乳清分离蛋白与葡聚糖的混合物在干热处理条件下， 发生了以褐变为特征的美拉德反应。 当葡聚糖分子量由67 kD增至150 kD时， 游离氨基含量分别下降了35.77%和30.53%， 糖链越长， 其接入到蛋白质肽链的难度越大。 采用荧光光谱对乳清分离蛋白-葡聚糖接枝物的性质进行分析。 内源荧光光谱图显示， 接枝产物在405 nm的最大荧光强度显著提高， 且350～500 nm范围内的荧光强度顺序为: G67>G150， 这说明接枝物中有Maillard反应体系所特有的荧光物质生成; 由外援荧光光谱图得出， 接枝产物在470 nm的最大荧光强度均有明显降低， 各溶液体系中荧光强度高低顺序依次为: WPI>G150>G67。 疏水性指数的测定进一步说明两种不同分子量的葡聚糖接入到蛋白质肽链中， 对乳清分离蛋白的疏水性均有一定的屏蔽作用。

The mixed whey protein isolate (WPI)-dextran was treated by dry-heating to prepare Maillard reaction products (MRPs), which was characterized by the browning. The free amino groups content significantly decreased by 35.77% and 30.53% in glycated protein samples, as the molecular weight of dextran increased from 67 to 150 kD, respectively. This suggested that it was more difficult to be linked with WPI molecule when the chain length of dextran was increased. The characteristic of WPI-dextran conjugate was studied by fluorescence spectra in the paper. The maximum fluorescence intensity at 405 nm was obviously enhanced and G67 showed high fluorescence intensity than G150 over the wavelength range form 350 to 500 nm. This result revealed that the flourescent substance, a feature in Maillard reaction model system, was generated. As showed in the fluorescence spectra, the maximum fluorescence intensity at 470 nm was significantly decreased and the fluorescence intensity in each solution was in the order as follows: WPI>G150>G67. Moreover, the measurement of surface hydrophobicity index further showed that the hydrophobicity of WPI could be suppressed due to these two kinds of different molecular weight dextran.