Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/1997
Publication Date: N/A
Citation: Interpretive Summary: Interpretive Summary Broccoli florets become yellow and unmarketable when commonly handled and stored at elevated temperatures of 5 to 10 degrees C. Yellowing results sfrom both degradation of chlorophyll and formation of yellow pigments. These processes are regulated by controlled biochemical reactions. Thus, yellowing could be minimized if the reactions can be manipulated. However, the pathway of chlorophyll degradation and pigment formtion are not clearly understood, particularly when florets are exposed to ethylene or placed under a controlled atmosphere. This study provides information to help understand the pathway of chlorophyll degradation in broccoli florets, and indicates that the pathway is not altered by ethylene or controlled atmosphere. Additionally, it reveals that specific pigments are modified and are expressed during the yellowing process. Information from this study will be useful to other scientists working on the regulatory mechanisms of chlorophyll degradation and yellow pigment formation.
Technical Abstract: Technical Abstract Chlorophylls and xanthophylls were monitored in broccoli (Brassica oleracea var. italica Plen.) florets stored in air, air plus 10 ppm ethylene, or 10 percent CO2 plus 1 percent O2 controlled atmosphere (CA) at 15C. Chlorophyll a and b, as measured with HPLC, decreased in florets held in air and the decrease was accelerated with ethylene treatment and suppressed in CA. Chlorophyllied a and pheoporbide a appeared in fresh broccoli florets, but levels decreased significantly in all treatments during storage. The oxidized product of chlorophyll a, 132-hydroxychlorophyll a, did not accumulate. Xanthophylls decreased but new pigments, suggested to be esterified xanthophylls, formed with yellowing in stored florets. The chlorophyll degrading pathway in broccoli florets was not altered by ethylene or CA and differed from that reported for parsley and spinach leaves.