| Blueberry fruits are harvested at high temperature and rainy season. Physiological metabolism of fruits speeds up after picked up because of the filed heat and the hearty respiration. Ripening and senescence have been delayed during the cold storage. But pitting developed severely under improper refrigeration, especially during shelf life after cold storage. The quality of commodity of blueberry fruits has been affected. Therefore, it’s significantly that studied the regularity and physiology and biochemistry mechamism accompanying pitting development. Blueberries(Vaccinium spp.’LanFeng’) are the experimental material in this paper. The objective of this research was to discuss the regulatity of pitting in blueberries by analyzing the occurrence of piting during postharvest natural-rippening, cold storage and shelf-life after cold storage. And the relationship between pitting and reactive oxygen metabolism, energy metabolism and membrane lipid metabolism was explored. On this basis, the physiology and biochemistry mechamism accompanying pitting development has been in-depth exploration, which provides the theoretical foundation for the control measures of storage of blueberries. The main research results are as follows:The storage life of blueberries was extended at low temperature, but fruits quality declined during shelf-life after long-term cold storage. And the pitting symptom showed up obviously at the shelf-life. The fruits stored directly at room temperature and low temperature showed no problem. The analysis, which is the morphological characteristics and ultrastructure during the cold storage and the shelf-life after cold storage, shows that the pitting of blueberries was aggravated as the shelf-life time went on. Profile map of fruits displays that juice yield increased and pulpa pinked accompanying pitting development. At the same time, the cellosilk was reduced and the outer structure was damaged in cell wall. Different levels of injure has been happened in cytomembrane, caryotheca and plasmalemma. The starch grain reduced even losed. The apparent changes show that pitting development in the root of fruits. The effect of pitting development accompanying cell ultrastructure has been stated at cellular level.The qualities of blueberries changed accompanying pitting development including low firmness and Vc content, rising decay incidence and the imbalance sugar-acid ratio, which made the original relish and quality losed. The symptom of pitting expressed more obviouse and the quality declined more serious along with the extended time of cold storage. Phenylalanine ammonia lyase (PAL) and peroxidase (POD) are key enzymes involved in plant stress responses. By analyzing the activity of PAL and POD, it’s concluded that the activity of PAL increased and POD declined abnormally accompanying pitting development of blueberries. The long-term cold stress may be the reason of pitting development of blueberries according to analyzing each index during different storage process. During the cold storage, the increased of·O2-producing rate and H2O2content, and the decreased of activity of SOD, CAT and APX were inhibited at a certain degree. However, the reactive oxygen metabolism appeared the difference when blueberries were transferred from low temperature to the shelf-life at room temperature. Blueberries stored at shelf-life after cold storage when pitting occurred had higher-02producing rate and H2O2content, and lower activity of antioxidant-related enzymes, including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), than those stored at room temperature. It appeared unusual variation trend. The correlation analysis showed that one of the important reason of pitting development in blueberries at shelf-life after cold storage was the increased of·O2producing rate and H2O2content, the decreased of activity of SOD, CAT and APX and the anomalous changes.Contents of ATP, ADP and EC level rapidly decreased as pitting development in blueberries while the membrane peroxidation aggravated. The occurance degree of pitting generally aggravated as storage time progressed, at the same time, contents of ATP, ADP and EC were lower, energy loss of the cell were serious, and the activities of mitochondria respiratory metabolism-related enzymes-H+-ATPase, Ca2+-ATPase, SDH and CCO decreased rapidly. These changes could lead to energy loss of the cell and inhibited the synthesis of energy. The cell membrane integrity was destroyed. Enzyme and substrate began to contact. These results presented here demonstrated the high energy level could protect the integrity of cell membrane and alleviate the pitting development and the closely relationship between pitting and energy level by exposing blueberries to shelf-life after cold storage.The blueberries are rich in kind and content of fatty acid by analyzing the kind and content of fatty acid. The relative percentage content of unsaturated fatty acid was67.598%. During the cold storage, the composition of fatty acid has not changed obviously, but the relative content of unsaturated fatty acid, unsaturation index and degree of unsaturation of fatty acid decreased gradually as the extending of the storage time. The cell membrane permeability increased sharply, the MDA content rised significantly and the membrane lipid peroxidation was severe accompanying pitting development. The correlation analysis showed that the closely relationship between pitting and content of membrane lipid composition, degree of unsaturation and the peroxide of cytomembrane. Another important reasons of pitting development in blueberries at shelf-life after cold storage was the decreased of unsaturated fatty acid content and the LOX activity, the increased of cell membrane permeability and proline content.LTC treatment effectively alleviated the pitting development in blueberries, maintained the higher firmness and Vc content, and inhibited the increase of cell membrane permeability and the accumulation of product of lipid peroxidation during shelf-life after cold storage. Meanwhile, it promoted the activity of reactive oxygen metabolism related enzyme (SOD, CAT and APX), maintained higher scavenging ability on free radical and reactive oxygen. The treatment always maintains the higher energy levels and prevents the physiology damage of blueberries due to the energy loss by regulating the activities of mitochondria respiratory metabolism-related enzymes. These results were furtherly confirmed the closely relationship between pitting and reactive oxygen metabolism, membrane lipid metabolism and energy metabolism. |
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