| As a nutritious cold-chain food,cheese is susceptible to be contaminated by Listeria monocytogenes,which is a typical food-borne pathogen.Citral,a natural active antibacterial substance,was introduced in this study to control Listeria monocytogenes in cheese safely and efficiently.Firstly,the antibacterial activity and mechanism of citral against Listeria monocytogenes were explored.Then,HP-β-CD was used as the wall material and citral as the core material to prepare the citral/HP-β-CD inclusion complex(IC)by the ultrasonic coupled freeze-drying method.Further,the citral/HP-β-CD-IC was embedded in Zein-based nanofibers through electrospinning.Moreover,the microscopic morphology,tensile properties,thermal stability,hydrophobicity,and release properties of nanofiber membranes were investigated comprehensively.Finally,the antibacterial effect of Zein nanofiber membranes encapsulated with citral/HP-β-CD-IC in the preservation of four kinds of cheese and its influence on color,texture and sensory of cheese were evaluated.The main research conclusions are as follows:(1)The MIC and MBC of citral against Listeria monocytogenes were both 0.4 mg/mL.The sterilization rate reached 99.999% after treatment of citral for 8 h(MIC)and 2 h(2MIC),respectively.Through the transmission electron microscope,it was observed that citral damaged the bacterial cell structure seriously.In addition,citral had a significant inhibitory effect on the hemolytic activity of Listeria monocytogenes;through molecular docking,it was speculated that citral may be bound to the fourth domain of the hemolysin protein,affected the oligomerization of hemolysin by hindering the binding of hemolysin protein to cholesterol.Besides,a large amount of intracellular nucleic acid of Listeria monocytogenes was lost after treatment of citral.By molecular docking,it was indicated that citral had a groove effect with DNA and formed a stable composite structure in the groove region of DNA,which destroyed the base stacking force that stabilizes the DNA structure,thus caused the alteration of DNA structure.(2)The nanofibers formed by the addition of the citral/HP-β-CD-IC were evenly distributed,with good continuity and smooth surface.Fourier transform infrared spectroscopy showed that citral was embedded into the hydrophobic cavity of HP-β-CD and a stable inclusion system was formed;it also showed that the citral/HP-β-CD-IC was successfully electrospun into Zein nanofibers.The tensile strength(TS)of the nanofiber membrane obtained by electrospinning after adding 4%(w:v)citral/HP-β-CD-IC reached4.20 ± 0.16 MPa,and the elongation at break(EAB)reached 62.67 ± 3.05%,the water contact angle(WCA)reached 101.92 ± 8.42°.In addition,the thermal stability of citral has been significantly improved after embedded in HP-β-CD and further loaded with Zein nanofibers.Finally,the release behavior of the nanofiber membrane indicated that the phenomenon of burst release occurred in the early stage(0-12 h),and slow release in the later stage(12-96 h).Although the porous structure in nanofibers was formed after 96 h of release,the basic morphology of nanofibers was still maintained,providing a reliable release carrier for the release of citral.(3)After packaged by Zein nanofiber membrane encapsulated with citral/HP-β-CD-IC under the storage conditions of 4 ℃ and 12 ℃,the growth of Listeria monocytogenes in four kinds of cheeses,such as Brie,Camembert,Cheddar,and Feta,was inhibited to a certain degree.At the same time,the texture and sensory quality of the four cheeses at the two temperatures and the color quality under the low temperature condition of 4 ℃ did not change significantly.In summary,Zein nanofiber membranes encapsulated with citral/HP-β-CD-IC has potential application prospects in the field of food active packaging. |
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