Inhibitory Effect Of Soybean Protein-polysaccharide System On Stevia Glycoside Bitterness And Emulsion Stability

Stevia glycosides(STE)can replace sucrose as a sweetener in food processing,but it has a strong bitter taste when used in high concentration.In this project,by the method of sensory evaluation,explored a compound formula of protein and polysaccharide for suppressing bitterness,which main raw materials were soybean protein isolate(SPI),soybean soluble polysaccharide(SSP)and stevia glycoside(STE).The mechanism which inhibited the aftertaste of STE was investigated by fluorescent spectrometry,infrared spectrometry and other methods.At the same time,the study could develop a bitterless and stable composite emulsion.1.By single factor experiments,the effect that SPI and SSP could restrain the bitter taste of STE was studied in aqueous solution and emulsion systems.Compared with the inhibition effect in aqueous solution,the effect in emulsion was better.Furthermore,the results showed that the optimal formula of suppressing bitterness was as follows: 1.0% SPI,0.3% SSP,0.5% STE,according to the the response surface methodology.2.The findings indicated that SPI,SSP and STE formed complexes mainly via hydrogen bond and electrostatic interactions.The interactions could cause that SPI formed the process of endogenous fluorescence quenching,increased the disorder of protein molecules,exposed the internal hydrophobic groups,and finally enhanced the hydrophobicity of protein.The causes of the phenomenon were as follows: the first reason may be that the hydrophobic environment was more likely to bind STE to hydrophobic aglycones,which hindered its binding to the receptor protein and thus inhibited the bitter taste;the second reason is that it hindered the occurrence of hydrogen bonding between STE and the amino acid residues of the bitter receptor.3.The adsorption behavior of SPI,SSP and STE mixture at the oil-water interface was characterized;simultaneously,the particle size distribution,Zeta-potential and emulsion stability of the composite emulsion were also studied.Results showed that the interfacial tension of the composite system decreases with the addition of SSP and STE.Accoring to the stability of the composite emulsion and the inhibitory effect of STE on the post-bitter taste,the optimal formula forming a bitter-free and stable emulsion system was 0.5% STE,0.3% SSP,and above 1% SPI.