| Mayonnaise is a kind of o/w-type sauce which is popular among people.However,the high fat content and cholesterol level of mayonnaise may lead to obesity and increase the risk of cardiovascular diseases.In recent years,the development of low-fat or cholesterol-free mayonnaise substitutes has become a hot spot in the field of food colloids.Protein-based high internal phase emulsions(HIPEs)can be used as good alternatives for mayonnaise-like products because of their superior stability and semi-solid texture.However,there are still some problems in related research,such as lack of protein resources,single species,limited emulsifying capacity,unsatisfactory viscoelasticity of emulsified system,and serious lipid oxidation.Based on this,the feasibility of stabilizing HIPEs with perilla residue protein was preliminarily explored in this paper.Subsequently,the perilla residue protein was functionalized by high-density ultrasound and phosphorylation treatment respectively,and the effect of modified protein on the stability of HIPEs was systematically studied.Furthermore,chitosan or chitosan-protocatechuic acid conjugates was introduced to finely regulate the stability,viscoelasticity,lipid oxidation rate and protective ability ofβ-carotene of HIPEs,and to explore the application potential of HIPEs in the development of reduced-fat and cholesterol-free mayonnaise substitutes,so as to provide reference for the development of new mayonnaise substitutes.The main research contents are as follows:(1)Perilla residue protein nanoparticles were prepared by pH-cycle-assisted homogenization treatment,and their potential to stabilize HIPEs was preliminarily explored.The results showed that the prepared perilla residue protein nanoparticles were spherical,with a particle size of 224.17 nm and a three-phase contact angle of 105.5°.When the concentration was as low as 1.0%,HIPEs with 75%oil phase could be constructed,and the gel-like network structure of the emulsion system was not easy to be destroyed by distilled water or 6 mol/L urea.Increasing the concentration of nanoparticles increased the adsorption rate of interfacial protein,reduced the droplet size and improved the viscosity and viscoelasticity of HIPEs.HIPEs constructed by 2%nanoparticles had good storage stability,could withstand 100～500 mmol/L ionic strength,and were resistance to heat treatment and high-speed centrifugation.However,the stability and the oil phase volume of emulsion system still had great room for improvement.(2)Subsequently,the effects of high-density ultrasonic treatment on the structure and functional properties of perilla residue protein(ZPI)was investigated.It was found that ultrasonic treatment significantly reduced the particle size of ZPI,resulting in the expansion of its molecular structure and the change of its spatial conformation,thus improving its solubility,water holding capacity,oil holding capacity and emulsifying ability,in a ultrasonic power-dependent manner.The o/w emulsion prepared by ultrasonic modification of ZPI had more uniform droplet distribution,smaller droplet size and higher interfacial protein adsorption rate,which indicated that it could prevent droplet aggregation and improved the stability of the emulsion systems.(3)Although ultrasonic treatment could improve the performance of ZPI to some extent,its effect was very limited.Based on this,phosphorylation treatment was adopted to modify its function.It was found that the covalent bonding of phosphate group to the main chain of ZPI increased the surface electronegativity of protein,which led to the expansion of its molecular structure,the exposure of its internal hydrophobic groups and the formation of many holes on its surface.All these changes ultimately increased the chance of protein combining with water molecules,thus significantly improving the solubility,emulsifying and foaming abilities of ZPI.In the homogenization process,phosphorylated perilla residue protein could be adsorbed to the surface of oil droplets faster,resulting in smaller droplet size and higher interfacial protein adsorption content,and the internal phase volume of HIPEs could be increased to 80%.(4)Furthermore,chitosan was introduced to construct phosphorylated perilla residue protein-chitosan(LZPI-CS)composite particles,and its effect on improving viscoelasticity of HIPEs was discussed.The results showed that the introduction of CS could improve the surface hydrophobicity of LZPI,enhance its ability to reduce the interfacial tension between oil and water,and promote the formation of viscoelastic film at the oil-water interface.Moreover,the addition of CS increased the thickness of the interface layer,promoted the formation of the interconnection network structure in the system,and effectively prevented the coalescence of droplets,thus improving the stability of HIPEs under storage,centrifugation and heat treatment,and endowing them with higher viscosity,viscoelasticity and thixotropy recovery ability.The cylinder model printed with HIPEs containing 0.5～0.6%CS showed good structural integrity,shape fidelity and printing resolution.However,due to the higher volume fraction of oil phase in the system,lipid oxidation was more serious.(5)Chitosan with different molecular weights was functionalized with protocatechuic acid(PA)by free radical grafting.UV,FTIR and ~1H-NMR spectra confirmed that PA was covalently bound to CS through amino bonds and ester bonds.Compared with CS,chitosan-protocatechuic acid(CSPA)conjugates exhibited significantly improved water solubility and antioxidant activity,with a CS molecular weight-dependent manner.In addition,Pickering emulsions constructed by CSPA conjugate particles showed a lower lipid oxidation rate.(6)The LZPI-CSPA complexes were constructed based on the hydrogen bond and electrostatic interaction between LZPI and CSPA conjugate,and the relationship between the concentration of CSPA conjugate and the interfacial behavior of the complexes,as well as the oxidation stability of HIPEs were deeply analyzed.The results showed that compared with LZPI,LZPI-CSPA complexes had more appropriate wettability and the ability to reduce interfacial tension,thus promoting their adsorption at the two-phase interface.Furthermore,the introduction of CSPA conjugate promoted the formation of interconnected network structure in LZPI-stabilized HIPEs,thus endowing them with good viscoelasticity.The dense interfacial film based on LZPI-CSPA complexes effectively delayed the lipid oxidation rate of HIPEs,and the effect of LZPI-2.3%CSPA complexes was the most significant.(7)The stability of HIPEs fabricated by LZPI-CSPA complexes against long-term storage,heat treatment,different pH values and ionic strength was explored,and the potential protective ability of HIPEs onβ-carotene was deeply analyzed.The results showed that the HIPEs had good storage stability(stored at room temperature for 20 days)and thermal stability(heated at 85°C for 30 min),and also displayed good stability at pH 3.0 and certain ionic strength(50～100 mmol/L Na Cl).Using the HIPEs as the encapsulation carrier ofβ-carotene could improve its stability against different environmental stresses(ultraviolet irradiation,natural photodegradation and thermal incubation).After simulated digestion in vitro,the bioavailability ofβ-carotene was significantly increased,and reached the highest value in HIPEs containing 1.5%CSPA conjugate.(8)Finally,based on HIPEs stabilized by the LZPI-1.5%CSPA complexes,the feasibility of developing reduced-fat or cholesterol-free mayonnaise substitutes was explored.The results showed that the reduced-fat mayonnaise obtained by replacing 10%～40%of oil in homemade mayonnaise with HIPEs was light yellow in appearance,fine in texture and smooth in surface,good in extrudability and spreadability,and excellent in storage stability and lipid oxidation stability.In addition,the rheological properties,flavor and aroma values of these reduced-fat mayonnaise were not much different from those of homemade mayonnaise,and the overall state was relatively ideal.Cholesterol-free mayonnaise with 65%oil phase volume developed by replacing egg yolk in homemade mayonnaise with LZPI-1.5%CSPA complexes had good viscoelasticity,spread ability,storage stability and oxidation stability.Compared with commercial mayonnaise,cholesterol-free mayonnaise had lower scores in flavor and aroma value,but better appearance,smoothness and overall acceptability,and could be used as a potential substitute for cholesterol-free mayonnaise. |
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