Involvement of chlorophyllase on chlorophyll degradation in stored broccoli florets and its control by UV treatment
A. Kaosamphan, N. Yamauchi, V. Srilaong, S. Aiamla-Or, C. Wongs-Aree and A. Uthairatanakij
Book of Abstracts, Southeast Asia Symposium Quality and Safety of Fresh and Fresh Cut Produce Greater Mekong Subregion Conference on Postharvest Quality Management in Chains, August 3-5, 2009, Radisson Hotel, Bangkok, Thailand.
2009
บทคัดย่อ
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, Child a, C132-OHChl aand Phy a levels were increasedin 8.8 kJ.m-2UV-B treated broccoli during storage at 15°C. Two types of chlorophyllase (Chlase) were identified by molecular exclusion chromatography. Type I was suppressed in UV-B treated broccoli on day 4, andthe Km valueof 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.