Deshmukh Pranjal S, Manjunatha S S, Raju P S
Department of Food Processing and Engineering, Karunya University, Coimabatore, 614 114 India.
Department of Fruits and Vegetables Technology, Defence Food Research Laboratory, Siddarthanagar, Mysore 570 011 India.
J Food Sci Technol. 2015 Apr;52(4):1896-910. doi: 10.1007/s13197-013-1222-5. Epub 2013 Dec 19.
Rheological behaviour of enzyme clarified sapota (Achras sapota L.) juice at different temperatures (10 to 85 °C) and total soluble solid content (10.2 to 55.6 °brix) corresponding to a water activity (aw) (0.986 to 0.865) was studied using controlled stress rheometer by coaxial cylinders attachment. The rheological parameter shear stress (Pa) was measured upto a shear rate of 1,000 s(-1). The investigation showed that the enzyme clarified sapota juice and its concentrates behaved like a Newtonian liquid and the viscosity (η) values were in the range 4.340 to 56.418 mPa s depending upon temperature and concentration studied. The temperature dependency of viscosity of enzyme clarified sapota juice was described by Arrhenius equation (r > 0.94) and activation energy (Ea) for viscous flow was in the range 5.218 to 25.439 KJ/mol depending upon concentration. The effect of total soluble solid content on flow activation energy was described by exponential relationship (r > 0.95, rmse% <13.5, p < 0.01) and that of water activity was described by power law relation (r > 0.99, rmse% <5.80, p < 0.01). The effect of total soluble solid content on viscosity of enzyme clarified sapota juice followed second order exponential type relationship (r > 0.99, rmse% < 3.53) at the temperature used. The effect of water activity on viscosity of enzyme clarified sapota juice followed power law equation (r > 0.98, rmse% < 4.38). A single equation representing combined effect of temperature and total soluble solid content/water activity on viscosity of enzyme clarified sapota was established.
采用同轴圆筒附件的控制应力流变仪，研究了酶解人心果汁在不同温度（10至85°C）和对应水活度（aw）（0.986至0.865）的总可溶性固形物含量（10.2至55.6°Bx）下的流变行为。测量了剪切应力（Pa）这一流变参数，直至剪切速率达到1000 s⁻¹。研究表明，酶解人心果汁及其浓缩物表现为牛顿流体，粘度（η）值在4.340至56.418 mPa·s范围内，具体取决于所研究的温度和浓度。酶解人心果汁粘度的温度依赖性由阿伦尼乌斯方程描述（r＞0.94），粘性流动的活化能（Ea）在5.218至25.439 kJ/mol范围内，具体取决于浓度。总可溶性固形物含量对流动活化能的影响由指数关系描述（r＞0.95，均方根误差百分比＜13.5，p＜0.01），水活度的影响由幂律关系描述（r＞0.99，均方根误差百分比＜5.80，p＜0.01）。在所使用的温度下，总可溶性固形物含量对酶解人心果汁粘度的影响遵循二阶指数型关系（r＞0.99，均方根误差百分比＜3.53）。水活度对酶解人心果汁粘度的影响遵循幂律方程（r＞0.98，均方根误差百分比＜4.38）。建立了一个表示温度和总可溶性固形物含量/水活度对酶解人心果汁粘度综合影响的单一方程。
