Preparation,Characterization And Application Of High Internal Phase Pickering Emulsions Stabilized By ?-lactoglobulin Nanoparticles

?-lactoglobulin(BLG)is the main whey protein component in milk,with rich branched chain amino acids and high market value and potential.However,the application of BLG in food industry is limited because of easily denatured in heating,alkaline environment,high pressure or metal ions.In recent years,solid particles stabilized Pickering emulsions have good application prospects in the pharmaceutical,food and cosmetics industries due to their advantages.In this study,?-lactoglobulin was used as a raw material,and ?-lactoglobulin nanoparticles(BLGNPs)were prepared by desolvation method with Genipin(GP)cross-linking.The high internal phase Pickering emulsions(HIPEs)were prepared by high-speed shear emulsification,and the properties and stability were explored.On the basis of this,the prepared HIPEs were used to minced meat products to replace animal fat,so as to improve the quality of products,and provide new ideas and theoretical references for the application of BLG and Pickering emulsions in food.The main conclusions are as follows:(1)According to different preparation sequences,four groups of BLGNPs were prepared by ethanol-desolvation combined with GP cross-linking: BLGNPs-1(pH adjustment ? ethanol desolvation ? GP cross-linking),BLGNPs-2(Ethanol desolvation ? pH adjustment ? GP cross-linking),BLGNPs-3(pH adjustment ? GP cross-linking ? ethanol desolvation)and BLGNPs-4(control group,pH adjustment ? ethanol desolvation).The particle sizes were between 200 ? 400 nm,and the absolute values of ?-potential were greater than 20 mV.FTIR detection and ? values showed that BLGNPs-1,BLGNPs-2 and BLGNPs-3 had occurred cross-linking reactions to varying degrees.SEM images showed that the ellipsoidal BLGNPs-2 had better potential to stabilize Pickering emulsion than other spherical BLGNPs.All four BLGNPs had good thermal stabilities and were more suitable for low temperature(4 ?)storage.The interfacial adsorption experiments showed that the structural rearrangement dominated the formation of BLGNPs interfacial film,and the initial adsorption stage was controlled by diffusion.BLGNPs adsorbed to the oil-water interface spontaneously at different pH,but the change in interface pressure was little.The diffusion rate of BLGNPs was the slowest at pH 7.0,and the degree of interface rearrangement was the highest at pH 9.0.The addition of NaCl reduced the diffusion rate of BLGNPs,improved the degree of interface adsorption and rearrangement,and made more BLGNPs participated in the stabilization of the interface.Based on particle size,three-phase contact angle,morphology,thermal and storage stabilities,BLGNPs-2 was selected to stabilize Pickering emulsions.(2)BLGNPs stabilized HIPEs were prepared by high-speed shear emulsification with soy oil as the oil phase,and the prepared HIPEs were characterized by appearance,particle size,rheology,and microstructure.The results showed that BLGNPs can cover up to 0.75 oil phase volume fraction(?),and showed good ability to stabilize Pickering emulsions at particle concentrations exceeding 1% and a wide range of pH(5-9).HIPEs had good thermal stability and can be remained stable after heating at 70 ? and 100 ? for 60 minutes.At 100 ?,heating promoted the further cross-linking reaction between the GP and BLG,thereby forming protein interconnections,so increasing the viscosity of HIPEs and improving the stability of HIPEs.HIPEs had good storage stability and could retain emulsion morphology at 30 d after 4 ? storage without water layer precipitation and demulsification.HIPEs also had good centrifugal stability,and still maintained a small creaming index under high centrifugal force(18000 g).HIPEs had an excellent ionic stability.The addition of NaCl increased the coverage of BLGNPs at the oil-water interface,resulting in a closer network between HIPEs droplets,thereby reducing the aggregation of HIPEs and the overflow of oil droplets,while increasing the freeze-thaw stability of emulsions.HIPEs could withstand more than 9 freeze-thaw cycles when the ionic strength exceeded 50 mM.(3)BLGNPs stabilized HIPEs were used to replace animal fat in meatloaf,and the replacement gradients were 0,25%,50%,75%,and 100%.As the replacement ratio increased,the color of the meatloaf before cooking gradually changed from pink to white.In HIPEs,GP and BLG were cross-linked to form a network,which tightly enclosed soy oil droplets.At the same time,the interaction between proteins was enhanced during heating,thereby forming a more stable and elastic network structure,which improved the cooking yield,water and oil retention,texture and other characteristics of meatloaf.The addition of HIPEs inhibited part of the lipid oxidation in the meatloaf,which made a~* value increase and b~* value decrease.At the same time,because the larger surface area of the soy oil spheroids produced more light reflection,the L~* value of the meatloaf was increased.The microstructure showed that all meatloaf samples had the characteristics of a cooked gel/emulsion system,that was,the protein matrix aggregated to lose continuity and produced a sponge-like(honeycomb)structure.And the cavity became larger with the increase of HIPEs replacement ratio,indicating that the combination of fat and myofibrillar protein decreased,and protein digestibility increased.