Study On The Antibacterial Effect And The Application Of The Extract From Blueberry Leaves In The Fresh-cut Bamboo Shoot

In this paper, blueberry leaves were selected as a natural preservative. The extracting conditions were optimized, and the antimicrobial activity and antimicrobial mechanism of the extract from blueberry leaves was studied, as well the application in the fresh-cut bamboo shoot.In order to obtain optimum conditions for extraction of antibacterial substance from blueberry leaves, on the basis of single factor investigations, response surface methodology(RSM)was used to study effects of ethanol concentration, extraction time and solid-liquid ratio on the extraction rate of antimicrobial substances. Results showed that the optimum conditions were as follows:ethanol concentration85.00%, extraction temperature66℃and liquid-to-material ratio9.2:1mL/g. Under the optimized conditions, the maximum diameter of inhibition zone was18.07mm.Using antimicrobial assays against7strains, the results indicated that the extract from blueberry leaves have a wide antimicrobial spectrum and the minimum inhibitory concentrations for the growth of bacteria are below25mg/mL. Their antimicrobial kineticses are similar, if not identical. Meanwhile the extract is stable to temperature and has better antimicrobial activity under acidic conditions. The results show that the main components of blueberry leaves are phenols, flavonoids, organic acids, carbohydrates, coumarins, tannins, alkaloids and so on by system preliminary experiments.Relied on different concentration and duration of the extract from blueberry leaves acting on microorganism, morphological espial and biochemical assay were made. Electron microscopic picture of Escherichia coli showed change of cell, such as cellular membrane ruptured and leakage of cytoplasm, when adding the extract to Escherichia coli at1MIC. The phenomenon of leakage of intercellular alkaline phosphatase, protein, lactic dehydrogenase, etc was happened, when adding the extract to Staphylococcus aureus and Escherichia coli. The results suggest that the extract could gradually destroy the membrane integrity of the strain. At first, the pore on the cellular membrane induced by the extract is small and leak ions and small organic compounds. Then the enlarged pore leads to disintegration of the membrane, which ensured efficient killing of the strain.In this study, fresh-cut bamboo shoot was treated with the extract from blueberry leaves. The results indicated that the extract has better inhibitory action to the microorganism. It can reduce the loss of the moisture and decrease respiratory intensity. It not only delayed the increase of activities of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase, but also can also keep a better texture such as hardness, springiness and chewiness.