Studies On Bacteriostasis Of Gingerols, Properties And Applications Of Gingerols-Chitosan Composite Films

Fresh ginger (Zingiber officinale Rosc.) originally from shandong laiwu were used as raw materials. The optimum technological conditions of microwave-assisted extraction of6-gingerol and macroporous adsorption resin purification of6-gingerol were investigated. The chemical compositions of purified product were identified. Antibacterial effect of gingerols were also studied. Physicochemical properties of Gingerols-Chitson biodegradable composite films were detected. Simulation experiment of chilled beef by using Gingerols-Chitson composite films were also investigated. The main results and conclusions in the present dissertation were summarized as follows:1. The optimum conditions for the6-gingerol extraction were obtained as follows:528W of microwave power,26mL/g of solid-to-liquid ratio,31s of extraction time and ratio of ethanol is78%. Under the optimum conditions the yields of6-gingerol is15.35±0.85mg/g. Compared with traditinoal extraction methods, such as soaking extraction, stirring extraction, hot reflux extraction and sonicate-assisted extraction, MAE can reduce the extraction time and improve the efficiency of extraction significantly. Besides, MAE extract can achieve higher clearance rate of DPPH and ABTS free radical compared with traditinoal extraction methods at the same concentration (P<0.05)2. The optimal6-gingerol purification condition of D101resin column condition are as follows:2mg/mL of mass concentration of crude gingerols,2mL/min of eluant velocity,3BV of deionized water elution,80%ethanol of eluant,2mL/min of eluant velocity,4BV elution volume. There were34kinds of components of crude gingerols identified by Gas Chromatography-Mass Spectromete including y-curcumene(13.2%) and6-gingerol (3%), etc. There were9kinds of components of purified gingerols identified by GC-MS including less volatile components,50.4%of purified gingerols were identified as Zingerone. There were22kinds of components of purified gingerols identified by High performance liquid chromatography-mass spectrometry including gingerols and diarylheptanoids.3. The aim of this study was to investigate the antimicrobial potential of gingerols against six food-related bacteria. The minimum inhibition concentration (MIC) of gingerols against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Shigella dysenteriae, Saccharomyces cereviseae, Aspergillus niger were determined to be ranged from8.0to22.0μg/mL, which showed that gingerols effectively inhibited the growth of all test bacterial pathogens. Electron micrographs confirmed the effects of the gingerols on morphological and ultrastructural alterations in the treated S. aureus, S. dysenteriae and A. niger. The micrographs of the cell or mycelia treated with gingerols illustrated aberrant morphology such as shrinkage, partial distortion, disruption of cell wall and cell membranes, depletion of cytoplasm, etc. Morphological alterations might be due to the effect on cell permeability through direct interaction of gingerls with the cell membrane.4. Active chitosan (CH) films incorporating gingerols (GO) of different concentrations were developed. With the increasing amount of GO, complex films showed tendency toward redness, yellowness and darkness, with less water content, solubility, tensile strength, puncture strength, water vapour permeability. CH/GO films also showed less degree of crystallinity and thermostability. CH films showed smooth and homogeneous surface. CH/GO (1%) showed discontinuous construction and bumpy surface with microporous. Antioxidant ingredients released CH/GO composite film from different food system simulation solutions were effected by temperature and ethanol ratio.5. The preservative effects of Gingerol-Chitosan complex films on the chilled beef. The result showed rapidly decreasing pH value, fading redness, E. coli, lactic acid bacteria, yeasts, molds reproduction and lipid peroxidation were effectively inhibited by Gingerol-Chitosan complex films during chill storage. Sensory tests showed the color and odor of beef could be improved by Gingerol-Chitosan complex films, which chould extend the shelf life. Ginger flavor could be controled in acceptable level by adjusting the concentration of gingerols in comlex films.