Type II Chlase may take in part of Chl degradation in stored broccoli florets.
Keywords
Broccoli, Chlorophyllase, Chlorophyll derivatives
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