Study On Extraction Technology And Properties Of Pectin From Leaves Of Premna Microphylla Turcz

Pectin is a family of complex polysaccharides mainly extracted from cell walls of higher plants.Because of its good physical function.pectin is widely used in industry such as food,medicine.cosmetic.The extraction technology of pectin from leaves of Premna Microphylla Turcz were studied in this paper. Then, the pectin has been prepared to study its physicochemical and rheological properties.As for the extraction of pectin from leaves of Premna Microphylla Turcz, the extraction rate of pectin and transmission of the pectin extract were utilized to evaluate two extraction methods, that is, acid water bath extraction and mixed acid ultrasonic-microwave synergistic extraction, while extraction rate served as the dominant indicator.For the water bath, the influence of type and ratio of different acids, pH, solid to liquid ratio, extraction time and temperature on extraction effect were studied.Based on single factor analysis,orthogonal test was designed to confirm the main factors and the optimum condition. The results showed that the optimum condition was as following:H3PO4 to H2SO3 ratio 1:2(v/v),solid to liquid ratio 1:35(w/v), pH1.5, extraction time 1.5h and extraction temperature 90℃. Under these conditions, the extraction rate of pectin and transmission of pectin extract were 18.53% and 92.70%, respectively.For the ultrasonic-microwave synergistic extraction, pH, solid to liquid ratio, extraction time and extraction temperature were chosen to assess the extraction result. The single factor analysis and orthogonal test were designed to confirm the main factors and the optimum condition.The results showed that the optimum condition was as following:pH1.5, extraction time 500s, solid to liquid ratio 1:15(w/v), microwave power 100W. Under these conditions, the extraction rate of pectin and the transmission of pectin extract were 19.41% and 92.50%, respectively.By comparison of the above two methods, ultrasonic-microwave synergistic extraction reached an ideal result, which was adopted in the following experiment.Concerning the discoloration of pectin extract, five types of macroporous resins, namely S-8,X-5,AB-8,D3520,D4020 were compared by their absorbing ability.The X-5 resin demonstrated an ideal result among various resins tested.Then, dynamic absorption process was adopted. Different flow rates were designed to optimize the discoloration process.Under optimized dynamic absorption condition (flow rate of 56mL/h), higher ratios of discoloration and pectin recovery for X-5 resin were observed.Then,the protein content before and after absorbing were tested and the result showed that ideal deproteinization effect was reached. Consequently, no additional deproteinization methods were utilized.Dialysis method was adopted to purify the pectin extract further.The water was changed every 6h in the process of 72h.Ethanol was used to precipitate pectin from the extract, several factors such as the concentration ratio of pectin solution, the concentration of ethanol, the precipitation time were used to optimize the precipitation process. The result showed that the optimized condition was as following:concentration ratio 1/4, concentration of ethanol 80%, precipitation time 1.5h. Followed by the above process, the physicochemical and rheological properties of pectin were studied. The influence of a number of parameters such as pectin concentration, pH, Ca2+ concentration, sugar content, temperature, different heating time on viscosities of pectin aqueous solution were studied. The result showed that the viscosity of pectin solution decreased with the increased shear rate and the pectin solution was a typical pseudoplastic fluid; the viscosity decreased under both acidic or alkaline condition; the viscosity increased with higher content of Ca2+ and sugar;the viscosity of pectin solution decreased and then become Newtonian fluid when heated for certain time.