Pea Protein Extrusion Texturization Mechanism And Process Optimization

Pea protein is widely welcomed by consumers because of the wide range of resources,nutrient-richness,healthy eating and other excellent features.However,there are many problems such as poor mobility and low utilization ratio in the processing molding.Pea protein extrusion technology can effectively solve the above problems improving its functional properties and nutritional value so that it can effectively be applied to meat products.This thesis in detail studied the effects and mechanisms of water content,temperature,pressure and shear as well as their durations on the solubility,gelation and texturization of the mixture or solution of pea protein blended with water.A optimized pea protein extrusion process was successfully developed and applied to emulsified sausages.The main work and conclusions are as follows:(1)The functional properties of pea protein were studied by various physical and chemical testing methods.The solubility of pea protein solution at different concentrations,PHs and temperatures were studied by Kjeldahl method finding that there is a maximum solubility when the concentration is 12%,PH 4.0 or temperature 65 ?,respectively.According to the criterion of the no slip and no collapse,the pea protein of 75D and 85D exhibited the minimum gel concentration of 18%and 24%.The texture test showed that gel strength and fracture distance of 85D were higher than 75D because the protein content of 85D was higher than 75D.Centrifugal test showed that the emulsification,water retention and oil retention of 85D were better than 75D.(2)DSC system was used to study the states of water in the extrudate of water/protein mixtures under different extrusion conditions.Capillary rheometer was used to prepare water/pea extrudates under different extrusion conditions.Then,DSC was used to test the enthalpy change and melting temperature while the moisture was melting.(3)The thermal and rheological properties of pea protein and SC/PPI mixtures were analyzed by dynamic rheological method.The effects of shear rate,water content and temperature on the viscosity of pea protein solution were comprehensively analyzed.The viscosity of pea protein was modelled reflecting that the higher the gelation temperature and the higher the gel strength.In the SC/PPI,the higher the content of corn starch in the solution,the better the fluidity,the lower the gelation temperature and the higher the gel strength.(4)The gelation process of pea protein at high pressure was first characterized by ultrasonic method.Ultrasonic wave velocity was recorded in pea mixture with different contents of water.The gelation time of pea protein was shortened by increasing the pressure,temperature and water content at 85 ?.The sound velocity became constant in balance at ca.60? for pea protein mixed with different contents of water,indicating the gelation was almost completed.(5)Using the sensory evaluation method,single factor analysis and principal component analysis,optimized was the pea protein extrusion process.The effects of pea textured protein on the emulsified sausage at different contents were analyzed.The optimized process conditions were established:the screw speed is 20Hz,extrusion temperature is 160?,feeding speed is 30Hz,material moisture is 50%.Emulsified sausage added with 4%pea textured protein exhibited best effect.The method of evaluating the texturized degree of pea protein extrudate was put forward.The texturization experienced the two steps of gelation and protein molecular orientation.This thesis is of great significance for understanding the gelation mechanism of plant protein and for developing textured products.