Gelation Mechanism and Hydrogen Bonding Behavior of Gellan Gum Studied by Vibrational Spectroscopy and Small Angle X-ray Scattering

结冷胶是一种由假单胞菌产生的胞外多糖，由四糖(葡萄糖、葡萄糖糖醛酸、葡萄糖、鼠李糖)重复单元组成，含有一个羧基。由于它能形成具有耐热和耐酸性质的透明凝胶，因此被广泛应用于食品工业和生物医学领域。结冷胶具有温度依赖性和阳离子诱导凝胶性的特点。这种凝胶作用包括形成双螺旋连接区，然后通过与阳离子络合和氢键与水形成结冷胶的双螺旋链段，形成三维网络。本文利用红外光谱和拉曼光谱研究了结冷胶的成胶机理。在螺旋向双螺旋转变的过程中，水和结冷胶之间的氢键很可能变得很弱。

Gellan gum is an extracellular polysaccharide produced by Pseudomonas elodea, and is composed of tetrasaccharide (glucose, glucuronic acid, glucose, rhamnose) repeating units, containing one carboxyl side group. It is widely used in the food industry and biomedical fields since it forms transparent gels which have a heat and acid resistant nature. Gellan gum has the characteristic property of temperature-dependent and cation-induced gelation. This gelation involves the formation of double helical junction zones followed by the double helical segments of gellan gum to form a three-dimensional network by complexation with cations and hydrogen bonding with water. In the present study, we have investigated gelation mechanism of gellan gum by using infrared and Raman spectroscopy. It is likely that the hydrogen bonding between water and gellan gum becomes weak during the coil to double-helix transition.