温度和pH值对鸡胸软骨Ⅱ型胶原蛋白的结构、黏度和热稳定性的影响

Effect of Temperature and pH on the Structure, Viscosity and Thermal Stability of Type Ⅱ Collagen from Chicken Cartilage

考察pH值和温度对鸡胸软骨Ⅱ型胶原蛋白稳定性的影响,用圆二色光谱仪和哈克旋转流变仪测定分析胶原蛋白的三螺旋结构和黏度,并通过二者的变化探究其热稳定性。结果表明:pH 2.0~4.0之间三螺旋结构完整;pH 5.0~9.0范围内三螺旋结构部分解旋(28%~57%);pH 10.0时解旋程度小(约7%)。黏度在pH 2.0~5.0之间先增大后减小,pH 5.0~9.0之间保持不变,pH 10.0时又增大。pH 2.0~4.0时,变性温度在37~39℃之间,热稳定性较低;pH 5.0~7.0时,变性温度在40~43℃之间,热稳定性高。黏度和结构随温度变化具有负相关性(P<0.05),温度越高,黏度越小,三螺旋结构解旋程度越大;与pH值变化也具有相关性(P<0.01),pH 3.0~9.0范围内,pH值升高,分子上的静电作用力减小,黏度减小,三螺旋结构解旋程度增大。因此,为了保持Ⅱ型胶原蛋白完整的三螺旋结构以及良好的加工特性,需要严格控制加工过程中的pH值和温度。

In order to investigate the effect of pH and temperature on the stability of chicken cartilage type Ⅱ collagen, we used circular dichroism spectroscopy and an HAAKE rotational rheometer to analyze the triple helix structure and viscosity of collagen. In addition, we also explored the thermal stability by examining changes in the two parameters. The experimental results showed that the triple helix structure remained intact at pH values between 2.0 and 4.0, partially untwisted(28%–57%) in the range of pH 5.0–9.0, and the degree of unwinding was small(about 7%) at pH 10.0. The viscosity firstly increased and then decreased with increasing pH from 2.0 to 5.0, and it remained unchanged between pH 5.0 and 9.0 but increased once again with further increasing pH to 10.0. At pH 2.0–4.0, the denaturation temperature was between 37 and 39 ℃, suggesting poor thermal stability. At pH 5.0–7.0, the denaturation temperature was between 40 and 43 ℃, indicating good thermal stability. The viscosity and triple helix structure were negatively correlated with temperature(P < 0.05). With increasing pH from 3.0 to 9.0, the intermolecular electrostatic force and the viscosity decreased, and the degree of unwinding of the triple helix increased(P < 0.01). Therefore, in order to maintain the intact triple helix and good processing properties of type Ⅱ collagen, it is necessary to strictly control the pH and temperature during processing.