| Chicory is a valuable medicinal and food plant,rich in many nutrients.Chicory polysaccharide is a natural fructan extracted from chicory,which has high edible and medicinal value and has broad research and development prospects.In recent years,the market for chicory polysaccharide in China has also been gradually expanded.In this study,chicory tuber was used as raw material,and the research progress of chicory polysaccharide was combined with the optimization of extraction and decolorization process and the study of its basic structure and properties.The extracted chicory polysaccharides were applied to defatted and full-fat fermented milk,and their basic physicochemical properties were systematically studied to lay a good foundation for the comprehensive utilization of chicory resources in the future.The main research results are as follows:1.The process of chicory polysaccharide extraction by complex enzyme-ultrasonic method was optimized by surface response testing.The results showed that the final yield of chicory polysaccharide was 56.47% when the material-liquid ratio was 1:33g/m L,the enzymatic digestion time was 2.6 h,and the ultrasonic time was 36 min,in which the best process conditions were achieved.In addition,it was proved that the regression model could optimize the parameters of chicory polysaccharide extraction process,which has some practical reference value.The AB-8 macroporous resin was selected for the optimization of polysaccharide decolorization,and the comprehensive evaluation of polysaccharide loss rate and decolorization rate of chicory polysaccharide was used as the index,and the resin wet weight ratio,p H and decolorization time were investigated by the single factor test method,and orthogonal tests were conducted to finally determine the best decolorization and purification process of chicory polysaccharide,namely,the resin wet weight ratio was 1:4 g/m L,decolorization time was 40 min,p H was 5,and the retention rate of polysaccharide was 90.55%,decolorization rate was 77.88%,and the overall score was 84.22.2.The chicory polysaccharide powder was extracted by a complex enzymeultrasonication method and obtained by deproteinization,depigmentation and dialysis,and the structural properties of chicory polysaccharide were initially analyzed by using infrared spectral scanning,X-diffraction,scanning electron microscopy,differential scanning calorimetry and thermogravimetry,etc.The infrared spectrum showed that the polysaccharide was a pyranose ring polysaccharide group linked by α-glycosidic bond;scanning electron microscopy and X-diffraction The results show that the surface of chicory polysaccharide is tightly packed with sheet-like structure,containing more pores,with fine particles attached to the surface of the sheet-like material,mainly in the form of crystals;thermodynamic analysis shows that chicory polysaccharide has good thermal stability in the range of 30℃～150℃.Static rheological analysis of chicory polysaccharide shows that its apparent viscosity exhibits a shear thinning phenomenon,which is a typical non-Newtonian fluid.Meanwhile,chicory polysaccharide has certain in vitro antioxidant activity and potential anti-glycolytic ability.3.Different amounts of chicory polysaccharide were added to skimmed and fullfat fermented milk,and it was found that the addition of chicory polysaccharide in appropriate amounts could improve lactic acid bacteria activity,physicochemical properties,texture,rheology,sensory and nutritional quality of fermented milk.The results showed that when 3% chicory polysaccharide was added to skim milk,its physicochemical index and sensory quality were the closest to those of blank whole milk,indicating that chicory polysaccharide could partially replace fat and improve the quality of skim fermented milk.4.The study on changes in antioxidant activity of fermented milk during storage period found that the scavenging capacity of DPPH free radicals increased by 0.381mg/100 g for skimmed 3% polysaccharide fermented milk and 0.286 mg/100 g for skimmed yogurt on day 3;it showed a decreasing trend from day 4 to 15,with a decrease of 12.6% for skimmed 3% polysaccharide fermented milk on day 15 and a decrease of 29.93%.The total antioxidant activity of 2% full fat polysaccharide fermented milk increased by 0.214 mg/100 g at day 3;it showed a decreasing trend from day 4 to 15,decreasing by 2.401 mg/100 g at day 15,and the rest of the fermented milk showed the same trend as above.In addition,comparing the total antioxidant activity of skim fermented milk,full-fat fermented milk,skim 2% polysaccharide fermented milk and full-fat 3% polysaccharide fermented milk on day 1,we found that the total antioxidant activity of full-fat fermented milk was 0.336 times higher than that of skim fermented milk;skim(full-fat)3% polysaccharide fermented milk was 0.88(0.84)times higher than that of skim(full-fat)fermented milk.In conclusion,the addition of chicory polysaccharide could significantly enhance the antioxidant activity of fermented milk and the antioxidant activity of full-fat fermented milk was stronger than that of skim fermented milk,and chicory polysaccharide could significantly delay the decline of antioxidant activity of fermented milk. |
PDF Full Text Request