The Syabilization Of Acid Soy Protein Dispersion By Carboxymethyl Cellulose And Pectin

Soy protein has poor solubility around its isoelectric point which can limit the development of acidic soy protein drinks and acidic soymilk.The objective of this study was to research the interactions between carboxymethyl cellulose(CMC)/pectin,two negatively charged polysaccharides,and soy protein in acid soy protein dispersion and emulated acid soymilk.It was also evaluated the stability of acidic soy protein dispersion and acidic soymilk.This study can improve the development of Chinese beverage market diversity,particularly the vegetable protein drinks,providing a theoretical basis and guidance for acidic soy protein beverage production.CMC is the most commonly stabilizer used in milk beverage.The interaction between different dosage of CMC and soy protein in acidic soy protein dispersion was studied by measuring the diameter and zeta potential of the particles during acidification sedimentation rate and viscosity of beverages.Results show that when CMC is added in soy protein dispersion,the particle size and the absolute value of zeta potential in dispersion were increased.The pH value of the dispersion influences particle size and zeta potential in different ways: particle size constantly decreased with pH decrease until the particles agglomerated with each other,but the absolute value of zeta potential firstly increased and then decreased.Higher CMC dosage 0.4%(w/w)led to bigger particle size,more negative particles charge and protein aggregation at lower pH.When added 0.2%(w/w)CMC in dispersion,bridging flocculation was observed but when added 0.4% CMC(or more),the changes of particle size and zeta potential in dispersion were identical over a range of pH It was also noticed that in acid soy protein beverage,the viscosity increased and the sedimentation rate decreased with higher CMC dosage.In acidic soy protein dispersion,CMC was attracted by the surface of the soy protein by the electrostatic force and prevents soy protein particles aggregation by steric hindrance.Thus,the presence of CMC in acid soy protein dispersion can prevent aggregation of soy protein and stabilize the dispersion.Pectin is other polysaccharide usually added into beverages and appreciated due to its ‘refreshing taste'.The study was also performed to evaluate the pectin effect over acid soy protein and shows that when dispersion was made with 0.4%(w/w)pectin,the dispersion's particle size and the absolute value of zeta potential were increased.The influence of pH can be described as firstly a particle size increase,secondly a stabilization step and then a small decrease of particle sizes.The effect of pH over absolute value of zeta potential also shows a rising of its value followed by its decline until reaching the protein aggregation point.When added 0.2%(w/w)pectin in dispersion,the aggregation of soy protein particles occurred at pH6.3;when added 0.4% or more pectin Bigger average particle diameter of the particles and lower protein aggregation pH point were observed when increasing the pectin dosage,but zeta potential was not affected by pectin dosage if the dispersion's pH value was higher than the aggregation pH point.During acidification,pectin was absorbed on the surface of soy protein and prevent soy protein aggregation by steric hindrance and electrostatic repulsion.Thus it was achieved better soy protein particle dispersion when using higher dosage of pectin and the stability of soy protein beverage was improved by adding enough amount of pectin.The stability of emulated acid soymilk was improved by adding CMC and pectin in soymilk which was beneficial to extend shelf life of acid soymilk.The stabilizing complex using pectin and carboxymethyl cellulose was optimized using Turbiscan stability index as response value by both single-factor experiment and response surface analysis.This results indicated that the optimum stabilizer complex was a mix of pectin 0.12%(w/w)and CMC 0.40%(w/w).Under this condition,the particle distribution of acid soymilk indicated that the particles of acid soymilk were well dispersed within the range of 0.04?m-8?m(D(4,3)=1.68?m).The viscosity of acid soymilk was 5.35 mpa?s.The delta backscattering intensity confirmed that the optimized complex stabilizer could significantly reduce the thickness of sediment layer,clarification layer(at top)and Turbiscan stability index(1.34).All this study led to the conclusion that the optimized complex stabilizer improved the acid soymilk significantly,therefore this work would offer the theoretical reference to optimize a complex stabilizer and develop nutritional acid soymilk.