基于甘油二酯的搅打奶油乳状体系品质变化规律与稳定机理研究

The hydrogenated vegetable oil used in whipped cream is harmful to human health. Diacylglycerol is one kind of low-calorie structured lipid. Because of its safety and reliability, it has attracted a wide range of concerns and recognition recently. Our preliminary study result showed that diacylglycerol could be used for whipped cream preparation. However, the mechanism of the effect of diacylglycerol on the stability of whipped cream emulsion system is not clear. In this program, therefore, the hydrogenated vegetable oil is substituted by diacylglycerol for preparing whipped cream. The physico-chemical properties of diacylglycerol-based O/W emulsion are determined. Several properties of the emulsion system are also analyzed, such as rheological properties, whipping performance, texture properties, sensory evaluation, and so on. The quality change of diacylglycerol-based whipped cream is illuminated, and the evaluation system is built. Several modern analytical instruments are used to study the lipid crystallization behavior and foam characteristic of emulsion system. The link between change of crystal network multi-scale structure (nano-glycerides molecular layer and micron crystal agglomerate)and partial coalescence, foam structure characteristics is investigated. The internal mechanism of effect of diacylglycerol crystallization properties on the stability of emulsion system is revealed. This research will provide theoretical values not only for improving the quality evaluation system of whipped cream, but also for explaining the effect of crystal network structure on the stability of whipped inflating emulsion system. In addition, it will provide a scientific basis for developing high-fat food emulsion systems with low-calorie diacylglycerol.

搅打奶油所普遍使用的氢化植物油对人体健康存在危害。甘油二酯是一类低热量结构脂，安全可靠，近年来受到国际普遍关注和认可。项目前期研究表明，甘油二酯可用于搅打奶油生产。针对甘油二酯对搅打奶油乳状体系稳定性影响及其机制尚未明晰，本项目采用甘油二酯替代氢化植物油制备搅打奶油，通过研究甘油二酯基O/W型乳状液的物化性质及体系的流变学特性，结合搅打性能、质构特性、感官评价等，阐明基于甘油二酯的搅打奶油品质变化规律，并构建系统的评价体系；借助现代分析手段研究乳状体系油脂结晶行为、泡沫特性，重点探究油脂晶体网络多尺度结构（纳米甘油酯分子层、微米的晶体束）变化与脂肪部分聚结、泡沫结构特征的关联性，揭示甘油二酯结晶特性对体系稳定性影响的内在机制。本项目研究结果在完善搅打奶油品质评价系统、解析油脂晶体网络结构对搅打充气乳状体系的稳定性影响具有重要的理论价值，为低热量甘油二酯在高脂食品乳状体系的开发提供科学依据。

甘油二酯（DAG）是近年新兴的一类功能性结构脂。本项目研究了基于DAG的水包油（O/W）型乳液稳定性影响因素，揭示了不同DAG替代量搅打奶油乳液的品质变化规律，并对其搅打性能、质构特性等进行了评价。结果表明，通过酶促反应和分子蒸馏可获得纯度为93.0wt%的高纯度DAG油，油品的酸价和过氧化值均达到国家食用油标准。利用DAG制备的新鲜O/W乳液具有良好的物理稳定性。DAG含量越高，样品的D4,3越小。经老化-解冻后，由于DAG的固体脂肪含量在低温时较大，乳液的脂肪聚结程度高，致使含DAG乳液的冻融稳定性较差，经14天储存出现分层。添加多糖的乳液对消化过程（模拟口腔、胃、肠环境）中的环境因素（pH、电解质的变化等）耐受性较好，与未添加多糖的样品相比，其脂肪酸释放程度稍低。经14天室温储存发现，添加黄原胶的DAG乳液的稳定性比瓜尔豆胶乳液较好，其中蛋白氧化程度较低，油脂氧化产物POV和TBARS的生成量也较少，表明一定浓度的多糖可以提高乳液的稳定性。在0-500mmol/L的NaCl浓度范围内，由于NaCl的静电屏蔽作用，多糖-乳清蛋白（WPI）体系在蛋白等电点附近的相分离区域变宽，多糖-WPI复合液的DH增大。随着NaCl浓度增大，乳液的剪切变稀现象加剧，降低了体系的粘度，D4,3增大，界面蛋白浓度升高。新鲜和冻融乳液在储存期间都发生了不同程度的分层，乳液的稳定性降低。采用DAG部分替代氢化植物油用于搅打奶油中，随着DAG替代量的增大，乳液的平均粒径大小、界面蛋白含量和脂肪部分聚结率均呈上升的变化趋势。与对照样相比，10%和20% DAG替代量未改变搅打终点所需时间，仍为4min，30% DAG替代量可缩短搅打时间至3min；随着替代量的增大，搅打奶油的硬度、稠度、内聚性和粘度等呈增加的趋势，与对照样相比，其感官品质变化不大。40% DAG替代量样品的搅打起泡率一直较低，难以形成稳定的泡沫结构，不宜用于本实验的搅打奶油中。本项目研究成果对于功能性DAG的开发具有良好的指导意义，可为低热量DAG在高脂食品乳状体系的开发提供科学依据。