Preparation,characterization And Application Of High Internal Phase Pickering Emulsions Of Myofibrillar Protein-konjac Glucomannan

Emulsified meat products contain high levels of animal fat,which increases the risk of cardiovascular disease in humans,but direct fat reduction tends to dehydrate and de-oil emulsified sausages.Pickering HIPEs（High Internal Phase Pickering Emulsions）have a solid gel state and are an excellent alternative to animal fat.Myofibrillar protein（MP）is a natural emulsifier in meat products.During the formation of emulsified meat products,MP is partly involved in the emulsification process encasing the fat globules and partly in the formation of a gel network structure during the heating process.Konjac glucomannan（KGM）has been shown to improve the gelability of MP,but its effect on MP emulsifying properties has not been reported.Therefore,in this paper,Pickering HIPEs were prepared using KGM-MP complexes as emulsifiers to explore the interaction between KGM and MP and the mechanism of its effect on emulsion properties.Pickering HIPEs were then used to replace animal fat for emulsified sausage processing,with a view to providing theoretical support for the KGM/MP synergistic emulsion mechanism and a new strategy for fat substitution.The main findings are as follows:（1）KGM-MP mixed systems were prepared and the effects of different KGM concentrations on MP properties were investigated by Fourier Transform Infrared Spectroscopy（FT-IR）,molecular docking,three-phase contact angle（θ）,and interfacial adsorption kinetics to infer the potential of KGM to improve the properties of MP emulsions.FT-IR spectroscopy analysis showed that the addition of KGM decreased theα-helix content and increased theβ-sheet content of MP（p<0.05）,indicating that the MP structure unfolded and the hydrophobic groups were exposed.At KGM concentrations greater than 0.5%,partially unfolded MP tended to reaggregate.FT-IR together with molecular docking confirmed that KGM was attached to the MP via hydrogen bonding and embedded in the MP molecular cavity,which resulted in a more compact MP network.The results forθshowed that KGM increased the surface hydrophobicity of MP,with aθof approximately 90°at 0.5%KGM addition,indicating near perfect amphiphilicity,which contributed to the firm adsorption of MP at the interface.The interfacial adsorption kinetics showed that 0.25-0.5%KGM increased the interfacial pressure（π）of MP and promoted the diffusion rate(K_diff),permeation rate（K_p）and rearrangement rate（K_R）of MP at the oil-water interface,thus facilitating the MP adsorption process,while 1-1.5%KGM competed for some of the MP adsorption sites at the interface and reduced the K_diffof MP.It can therefore be inferred that KGM（especially 0.5%KGM）has the potential to improve the performance of MP emulsions.（2）Pickering HIPEs were prepared by a one-step homogenization method using KGM-MP mixed systems as the aqueous phase and perilla seed oil as the oil phase.The effects of particle size,storage stability,microstructure,interfacial protein adsorption percentage（AP%）,Low Field Nuclear Magnetic Resonance（LF-NMR）,rheology and lipid oxidation of Pickering HIPEs with KGM concentration were investigated.The AP%and scanning electron microscopy（SEM）results indicated that 0.25%-1%KGM promoted the formation of MP adsorption layers at the interface and dense MP networks in the aqueous phase.Together,they acted as a spatial site barrier to prevent droplet aggregation and blocked contact between the pro-oxidant and the lipid,resulting in a decrease in particle size,water mobility and lipid oxidation,as well as an increase in storage stability and energy storage modulus（G’）of Pickering HIPEs.The maximum effect of these promotions is achieved at a KGM concentration of 0.5%.However,the addition of 1.5%KGM led to a reduction in AP%,while KGM absorbed large amounts of water to form a continuous viscous hydrogel,which physically prevented MP from aggregating with each other,resulting in a loose MP network structure.These two effects led to a reduction in spatial site resistance and therefore oil droplet aggregation,resulting in larger droplets of Pickering HIPEs and a reduction in storage stability and G’.In summary,the best stability of Pickering HIPEs was achieved with the addition of 0.5%KGM.（3）Emulsified sausages were processed with Pickering HIPEs stabilised with chicken protein/KGM complex as a substitute for pig fat.The effects of different fat substitution rates on the chemical composition,colour,p H,emulsion stability,texture,rheological properties,moisture distribution,fatty acid composition and taste of the emulsified sausages were investigated.The fat substitution group was characterized by low fat,high moisture content and high protein.The L*and b*values,emulsion stability,textural properties and rheological properties of the emulsified sausages increased significantly with increasing substitution ratio,while the a*values decreased significantly（p<0.05）and p H did not differ significantly（p>0.05）.SEM showed that as the addition of Pickering HIPEs increased,the cavities in the emulsified sausages became smaller or even disappeared,and the gel network became denser and flatter.LF-NMR and magnetic resonance imaging（MRI）showed that the addition of Pickering HIPEs reduced the water mobility of emulsified sausages（p<0.05）and the water distribution became more uniform as the percentage of substitution increased.Substitution of animal fat by Pickering HIPEs resulted in a significant increase in theα-linolenic acid andγ-linolenic acid content of the emulsified sausages and a decrease in the saturated fatty acid to unsaturated fatty acid ratio（SFA/UFA）,atherosclerosis index（AI）and thrombosis index（TI）,as well as increasing the salinity and richness of the emulsified sausages（p<0.05）.The textural parameters and microstructure of the emulsified sausages were significantly better than those of the full-fat control at substitution rates of 75%and 100%.As the emulsified sausages produced at 100%substitution had the best overall evaluation in terms of emulsion stability,texture and nutritional quality,the Pickering HIPEs were finally determined to be the most suitable for replacing 100%pork fat.