Study On Complex Enzymes-assisted Extraction Of Sunflower Pectin And Its Characterization

As a kind of green food additive, pectin is widely used as gelling agents, emulsifyingagents，thickeners and stabilisers in food industry. More and more attention is being paid tolow methoxyl pectin, which can be used for preparation of low sugar and low-calorie healthfoods. In this paper, sunflower head was selected as raw material and complex enzymes(cellulase, hemicellulase and papain) assisted extraction of pectin from sunflower wasperformed. An orthogonal experimental design and response surface methodology withBox-Behnken design (BBD) was implemented to establish the optimum pectin extractionconditions. The basic physical and chemical properties of optimized pectin product werestudied and the viscosity and the molecular weight distribution of sunflower pectin weredetermined.Based on single factor test of single enzyme (cellulase, hemicellulase or papain), theamount of complex enzymes were determined by the optimization of orthogonal experimentaldesign. When the enzyme amount was1.0%cellulase,1.0%hemicellulase and0.5%papain,the yield of pectin was11.41%. On the basis of single factor test of complex enzymesextraction, response surface experimental design was used to determine the optimal extractionprocess as follows: solid-liquid ratio (1:27), hydrolysis time1.9h, reaction temperature60.5℃, hydrolysis pH=5.3, pectin yield was11.94±0.38%.Drying weightlessness, ash content and acid insoluble solids content of pectin inoptimized conditions were measured. The results are as follows: loss on drying7.86%, ashcontent1.17%, acid-insoluble solids content0.24%. The results above are in the range of therequirements of the pectin relevant standards. Galacturonic acid (GA) content and degree ofmethoxylation (DM) of pectins extracted by chemical methods (hydrochloric acid orammonium oxalate) and complex enzymes method were compared. It was showed that GA and DM of pectin in the enzyme-assisted extraction was76.53%and42.18%. GA ofhydrochloric acid and ammonium oxalate metnods were83.61%and81.25%. Their DM were32.24%and34.89%. Compared with the chemical methods, the pectin of enzyme-assistedextraction had lower GAcontent and higher DM value.Relative molecular weight (Mw) and its distribution of pectins from various sources andsunflower pectins from different extraction methods were determined. Compared with Sigmacitrus pectin standard, commercial low methoxyl pectin and sunflower pectins in chemicalextraction methods, the molecular weight distribution of sunflower pectin extracted bycomplex enzymes method was wider. Pectin in enzyme-assisted extraction is composedmainly of two parts. Mw of the large molecular weight fraction, which was at lower content,was lager than Mw of all other samples. And Mw of the other one was lower than Mw ofmajor fraction of all other samples.There were some effects of drying methods on the physicochemical properties of pectin.Mainly, the Mw and its distributions were different in different drying methods. It was foundthat the Mw of oven drying, followed by that of freeze drying and spray drying.Effects of pectin concentration, temperature, pH, calcium ion concentration on pectinsolution viscosity were studied. As pectin concentration increased, the solution viscosityrapidly increased. The higher the solution temperature was, the lower the viscosity was. Andin the range of20℃-50℃, solution viscosity showed a sharp decline. The value of pH=3.0isthe turning point of pectin viscosity. When pH>3.0, the viscosity accelerated decline with thereduction of pH values. The addition of calcium ion can increase the viscosity of the pectinsolution. But when the calcium ion concentration is bigger than35mg/g, the viscosity showeda downward trend. The pectin solution is no longer homogeneous and there was appearance ofsmall particulate gels.