Glucosinolates in Broccoli Stored under Controlled Atmosphere

Abstract

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% O2, 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% O2 + 20% CO2 or 20% CO2 atmosphere. In contrast, the 4-methoxyglucobrassicin content increased during storage under low O2 atmosphere and increased further after transfer to air.