Preliminary study on the relationship between quality and surface tension and viscosity coefficient of milk | 利用表面张力系数和黏滞系数检测牛奶品质初探

Chinese. 探讨用牛奶表面张力系数和黏滞系数表征其内在品质的可行性。将鲜牛奶分为2组，1组置于（40±1) ℃ 温度下，测量不同放置时间（0～12 h）牛奶表面张力系数和黏滞系数的变化；另1组置于室温（25±1） ℃ 条件下，研究不同掺水量（V水∶V总分别为0%，10%，20%，30%，40%，50%）对牛奶表面张力系数和黏滞系数的影响。随放置时间的不断延长，牛奶表面张力系数在0～1 h急剧下降，1～7 h先缓慢上升后下降，7～9 h急剧上升，9～12 h缓慢上升；而牛奶黏滞系数在0～11 h变化不大，11 h后呈剧烈上升趋势。牛奶表面张力系数和黏滞系数与掺水量之间均呈极好的线性关系，相关系数分别为0.943 6，0.954 9，其中掺水量达到10%时，牛奶品质即发生较大变化，其2个参数值分别显著下降4.05%和0.28%。表面张力系数较黏滞系数的灵敏度高，但稳定性较低；黏滞系数的灵敏度低，但稳定性较高。因此，可以将二者结合起来作为表征牛奶品质的物理指标。

English. The study was intended to explore the relationship between the quality of milk and its physical properties. For the first group, we detected the surface tension and viscosity coefficient at different time (0-12 h) at (40±1) ℃. For the second group, we added different amounts of water to milk (Vwater:Vtotal respectively was 0%, 10%, 20%, 30%, 40%, 50%), and then detected their surface tension and viscosity coefficient at (25±1) ℃. The first group’s coefficient of surface tension decreases sharply during 0-1 h, first rose, then went down slowly during 1-7 h, then rose sharply again during 7-9 h, and then slowed down during 9-12 h. While the viscosity coefficient of pure milk remained almost constant during 0-11 h, it increased sharply after 11 h. In the second group, the relationships between the amount of added water and surface tension, viscosity coefficient were all liner, their correlation coefficients were 0.943 6 and 0.954 9 respectively. When the amount of water was 10%, the quality of milk changed greatly, and the surface tension and viscosity coefficient decreased 4.05% and 0.28% respectively. The sensitivity of surface tension was better than viscosity coefficient, while the stability of surface tension was poorer than viscosity coefficient. So it’s a wiser way to combine them to reflect the quality of milk.