Rheological Characteristics of the Polysaccharides Extracted from Mulberry (Morus alba L.)Leaves

• Main Authors: Jui-Chu Tsai, 蔡瑞珠
• Other Authors: 賴麗旭
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/80891957311272739084

碩士 === 中興大學 === 食品暨應用生物科技學系 === 95 === Polysaccharides were extracted from the mulberry leaves by sodium bicarbonate solutions. Rheological properties of the mulberry leaves polysaccharides and salts addition were studied using Canon-Fensky glass capillary viscometer and dynamic rheometer. It was found that the weight average molecular weight of mulberry leaves polysaccharides was about 690,000, with a Mark – Houwink constant (k×106) and Mark – Houwink expoent in the range of 50.1 and 1.24, respectively. It was found the intrinsic viscosity of mulberry leaves polysaccharides decreased with increasing ionic strength. The salt tolerance was 12.34 to 13.42 ml M0.5 /g. The chain stiffness parameter of mulberry leaves polysaccharides was about 0.004 with mono-valent salts addition, and from 0.003 to 0.0004 with divalent salts addition. The low values of chain stiffness parameter indicated the stiff backbone characteristics of mulberry leaves polysaccharides. The specific viscosity versus concentration plot exhibited a power-law dependence on concentration. The coil overlap parameter of the mulberry leaves polysaccharides was 5.55 to 6.68, and the exponent b ranged from 0.94 to 1.03 in the dilute domain and from 2.09 to 3.06 in the semi-dilute domain. During steady shear measurements, mulberry leaves polysaccharides showed shear thinning behavior, which could be analyzed by a power law model. The consistency index of mulberry leaves polysaccharides increased, and the flow behavior index decreased with increasing concentration. During dynamic shear measurements, within the frequency range tested, results indicated that the storage modulus were greater than loss modulus with 6% to 8% mulberry leaves polysaccharides solution. The mulberry leaves polysaccharides solution can be classified rheologically as those of concentrated solution with 2% to 4% concentration and gel behavior with 6% to 8% concentration depending on the concentration. The storag and loss modulus of mulberry leaves polysaccharides solution increased with increasing sodium, potassium, magnesium, and calcium ion concentrations. The phase-separated network showed less water syneresis phenomenon with calcium chloride addition was 68 to 200 mM.