Preparation Technology Of Mulberry Leaf Protein And Its Nutritional Evaluation

Mulberry leaf protein which was rich in amino acid and nutritionally balanced was a superior protein resource. This paper mainly studied factors that influenced extraction effects, contents of active substances and nutritional evaluation of mulberry leaf protein.It also prospected future research directions in this field and provided a theoretical basis for development and utilization of mulberry leaf research. The results were consisted of three parts:1. Optimization of technology for preparation of Mulberry leaf proteinWe used mulberry leaf powder as raw material to extract proteins and produce protein powder, Single factor experiments were carried out to research technologies for extraction method of mulberry leaf protein such as leaf dry method, type of protein leaching agent, protein precipitation method and protein dry method. The results indicated that mulberry leaf dried naturally or 60℃ oven dried, smashed, sonicated 20 min, extracted 1h with 5 g/L Na OH as leaching agent solid to liquid concentration of 40 g/L, extraction temperature of 40 precipitated by hydrochloric acid. Under this condition, the extraction ratio of mulberry ℃leaf protein would be 14.42%, protein mass fraction can reach 49.58%. It improved the extraction ratio of mulberry leaf protein and produced mulberry leaf protein powders of high quality by optimizing the above four technologies.2. Contents determination of active substances of mulberry leaf proteinMulberry leaves are rich in polysaccharides, flavonoids and other active substances which could reduce blood pressure and blood sugar and made human healthy. This part studied the influence of mulberry leaf protein precipitation method and protein dry method on contents of four kinds of active substances in mulberry leaf protein, such as polysaccharides, flavonoids, DNJ and gamma aminobutyric acid(GABA).This also provided the basis for preparation technology of mulberry leaf protein. The results showed: mulberry leaf protein from different precipitation methods and protein dry methods has significant difference in its contents of these four active substances. Flavonoids, polysaccharide, GABA and DNJ of mulberry leaf protein obtained from hydrochloric acid precipitation and vacuum freeze-dried method reached 61.27 mg/g, 12.32 mg/g and 12.75 mg/g and 147.65mg/g respectively, which is significantly higher than that of flavonoids(36.42 mg/g), polysaccharide(18.06 mg/g), GABA(2.05 mg/g) and DNJ(42.34 mg/g) of mulberry leaves. Thus we can infer there are more abundant flavonoids and other active substances of mulberry leaf protein compared to mulberry leaves.3. Amino acids in and nutritional evaluation of mulberry leaf proteinThe nutritional values of protein are closely related to amino acid composition of protein. This part discussed effects of protein precipitation methods and protein dry methods on nutritive value of mulberry leaf protein and comparison of mulberry leaf protein with alfalfa leaf protein and other three kinds of plant leaf protein according to the ratio coefficient of amino acid. The results indicated that different leaf protein get from different precipitation methods had different contents and composition of amino acid, but it was not suitable for protein dry method. Compared to alfalfa leaf protein and other three leaf protein concentrates, mulberry leaf protein had a unique content and proportion of amino acids. Except methionine, the rest of essential amino acids were consistent with standard protein requirements of FAO/WHO; Aspartic acid, proline and glutamic acid were abundant in mulberry leaf protein, Their contents were 43.1, 42.2, and 43.1 mg/g respectively. The SRC value of mulberry leaf protein was 69.29, which was less than that of soybean(76.32) and alfalfa leaf protein(77.37), but close to astragalus sinicus leaf protein(70.32). So we consider that mulberry leaf protein is a high-quality plant protein which is rich in amino acid and balanced.