Rheological Properties And Structure Relationship Of Chicory Root Pectin

In recent years,with the development of chicory processing industry,a large number of by-products,such as chicory pulp,is produced in the processing process.Chicory root pulp is rich in pectin polysaccharides.Therefore,this study gives a full description of chicory root pectin function characteristics,which is potential for the source of commercial pectin,the main results are followed:The first part aimed to extract gelatinous chicory root pectin(CRP)and evaluated the rheological behavior of the dispersions and gels.CRP was extracted by citric acid(CEP),alkaline(AEP),ammonium oxalate(OEP)and sodium citrate(SEP).The yield,molecular weight(Mw)and the degree of esterification(DE)of pectin samples varied from 8.8 to 14.8%(w/w),204 to 336 k Da and 4.0 to 47.4%,respectively.AFM studies showed self-organize on mica of CEP,revealing a random coil conformation due to the interaction of multiple branching,whereas,AEP exhibited long linear filamentous structures.The flow behavior study verified the pseudoplastic character of CEP and SEP at 25°C,while OEP and AEP belonged to dilatant fluid,besides,a closed hysteresis loop was observed when the CEP concentration increased to1.5%.OEP gel was thermo insensitive and stiff,AEP gel presented most sensitive to calcium ion but more brittle,and SEP was observed a weak syneresis in spite of the poor gelation property.The texture analysis indicated OEP gel had a superior firmness and chewiness.These findings demonstrated that CRP may be attractive as a thickener or gelling agent to modulate textures of sugar-free and calcium content food.The functional properties of pectin products vary with the extraction procedure,this part aim at the evaluating the gelling and emulsification capacity of chicory root pectin,which was isolated by using organic-acidic chelator and its salt(citric acid,sodium citrate,oxalic acid,ammonium oxalate).these mild extraction methods resulted in a high average molecular weight,low degree of esterification and acetylation of RG-I pectin.The rheology study of pectin was carried out to proof the gelation property of CRP in a wide range of p H.Although the addition with different type of Ca²⁺effected the elastic modulus,CRP networked a stiff gel in p H 11,which might be due to the de-esterification reaction provided more crosslink sites.The molecular structure of pectin has a great influence on the interfacial activity,the pectin extracted by acidic chelator was superior to stabilizing 10%oil-in-water emulsion in p H 3.5.Otherwise,the emulsion of NEP and OEP showed a better resistance to p H changes owing to its stronger steric hindrance,inferring by a relatively smaller d_4,3,and more sensitive to the change with Ca²⁺.In emulsion storage,the acidic condition of emulsion is conducive to alleviate the droplet aggregation,while a depletion flocculation was occurred in CEP emulsion for lacking of H-bond in p H 8.the NEP was able to promote the long-term stability of emulsion,and an unexpected emulgel formed after 30 days with Ca²⁺.The mechanism of the formation of emulsion gelation might be the aggregation of charged droplet in low level of Ca²⁺,while in the higher content of Ca²⁺,the oil-in-water droplets were immobile by the crosslinking of pectin in aqueous phase.The chemical structure of pectin under heat in 85°C was analysed to figure out the stability of functional group.In alkaline condition a slight heat treatment accelerated chemical reaction,resulting in degradation of the main chain and low esterification degree.While in the acidic condition,the side chain degraded in great deal,as well as main chain.In terms of gel properties,slight heat treatment helped to form a larger elastic modulus gel in mild alkali.CRP emulsion gel belongs to emulsion filled gel,while the structure of the pectin is damaged.The thermal stability of pectin is reduced after heat treatment referred by TG result.When the CRP electrostaticly bonded with WPI,the strength of the hydrogel and emulsion gel formed by pectin depended on the combination degree.as the weak electrostatic compound is formed,the presence of WPI facilitates the crosslinking of CRP in the water phase to form a strong gel network,and the stronger would lead to weak gel.