Preperation Of Grapefruit Pectin And Its Synthetical Evaluation On Physico-chemical Properties

As a kind of hydrophilic colloid, pectin was widely used in food, pharmaceuticaland cosmetics industries as a water binder, thicker, emulsifier and stabilizerand, so thequality of pectin is determined by its nature. In this work, the pectin extracted fromgrapefruit peels such as hydrochloric acid, ultrasound-assisted techniques,microwave-assisted techniques, coupled method,solvent method and thephysicochemical properties of pectin was characterized by pectin yield, uronic acidcontent, degree of esterification, protein content, molecular weight, rheology behaviorand emulsibility, the relationship to properties of grapefruit pectin was investigated. Thequality of pectin extracted from grapefruit peels by the different methods was evaluatedand choose an optimal emulsibility pectin as an emulsifier comparing with commercialpectin, emulsion was made with a mix of essential oil extracted by grapefruit peels, andapplication on grapefruit pectin was maked some exploration.The main conclusions andresults indicated as follow:(1)In the traditional acid method, orthogonal test L9(33) show that under theextracting condition of70℃, pH1.5and solid/liquid ratio1:20(g/ml), the pectin had abetter thickening and emulsifying properties, however the pectin yield of thistechnology (18.31%) was less than the highest yield (23.32%), the extraction process is90℃, pH1and solid/liquid ratio1:20(g/ml).(2) In the ultrasound-assisted techniques, orthogonal test L9(33) show that under theextracting condition of60℃for20min of extraction at80KHz, the pectin had a betterthickening and emulsifying properties, however the pectin yield of this technology(17.24%) was less than the highest yield (18.97%), the extraction process is65℃for20min of extraction at100KHz.Results showed that the pectin yield had no positivecorrelation with the pectin properties.(3)The pectins extracted by the method of microwave-extraction and the coalitionmethod of microwave-extraction and ultrasonic-extraction were compared with thepectins with the better thickening and emulsifying properties extracted by the method oftraditional acid extraction and the ultrasound-assisted, The conclusion that the pectinextracted by the coalition method of microwave-extraction and ultrasonic-extraction hada better thickening and emulsifying properties, but the pectin yield(23.92%) of thistechnology was less than the highest yield (24.45%).(4)In the solvent method, the mass concentration of1%EDTA-2Na under theextracting condition pH1.5, the pectin had a better thickening and emulsifyingproperties; however the pectin yield of this technology (26.31%) was less than thehighest yield (33.34%).(5) There was no directly relationship between the yield of pectin and the pectinproperties. Therefore, both of the yield and the comprehensive properties of pectinshould be taken into account for the main evaluation standards in optimizating the extraction technology.(6) There was a close relationship among the pectin for emulsifying property,protein content and viscosity, it was that the more the protein content of grapefruitpectin is, the better the emulsifying activity of grapefruit emulsion is; the higher theviscosity of grapefruit pectin is, the better emulsion stability of it, but the size of themolecular weight for the grapefruit pectin have an effect on the viscosity of itself. Itmeans that there is a complex relationship to the properties of grapefruit pectin eachother.(7)By comparison pectins with better thickening and emulsifying properties eachother for every method from chapter2to chapter5,the result was that in the solventmethod,the mass concentration of1%EDTA-2Na under the extracting condition pH1,the pectin had a better thickening and emulsifying properties, and it was made emulsionwith a mix of essential oil extracted by grapefruit peels, the emulsion storaged at60℃with different time, it proved that grapefruit pectin was better than commercial pectin onphysical stability (the variational trend of the size distribution of emulsion)andchemical stability (the main component content of the essential oil of grapefruit).