The Effects Of O₂/CO₂ Controlled Atmospheres On Storage Quality Of Broccoli

Broccoli is a highly perishable vegetable and easily loss its nutritional and market values under normal temperature, which behaves degree at 2-3 days. Studies demonstrated that controlled atmospheres (CA) is the one of the most effective and advanced way in postharvest storage of fruits and vegetables. In traditional CA, the gas concentration usually used low O2 (2%to 3%) and high CO2 (more than 5%) during storage, which can increase products storage quality in certain content, but negative effects such as CO2 injury and off-flavor may be occured. Whether relative high O2 level (above 21%) could enhance the endurance capability of horticultural products to high CO2 concentration, whether the combination atmospheres of high O2/CO2 could extend the shelf life of horticultural products, little information is available from literatures. In this article, the effects of O2/CO2 controlled atmospheres on storage quality of broccoli were studied. The conclusions are as follows:1. In this research, the effects of CA with different O2/CO2 levels, i.e.70% O2+ 30% CO2,60% O2+40% CO2,50% O2+50% CO2,40% O2+60% CO2,30% O2+ 70% CO2, and air (Control) on the physiological and biochemical properties of broccoli during storage were investigated at storage temperatures of 0,10 and 20℃, respectively. The relative humidity was controlled at 80%-90%. Respiration rate, ethylene production, chlorophyll, ethanol, acetaldehyde, H2O2, O2- and Vc contents and yellowing rate, malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD) activity of broccoli florets were measured at regular intervals during storage. Results showed that treatments of 60% O2+40%CO2 at 0℃,50%O2+50%CO2 at 10℃, and 40%O2+60%CO2 at 20℃ could maximum inhibit respiration rate and ethylene production, maintain chlorophyll and ascorbic acid content and high SOD, POD activity, reduce the accumulation of H2O2, O2-, acetaldehyde, ethanol and MDA content, and extend the shelf life of broccoli heads from 28,12 and 3d to 49,31, and 14d, respectively.2. Effect of treatments of 70%O2+30%CO2,60%O2+40%CO2,50%O2+50% CO2,40%O2+60%CO2,30%O2+70%CO2 at 10℃ (natural air as CK) on respiratary pathway such as embden-meyerhof-parnas (EMP), tricarboxyfic-acid-cycle (TCA), phosphopentose pathway (PPP or HMP), cytochrome pathway (CCP), and their key enzymes of broccoli florets were measured during storage. The results indicated that 50% O2+50% CO2 lead to an obvious decrease in respiratory rate of broccoli and it could keep higher rate of HMP and higher activity of G-6-PDH,6-PGDH. It also could inhibit the activity of SDH,6-P-F and CCO.3. To study the residual effect of CA on broccoli preservation at 15℃, broccoli heads were treated with 40% O2+60% CO2 just for 1,2 and 3 days respectively, then put these broccoli heads in the air with the same temperature. The results showed that the shelf life of product treated with 40%O2+60%CO2 for 3 days was 9 days, while with 40%O2+60%CO2 for 1,2 days was 5,7 days.