Study On The Characteristics Of Pea Protein-Polysaccharides Composite Emulsion Gel As Animal Solid Fat Mimetics

As an important component of meat products,animal fat can provide good texture,flavor,mouthfeel and processing qualities for food.However,the structure of animal solid fat is very complex,consisting of high-strength elastic gel networks formed by collagen self-assembly and fat cells containing a crystalline network of plastic oil droplets.At present,one of the strategies for the preparation of animal fat mimetics is to prepare emulsion gel systems,but the defects of plasticity and elastic behavior are significant issues that prevent them from accurately simulating animal solid fats.Therefore,this project took the pea protein-polysaccharide emulsion gel formed by the covalent crosslinking of pea protein isolate(PPI)induced by glutamine transaminase(TG)as the research object and investigated the impacts of polysaccharide types and concentration on gel properties.Then,the oil phase structure of the gel system was modified,the effects of plantsterol(β-Sit)concentration and oil phase types on the emulsion gel properties were investigated,the emulsion gel with both elastoplastic and melting properties was constructed,and its application in common steaned sausage was evaluated.The main research contents and results were as follows:Firstly,the impacts of κ-carrageenan(κC),gellan gum(HA)and konjac gum(KGM)on the functional properties of PPI emulsion gel were investigated.The microstructure indicated that the κC-rich phase appeared as black irregular block,the HA-rich phase showed irregular threadlike inclusions and the KGM-rich phase appeared as spherical or ellipsoidal holes.The three types of polysaccharides all enhanced the texture properties such as hardness and chewiness of emulsion gels,and the enhancement effect of κC was the largest and the KGM was the weakest.The rheological results showed that the G’ and G” values of PPI-κC emulsion gel were greater than that of PPI-HA and PPI-KGM,and the G’ curve of PPI-κC emulsion gel showed kinking phenomenon,which reflected the existence of two gelation behaviors of protein and carrageenan in the system.Therefore,κC had the most pronounced enhancement effect on the emulsion gel properties.The water holding capacity of PPI-polysaccharide emulsion gels was not affected by the microphase separation of polysaccharide.During the gel formation process,the covalent bond formed by PPI crosslinking was the main force to maintain the gel structures.The three polysaccharides were used as filling particles of protein gel network to strengthen the emulsion gel structure by enhancing the total biopolymer concentration and forming polysaccharide gels.PPI-κC emulsion gel with a high polysaccharide content(1.0%)reached a similar level in hardness with pig back fat.However,there were still differences in springness and cohesiveness.Secondly,based on the β-Sit crystallization behavior,the sunflower oil,cocoa butter and palm stearin: sunflower oil were used as the oil phase,to study the effects of oil phase types and β-Sit on the gel structure and functional properties of PPI-κC composite emulsion gel.In terms of microstructure,low content of β-Sit(5%)had very little effect on the microstructure of emulsion gel.When the β-Sit content reached 10%,both granular crystal structure of solidified oil and needle or flaky crystal structure of β-Sit were observed in the emulsion gels.With the further increase in β-Sit content,the crystal size increased significantly,which led to punctures of oil droplets,aggregation and irregular deformation of oil droplets,and different degrees of oil-water separation,even phase inversion of the cocoa butter based emulsion gel.In terms of mechanical properties,with the increase of β-Sit content,the hardness of the emulsion gel increased,while the recovery,cohesion and springness decreased,which reflected that the elastic characteristics of the emulsion gel became weaker and the plastic characteristics became stronger.However,the 20% β-Sit would form large-size crystals that destroied the structural stability of the emulsion gel,resulting in a decrease in texture properties.In terms of melting characteristics,due to the presence of solid fat,emulsion gels had melting properties that were comparable to pig back fat,and the emulsion gels containing palm stearin: sunflower oil had a lower enthalpy of melting than the cocoa butter group.Therefore,the addition of appropriate amounts of β-Sit and solid fat in the oil phase was conducive to the formation of the crystal network of oil droplets.The emulsion gels containing palm stearin: sunflower oil(15%β-Sit)had the most similar textural and melting characteristics to pig back fat.Finally,the emulsion gel containing palm stearin: sunflower oil(15%β-Sit)was used as fat mimetics and further applied to the preparation of cooked sausages.The effects of different replacement rates of fat on the physical and sensory characteristics of sausage were investigated.The results showed that different fat replacement rates only caused a small increase in hardness and chewiness,and had no significant effects on springness,cohesion,cooking loss rate.With the increase of fat replacement rate,the tightly packed pig back fat cell structure gradually became loose,and the structure of protein aggregate-like gel network was gradually increased.Through the sensory evaluation of electronic nose and electronic tongue,it was considered that the substitution of fat mimetics would introduce the characteristic flavor compounds of pea protein,such as 2-hexenal,decylaldehyde,isoamyl alcohol and 2-nonanol,etc,but it did not change the dominant position of the characteristic flavor compounds(aldehydes and ketones)of pork.In the aspect of taste,the perception of sour and savory taste of fat mimics was weaker than that of pig back fat,and the perception of bitter taste was higher than that of pig back fat.Because lean meat contributed more to sausage flavor than fat,the variation in sausage flavor at various replacement rates was comparatively minor.In general,when the fat replacement rate was 75%,the sausage structure was less damaged and the physical and sensory properties were in the best acceptable range.