Structure Characterization Of Potato Pulp Pectic Polysaccharide And Its Application In The Stabilizing Of Acidified Milk Drinks

Potato pulp is a by-product of potato starch processing.It is mainly composed of residual starch and cell wall fragments.It contains 10%～25% pectic polysaccharide(dry base).The use of physical and chemical methods to extract pectic polysaccharide has become an important development approach for potato pulp.The effects of extraction methods as well as gradient alcohol precipitation on the structure and composition of potato pulp pectic polysaccharides were analyzed.On this basis,purification and fine structure analysis were continued.In addition,in order to broaden the application of potato pulp pectic polysaccharides,its stabilizing effect on acidified milk drinks were discussed.The main research contents and results are as follows:(1)The effect of extraction method on the structure and composition of potato pulp pectic polysaccharideUsing de-starched potato pulp as raw materials,various extraction methods including acid,chelating agent,buffer,alkali(dilute and concentrated),enzyme extraction were used to prepare potato pulp pectin polysaccharides.The results showed that the structure of the pectic polysaccharides obtained by different extraction methods was significantly different.Chelating agent extraction yielded a large amount of pectic acid components.Acid and diluted alkali resulted in potato pulp pectic polysaccharide containing a large amount of galactan side chains.Enzymatic extraction obtained high molecular weight potato residue pectin polysaccharide with relatively complete structure.Under concentrated alkali extraction,both the HG and the neutral sugar side chains were degraded to a certain extent.Buffer extraction obtained more cellulose and hemicellulose components,so it is not suitable for the extraction of potato pulp pectic polysaccharide.(2)Physical and chemical properties of potato pulp pectic polysaccharides obtained by gradient ethanol precipitationThe one-step alcohol precipitation method will collect several pectic polysaccharides components with very different structures at the same time,which will aggravate the heterogeneity.Under acid extraction conditions,one-step alcohol precipitation was replaced by gradient alcohol precipitation(40%,60%,80%),and the potato pulp pectic polysaccharides(A40,A60,A80)under each ethanol gradient were collected.The purpose was to explore the feasibility of separating different structures of potato pulp pectic polysaccharides by gradient alcohol precipitation.The results showed that with the increase of ethanol concentration gradient,the content of uronic acid and esterification group decreased,and the content of neutral sugar increased.Molecular weight changing trend is not obvious,but the molecular weight of A80 collected with high concentration gradient is the lowest.The structural characteristics of the three graded alcohol-precipitated potato pulp pectic polysaccharides were that A40 had a high proportion of HG,A60 was mainly composed of RG-I,and A80 was composed of low polymerization degree of pectic and non-pectic neutral polysaccharides.There are also differences in the rheology and emulsification properties of the three.Among them,the A40 showed higher apparent viscosity and better emulsification.(3)Purification of potato pulp pectic polysaccharides and primary structure analysis for the RG-I domainCapto Q anion exchange column was used to separate and purify A40 and A60,and the main purified components were collected for physical and chemical analysis.Methylation and nuclear magnetic resonance analysis were used to clarifiy the primary structure of the purified components mainly including RG-I structure.It can be inferred that around 58% of the Rha residues of the RG-I backbone are substituted by neutral sugar side chains.The branched neutral sugar side chains are mainly composed of →4)-α-Gal Ap-(1→;→3)-α-Gal Ap-(1→;→3,4)-α-Gal Ap-(1→three galactose residues,and two arabinose residues that are →5)-α-Araf-(1→;→3,5)-β-α-Araf-(1→.(4)Effect of potato pulp pectic polysaccharide on the stabilizing acidified milk drinksComparison study was made among potato pulp pectic polysaccharide(A40)and commercial pectin(HMP,LMP)in stabilizing acidified milk drinks.From the point of view of particle size and sedimentation,it is found that the stabilizing effect of A40 is better than that of LMP,but not as good as HMP.Inferred from Zeta potential and rheological analysis,A40 mainly stabilized casein micelles through steric hindrance of the side chain,rather than electrostatic repulsion and thickening effect.In practical applications,it can be modified or compounded to increase the charge density and viscosity to improve the stability of A40.