Studies On Chilling Tolerance Of Three Kinds Of Vegetables Reduced By Ice-temperature

Ice-temperature storage has been widely applied in the preservation of fruit and vegetable. In this study, spinach, pepper and tomato treated by ice-temperature were used to investigate the storage quality and the mechanism of cold resistance induced by cold shock. We also selected the optimum conditions of ice-temperature cold shock. Besides, intermittent freezing and spermidine were used in order to alleviate the chilling injury of pepper and tomato. We observed the influence of different treatments on chilling injury of pepper and tomato and explored the mechanism of chilling injury such as membrane lipid peroxidation and active oxygen metabolism. For spinach, calcium lactate and alkaline electrolyzed water were also used to investigate the optimum treatments as well as their effects on the quality and physiological changes of spinach. The main results were as follows:1. Ice-temperature storage was conductive to preservation of chlorophyll, vitamine C, soluble protein and postponement of respiratory climacteric. Ice-temperature treatment could induce the activities of SOD、CAT、POD, maintain the balance between the formation and detoxification of active oxygen species and inhibit the accumulation of MDA, thereby prolonging the shelf life of peppers. However, ice-temperature treatment led to slight chilling injury, resulting in depression, thus decreased the sensory quality of pepper.2. The inhibition of post-ripeness, reddening and respiration rate maintenance of Vc and soluble protein were observed in tomato treated by ice-temperature. After20-day storage, the commodity rate was remained about80%. Ice-temperature could reduce the chilling injury through the induction of the activities of radical scavenging enzymes such as SOD、POD、CAT, thus decreasing the membrane lipid peroxidation and the accumulation of MDA. 3. The optimum condition of ice-temperature cold shock was that pepper and tomato were treated by ice-temperature cold shock for6h. The optimum treatment could delay chilling injury incidence and remain minimum chilling injury index. The second was cold shock for2h. It would accelerate chilling injury if pepper and tomato were treated more than12h. At the end of storage, the chilling injury index of pepper treated for6h was34.04%less than2h treatment, for tomato was10.26%.4. Three treatments, ice-temperature cold shock, intermittent freezing (10℃for3h,4℃for3h then ice-temperature for6h), spermidine (1mmol/L for10min), could prohibit the increase of LOX activity of pepper and tomato especially during the end of storage and avoid excessive accumulation of MDA. Different treatments exerted significant influence on chilling injury alleviation of pepper and tomato by inhibiting membrane lipid peroxidation and structural damage. Spermidine has the best effect on suppressing the accumulation of MDA and increase of membrane relative conductivities of pepper and tomato.5. Three treatments, ice-temperature cold shock, intermittent freezing (10℃for3h,4℃for3h then ice-temperature for6h), spermidine (1mmol/L for10min), could enhance the activities of SOD、CAI、POD, prevent the tissues from damage of accumulated free radicals and improve the cold resistance of pepper and tomato. Spermidine was more effective in improving the activities of anti-oxidation enzymes of pepper, while ice-temperature cold shock was more effective in tomato.6. The optimum concentration of calcium lactate for spinach storage was1.0%.7. Both of the treatments,1.5%calcium lactate and alkaline electrolyzed water treatments, could inhibit respiration and delay the appearance of respiration peak. Compared with the control group, these two treatments were more effective in inhibiting the degradation of chlorophyll and vitamine C as well as the accumulation of nitrate. Spinach were kept green by the two treatments after8-day storage.1.5%calcium lactate and alkaline electrolyzed water treatments have also been found to play an important role in enhancing the activities of POD, CAT especially during the later storage period. As a result, the membrane lipid peroxidation was decreased and membrane integrity was maintained. After15-day storage, the MDA content of treated group were20.08%,26.33%smaller than that of control group.8. After one week storage, spinach treated by ice-temperature (-1±0.5℃) and simple low temperature (4℃) remained high commodity rate (more than80%), while spinach in room temperature has rotten and the commodity rate was less than50%. The experimental results showed that treatment of ice-temperature storage could delay the decrease chlorophyll and Vc content and remain good storage quality of spinach. Besides, it could also improve the ability of active oxygen scavenging and reduce the accumulation of hazardous substance.