Effects of different postharvest treatments on the antioxidant properties and postharvest physiology of broccoli (Brassica oleracea L. var. italica)

In this research, the effects of different postharvest treatments on storage time, nutrient content and postharvest quality of 'Marathon F1' broccoli cultivar were studied. After harvest broccoli heads were separated into five groups. First group of broccoli heads were treated with 1000 ppb 1-Methylcyclopropene (1-MCP), the second group were stored in modified atmosphere packaging (MAP), the third group were treated with 1000 ppb 1- MCP and packed with MAP, the fourth group of broccoli heads were stored in palliflex storage system containing CO2 %6 +O2 %1.5 in the first year and the second year heads were stored in controlled atmosphere instead of palistore system using same CO2 and O2 levels and finally, the fifth group were stored as control. All groups of broccoli heads were stored at 0°C and 90-95% RH for 60 days. Some broccoli heads were kept at 20°C for 2 days for simulation of shelf-life conditions. During storage and shelf-life periods weight loss, surface color, titratable acidity, soluble solids, total phenolics, Vitamin C, chlorophyll and carotenoid content and antioxidant activity of broccoli heads were determined. Ethylene production of the broccoli heads was also determined at 20°C by Gas Chromatography. Total soluble solid content of broccoli heads increased in control and 1-MCP treated groups while it decreased constantly in others. Storage time decreased the weight and titretable acid amounts relative to storage time in all broccoli heads. The lowest weight loss was obtained from broccoli heads stored in MAP for both years. The most effective treatments in maintaining green color and preventing the yellowing (a* and b* values of broccoli heads, respectively) were MAP, palistore and CA in both years. Vitamin C content of the heads was decreased in all treatments during storage. The best treatments for prolonging Vitamin C degradation were palliflex and 1-MCP+MAP storage systems in first and second year, respectively. In both years, total phenolics and antioxidant activities increased within the first 30 days of storage and decreased afterwards. The lowest antioxidant activity was measured in control group for both years. The highest activity was, on the other hand measured in 1-MCP+MAP combination (in first year) and MAP (in second year) treatments. In both years, the most effective treatment for preventing chlorophyll degradation was obtained from 1-MCP+MAP combination. The highest carotenoid content was found be in MAP applied broccoli heads. In general, ethylene production of broccoli heads was low (around <2 µl.kg h-1).However, ethylene production rates in all the treated heads were lower than that of other non-treated (control) ones. Furthermore, ethylene production rate in 1-MCP treated heads was even lower than that observed in all other treatments. The tasting evaluation has revealed that the highest score was obtained from MAP and 1-MCP+MAP treated broccoli heads for appearance, taste and marketability. During entire storage and shelf-life periods, no decay and physiological disorder development were observed. Storage of broccoli heads in palistore, CA and MAP treatments significantly reduced weight loss and maintained visual appearance. These treatments also helped to prevent noticeable changes in surface color, measured as L*, a* and b* at the end of the cold storage and during the shelf-life. The best treatment for maintaining green color of the heads at the end of cold storage was palistore, CA and MAP treatments, respectively. It can be concluded that 'Marathon F1' broccoli heads can be stored at 0°C and 90-95% humidity up to 60 days by using MAP and 1-MCP + MAP combination without decay or serious loss in weight and head quality. KEYWORDS: Broccoli, palistore, controlled atmosphere, 1-MCP, MAP