Utilization of nanoemulsion gels for novel structure and functional properties of food

乳剂在许多天然和加工食品（如牛奶、蛋黄酱和饮料）中起着关键的结构作用。纳米乳剂是一类相对较新的乳剂，其平均液滴半径通常小于100纳米。由于其极小的液滴尺寸，纳米乳液具有许多在食品配方中有利的功能特性；例如，它们可以显著提高生物活性化合物的稳定性或作为具有高生物利用度的有效递送介质。到目前为止，纳米乳剂在食品中的应用仅限于液体产品。最近，研究表明，通过减小液滴尺寸，水包油纳米乳液可以转化为固体状基质，称为纳米凝胶，其含油体积分数（~20%）远低于常规乳液凝胶（约60%）。这些纳米凝胶可以提供一种新的结构，可以显著提高许多乳化食品的稳定性和促进健康的特性，包括酸奶、蛋黄酱类酱和奶酪。然而，缺乏对纳米液滴大小、电荷和界面化学的影响的理解限制了它们在食品工业中的应用。该研究计划的长期目标是深入了解水包油纳米乳中的界面和液滴之间的相互作用，从而创造出具有可调物理化学性质的纳米凝胶，以改善食品和相关软材料的结构、功能和促进健康的特性。未来5年的短期目标是：1)优化尺寸和液滴间相互作用对纳米液滴随机阻塞网络形成的影响；2)研究纳米凝胶的多尺度结构和形成机理；3)优化纳米凝胶的弹性和流动特性；4)展示纳米凝胶在食品和相关软材料中的稳定性和应用。研究了两种不同的纳米凝胶形成方法：通过减小液滴尺寸和增加界面壳厚度来增加有效油相体积分数，从而使纳米液滴形成随机堵塞结构；并诱导纳米液滴之间有吸引力的相互作用，从而形成强大的聚集体。利用小角x射线散射技术研究纳米液滴凝胶化的内部结构和机理。纳米凝胶的体积和界面流变行为将被研究，以了解液滴间力和界面刚度的性质如何控制它们的弹性和流动行为。这些信息将用于开发一个通用模型来预测纳米凝胶的弹性行为和长期稳定性。最后，将展示纳米凝胶在递送和快速释放生物活性化合物以及替代含高脂肪的传统乳液凝胶方面的应用。食品级纳米凝胶代表了一种潜在的新型成分，可以改善加工食品的结构（例如，酸奶、蛋黄酱类涂抹酱、奶酪）。目前，这些食品是由传统的乳液凝胶制成的。低油纳米凝胶在减脂食品中的成功应用和生物活性化合物的快速释放有望显著改善加工食品的健康促进特性。这项研究的重大发现、影响、专利申请和未来技术转移将直接使加拿大农业和食品部门受益，并对制药和化妆品行业具有潜在优势。

Emulsions play a key structural role in numerous natural and processed foods (e.g., milk, mayonnaise, and beverages). Nanoemulsions are a relatively new class of emulsions with an average droplet radius typically less than 100 nm. Due to their extremely small droplet size, nanoemulsions have a number of functional properties that can be advantageous in food formulations; for example, they can significantly improve stability or act as an efficient delivery medium with high bioavailability of bioactive compounds. So far, applications of nanoemulsions in food have been limited to liquid-based products. Recently, it has been shown that by reducing droplet size an oil-in-water nanoemulsion can be transformed into a solid-like matrix, called a nanogel, at a much lower oil volume fraction (~20% oil) than conventional emulsion gels (>60% oil). These nanogels could provide a novel structure that may significantly improve stability and health-promoting properties of a number of emulsion-based foods, including yoghurt, mayonnaise-type spreads and cheese. However, a lack of understanding of the influence of nanodroplet size, charge, and interfacial chemistry is limiting their use in the food industry. The long-term objective of the proposed research program is to develop an in-depth understanding of the interfacial and interdroplet interactions in oil-in-water nanoemulsions so that nanogels with tunable physicochemical properties can be created to improve the structure, functionality, and health-promoting properties of foods and related soft materials. The short-term objectives to be addressed over the next five years are to: 1) Optimize the influence of size and interdroplet interactions on the formation of a random-jammed network of nanodroplets; 2) Investigate the multi-scale structure and mechanism of formation of nanogels; 3) Optimize elasticity and flow behaviour of nanogels; 4) Demonstrate stability and applications of nanogels in food and related soft materials. Two different approaches of nanogel formation will be investigated: increasing the effective oil phase volume fraction so that nanodroplets can form a random-jammed structure by reducing their droplet size and increasing their interfacial shell thickness; and inducing attractive interactions among the nanodroplets so that strong aggregates can be formed. The internal nanostructure and mechanism of nanodroplet gelation will be investigated using small angle X-ray scattering techniques. The bulk and interfacial rheological behaviour of the nanogels will be studied in order to understand how the nature of interdroplet forces and interfacial rigidity controls their elasticity and flow behavior. This information will be used to develop a universal model for prediction of elastic behaviour and long-term stability of nanogels. Finally, the applications of nanogels in delivery and rapid release of bioactive compounds and replacement of high fat containing conventional emulsion gels will be demonstrated. Food-grade nanogels represent a potential new class of ingredients to improve the structure of processed foods (e.g., yoghurt, mayonnaise-type spreads, cheese). At present, these foods are made out of conventional emulsion gels. The successful application of low-oil containing nanogels to reduced-fat foods and the rapid release of bioactive compounds is expected to lead to significant improvements in health-promoting properties of processed foods. The major discoveries, impact, patent applications, and future technology transferred from this research will directly benefit the Canadian agricultural and food sectors, with potential advantages for pharmaceutical and cosmetic industries.