采用荧光光谱和荧光寿命技术研究了温度对奶粉荧光特征的影响.通过比较奶粉与酪蛋白、乳糖及维生素的荧光光谱, 确定了奶粉的荧光主要来自酪蛋白的贡献.随着温度的升高, 奶粉和酪蛋白的荧光强度减小, 其中幼儿配方奶粉和成人普通奶粉的荧光强度随温度升高减小的趋势基本相同, 而婴儿配方奶粉的荧光强度随温度的升高出现了一个相对变化缓慢的平台区, 酪蛋白的荧光强度随温度升高呈缓慢下降的趋势, 下降的速度比奶粉的要缓.酪蛋白加热到90℃然后冷却至25℃, 荧光强度部分恢复, 说明一部分蛋白质的结构变化或者荧光基团的活性变化是可逆的.测量了不同温度下奶粉和酪蛋白的荧光寿命.奶粉和酪蛋白的荧光寿命曲线在双指数拟合之后, 都有两个寿命, 这两个寿命可能来自于色氨酸和苯丙氨酸.随着温度的升高, 奶粉和酪蛋白的两个荧光寿命都减小.

The effect of temperature on the fluorescence of milk powder was studied by fluorescence spectra and fluorescence lifetime technology. Firstly, the fluorescence of milk powder is mainly from casein determined by comparing the fluorescence spectra of milk powder, casein, lactose and vitamins. Secondly, as the temperature increases, the fluorescence intensity of infant formula powder, toddler formula powder, adult ordinary milk powder and casein are generally reduced. The trend of fluorescence intensity with temperature of toddler formula powder and adult ordinary milk is almost same. The change of the fluorescence intensity of infant formula powder with temperature is different, which shows a relatively slow-changing platform area. Casein′s fluorescence strength is a slow downward with increasing temperature, falling slower than milk. When heated to 90 degrees and then cooled to 25 degrees, casein was partially recovered, indicating that changes in the activity of the protein structural or fluorophore are partially reversible. Finally, the fluorescence lifetime of milk powder and casein at different temperatures were measured. Milk powder and casein have two lifetimes after double exponential fit, which can be derived from tryptophan and phenylalanine. As the temperature increases, fluorescence lifetimes of milk powder and casein are decreasing.