Evaluation of Antibacterial Activity of Flavonoid Extracts from Trapa bispinosa Roxb Shell and Its Effect on Growth Characteristics of Pseudomonas in Duck Meat

The research was designed to investigate the antibacterial ability of the flavonoid extract of Trapa bispinosa Roxb shell and its effect on growth characteristics of Pseudomonas in duck meat. Inhibition of six common microbial growth in foods was evaluated by inhibition zone method,MIC value determination and liquid growth curve. A first-order growth prediction model of Pseudomonas in the duck meat matrix treated with a concentration of 2.5 mg/mL of flavonoids was established. The results showed that the flavonoid extract of Trapa bispinosa Roxb shell had obvious inhibitory effects on Pseudomonas and Staphylococcus aureus. The purified flavonoids had better antibacterial activity against Pseudomonas and Staphylococcus aureus and the inhibition zone diameters were(47.01±0.43)and(45.06±0.35)mm. The flavonoid extract of Trapa bispinosa Roxb shell had a certain inhibitory effect on Brochothrix Thermosphacta,and had no bacteriostatic effect on Escherichia coli,lactic acid bacteria and Saccharomyce. The MIC values of crude extracts and purified extracts of flavonoid were 3.125 mg/mL for Pseudomonas,and the MIC values for S. aureus were 12.000 and 3.125 mg/mL. The duck meat was stored at different temperatures after treatment with the purified porphyrin flavonoids(2.5 mg/mL)which had the best antibacterial effect on the test bacteria. It was found that compared with the high temperature group(10,15 and 20 ℃),the low temperature group(0 and 5 ℃)could extend the shelf life of chilled duck meat to more than 8 days. From the first-level model of the duck meat matrix treated with the purified P. monocytogenes treated with 2.5 mg/mL of flavonoids,the extract of the water chestnut shell as a preservative had better antibacterial effect and could effectively prolong the shelf life of the food when it was stored at 0~15 ℃. However,the antibacterial ability of the purified flavonoids of Trapa bispinosa Roxb shell gradually weakened with the increase of temperature. The experimental results provided a theoretical basis for the development of Trapa bispinosa Roxb shell as a natural bacteriostatic agent.