The Study On Freshness Keeping Mechanism Of Oligochitosan To Tomato Fruit

Oligochitosan is a kind of natural functional oligosaccharide polysaccharide with a variety of biological activities.In recent years it has been widely used in agriculture and medical field.It can not only inhibit the growth of pathogenic bacteria,induce the resistance of plants,but also improve the storage quality of fruit and vegetable,regulate postharvest physiology regulate metabolism.So it plays a important role in the preservation of fruits and vegetables.Tomato as a climacteric fruit,shelf life is very short,ripening fast,and easy preservation.This mauscript studied the physiological metabolism and the quality of tomato fruit in preservation process,in order to explore the quality preservation mechanism of Oligochitosan,and provide theoretical basis for further application of Oligochitosan.The results showed that the concentration of oligochitosan solution range from 50?100 ug/ml has a significant effect on physiological metabolism and storage quality.Oligochitosan solution treatment can significantly inhibit the generation of ethylene,ethylene release peak appear delayed two days,ethylene release rate 21.73 ?L/(kg·h),ethylene production inhibition rate of around 9%-10%;the same time,also delayed the respiratory peak,treated climacteric peak than the control group appears delayed two days,breathing intensity treatment group was 23.56 mg/(kg · h),respiration rate inhibition rate of 11%,effectively delaying the aging of the fruit.In addition,the process slowed oligochitosan reduced fruit firmness,delayed the change of fruit sweetness,effectively keeping the fruit color and ascorbic acid content,increased total phenolic content,is conducive to the formation of improving the taste of fruit and a good flavor.The application of oligochitosan on fruit inhibited ACC synthase activity,ACC content and ACC oxidase activity,and the trend curve and ethylene production of three roughly is same.The expression of LeACO1,LeACS2,LeACS4 was significantly inhibited in the process of exogenous oligochitosan induction,and the inhibition is consistent with changes in ACC synthase and ACC oxidase.Oligochitosan solution concentration within the range of 50?500 ?g/mL inhibition of Alternaria is not obvious.The inhibition of oligochitosan within this concentration range for spore germination is much greater than the yield of mycelium and inhibition of spore.After 6 h,500 ?g/mL oligochitosan treatment group on spore germination inhibition rate reached 100%,even 100 ug/mL oligochitosan treatment group of spore germination inhibition rate was over 50%.Comparison by scanning electron microscopy,the concentration range within 50?500?g/mL range of chitosan and oligochitosan on Altemaria fungus mycelium growth have damaging effects,mainly as mycelium shrunken,shriveled,surface rough,uneven,holes,and the destruction of the chitosan stronger than oligochitosan.The inhibitory concentration of chitosan and oligochitosan is different,chitosan,with the increase of concentration of hyphae damage increased,but the high concentration of chitosan,successful film in mycelium surface phenomenon,has certain protective effect to the hypha,concentration shall not be higher than 500 ?g/mL.The greater concentration of oligochitosan,the damage of hyphae is more serious.