Preparation,stability And Antimicrobial Activity Of Oregano Essential Oil And Resveratrol Emulsions

Food is a complex and multi-components system,and it can provide microorganisms a favorable environment for microoganisms growth,so food is easily vulnerable to microbial contamination and deterioration.Traditional antimicrobial agents can delay the growth of microorganisms or kill microorganisms,but their metabolic products will cause the changes of food smell,flavor and texture.While,natural antimicrobials have the property of green,nature and safety,so they become a new choice for the food processing.The shortage of low solubility of resveratrol,strong aromatic odor and easy volatility of oregano essential oil(OEO),and poor stability of them have limited their application in foods.Encapsulation can improve the shortage of OEO and resveratrol,and it makes their application in the food system.Preparation of resveratrol and OEO emulsions embedded by sodium caseinate(SC),SC-inulin and SC-gum Arabic(GA),were studied,and antimicrobial effect of them on Staphylococcus aureus,Salmonella Typhimurium,and Saccharomyces cerevisiae in pure culture was further studied.Finally,storage stability of them was analyzed,and bacteriostatic effect in fresh-cut cabbages was also studied.The main results are as follows:1.Compared to 0.1%/0.2%/0.4%SC and 0.1%/0.2%/0.4%SC-2.0%inulin/GA emulsion systems,polydispersity index(PDI)of 0.25%SC and 0.25%SC-2.0%inulin/GA emulsions were lowest,and the absolute values ofζ-potential were above 40 mV,indicating that the emulsions were homogenous distributed and most stable.Addition of 2.0%inulin/GA could improve the interfacial protein content,the retention of OEO and resveratrol.2.OEO-resveratrol emulsions had a better antimicrobial effect on S.aureus,S.Typhimurium and S.cerevisiae,and the bacterial activity of emulsions was better than that of free systems,and it could also be improved by polysaccharides.OEO and resveratrol had synergistic effect on the three target microorganisms.Addition of polysaccharides could significantly improve storage stability of emulsions and protect the biological activities of OEO and resveratrol.For example,0.25%SC-2.0%GA emulsions(OEO-resveratrol)still inhibited the growth of S.Typhimurium,and the number decreased by 1.26 log stored at 4~oC for 20 days.S.Typhimurium was most sensitive to antimicrobials,followed by S.cerevisiae and S.aureus.3.300μg/mL OEO-500 ng/mL resveratrol emulsions could still effectively inhibit the growth of the microorganisms and the growth of natural flora(bacteria,yeast and mold)on fresh-cut cabbages.For example,when stored at 8~oC for 4 days,0.25%SC-2.0%GA emulsions(OEO-resveratrol)decreased the number of bacteria,yeast and mold by 2.98,2.39 and 1.98 log CFU/g,respectively.4.OEO and resveratrol could damage the permeability of cell membrane,and the damage was gradual and it got more serious over time.