| 30 kinds of plant material are used to extract antimicrobial active ingredients with water, ethanol and petroleum ether, respectively. Then using disk diffusion method to study the effects of plant extract on the harmful micro-organisms in foods, results show that: Chinese herbal medicine have different antibacterial effect, the effect of ethanol as extraction solvent is better than the other two kinds of solvents. Coptis chinensis and magnolia officinalis have the strongest effect on Staphylococcus aureus, and the maximum bacteriostatic diameter is more than 30mm. Coptis chinensis, magnolia officinalis, lonicera have the strongest effect on Bacillus subtilis, all the bacteriostatic diameter is more than 20mm, coptis chinensis and polygonum cuspidatum have the strongest effect on Escherichia coli and the inhibitory bacteriostatic diameter is 15mm. Cloves and coptis chinensis have the strongest effect on Saccharomyces cerevisiae, the inhibitory diameters is respectively 24 mm and 20 mm. Cloves has the strongest effect on Mucor, Aspergillus flavus, Aspergillus niger, Penicilliumrole in the most strong-strong, and the inhibitory suppression bacteria diameters isof respectively 35 mm, 25 mm, 30 mm and 30 mm, while the inhibitory bacteriostatic diameter to Rhizopus nigricans is 14 mm, but compared to other raw materials, compared to the inhibition action is still the strongest.Then, using coptis chinensis, magnolia officinalis, clove and cinnamon, the optimum extraction craft of antimicrobial active ingredients was further studid. The results showed that the optimum extraction process using coptis chinensis were: in a water bath at 90℃, with 95% ethanol as solvent, according to 1:8 of the solid-liquid ratio, extraction for 4h. The optimum extraction process using magnolia officinalis were: at 65℃in a water bath, with 95% ethanol as solvent, according to 1:10 of the solid-liquid ratio, extraction for 4h. The optimum extraction process using clove were: in a water bath at 85℃, with 95% ethanol as solvent, according to 1:12 of the solid-liquid ratio, extraction for 5h. The optimum extraction process using cinnamon were: in a water bath at 90℃, with 95% ethanol as solvent, according to 1:8 solid-liquid ratio, extraction for 4h.The minimum inhibitory concentration (MIC), the optimal pH range and thermal stability of four material extracts were further studied. Results showed that the characteristics of coptis chinensis extract was: MIC was between 3.125～12.5 mg/mL, treatment at 121℃ for 15min was still stable, pH range was 4～8 for bacteria and pH range was 6～8 for fungi. The characteristics of magnolia officinalis extract was: MIC was 25 mg/mL, treatment at 121℃for 15min is still stable, pH range was 4～8. The characteristics of clove extract was: MIC was 3.125 mg/mL, the antimicrobial activity decreased slightly when treated at 121℃for 15min, pH range was 4～8.The characteristics of cinnamon extract was: MIC was 3.125 mg/mL, but its thermal stability was very bad, the antimicrobial activity decreased evidently when treated at 80℃for 15min, pH range was 4～8.The combined test of four material extract showed that the bacteriostatic effect of halving was stronger than trisecting, the effect of quartering was the weakest. The effect of halving of coptis chinensis and cloves was the best, the average antibacterial diameter was 22mm. The average antibacterial diameter of quartering of these materials was 16mm. Trisecting of coptis, clove and cinnamon had best effect, the average antibacterial diameter was 20mm, it showed that there was synergistic effect among them. After adding the material extract to different food and placed for some time at room temperature, it was evident that the extract could inhibit food spoilage.
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