| To determine the antibacterial activities of AOF (Alpinia oxyphylla Miq.), the study was aimed to optimized to enhance the antibacterial activities of ethanol extracts from AOF with ultrasonic-microwave assisted extraction method and to identify the components in it. Moreover, the keeping properties of fresh tilapia and mango was experimentized.1. Optimization of antibacterial compounds with UMAE from AOFThe part was optimized to enhance the antibacterial activities of ethanol extracts from Alpinae Oxyphyllae Fructus with ultrasonic-microwave assisted extraction method. After determining the preliminary range of the extraction variables though preliminary experiments, a four-variable with ethanol volume (Xi), solid-liquid ratio (Xi), extraction time (X3), temperature (X4) three-level(-1,0,1) Box—Benken design (BBD) was applied to determine the best combination of extraction variables for the antibacterial activities. The optimum conditions were as follows:ethanol concentration73.3%, extract temperature54.4℃, liquid-material ration15.2and extract time45.6min. We concluded that the order of factors influencing the response value of was as follows:ethanol concentration> extract temperature> extract time> the solid-liquid ratio.2. Research of the active ingredient from AOFPhenolics and oil was also determined by HPLC-DAD and GC-MS, respectively. Catechin, sygric acid, rutin, ellagic acid, chlorogenic acid, nootkatone, beta.-Humulene in AOF was considered as the potential antibacterial composition. And according to the disc diffusion assay test of different extract phases, the fraction of petroleum ether and ethyl acetate was determined by silica gel chromatography and GC-MS. The fraction of better antibacterial activities was10:1in the petroleum ether phase and19:1in the ethyl acetate phase. With the more significant antibacterial activities, the fraction was analyzed through GC-MS.3. Antibacterial activities of AOFOn the basis of the optimized extract conditions, the extract showed significant activities against the E.coli, B.subtilis, S. aureus. And according to the stability test, the AOF was presented heat, pH and uvioresistant stability. The significant antibacterial activities, relationship between three different samples, mechanism of the antibacterial activity was also tested in bacteria growth kinetic and SEM. The images directly illustrated the destructive effects of the AOF on the tested bacteria.4. Fresh-keeping of the tilapia and mango with AOF (1)Fresh-keeping of the tilapia with AOFTo study the influences of bio-preservative combined with AOF extract on the shelf-life of tilapia, through response surface methodology was designed by the optimum ratio of Microbiological (total viable count) and on the basis of the ratio of the bio-preservative coating, sensory characteristics and chemical (pH, TBA, TVB-N) was tested. The optimum ration was AOF0.94%, chitosan0.88%, acetic acid0.6%. And the coating presented excellent effect.(2)Fresh-keeping of the mango with AOFAOF were used as main materials of plastics to experiment on mango preservation at28℃～33℃, humidity being85%-90%. The result showed that the extract-sodium alginate composite coating had better preservation effect than positive control group and blank group. The mango could be stored10days with the weight loss rate being12.85%. The composite coating can restraint skin yellowing and decay of mango observably, reduce moisture loss, maintain good quality and high Vc content. Compared to blank group, the weight loss rate, decay index, skin yellowing index, soluble solid content and MDA content of the composite coating had reduced22.33%,46.67%,33.00%,8.74%,52.20%, VC loss had reduced69.19%, total phenols content had increased51.06%. |
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