Abstract: Energy plays an essential role in the postharvest senescence of fruits and vegetables. In order to study the effect of O2/CO2 controlled atmosphere packaging on the energy metabolism and storage quality of broccoli at 10 ℃, different controlled atmospheres: 20% O2 + 80% CO2, 50% O2 + 50% CO2, and 80% O2 + 20% CO2 were employed as the experimental groups while natural air was used as the control. pH, the activities of pyruvate dehydrogenase (PDH), succinate dehydrogenase (SDH) and cytochrome c oxidase (CCO), energy charge, ascorbic acid, color value (hue, H) and water content were periodically measured during storage. The results showed that compared with the 50% O2 + 50% CO2 treatment, excessive proportion of CO2 such as 20% O2 + 80% CO2 significantly decreased the pH, PDH, SDH and CCO activities, and energy charge, and finally resulted in a decrease of VC content, H value and water content in broccoli during storage. Excessive proportion of O2 such as 80% O2 + 20% CO2 increased the activities of PDH, SDH and CCO during the early storage period followed by a rapid drop during the later storage period, which hindered the establishment of a stable and continuous energy supply system. Appropriate controlled atmosphere with 50% O2 + 50% CO2 regulated the pH and respiratory key enzyme activity in broccoli during the whole storage period to establish a sustainable and stable energy supply system, and consequently ensure the quality maintenance of broccoli during storage. The correlation analysis showed a highly positive correlation between energy charge and VC, energy charge and H value, and energy charge and water content, with the highest correlation coefficient of 0.996. Therefore, energy charge can be used as an important indicator in measuring and optimizing the storage conditions for broccoli.

Key words: broccoli, O2/CO2 controlled atmospheres, energy, preservation, correlation analysis