Chuy S, Bell L N
Kellogg Co., Battle Creek, MI 49017, USA.
J Food Sci. 2009 Jan-Feb;74(1):C56-61. doi: 10.1111/j.1750-3841.2008.01015.x.
The kinetics of an acid-base catalyzed reaction, aspartame degradation, were examined as affected by the changes in pH and pK(a) values caused by adding polyols (sucrose, glycerol) to phosphate buffer. Sucrose-containing phosphate buffer solutions had a lower pH than that of phosphate buffer alone, which contributed, in part, to reduced aspartame reactivity. A kinetic model was introduced for aspartame degradation that encompassed pH and buffer salt concentrations, both of which change with a shift in the apparent pK(a) value. Aspartame degradation rate constants in sucrose-containing solutions were successfully predicted using this model when corrections (that is, lower pH, lower apparent pK(a) value, buffer dilution from the polyol) were applied. The change in buffer properties (pH, pK(a)) from adding sucrose to phosphate buffer does impact food chemical stability. These effects can be successfully incorporated into predictive kinetic models. Therefore, pH and pK(a) changes from adding polyols to buffer should be considered during food product development.
研究了添加多元醇（蔗糖、甘油）至磷酸盐缓冲液所引起的pH值和pK(a)值变化对酸碱催化反应（阿斯巴甜降解）动力学的影响。含蔗糖的磷酸盐缓冲溶液的pH值低于单独的磷酸盐缓冲液，这在一定程度上导致了阿斯巴甜反应活性的降低。引入了一个涵盖pH值和缓冲盐浓度的阿斯巴甜降解动力学模型，这两者都会随着表观pK(a)值的变化而改变。当进行校正（即较低的pH值、较低的表观pK(a)值、多元醇引起的缓冲液稀释）时，使用该模型成功预测了含蔗糖溶液中阿斯巴甜的降解速率常数。向磷酸盐缓冲液中添加蔗糖导致的缓冲液性质（pH值、pK(a)）变化确实会影响食品化学稳定性。这些影响可以成功纳入预测动力学模型。因此，在食品产品开发过程中应考虑向缓冲液中添加多元醇引起的pH值和pK(a)变化。
