Studies On Extracion And Application Of Mulberry Leaf Protein

Mulberry is a traditional medicine in China, which was application for thousands of years. In1993,mulberry is officially listed as one of drug Edible by National Ministry of Health. It contains abundant functional ingredients. Mulberry leaf protein(MLP) content was higher in the plant, its amino acid composition is reasonable. Our country is the world’s most resource-rich countries due to a maximum of mulberry cultivation. At the same time, rare use of mulberry leaves cause serious waste. In this research,taking mulberry leaves of Jinhua city in Zhejiang Province as the materials, determined and optimized the extraction process of MLP. By comparing the quality of MLP in different seasons,functional properties of MLP. At last, take a preliminary research on the products was related with mulberry protein and preparation of proteolytic peptides,we tried to provide basis for further development and utilization of mulberry leaves.The main results of this study:(1)The optimal extraction conditions of MLP was:0.4%for salt concentration,1:30(g/mL) for mulberry leaf to water ratio, under the400W power ultrasonic20min, then extraction80min at40℃and pH2.0-3.0for precipitation.The yields of crude protein from mulberry leaf was10.23%and its protein content was56.8%.(2) By studying the changes of mulberry protein content in eight months of the entire mulberry harvest from April to November, we found that the mulberry protein content was higher in the months from April to September and then the protein content in the mulberry decreased Significantly. The discovery of the amino acid composition of the mulberry protein in different seasons showed that the mulberry protein contains at least18kinds of amino acid. The essential amino acid’s content was30-40percent in the total amino acid content.The ratio coefficient of amino acid was70.61that is a kind of high nutritional value of protein. The first limiting amino acid was isoleucine. Spring and fall are the best seasons of mulberry leaf protein.(3)The features of mulberry proteins to be studied under different environmental conditions. Results indicated that better solubility, water-holding capacity, emulsifying capacity and emulsion stability, foaming capacity of mulberry leaf proteins were observed at pH far away from isoelectric point(pl=5). The water-holding capacity, solubility and foaming capacity of mulberry leaf proteins had respective positive correlation with NaCl concentration within the range of0-1.0mol/L. The highest emulsifying capacity was observed at0.8mol/L and the highest emulsion stability at0.6mol/L and a higher level of NaCl concentration resulted in a remarkable decline in both of them; as sucrose concentration increased, the water-holding capacity increased but the solubility and foaming capacity decreased and no pronounced changes in the emulsifying capacity and emulsion stability were observed; the oil-absorbing capacity or foaming capacity of mulberry leaf proteins were positively correlated with temperature, while the water-holding capacity, solubility, emulsifying capacity and emulsion stability of mulberry leaf proteins were the best at60℃.(4) According to the mulberry protein extraction technology, we developed mulberry nutrition instant powder. By adding the β-cyclodextrin and pectinase, cellulase, neutral protease on solubility, taste, color, clarify the qualities of the products and the content of protein, identified the following process:After adding0.4%salt solution in accordance with1:30and under the400W power ultrasonic20min,adding complex enzyme (10000U/g neutral protease+100U/g cellulase+50U/g pectinase) and5%β-CD to the mixture, extracted in50℃for40min. Extraction was concentrated in vacuo, spray-dried. Mulberry nutrition powder with good solubility was obtained.Its yield was14.5%, which contained24.79%protein,18amino acids (y-aminobutyric acid content28.95ug/g)in it,72.17%polysaccharide,0.047%flavonoid content,7.93%ash, and3.175%water. The nutrient powder had good solubility,with yellow-brown, translucent soup, sweet smells, delicate taste.(5) In this study, the extraction process of mulberry proteolytic peptides was researched by degree of hydrolysis (DH) and combined with in vitro antioxidant activity. The optimum hydrolysis conditions for MLP was concentration of MLP5%(w/v), temperature55℃, pH8.0-9.0, enzyme dosage8000U/g, rection time4h, the liquid was centrifuged. The supernatant was desalted by using macroporous resin, and then concentrated under vacuum. At last, the leaf protein hydrolysate was obtained by freeze drying. Among the five antioxidant model combined with Vc as the reference, mulberry proteolytic peptides have strong antioxidant activity. Experiments show that mulberry proteolytic peptides were found to have excellent DPPH·,·OH,O2-· scavenging activities and oxidation of linoleic acid inhibitory effect.