Study On Structure And Physicochemical Characterization Of Garlic Oligosaccharide

Garlic, an important plant, has been used as medicine and food for thousands of years. China is world’s biggest garlic planting country, as well as consumption and exporting. The garlic industry plays an important role in vegetable production. Carbohydrates are the main functional compositions of garlic which shall have a lot of applications in food industry. The purpose of this paper is to set up a method to purify garlic oligosaccharide (GOS), and to determine its structure and physicochemical characterization. The results of this paper would provide the elemental parameters for the structure-functional relationship and industrial application of GOS.The purification effects of polyamide chromatography, DEAE-cellulose (OH") chromatography, ethanol precipitation method and Sephadex G-25chromatography on GOS were explored respectively. The results implied that polyamide column chromatography could remove66.8%of the protein and the GOS recovery ratio was98.9%. The GOS was separated to3groups by DEAE-cellulose (OH-) chromatography. Ethanol precipitation method could separate the GOS into8groups. After purified with Sephadex G-25, the purification of GOS reached to99.2%. The Mw/Mn was1.31.The physicochemical characterization of GOS was elucidated by chemical, Dynamic Rheometer and DSC analysis. The results showed that GOS was soluble in water but insoluble in organic solvents. Its water solubility was27.7g, and the intrinsic viscosity was3.06mL/g. The thermostability of GOS was descending with the increasing of moisture content.The molecular weight distribution, glycosyl composition, glycoside linkage, back bone and types of branched chain, attached position and, branch degree of GOS was identified by the means of UV, IR, HPLC, GC and NMR instrumental analysis and chemical analysis including periodate oxidation and smith degradation. The microstructure of GOS was observed by using AFM and SEM.The results showed that the molecular weight of GOS was1770D, and it was a kind of fructosan which was mainly composed of fructose with a little glucose. The main glucose residue was P-D-fructofuranose with a little glucose. The chemical bond of GOS’s back bone was β-2,1chemical bond, and the branched chain was connected by β-2,6chemical bond. The branch degree was18.1%. The particles with ellipsoid shape could be observed by AFM, and the size of spherical molecular was relatively uniform. According to the SEM photographs, the surfaces of GOS showed an aggregative state of unconsolidated fragments.The suggested structure of GOS was as follows: )-β-D-F-(2,1)-β-D-F-(2,1)-β-D-F-(2,1)-β-D-F-(2,1)β-D-F-(2,1)-β-D-F-(2,1)-β-D-F-(2,1)-β-D β-D-F β-D-F...