Preparation, Functionality And Application Of Hempseed Protein Isolate

Hempseed protein (HP) from Cannabis sativa L. is a new, exellent plant protein. The scientific investigation and application of HP can improve utility ratio of hempseed and develop hemp industry. In this work, hempseed protein isolate (HPI) were prepared from defatted hempseed and its physicochemical property, functionality, and nutritional property were comprehensively studied. In addition, improving functionality through limited enzymolysis reaction and application in baked products were studied.Firstly, preparation of HPI were investigated through a traditional method of alkali extraction and acid precipitation. The protein yield, protein content and solubility index of HPI were fully investigated under different circumstance of temperature, ratio of solid to water, pH and time. Optimizing preparation conditions through a three-level four-factor orthogonal design was also carried out. Under optimized conditions(ratio of solid to water 1:20, temperature 40℃, pH8.0, time 70min), the protein yield, protein content and solubility index of HPI reached 70.56%, 92.39% and 31.89%, respectively.Secondly, the nutrition value and functionality of HPI were studied. Amino acid analysis indicated that amino acid composition of HPI were completed and content of HPI were rich, so HPI was an excellent plant protein. Tryptophane was the first limiting amino acid and content of the other amino acids were fully above the recommended intake for children from 2 to 5 years old by FAO/WHO. Thermal stability test indicated that the endothermic peak of HPI was 88.4℃and heat of denaturation was 1.544 J/g. Hydrophobility index analysis indicated that the amount of hydophobic amino acid residue was high. Emulsifying property, fat adsorption capacity and water holding capacity of HPI were higher than that of soy protein isolate, but foaming capacity was lower. Solubility index of HPI was so low that utilization in liquid food was limited. Raising of temperature improved solubility index and emulisifying property. Solubility index of HPI went down in low salt concentration and went up in high one.Limited enzymolysis reaction improved functionality of HPI remarkably. Solubility index, emulisifying property, foaming capacity and water holding capacity improved slightly, but emulsifying stability, foaming stability and fat adsorption capacity were unslightly reduced with the degree of hydolysis of 3.01%.Finally, application of HPI in baked products was studied. Content of the first limiting amino acid lysine of flour protein improved about 42.31% with replacement amount of 3%. The application in paste improved floured property slightly and reduced stretching property unslightly with the dose of 1%～3%. The application of HPI in bread improved nutrition value and dehydration degree was reduced, but generated disadvantageous affection in specific volume and color of the bread. Comprehensive consideration of nutrition value and sensory quality, the suitable replacement amount of HPI was 1%～3%.