不同制备方法桑叶蛋白功能性质的比较

以广东桑大10为原料,采用水提法制备叶蛋白浓缩液,用加热法、酸沉法、酸热法、盐析法沉淀叶蛋白,分别得到蛋白样品RC、SC、SR、LC。对所得样品进行功能性质测定,与大豆分离蛋白对比,得出不同样品的功能特点。结果表明,异亮氨酸、赖氨酸分别为桑叶粉的第一、第二限制性氨基酸。不同沉淀方法对叶蛋白的功能性质有显著影响:LC的溶解性、起泡性、乳化性、吸油性最好,均优于SC、SR及RC;SR的持水性优于SC及RC,但乳化性、起泡性较差;RC、LC的胶凝性最好。与SPI相比,4个样品的吸油性均优于SPI,持水性、胶凝性则显著低于SPI(p0.05);LC的乳化稳定性(68.57%)及SC的起泡性(40%)最好,显著优于SPI(54.86%、37.67%),RC与SPI相当,SR最差,显著低于SPI(p0.05)。LC电镜扫描结果显示其具有典型的蜂巢结构。

Functional Properties of Mulberry (Morus atropurpurea Roxb.) Leaf Proteins Extracted by Different Methods

Leaf protein concentrates were extracted from mulberry Da10 by water, and the leaf proteins were precipitated using the heating method, acid method, acid-heating method, and salting-out method to yield the corresponding protein samples RC, SC, SR, and LC, respectively. The functional properties of the obtained samples were measured and compared with those of soy protein isolate (SPI) in order to determine the functional characteristics of each sample. The results showed that isoleucine and lysine were the first and second limiting amino acids, respectively, in mulberry leaf flour. The precipitation methods had significant impacts on the functional properties of the mulberry leaf proeins. The LC sample showed the highest solubility, foaming capacity, emulsifying activity, and oil absorption capacity, which were significantly better than those of SC, SR, and RC (p < 0.05). SR displayed a higher water holding capacity than SC and RC but showed relatively poor emulsifying activity and foaming capacity. LC and RC had the best gelling property. Compared with SPI, the four samples exhibited better oil absorption capacity, significantly lower water holding capacity, and poor gelling property. The best emulsion stability (68.57%) and foaming capacity (40%) were found in the LC and SC samples, respectively, which were significantly better than those of SPI (54.86%, 37.67%, p < 0.05). The emulsion stability and foaming capacity of RC were comparable to those of SPI while the two properties were the lowest for SR and were significantly lower than those of SPI (p < 0.05). The scanning electron microscopy result showed that LC had a typical honeycomb structure.