Study On Emulsifying And Antibacterial Properties Of Nanoemulsions Loaded With Photosensitizer

The development of safe and efficient antibacterial methods has always been one of the research hotspots in the food industry.Photodynamic antibacterial technology has attracted widespread attention in the scientific community due to its safe performance and effective antibacterial effect.In order to improve the low solubility and low stability of photosensitizer,we used nanoemulsions as photosensitizer carrier to prepare food-grade nanoemulsions with high stability,bioacceptability and then applied to food antibacterial and fresh-keeping process.This article took nanoemulsions as the main research object,adopt different emulsifiers,and prepared nanoemulsions loaded with photosensitizer through high-speed shear-high pressure homogenization technology.The stability of this nanoemulsions and the coating effect of photosensitizer were studied.And using photodynamic antibacterial technology,the antibacterial effect of nanoemulsions under the excitation of 460 nm blue LED was tested.1.Four small molecule emulsifiers(Tween 80,Span 80,sodium lauryl sulfate,lecithin)and one protein(soy protein isolate)were used as emulsifiers to prepare nanoemulsions which coated the photosensitizer curcumin.We measured the stability of the emulsions,the coating properties of curcumin,and the emulsification mechanism of various emulsifiers at the oil-water interface.Finally,the photodynamic inhibitory effect of Escherichia coli was confirmed.Tween 80 provided the best emulsions stability and curcumin coating effect due to its suitable ratio of hydrophilic and hydrophobic groups.Soy protein isolate and lecithin provided the best light stability for curcumin in the emulsion,which stemed from the hydrophobic interaction of soy protein isolate and the lipophilicity provided by the dialkyl hydrophobic segment of lecithin.The photodynamic antibacterial effect of all emulsions on Escherichia coli could be more than 85%.2.Using soy protein isolate as the main emulsifier,and the above four small molecule emulsifiers as co-emulsifiers,nanoemulsions coated with the photosensitizer riboflavin tetrabutyrate were prepared.The stability of the emulsions,the coating properties of riboflavin tetrabutyrate and the emulsification mechanism of various composite emulsifiers at the oil-water interface were measured.Finally,the photodynamic inhibitory effect of Staphylococcus aureus was clarified.The key to synergistic adsorption between Tween 80 and soy protein isolate lay in its proper ratio of hydrophilic and hydrophobic groups,which resulted in higher storage stability and thermal stability of soy protein isolate + Tween 80.The small hydrophilic head group and strong lipophilicity of Span 80/lecithin made them occupy the position of soy protein isolate at the interface,which causing competitive adsorption,so it was characterized by low emulsions stability and the poor coating properties of riboflavin tetrabutyrate.Compared with Tween 80,sodium lauryl sulfate with the smaller molecular weight and size had extremely strong diffusivity,so it completely occupied the oil-water interface,and the electrostatic interaction between sodium lauryl sulfate and protein made the protein become the small particles.Finally,Pickering emulsions was formed.Therefore,soy protein isolate + sodium lauryl sulfate provided the best emulsions stability and riboflavin tetrabutyrate coating effect.The photodynamic antibacterial effect of all emulsions on Staphylococcus aureus could reach more than 70%.