Preparation Of Calcium Protein From Broussonetia Papyrifera Leaves And Development Of Its Functional Products

Broussonetia papyrifera(L.)Vent.,a deciduous tree belonging to Broussonetia of Moraceae,is rich in resources and widely distributed in China.It is the preferred tree species for afforestation of barren hills and conversion of farmland to forests.Looking at the whole Broussonetia papyrifera,its most valuable part is its leaves,which are rich in calcium,selenium,iron,manganese,zinc,cobalt,iodine and other mineral elements.In addition,the protein content of Broussonetia papyrifera leaves is high,reaching 24%,and the calcium content of protein is also high,therefore,Broussonetia papyrifera leaves are excellent raw materials for high-quality protein development.At present,utilization of Broussonetia papyrifera leaves is only used as feed to feed animals,but it is not developed and utilized,resulting in a great waste of resources.Therefore,in this paper,Broussonetia papyrifera leaves were selected as raw materials to prepare antioxidant peptides on the basis of calcium protein extraction,and the active peptides were microencapsulated to prepare microcapsules with sustained-release function.The main research contents and research results are as follows:(1)Optimizing the extraction method and extraction process of calcium protein from Broussonetia papyrifera leaves;The extraction of calcium protein from Broussonetia papyrifera leaves was carried out by water extraction,alkali extraction,alcohol extraction and salt extraction.The results showed that the yield of protein from Broussonetia papyrifera leaves extracted by alkali extraction and the content of calcium in protein were higher.Single factor and orthogonal experiments were carried out to optimize the extraction temperature,extraction time,NaOH concentration and solid-liquid ratio that affect the extraction yield of calcium protein by alkaline extraction.The optimal extraction conditions of calcium protein by alkaline extraction were obtained as follows:solid-liquid ratio 1:50,temperature 60?,extraction time 3 h,NaOH concentration 0.08 mol/L;The protein yield was 10%,and the calcium content in protein was 2.14%.(2)Broussonetia papyrifera leaf polypeptide was prepared by enzymatic method,and its preparation process conditions were optimized;Using the calcium protein as material,the effects of protease type,enzyme dosage,enzymolysis temperature,enzymolysis time and pH on the yield of Broussonetia papyrifera leaf polypeptide were studied by single factor experiment.On this basis,response surface methodology was used to optimize the technological conditions for the preparation of Broussonetia papyrifera polypeptide.The results showed that pancreatin was the best proteolytic enzyme for the preparation of Broussonetia papyrifera polypeptide.The optimal technological conditions for the preparation of Broussonetia papyrifera polypeptide by pancreatin were as follows:enzyme dosage 640 U/g,enzymolysis time 3.0h,enzymolysis temperature 60?,pH 7.31.Under this technological condition,the actual yield of Broussonetia papyrifera polypeptide was 84.2%.(3)Ultrafiltration membrane was used to separate and classify the peptide of Broussonetia papyrifera leaves,and the antioxidant activities of the calcium protein and polypeptide with different molecular weight were studied in vitro;The Broussonetia papyrifera leaf polypeptides were separated by ultrafiltration membrane,and the antioxidant activities of Broussonetia papyrifera leaf calcium protein and different molecular weight polypeptides were determined in vitro with Vc as control.The results showed that all peptides had certain scavenging ability of ABTS+free radicals and hydroxyl free radicals,but the scavenging rate was lower than that of calcium protein and VC.However,the DPPH radical scavenging activity of each peptide was significantly higher than that of Broussonetia papyrifera leaf protein,which was similar to Vc.Among them,polypeptides below 3 KD have good antioxidant capacity,and they have good scavenging capacity for DPPH radical and hydroxyl radical.(4)The microencapsulation conditions of the polypeptide of Broussonetia papyrifera were optimized,and the sustained-release properties of the microcapsule in vitro were tested;The microcapsules of Broussonetia papyrifera leaf polypeptide were prepared by the method of sharp hole coagulation bath,and the effects of temperature,sodium alginate concentration,calcium chloride concentration and core-wall ratio on the preparation of microcapsules were investigated.On this basis,the preparation conditions were optimized by response surface methodology.The results showed that the optimum conditions for microcapsule preparation were temperature 38?,calcium chloride concentration 2.1%,sodium alginate concentration 1.89%,and core-wall ratio 0.89:1.Under these conditions,the embedding rate was 81.3%.The sustained release performance of Broussonetia papyrifera microcapsules in artificial gastrointestinal fluid was simulated.The results show that it can exist stably in gastric juice and has good release performance in intestinal juice,with the cumulative release rate reaching 93%within 3 h.