时温叠加技术在搅拌型酸奶中的应用研究

Studies on the Technology of Time and Temperature Superimposition on the Application in the Stirred Yoghurt

以七类酸奶为研究对象,本文应用流变仪分别进行5、10、15、20、25、30、35℃七个不同温度下的频率扫描实验,然后,某一温度点为参考温度,通过时温叠加技术(TTS)生成一条该温度时的主曲线。结果表明:生成的主曲线频率范围更宽,就低频区域而言,5℃与25℃时最低分别达到10-8、10-4Hz数量级,通过Cox-Merz定律转换得到剪切速率范围亦更宽,5℃与25℃时最低速率分别达到10-7、10-3/s数量级。根据极低频率下的模量或极低剪切速率下的粘度及由曲线拟合得到的零剪切粘度,可以用来表征酸奶的微观结构与体系稳定性。因此,TTS技术避免了花费更多时间甚至数天或数周来得到极低频率或剪切速率下的数据,也实现了现有流变仪由于仪器性能限制的原因在正常测试条件下无法得到高频率或高剪切速率下的数据的可能性。

In this paper, the experiments of frequency sweep on 7 kinds of stirred yoghurt as objects of study at 5、10、15、20、25、30、35℃ were conducted respectively. Then, taking a certain temperature point as the reference temperature, a main curve was generated by time-temperature superposition technique(TTS). The results showed that the frequency range of the main curve was wider, and in the part of the lower frequency area the lowest frequency could reach to 10-8Hz and 10-4Hz orders of magnitude at 5℃ and 25℃ respectively. Also, the range of shearing rate was also wider through the transformation of Cox-Merz law with the lowest shearing rate of 10-7 and 10-3 /s orders of magnitude at 5℃ and 25℃ respectively. According to the modulus at very low frequency or the viscosity at very low shearing rate and the zero shearing viscosity obtained by curve fitting, the microstructure and system stability of yoghurt could be characterized. Therefore, TTS technology avoided spending more time, even days or weeks, to obtain data at very low frequencies or shearing rates, and also realized the possibility that existing rheometers could not obtain data at high frequencies or at high shearing rates under normal test conditions due to instrumental performance constraints.