Glucosinolates in Broccoli Stored under Controlled Atmosphere

Content of total and individual glucosinolates were determined in, 'Marathon' broccoli florets (Brassica olerucea L. var. italica stored 7 days at 10C under air, 0.5% O 2, 0.5% O2 + 20% CO2 or 20% CO2 atmosphere, followed by transfer to air for 2 days. 'Marathon' broccoli contained glucoraphanin, glucobrassicin, neoglucobrassicin, glucoiberin, 4- methoxyglucobrassicin, progoitrin, glucoalyssin, and gluconasturtiin. The methylssulfinylalkylglucosinolates (glucoiberin and glucoraphanin) and the indol-3-ylmethylglucosinolates (glucobrassicin, neoglucobrassicin and 4- methoxyglucobrassicin) accounted for 78% and 20% of the total content, respectively, in freshly harvested broccoli. CA treatment and storage time had no significant effect on the relative content of these two groups of glucosinolates. Freshly harvested broccoli contained 47 µmol glucosinolate/g dry weight. The total glucosinolate content increased 42% and 21% during 7 days storage under air and 0.5% O2 + 20% CO2, respectively, as compared to freshly harvested broccoli, and decreased 15% in broccoli stored under 20% CO2. Treatment with 20% CO2 in the absence of 0, resulted in visible CO, injury and water soaking of the tissue. Aeration had no significant effect on total glucosinolate content but reduced the glucobrassicin content 35% in broccoli stored 7 days under 0.5% O 2 + 20% CO2 or 20% CO2atmosphere. In contrast, the 4-methoxyglucobrassicin content increased during storage under low O2 atmosphere and increased further after transfer to air. Plants belonging to the order Capparales including Brassicaceae, are characterized by their content of glucosinolate s (Bjerg and Sorensen, 1987a). Glucosinolates and their breakdown products are important aroma and flavor compounds in Brassica vegetables (MacLeod, 1976), such as cabbage, Brussels sprouts, broccoli, cauliflower, and horseradish. The most notable example is ally1 isothiocyanate in mustard and horseradish arising from enzymic breakdown of sinigrin. This compound causes a pungent and lachrymatory response upon cutting and chewing (Gilbert and Nursten, 1972). Indol-3-ylmethylglucosinolates, which occur in appreciable amounts in several Brassica vegetables, are of interest for their potential contribution of anticarcinoge nic compounds to