“奶油感”是最受消费者喜好的发酵乳感官属性, 反映令人愉悦的特征。 为开发无添加但“奶油感”增强型的发酵乳, 首先必须明确具备高“奶油感”发酵乳的质构特征。 目前关于发酵乳“奶油感”的定义和评价标准尚未统一, 关键质构特征尚不清晰。 前人研究表明, 发酵乳的凝胶网络形成过程及强度、 稳定性和表观黏度可能是影响发酵乳感官感知的主要因素。 该研究采用多种光谱学手段, 解析具有不同强度“奶油感”发酵乳的关键质构特征。 以经描述型感官评价得到的五种具备不同“奶油感”强度的发酵乳为研究对象, 通过多散斑扩散光谱技术测定发酵乳凝胶网络的形成过程及凝胶强度, 通过多重光散射技术来研究发酵乳的稳定性, 再辅以流变学分析发酵乳的表观黏度。 首先采用多散斑扩散波光谱技术研究具有不同强度“奶油感”发酵乳凝胶过程粒子均方位移的变化, 结果显示凝胶的弹性指数突变时间按“奶油感”由弱到强分别为108, 115, 106, 132和143 min, 表明发酵乳形成凝胶的时间基本呈逐渐增加趋势; 凝胶时间的增加可能是因为酪蛋白充分重排聚集形成了更均匀的凝胶网络, 从而增强了“奶油感”的感知; 弹性指数的终点值代表发酵乳的凝胶强度, 结果显示凝胶强度处于适中水平的发酵乳“奶油感”较强。 接着利用多重光散射技术评价了发酵乳的稳定性, “奶油感”由弱到强的发酵乳稳定性动力学指数分别为2.2, 2.1, 1.9, 2.0和1.4, 表明发酵乳稳定性与发酵乳“奶油感”的感知强度呈正相关。 最后利用流变学方法测定了发酵乳的表观黏度, “奶油感”由弱到强的发酵乳表观黏度分别为(0.362±0.016), (0.271±0.013), (0.251±0.021), (0.479±0.031)和(0.343±0.024) Pa·s, 表明发酵乳的表观黏度和“奶油感”感知强度不存在相关性。 发酵乳的凝胶时间及凝胶稳定性与“奶油感”的感知密切相关。 研究为明确发酵乳“奶油感”的关键质构、 开发“奶油感”增强型的发酵乳制品提供理论依据。

Creaminess is one of the most favorite sensory properites of fermented milk for consumers, reflecting the pleasant characteristics. To develop fermented milk with high creaminess intensity without additional additives, the key textural characteristics of fermented milk with high creaminess intensity should be revealed. However, the definition and evaluation criteria for creaminess have not been unified, and the key textural characteristics of fermented milk with high creaminess intensity have not been clearly clarified. Previous studies have shown that the gelation process and gel strength, the stability and the apparent viscosity of fermented milk may be the key textural characteristics that affect the sensory perception of fermented milk. In this study, the spectroscopy methods were applied to analyze the key textural characteristics of fermented milks with different creaminess intensities. Five samples with different creaminess intensity selected from the descriptive sensory evaluation were used in this research. The gelation process and gel strength of fermented milk were measured by diffusing wave spectroscopy. The stability of fermented milk was studied by multiple light scattering spectrum. In addition, the rheological technology was used to analyze the apparent viscosity of fermented milk. First, the multi speckle diffusing wave spectroscopy technique was used to investigate the changes of the mean square displacement of particles during the gelation of fermented milk gels. The results showed that the critical points of the elasticity index of the gel were 108, 115, 106, 132 and 143 min, respectively, indicating that the gelation time of fermented milk basically increased gradually. The reason might be due to the sufficient rearrangement and aggregation of casein micelles to form a more uniform gel network, which enhanced the perception of creaminess. The final value of elasticity index represents the gel strength of fermented milk. The results showed that the creaminess intensity of fermented milk was stronger when the gel strength was at a moderate level. Furthermore, the stability of fermented milk was measured by using multiple light scattering technology. It was found that the turbis can stability indexes of fermented milks were 2.2, 2.1, 1.9, 2.0 and 1.4, respectively, indicating that the stability of fermented milk was positively correlated with the perceived intensity of creaminess of fermented milk. At last, the apparent viscosity of fermented milk was measured by rheological technology. The result showed that the apparent viscosities of fermented milks were (0.362±0.016), (0.271±0.013), (0.251±0.021), (0.479±0.031) and (0.343±0.024) Pa·s, respectively. The results showed that there was no correlation between the apparent viscosity of fermented milk and the perceived intensity of creaminess. In summary, the gelation time and stability of fermented milk can significantly affect its creaminess perception. This study provides a theoretical basis for determining the key texture characteristics of the creaminess off ermented milk and developing fermented dairy products with enhanced creaminess intensity.