Effects Of DBD Plasma On The Interfacial Properties Of Ovalbumin And Its Application In Low Phosphorus And Low Salt Content Processed Cheese

The interfacial properties are important functional characteristics of the ovalbumin(OVA),which directly affects the application of the protein.As an innovative technology in non-thermal food processing,cold plasma has become a focused area in the modification of macromolecules in food.The current study took OVA as the research object and used spectroscopy,interfacial adsorption kinetics,rheology,and other analytical techniques to explore the influence of dielectric barrier discharge(DBD)plasma treatment on the interfacial properties of OVA from the perspective of structure,properties,stabilization and application characteristics.The mechanism of enhanced stability at the emulsion interface was found.Plasma-treated OVA was used to replace emulsifying salt in making low-phosphorus and low-salt processed cheese products,which provided a theoretical basis and technical support for the application of cold plasma in the future food industry.The main conclusions are as follows:1.The influence of cold plasma on the structure and properties of OVA was analyzed.The results of Raman spectroscopy showed that the peak intensity at 510-550 cm^-1 increased from2.64 to 4.47 after plasma treatment for 1 min,which represented the rupture of old disulfide bonds and the formation of new disulfide bonds.The results of circular dichroism spectroscopy showed that after 4 min of plasma treatment,the?-helix content of OVA decreased from 22.54%to 19.45%,while the?-sheet content increased from 12.62%to 13.48%,and the random coil content increased from 42.93%to 45.75%,indicating that the protein molecule transitioned from stable structure to disordered structure.The results of UV and fluorescence spectra showed that the UV absorption of the plasma-treated OVA was enhanced because of the exposure of hydrophobic amino acids,and the fluorescence intensity decreased due to fluorescence quenching.After 4 min of plasma treatment,the surface hydrophobicity of the OVA sample increased by 1.7 times,and the content of free sulfhydryl groups increased from 0.12?mol/g to2.32?mol/g,which laid the foundation for OVA to unfold and rearrange on the interface to form an elastic interfacial film.2.The adsorption kinetics and rheological properties of the emulsion stabilized by plasma-treated OVA were investigated.The results of dynamic interfacial tension showed that the ability of plasma-treated OVA to reduce interfacial tension was significantly higher than that of natural OVA.The OVA sample with 1 min of plasma treatment had the highest diffusion rate(Kdiff=0.41),permeation rate(K1=14.1×10⁴),and the largest degree of rearrangement(K2=70.5×10⁴).However,the interfacial protein adsorption rate was only 61.19%.The OVA sample with 4 min of plasma treatment had a high protein adsorption rate(92.25%),although both the adsorption and expansion rate were low.The ratio of storage modulus to loss modulus(tan?)of the plasma-treated OVA emulsion showed tan?<1,indicating that the plasma-treated OVA formed a gel network in the emulsion and gave the emulsion a solid property that was mainly elastic.After 4 min of plasma treatment,the?-potential absolute value of the plasma-treated OVA emulsion reduced by 8.53 m V,making the protein easier to absorb.The above results showed that the plasma-treated OVA adopts the mechanism of“low adsorption,high expansion,thin interfacial film”and“high adsorption,low expansion,thick interfacial film”with the plasma treatment of 1-2 min and 3-4 min,respectively.3.The stability of emulsion constructed by plasma-treated OVA was evaluated.The results of the creaming index showed that the creaming of the emulsion constructed by natural OVA proceeded most rapidly,while the creaming index of emulsion stabilized by OVA with 1 min of plasma treatment was the lowest within 4 h.The results of optical microscope observation showed that the interfacial films were fused in the emulsion stabilized by natural OVA.In the emulsion stabilized by OVA after 1 min plasma treatment,the droplet size increased(755.8 nm),without coalescence occurred.However,in emulsion with OVA after 4 min of plasma treatment,the droplet size was significantly reduced(597.9 nm),and a network system based on junctions of droplets was formed.The above results showed that with the increase of plasma treatment time,the interfacial performance of the modified OVA was improved.Emulsion with smaller droplet size,more uniform distribution,and longer storage time was created.4.Plasma-treated OVA was used in the production of low-phosphorus and low-salt processed cheese instead of emulsifying salts.The results of texture analysis showed that the processed cheese prepared by plasma-treated OVA had significant improvement in hardness,adhesiveness,and chewiness.The L^*of the cheese sample with plasma-treated OVA decreased,while the b*increased,which leads to better apparent color.The analysis of meltability and oil separation showed a lack of fluidity in the cheese samples with natural and OVA with 1 min of plasma treatment,and they release less oil,while samples with OVA after plasma treatment for2-4 min showed great fluidity and free oil release ability.The above results showed that cheese prepared under low salt and low phosphorus condition has a more stable emulsification system,better texture characteristics,apparent color,and fluidity.