Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/1997
Publication Date: N/A
Citation: Interpretive Summary: Broccoli florets become yellow and unmarketable when they are handled and stored at the usual commercial temperatures of 5 to 10 degrees C. Yellowing is the result of chlorophyll degradation and the formation of yellow pigments. Both of these processes are regulated by biochemical reactions, so yellowing can be retarded if these reactions are manipulated. However, the pathways of chlorophyll degradation and yellow pigment formation are not clearly understood, particularly when florets are exposed to ethylene or placed in controlled atmosphere storage. This study provides information leading to a better understanding of the chlorophyll degradation pathway in broccoli florets and shows that the pathway is not affected by ethylene or controlled atmosphere. Additionally, specific pigments become modified and are expressed during the yellowing process. The information resulting from this research will be useful to other scientists studying the regulatory mechanism of chlorophyll degradation and yellowing pigment formation.
Technical Abstract: Chlorophylls and xanthophylls were monitored in broccoli (Brassica oleracea L. 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. Chlorophylls 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. Chlorophyllide a and pheoporbide a were present in fresh broccoli florets, but the 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, apparently 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.