Preparation And Application In Meat Products Of A Stimuli Responsive Nutmeg Oil Liposome

Meat and its products are rich in protein, lipids and have suitable moisture content, which make them ?natural media? of microorganisms. To keep meat and meat products free of bacterial contamination, refrigeration storage is the most popular preservative approach to the products. Numerous synthetic additives have been used to extend refrigerated storage time. But, Listeria monocytogenes(L. monocytogenes), one of main pathogenic bacteria in refrigerated meat products, is a notable food-borne pathogen due to the high mortality rate. It could exist in every processing stage, leading to cross-contamination and food-borne diseases. Nutmeg oil exhibits antioxidant, anti-inflammatory, and antibacterial activities. Moreover, nutmeg oil has been classified as a kind of substances generally recognized as safe(GRAS) for food preservation by the Food and Drug Administration. However, it is well known that the volatility of essential oil and the sensibility toward oxygen, light, water and high temperatures reduce its stability in processing and storage ultimately decrease its bioavailability. In order to enhance the stability and bioavailability of essential oil during its application, some molecules embedding processes have been introduced, among which is the use of liposomal encapsulation.In this work, the antibacterial activities of nutmeg oil and nutmeg oil encapsulated in liposome were evaluated first. Then we measured the stability of liposome and its application in meat products. The main contents and results are as follows:(1)Thirty chemical compositions of nutmeg oil were analyzed by gas chromatography–mass spectrometry(GC–MS). The major volatile components of nutmeg oil were sabinene(39.12%) and alpha-pinene(11.96%). Nutmeg oil showed significant antibacterial activity, minimum inhibitory concentration(MIC) and minimum bactericide concentration(MBC) of Escherichia coli O157: H7 is 0.2% and 0.4% respectively, Listeria monocytogenes is 0.1% and 0.2% respectively. And MIC and MBC of other 5 foodborne pathogens are 0.05% and 0.1% respectively. The nutmeg oil also had a significant effect on inhibiting the growth of Listeria monocytogenes.(2) In order to reveal the possible antibacterial mechanisms of nutmeg oil against pathogens, the damage of cell membrane was observed, the loss of 260nm-absorbing material, the cellular ATP concentrations and the decrease of nucleic acid was tested. These results indicated that the antibacterial mechanisms of the nutmeg oil against bacteria might be interpreted as disrupting cell membrane and inhibiting synthesis of DNA.(3) Nutmeg oil was encapsulated in liposome to enhance its chemical stability by the thin film dispersion method. Particle size was about 140 nm, polydispersity index(PDI) was about 0.2, and turbidity were about 1000. The optimal Zeta potential(-49.2 mV) and entrapment efficiency(28.50%) of liposome were achieved at 4.0 mg/m L nutmeg oil encapsulation.(4) Fourier transform infrared spectrometer(FTIR) demonstrates the nutmeg oil has been wrapped in liposome. Selective antibacterial activity for L. monocytogenes by Listeriolysin O(LLO) to trigger nutmeg oil release from liposome was testified by Time-kill analysis and GC-MS assay.(5) Long-term antibacterial activity illustrated that nutmeg oil encapsulated in liposome could extend the treatment time and improve the antibacterial effect on L. monocytogenes in pork, chicken and beef. After treated by nutmeg oil liposome, L. monocytogenes has been reduced 99.9%. After three days, nutmeg oil did not have antibacterial effect. And liposome will not influence the pork quality.