Cell wall degrading enzymes activity is altered by high carbon dioxide treatment in postharvest 'Mihong' peach fruit

Peach fruits are ripen rapidly after harvest, especially at room temperature. It is difficult to handle because they are scars easily and easy to decay. It is generally acknowledged that modified atmospheres with elevated CO2 inhibits fruit ripening by reduces ethylene biosynthesis. This study was to investigate the affect of high concentration CO2 treatment on ethylene biosynthesis, ACO and softening-related enzymatic activity. Peaches were treated with high CO2 (90 pKa) at the time of sealing in the plastic chambers and then the chambers were ventilated after 3 and 12 h. Fruits treated with 90 kPa CO2 for 3 or 12 h exhibited a significant delay in firmness when compared to control fruits. In addition to fruit softening inhibition, the decay rate was also inhibited by CO2 treatment. Four days after storage at room temperature, CO2 untreated peaches had decay rate of 14%, whereas the decay rate was 6% and 3.5% in fruits treated with 90 kPa CO2 for 3 and 12 h. The ACO was inhibited by CO2 and the inhibition was enhanced with higher CO2 exposure time. Also High CO2 treatment inhibited the activities of softening-related enzyme such as PG, beta-Galactosidase, PEL promoted by ethylene biosynthesis in peaches. These results indicate that increasing levels of CO2 inhibit ethylene biosynthesis by reducing the ACO activity of peach fruits. Results suggest that the effect of CO2 on ethylene production in 'Mihong' peach fruit depended on exposure time and CO2 level. Also a short-term treatment with a high concentration of CO2 may be used to reduce ethylene biosynthesis, which may be induced after postharvest of fruit.