Effect Of Solution Environment On Molecular Structure,Interfacial Mechanics,Kinetics And Rheology Of Ovotransferrin

Ovotransferrin(OVT)has strong interfacial activity,which makes it have great application prospects in emulsion and foam systems.There are few studies on the interfacial properties of OVT,and the interfacial behavior of OVT is closely related to its structure.Therefore,in this paper,the effects of different treatments on the structure of OVT were analyzed by measuring the zeta potential,average particle size,particle size distribution,surface hydrophobicity and free sulfhydryl group content of OVT solutions treated with different pH,ion type,ionic strength or temperatures.Then,by measuring the interfacial pressure,interfacial dynamics and interfacial viscoelasticity of different treatment OVT solutions at the air-water interface and the oil-water interface,the effects of different treatment on the interfacial behavior of OVT at the air-water interface and the oil-water interface were analyzed.Furthermore,the relationship between the structure changes and the interface properties of OVT treated with different treatments was analyzed to provide basic data for the subsequent research on emulsification and foaming properties.The main conclusions are as follows:1.In the pH range of 3 to 13,the zeta potential of OVT varied from+10.24 to-18.83m V.The average particle size of OVT increased first and then decreased.In addition,the surface hydrophobicity of OVT was enhanced,and OVT exposed more-SH when pH deviated from 6.5.At the air-water interface,the E_d,E_vand?of natural OVT were 42.88,12.92 and 22.824 m N/m,respectively.Compared with the natural OVT,the dilatation viscoelasticity of OVT(E_d,E_v=46.32 m N/m,16.33 m N/m)was significantly enhanced at pH 5.When the pH value was 3,the dilatation viscoelasticity of OVT(E_d,E_vwere 35.86m N/m,3.79 m N/m,respectively)was obviously weakened.The?at pH 13(25.384 m N/m)was significantly enhanced,and the?at pH 3(13.579 m N/m)was significantly enhanced,while K_diff,K_pand K_rwere decreased.At the oil-water interface,as the pH increases from6.5 to 11 or decreases from 6.5 to 4,the interfacial pressure of OVT decreased continuously,and then when the pH continues to rise to 13 or decreases to 3,the interfacial pressure increased.In the range of pH 7?13,E,E_dand E_vdecreased gradually,but increased at pH 11;in the range of pH 7?3,E,E_dand E_vdecreased gradually,but increased at pH 3.With the increase of pH from 6.5 to 13,K_diff,K_pand K_rall showed a trend of first increasing and then decreasing.As the pH decreases from 6.5 to 3,K_diff,K_pand K_rfirst decreased and then increased.2.The addition of Fe³⁺,Cu²⁺,Ca²⁺or Zn²⁺can decrease the average particle size,change the surface hydrophobicity and increase the free sulfhydryl group of OVT.The most obvious was that,compared with the control group,when the molar ratio of Zn²⁺to OVT was 3,the particle size decreased by 90.84%.When the molar ratio of Cu²⁺to OVT was 3,the change of OVT surface hydrophobicity was the most obvious.When the molar ratio of Ca²⁺to OVT was 3,the free sulfhydryl group content of OVT increased by 58.58%.At the air-water interface,the addition of Fe³⁺,Cu²⁺,Ca²⁺or Zn²⁺had a negative effect on the?,K_diff,K_pand K_rof OVT,while the addition of these ions had a positive effect on the interfacial expansion viscoelasticity of OVT.When the molar ratio of Fe³⁺,Cu²⁺,Ca²⁺or Zn²⁺to OVT was 3 or 2,or 3 or 2,respectively,the value of interfacial pressure was the minimum,and the value of dilatation modulus was the maximum.The addition of Cu²⁺had the greatest effect on the interfacial pressure and dilatation viscoelasticity of OVT.Compared with the control group,the interfacial pressure decreased by 5.851m N/m,and E,E_dand E_vincreased by 27.2,24.38 and 6.89m N/m,respectively.At the oil-water interface,the addition of Fe³⁺,Cu²⁺,Ca²⁺or Zn²⁺had a negative effect on the?of OVT,and the addition of Fe³⁺or Ca²⁺has a negative effect on the interfacial dilatation modulus of OVT.When Cu²⁺was added to OVT,E and E_dfirst increased and then decreased with the increase of Cu²⁺,and E_vgradually increased.The maximum value appeared when the molar ratio was 2,which was higher than that of the control group.With the addition of Zn²⁺in OVT,E and E^dgradually increased with the increase of Zn²⁺,and E_vwas smaller than that of the control group during the whole experiment.3.The surface hydrophobicity of OVT increased with the increased of water bath heating temperature in the range of 25?60?.When the temperature of water bath was higher than 60?,the surface hydrophobicity of OVT was decreased.However,compared with the control group,the surface hydrophobicity of OVT was enhanced when the temperature of water bath was higher than 60?.With the increased of water bath heating temperature,the content of free sulfhydryl group in OVT increased gradually.However,when the temperature of water bath was higher than 60?,the content of free sulfhydryl group did not change significantly.At the air-water interface,the induction period increased gradually in the range of 25?60?water bath heating,and the induction period was basically the same when the water bath temperature further increased.The interfacial pressure decreased with the increase of water bath heating temperature.The effect of water bath heating on the interfacial dynamics of OVT at the air-water interface is negative.In addition,E,E_dand E_vgradually decreased with the increase of water bath heating temperature,and there was an obvious difference between E and E_dvalues at 60?,75?and 90?.At the oil-water interface,the induction period and interfacial pressure of OVT with different water bath heating treatments were similar to those at the air-water interface.The effect of water bath heating on K_diffand K_pof OVT at the oil-water interface was negative,but the effect on K_rwas positive.The E,E_dand E_vgradually decreased with the increase of water bath heating temperature,and there was no significant difference between the values of E and E_dat 60?,75?and 90?,and the values are small.