Structural Characterization Of Glycyrrhiza Polysaccharides With Acid-extracted And Its Application In Yogurt

Glycyrrhizal are both medicine and food medicinal materialswith mild medicinal properties and is the largest medicinal herb.The Glycyrrhizal residues are the solid waste residues after extraction of licorice root（extract）concrete through traditional hot water,and contains part of Glycyrrhiza polysaccharides,which can be extracted by acidic or alkaline solution.These polysaccharides may also have various physiological activities.Therefore,it is important to resolve the structures of polysaccharides from Glycyrrhiza residues obtained by acid and alkali extraction.With the increasing concern for health issues,the functional foods will usher in greater development in China.The use of Glycyrrhizal polysaccharides in functional foods has been adapted to the needs of The Times.Therefore,in this study,Glycyrrhiza polysaccharides（GP）were extracted from Glycyrrhiza residues by acid and alkali extraction,and systematically elucidated the structure and physicochemical properties of Glycyrrhiza polysaccharides,and to explore the effect of Glycyrrhizal polysaccharide on the overall quality of functional yogurt.The main research results are as follows:（1）Preparation,structure and physicochemical properties of Glycyrrhizal polysaccharidesThe water-soluble Glycyrrhizal polysaccharides were obtained by acid extraction at different pH values（pH 1,3 and 5 HCl）,ethanol precipitation and freeze-drying after purification,and were named P1,P3 and P5,with yields of 3.12%,2.08%and 1.83%,respectively,The Fourier infrared spectra and nuclear magnetic resonance analysis showed that the three Glycyrrhizal polysaccharides may be dominated by→4)-β-D-Glcp-(1→linked units;Congo red experiments showed that P1 and P5 may have a three-stranded helical conformation;Scanning electron microscopy showed that P3 and P5 have similar rounded granular shapes.The atomic force microscopy showed that all the three polysaccharides were in the form of inter-branched and entangled microstructures.X-ray diffraction analysis showed that P1 had a crystalline and amorphous structure,while P3 and P5 had an uncrystalline structure.Zeta potential showed that all three polysaccharides had a negative charge.They all had higher thermal stability.（2）The study of Glycyrrhizal Polysaccharide YogurtThe addition of Glycyrrhizal polysaccharide promoted the growth of fermenting bacteria,and the maximum number of live bacteria was 8.45×10⁸CFU/mL^-1at 0.02%of the polysaccharide addition.The addition of Glycyrrhiza polysaccharide improved the water-holding capacity of yogurt and reduced the precipitation rate of whey,with the maximum water-holding capacity of 88.68%and the lowest whey precipitation rate of 3.98%at 0.06%.The structure and texture of the yogurt product could be improved with the addition of Glycyrrhiza polysaccharides.A total of 22 volatile flavor substances were detected in Glycyrrhizal polysaccharide yogurt,including 7 esters,2 alcohols,5 ketones,5 acids and 3 other compounds.The acids with the highest relative content were octanoic and capric acid.Acid compounds are the most important flavouring substances in yogurt and have an important influence on the taste and texture of yogurt.Meanwhile GP0.06 yogurt had the highest sensory score.