Extraction Optimization and Antibacterial Property of Total Flavonoids from Zizania Latifolia Bracts and the Effect on Chilled Pork Preservation

Zizania latifolia isa widely distributed aquatic vegetable, and its bracts are an agriculturalwaste with a large proportion. In this study, Total Flavonoids of Z. latifoliaBracts (TFZB) were extracted with Ultrasound-Assisted Enzymatic Extraction(UAEE) for the first time, and the extraction process was optimized usingResponse Surface Method (RSM), and compared with other methods. Then, theantibacterial activity of TFZB extracted with optimized UAEE was assessed andthe effects on chilled pork preservation were investigated. The optimal UAEEconditions for TFZB were: Cellulase dosage of 0.7%, enzymolysis time of 60 min,ultrasonic power of 704 W, and ultrasonic time of 47 min. Under theseconditions, the TFZB extraction rate was up to 1.92%, which was significantlyhigher than those of other methods. The Scanning Electron Microscope (SEM)observation verified that the cytoskeletons of bracts had been severelydamaged, resulting in a large release of TFZB. The infrared spectrum confirmedthat TFZB has the typical characteristics that belong to natural flavonoids.Moreover, the TFZB extracted with optimized UAEE exerts significantantibacterial activities against Escherichia coli and Staphylococcus aureus with Minimal Inhibitory Concentrations (MIC) of2.5 and 1.25 mg/mL, respectively. Finally, the TFZB solutions were sprayed ontothe surface of fresh pork, and the indexes of the sensory score, pH, TotalVolatile Basic Nitrogen (TVB-N), Metmyoglobin (MetMb)%, and total count ofbacterial colonies during the storage period of chilled pork were measured. Theresults indicated that TFZB at 1.0 mg/mL can significantly improve the sensoryquality of chilled pork via inhibiting microbes, and better preserve thefreshness of pork when compared with sodium benzoate at 5.0 mg/mL. The presentinvestigation implied that the TFZB extracted with optimized UAEE can be usedas a natural flavonoid alternative resource to produce environmentaldisinfection products and novel preserving agents for chilled porkpreservation.