Study On The Deesterification Of Soluble Soybean Polysaccharide Catalyzed By Solid Base And The Properteis Of The Products

Soluble soybean polysaccharide?SSPS?is a water-soluble spherical or comb-like polysaccharide with structure similar to pectin.SSPS has many excellent functional characteristics,and broad application space.Among them,the ability of SSPS to stabilize proteins under acidic conditions relates to the degree of esterification?DE?and molecular weight.SSPS with low DE and large molecular weight has better stability.At present,the industrial method of producing low-DE SSPS is mainly alkali deesterification process,which has the problems of serious side reactions in deesterification process,deep product color,and the need for decolorization or bleaching treatment.Based on the principle of deesterification,this paper proposed a new solid base catalytic deesterification process to achieve effective deesterification and ensure the molecular weight of the product,while reducing the side reactions and improving the color of the product.The specific research content and results are as follows:Firstly,seven kinds of solid base such as MgO500?,MgO700?,MgO/Al₂O₃,MgO/SiO₂,MgO/Nb₂O₅,MgO/ZrO₂,and magnesium aluminum hydrotalcite were synthesized as catalysts.Taking the DE and the product molecular weight of the product SSPS as indicators,the effects of different solid bases catalyzing the deesterification of SSPS were studied.The results showed that MgO500? had the best catalytic effect.Under the conditions of SSPS concentration was5.0 wt%,reaction temperature 100?,reaction time 4 h,and catalyst feeding ratio was was 1:5?w:w,catalyst:SSPS?,the DE of the MgO500? deesterification product reduced to 28.52%,the weight-average molecular weight?M_w?reduced to 4.56×10⁵ Da,the polydispersity index?PDI?increased to 2.66.The result of CO₂-programmed temperature desorption showed that the CO₂ adsorption capacity of MgO500? was 3521?mol/g,and MgO500? had relatively strong alkalinity and alkalinity.X-ray diffraction spectra and scanning electron microscopy results indicated that the high catalytic activity of MgO500? during the deesterification of SSPS might relate to its crystal structure and apparent morphology.Then,using MgO500? as solid catalyst,the effects of reaction temperature,reaction time,and catalyst feeding ratio on DE,molecular weight,and monosaccharide composition of produces were studied.This indicated that the reaction temperature,the deesterification time,and catalyst feeding ratios had greater influence on the MgO500? deesterification products.However,when the deesterification time exceeded 4 h?4?7 h?or the catalyst feed was further increased,M_w,PDI,and DE of the product did not change significantly.The results of monosaccharide composition showed that after MgO500? deesterification process,the content of neutral sugar of the product decreased rapidly.As the deesterification process deepened,the ratio of galacturonic acid to rhamnose increased first and then decreased,which indicated that MgO500? firstly catalyzed the removal of neutral sugar residues on the SSPS side chain,while the degradation of polyarabinose and polygalactose side chains was slower than the main chain of SSPS.Four groups of low-DE SSPS with similar DE were prepared using solid base MgO500? deesterification process and alkali?NaOH?deesterification process.The differences in products molecular weight,monosaccharide composition,protein content,and color were compared.The results showed that when the DE was greater than 30%,the alkaline process product had higher molecular weight;when the DE of the product was less than 30%,the solid base MgO500? process products had higher molecular weight.The content of monosaccharide components of NaOH deesterification products was relatively stable,indicated that NaOH has no selectivity for the hydrolysis of the main chain or side chain of SSPS.On the other hand,the solid base MgO500? deesterification resulted in a very low protein content in the product.In the case of NaOH deesterification process,the protein content of products was relatively stable and the protein content did not decrease significantly as deesterification increased.Although the solid base MgO500? deesterification caused the protein in the SSPS structure falling off more seriously,it did not cause the product to be darker.However,in the alkaline?NaOH?deesterification process,to reduce the product DE to below 20%,the product color was close to black.Finally,the paper examined the application properties of MgO500? deesterification products of stabilizing milk protein under acidic conditions,foamability.and emulsification.The SSPS prepared by the MgO500? deesterification process was used in acidic milk beverages.The application results showed that the SSPS prepared by the MgO500? deesterification process had a clarification index of yogurt greater than 0.92 at a dosage of 0.1%,which indicated that the product SSPS concentration of 0.1%did not effectively stabilize the acidified milk beverage.At 0.3%,the products with low de-esterification had almost no stabilizing ability.With the increase of the degree of deesterification,the stability of SSPS was significantly improved.At 0.6%dosage,even the samples with insufficient deesterification had certain stabilizing ability.The degree of deesterification of SSPS had increased,and the stability of acidified milk had also been continuously improved.Compared with commercial products,SSPS prepared by solid base MgO500? deesterification process had poor foaming and foam stability,emulsification and emulsification stability.This might be related to the extremely low protein content of SSPS prepared by the solid base MgO500? deesterification process.