SO₂ Injury Mechanism Of Red Grape

SO2 is the main grape storage preservatives and has been used for more than 100 years, which mainly by sustained in two ways-release agents and sulphite dioxide gas direct fumigation. However, with the different varieties, origin, maturity and storage method of grape, the fruit injury susceptibility is differences.Red grape from the Yili district of Xinjiang were studied fruits and stems of SO2 sensitivity and patience to research the SO2 resistance of different fruits orchard and sampled for fruit storage and shelf life physiological indicators by different SO2 treatment regularly to analysis of the SO2 injury mechanism to establish the specific SO2 treatment of red grape.(1) The injury threshold studies. It showed that 0.5h treatment period with the concentration more than 3000μL/L and 2h treatment period with the concentration more than 800μL/L appeared skin bleaching and skin gloss rose rapidly, fruiting pedicels chlorophyll accelerating and pericarp anthocyanin degradation. Therefore, the SO2 damage threshold of red grape is 3000μL/L×0.5h、800μL/L×2h.(2) Analysis of trace elements. Under the same SO2 treatment, the Zinc content of fruit with skin bleaching index, color difference of L*, as well as changes in pedicels chlorophyll and pericarp anthocyanin, showed significant negative correlation and no significant influence with the content of Copper. In consequence, the enzyme and antioxidant enzyme systems of systems with Zinc are the key factors for stimulate or induce SO2 resistance.(3) SO2 injury mechanism.3000μL/L×0.5h of SO2 treatment, during shelf-life and low temperature storage, were both appeared SO2 injury phenomenon that PPO and POD enzyme activity first increased and then sharply declined, CAT enzyme activity quickly declined; relative conductivity and MDA quickly climbed and titration acid content increased prompting pedicels chlorophyll and pericarp anthocyanin content declined. The wax layer of skin surface disorderd and skin cell wall structure damaged leading skin surface appeared hole. The SO2 residues, when the tenth day of shelf life was 11.35mg/kg and when the 120th day of the low temperature storage was 12.56mg/kg, exceeded the FDA limits (10mg/kg). Therefore, SO2 injury led the skin surface wax layer and membrane organization structure damaged, coloring materials degradation, the bleaching phenomenon appeared, the acid alkali system of homeostasis broken and anti-oxidation system of resistance capacity damaged. In addition, SO2 accumulated within the organization. With the (1) part analysis, SO2 injury phenomenon is more obvious with the extension of storage time.(4) The red grape specific SO2 treatment research.800μL/L× 2h during shelf life and low temperature storage could maintain firmness, prevent membrane damage, delay nutrients decreased antioxidant system of avoiding damaged and control weight loss, decay and threshing phenomenon. The SO2 residues, when the tenth day of shelf life was the was 8.63mg/kg and the when the 120th day of low temperature storage was 8.79mg/kg, did not exceed the FDA limits (10mg/kg).Therefore,800μL/L×2h is the red grape specific SO2 treatment.