Research On Plant-based Acid Frozen Whipping Emulsion And Its Quality Characteristics

Plant-based yogurt and yogurt ice cream have broad market prospects and value due to their absence of allergens such as milk protein and greatly meeting the needs of vegetarians.Due to the poor functional characteristics brought about by the structural defects of plant protein denseness,commercially available plant-based yogurts often require the help of milk proteins or additives to enhance the product texture,while commercially available yogurt ice cream is less common in plant protein components.Bean odor is another major challenge for plant protein product development.Therefore,the development of plant-based yogurt and yogurt ice cream with stable texture and excellent flavor has become a new research trend.In this project,a stable plant yogurt system was constructed by using mung bean protein isolate,and the effects of p H₁₂-shifting treatment,transglutaminase（TG）crosslinking,and component filling such as emulsified oil and quinoa flour hydrolysate（QFH）on the texture characteristics of yogurt were explored.Subsequently,the fermented mung bean protein was used as an aqueous phase protein to construct an acidic water-in-oil（O/W）emulsification system and applied to the acid freeze-whipping emulsion,and the relationship between the stability of the emulsion and the quality characteristics of the frozen whipping emulsion was explored.Firstly,the effects of p H₁₂-shifting treatment and TG crosslinking on the aggregation rate,aggregation degree,viscosity and moisture distribution of MBP during yogurt formation were studied.The results showed that the p H₁₂-shifting treatment could induce the partial expansion of the protein structure and promote the hydrophobic aggregation of the protein during acidification,mainly in the changes of turbidity and protein conformation.After the addition of TG,MBP yogurt formed a denser network structure,which showed that TG crosslinking could effectively connect the internal binding sites of MBP that had been expanded by p H₁₂-shifting treatment,mainly in the viscosity increased by 20.0%.The p H₁₂-shifting treatment coordinated with TG crosslinking significantly improved the ability of（P<0.05）MBP gel to bind protons internally,indicating that the gel had excellent water holding capacity.On this basis,the effects of p H₁₂-shifting treatment,TG crosslinking and emulsion filling on the texture characteristics of MBP composite QFH yogurt gels were studied.The results showed that the p H₁₂-shifting treatment of the modified protein gel hardness and water holding force increased by 40.8%and 50.9%,respectively,in the post-fermentation protein gel,which might be due to the enhanced interaction between molecules by the modified protein.QFH as a filler in the protein network further increased gel hardness and water holding by 57.8%and 78.2%,respectively.After the emulsified oil droplet filling,the hardness of the emulsion gel containing natural conformational proteins increased by 5.6%,while the hardness of the emulsion gel containing the modified protein increased by 34.0%,indicating that after the p H₁₂-shifting treatment,the protein emulsification characteristics were strengthened,forming an interface protein membrane with more active sites,which helped to enhance the continuity and integrity of the protein matrix filled by the emulsion,mainly in the smaller droplet particle size.TG crosslinking did not significantly improve the water retention,but further increased gel hardness by 5.2%.The above MBP yogurt was applied to the acid frozen whipping emulsion system and found that the p H₁₂-shifting treatment reduced the stability of the emulsion by 9.7%,and partial fat was excessively aggregated,which reduced the overrun value of the whipping emulsion containing modified protein by 50.0%and the hardness by 51.0%.The interaction between hydrolyzed peptides and MBP in QFH and the stabilizing effect of carbohydrates on the interface increased the stability of the emulsion before whipping by 29.0%,and at the same time promoted the aggregation of partial fats,which increased the overrun value of the whipping emulsion by 63.2%.The addition of QFH to an emulsion containing modified proteins could significantly improve the overrun value and hardness of the whipping emulsion（P<0.05）.Finally,four different HLB emulsifiers were introduced into the O/W emulsion system to further enhance the stability of the emulsion before whipping,and the influence of the physical characteristics of the emulsification system and the oil crystallization behavior on the overrun value and hardness of the frozen whipping emulsion was deeply analyzed.The results showed that with the increase of the value of the emulsifier HLB,the stability of the emulsion gradually increased,and the stability of the emulsion containing modified protein was significantly higher than that of the emulsion containing natural conformational protein（P<0.05）.Glyceryl monostearate（HLB=3.8）induced the formation of fine lipid crystalline particles.With the increase of the value of the emulsifier HLB,on the one hand,the degree of aggregation of crystalline particles increased,and it was easier to form a partial fat aggregation network structure when whipping,and on the other hand,it promoted the formation of fine crystal particles.Whipping emulsion containing sucrose ester-1570（HLB=15.0）increased by 8.0 times and hardness by 86.0%.From the perspective of suitable organoleptic characteristics,polyglycerides（HLB=7.0）were added to the emulsion containing TG or QFH,resulting in a plant-based acidic frozen whipping emulsion with excellent overrun value,hardness,smooth and delicate taste and certain fruit aroma.