Study On The Effect Of Structural Modified Pea Proteins On The Quality Characteristics Of Frozen Aerated Emulsions

Frozen aerated emulsions,including ice cream,and whipped toppings,belong to complex foamed emulsion system in relation to the foaming and emulsifying properties.Milk protein is the most wildly used protein source in frozen aerated emulsions.But milk protein has high calories and is not friendly to allergic people.Pea protein isolate is one of the important plant proteins with low allergenicity and high nutritional value.However,the limited functional properties such as solubility and interfacial properties restrict its application in food products.Therefore,the aim of this work was to explore the effects of pH-shifting and ultrasonic treatment treated pea protein used in preparing frozen aerated emulsions in the presence of coffee exaction.The main results are as follows:Firstly,the effects of pH-shifting treatment(pH12,1 h),ultrasonic treatment(475 W,20 k Hz,5 min)and their combination on the structural and functional properties of pea protein were studied.The pH-shifting treatment could make protein structure unfold and promote the dissociation of subunits,thereby,improving the surface hydrophobicity.Ultrasonic treatment could also expose more hydrophobic groups to improve protein hydrophobicity synergistically Both pH-shifting and ultrasonic treatment reduced the particle size of protein solution.In terms of dispersion properties of pea protein,the results showed that both pH-shifting and ultrasonic treatment could significantly improve the solubility.The turbidity of protein solution decreased after pH-shifting combined ultrasonic treatment.The effects of modification methods on the functional properties of protein were investigated.pH-shifting treatment could increase the surface activity of the protein,resulting in a higher surface pressure.However,ultrasonic treatment would reduce the surface pressure of protein.The results showed that the emulsifying properties of protein was improved by pH-shifting treatment and ultrasonic.The synergistic effects of the two methods increased the emulsifying properties by 68.90%.The foaming properties and foaming stability of protein were improved.The effects on the presence of coffee exaction of different total phenol content(12.5-50mg/m L)of the structural and protein's functional properties were further studied.The results showed that coffee could further promote the change of the secondary and tertiary structure of protein.The structure of the protein was further unfolding.However,coffee could decrease the hydrophobicity and solubility of protein and increase its turbidity.Low concentration of coffee increased the emulsifying properties,but with the increase of coffee concentration,the emulsifying properties of protein decreased.The emulsifying stability decreased with the increase of coffee concentration,too.After adding coffee,the surface activity and foaming ability of protein increased.But the stability was negatively correlated with coffee concentration.Then,the different modified proteins with or without coffee were applied to the frozen aerated emulsion system.The physicochemical properties and fat crystallization behavior of the emulsion before and after whipping were analyzed.The effect of the change of protein interface properties on the frozen aerated emulsion system was further analyzed.After pH-shifting and ultrasonic treatment,the particle size of the emulsions decreased,but the viscosity increased.More dense fat clusters could be observed in emulsions,which would promote the puncture of fat crystals in the droplets.Partial coalescence of fat is conducive to the retention of bubbles.After whipping,the overrun of aerated emulsions after pH-shifting combined with ultrasonic treatment reached 58.2%,which was 1.5-fold than that of NPP emulsion(27.6%),It had better shape retention,which indicated that emulsion formed a good three-dimensional fat network structure after whipping and inhibited the migration of fat crystals.The pH-shifting and ultrasonic treatment improved the interfacial properties of protein and contributed to the fat crystallization behavior in emulsions and improved the rheological properties of emulsions.The viscosity of the frozen aerated emulsions containing coffee decreased,which was beneficial to the later whipping process.Coffee obviously promoted the fat crystallization behavior and more fat partial coalescence behavior were observed in emulsions.At the same time,coffee reduced the emulsions' stability,which were easier to trap air bubbles in whipping process.Further,the overrun was increased,and the melting rate were decreased.Overall,the results of this study showed that after pH-shifting and ultrasonic treatment,the structure of pea protein unfolded and the subunits are dissociated,which could improve the functional and interfacial properties of pea protein.Modified protein cooperating coffee could be used in frozen aerated emulsions,further expanded its application in food industry.The results of this study proved that the pea protein isolate treated by pH-shifting,ultrasonic treatment,and pH-shifting combined with ultrasonic treatment has an unfolded structure and the subunits were dissociated.Therefore,modified proteins were used in frozen aerated emulsion,which improved the overrun,melting rate and shape retention of aerated emulsion.Finally,the modified protein was applied to ice cream system containing coffee.The interaction between polyphenols in coffee and proteins further increased overrun of ice cream,decreased the melting rate of ice cream,further expanded its application in the food industry.