Emulsion's Stability And Influence Of Glutelin From Zanthoxylum Armatum DC. Seed

Sichuan pepper is a traditional condiment in China,which belongs to the Zanthoxylum genus.The planting area and yield of Zanthoxylum armatum DC.have increased in recent years.Therefore,there are a large number of Z.armatum seeds every year in China.It will produce high economic and social benefits if it can be fully utilized and applied to various industries,like food and fodder.The effect of konjac glucomannan on the emulsion stability of glutelin from Z.armatum seeds and its mechanism were studied in order to promote the research of protein emulsion in the food field and its application in industry.In this study,the four different proteins were extracted from the Z.armatum seeds kernel,and their properties were explored.Next,the emulsion stability of Z.armatum seeds kernel glutelin hydrolysate with trypsin and the effect of konjac glucomannan on its stability were investigated.Eventually,the interaction mechanism of Z.armatum seeds kernel glutelin-konjac glucomannan in solution was explored.The main findings obtained are as follows:1.The main objective is to explore the composition and physicochemical properties of Z.armatum seeds kernel protein.The four kinds of proteins including albumin,globulin,prolamin and glutelin from Z.armatum seed were extracted using the Osborne method.The results showed that the content of four type proteins were 23.06%,21.64%,6.41%and40.02%,the isoelectric points were 3.0,3.3,2.0 and 3.3,respectively.The scanning electron microscope showed that albumin surface was meticulous multilayer,glutelin was ridge-shaped,albumin and glutelin molecules were closely connected,with holes locally and large aperture.Globulin surface was smooth,loose and less holes,with synaptic stratification.Prolamin molecules were tightly connected,with irregular spherical,and connected to larger molecular groups.The DSC results showed that the thermal denaturation temperature were 35.71,37.75,33.44 and 40.01?,respectively.The results of SDS-PAGE analysis showed albumin subunits were roughly distributed in 34.414,21.841,11.059 kDa,globulin subunits were probably distributed in 32.924,20.683 kDa,prolamin had no spectral bands,glutelin subunits were probably distributed in 32.441,19.801,11.059 kDa.2.Z.armatum seed glutelin?ZSG?was prepared and hydrolyzed with trypsin.Glutelin hydrolysates?ZSGH?with three different degrees of hydrolysis?DH??3%,6%and 8%respectively?were obtained.The structural and functional properties of ZSGH were investigated.These results confirmed the presence of aggregates in hydrolysates with a DH of 8%.The PS level was significantly improved by the enzymatic hydrolysis at all DHs.The emulsion activity and emulsion stability were found to increase from 33.59 m²/g to 118.32 m²/g and from 31.86%to 85.91%for ZSG and ZSGH?DH 3%-6%?,respectively,before decreasing to 89.72 m²/g and 74.86%,respectively?DH 8%?.A similar trend was observed for foam capacity and foam stability,which increased from 83.33%to 216.67%and from 34.92%to 74.95%for ZSG and ZSGH?DH 3%-6%?,respectively,then decreased to 200.00%and 68.67%,respectively?DH 8%?.3.In order to investigate the glutelin emulsion stability of ZSG,oil-in-water emulsions were prepared from ZSG with different degree of hydrolysis?DH??3%,6%,and8%?and their stability to storage,pH,ionic strength,and thermal processing were assessed,too.The storage stability of the glutelin emulsions with different hydrolysis degrees was poor.There were similar results about average particle size with these three kinds of emulsions at pH 3-9,and they showed unstable ability at some cases,which was high ion concentration and near the isoelectric point.However,DH has a significant effect on the formation of stable emulsion.The ZSG emulsions with 6%DH kept stable at the following conditions:NaCl<200 mM;temperatures<70?;pH 7-9.4.The konjac glucomannan?KGM?as the representative of polysaccharides.The objective was to investigate the influence on physical stability of protein emulsions by polysaccharide.The effect of KGM on the emulsion stability of ZSGH with trypsin was studied.The results showed that 0.3%KGM has a stable effect on the stability of ZSGH emulsion.The emulsion containing KGM has good pH stability?5-7?,ionic strength stability?0-400 mM/L NaCl,pH 3?and thermal stability?30-90?,0 mM/L NaCl,pH 3?.5.Interaction between KGM and ZSG was believed to influence the conformational and physicochemical properties of ZSG.We investigated changes in fluorescence,ultraviolet-visible?UV–Vis?and fourier transforminfrared?FTIR?spectroscopies to explore the interaction mechanism of ZSG and KGM.The Stern–Volmer quenching constant(K_SV)at three temperatures was evaluated in order to determine the quenching mechanism.The results showed that KGM quenches the fluorescence intensity of ZSG through a static quenching process.The fluorescence quenching of ZSG by KGM was the result of the formation of ZSG–KGM complex and the effective quenching constants(K_SV)were 5.66×10⁷,5.43×10⁷,and 5.40×10⁷ at 291,298 and 310 K,respectively.Static quenching effect of KGM was verified by linear Stern-Volmer plots and K_SV values.Thermodynamic parameters at different temperatures demonstrated that the interaction between KGM and ZSG was mainly favored by van der Waals force and hydrogen bonding force.