Edible Oleogels for Reduction of Saturated Fat

从食物中去除饱和脂肪是非常可取的，因为它对健康有益，但这不是一项微不足道的运动，因为固体脂肪对许多普通食物的质地有很大影响。它们在许多配方食品（如烘焙食品、饼干、黄油、人造黄油、酱料和糖果）的结构形成中起着重要作用。然而，它们会提高血液中的胆固醇水平，是患冠心病的一个危险因素。用单不饱和油或多不饱和油代替它们是不可行的，因为它们在环境温度下是液态的，所以用油代替固体脂肪的食物会缺乏理想的固体质地。即使是标榜多不饱和脂肪含量高的食物，如人造黄油和黄油酱，也必须含有相对较高比例的饱和脂肪，以保证正确的口感。饱和脂肪在酱料中的作用是提供一个脂肪晶体网络，将液体油捕获并固定在半固体基质中。如果食品制造商要开发去除饱和脂肪的食品，他们将需要找到替代方法来形成半固体结构。食品科学家正在开发的一种解决方案是使用可食用的油凝胶。在这些方法中，被称为凝胶的分子被添加到液体油中，以模仿固体脂肪晶体的结构效果。凝胶相互结合，形成非常长而薄的纤维或小管，这些纤维或小管通过交联形成网络。凝胶纤维的这种“晶格”的作用类似于固体脂肪晶体的网络，并将液体油困在结构中的孔隙中。一组可以用来制造油凝胶的分子是植物固醇。它们本身也被发现可以降低血液中的胆固醇水平，因此被添加到一些功能性食品中。原则上，油凝胶可以像传统的黄油和人造黄油一样具有固体状的质地。在实践中，开发这种技术已经被证明是困难的，迄今为止，它们还没有用于商业食品。一个原因是很少有可以形成有机凝胶的固醇。由于人们对什么是理想的凝胶知之甚少，因此不可能为特定的食品应用制作新的凝胶。此外，油凝胶的结构和质地对少量水的存在非常敏感，因此人造黄油（含有小水滴）已被证明很难制造。更糟糕的是，当证明确实有可能制造油凝胶时，通常很难持续这样做。同样，人们对油凝胶的形成知之甚少，这使得控制它们的质地变得困难。在这个项目中，我们将解决阻碍食用油凝胶在食品中使用的问题。我们采用实验和计算机模拟相结合的方法来探索凝胶聚集、小管形成和凝胶化的机制。我们的目标是了解这些分子是如何形成小管的，以及这些小管是如何在液体油中形成半固体结构的。计算机建模使我们能够从分子细节上观察小管的结构，并了解使其形成油凝胶的植物甾醇分子的特征。了解最佳凝胶分子的关键结构特征，可以在食品中合成和测试新的凝胶，从而导致更广泛的甾醇凝胶和更广泛的应用于油性食品。即使有更有效的凝胶，可食用油凝胶的配方也会很困难。我们还将使用一系列实验技术来研究凝胶形成的机制和控制，最终目标是我们将利用这些知识来控制油凝胶结构，并最终在食品中展示油凝胶技术。可食用油凝胶的成功配方将使更健康的油基食品减少饱和脂肪，但保持理想的半固体或固体质地。

Removing saturated fats from foods is highly desirable because of the health benefits that would be realised, but this is not a trivial exercise because solids fats contribute greatly to the texture of many common foods. They are important in forming the structure in many formulated foods such as baked goods, biscuits, butter, margarine and spreads and confectionery. However, they raise cholesterol levels in the blood and are a risk factor for coronary heart disease. Replacing them with mono-or polyunsaturated oils is not feasible as these are liquid at ambient temperatures and so food where solid fat is replaced by oil would lack the desired solid texture. Even foods that are branded as high in polyunsaturated fats, such as margarines and spreads must contain a relatively high proportion of saturated fat to give the correct texture. The role of the saturated fats in spreads is to provide a network of fat crystals that trap and immobilize the liquid oils in a semi-solid matrix. If food manufacturers are to develop foods with the saturated fat removed they will need to find alternative methods to form the semi-solid structure. One solution that food scientists are developing is the use of edible oleogels. In these, molecules known as gelators are added to liquid oils to mimic the structuring effect of solid fat crystals. The gelators associate with each other to form very long, thin fibres or tubules which crosslink to form a network. This "lattice" of gelator fibres acts in similar way to the network of solid fat crystals and traps the liquid oils in pores in the structure. One group of molecules that can be used to make oleogels are the plant sterols. These also have been found to reduce blood cholesterol levels in their own right, and are added to some functional food spreads for this reason. In principle, oleogels can have a solid-like texture the same as conventional spreads and margarines. In practice it has proven difficult to develop this technology and to date they have not been used for commercial foods. One reason is that there are few available sterols that form organogels. Since little is known about what makes the ideal gelator it is not possible to make new gelators for a particular food application. In addition the structure and texture of an oleogel is very sensitive to the presence of small amounts of water, and so margarines (which contain small water droplets) have proven difficult to make. To make matters worse, when it does prove possible to make an oleogel, it is often difficult to do so consistently. Again, little is known about how oleogels form, and this makes the control of their texture difficult.In this project we will address the problems that are holding back the use of edible oleogels in foods. We use a combination of experimental and computer modelling methods to explore the mechanisms of gelator aggregation, tubule formation and gelation. Our aim is to understand how these molecules are able to form tubules, and subsequently how these tubules are able to form a semi-solid texture in liquid oils. Computer modelling allows us to look at the structure of tubules in molecular detail, and to understand the features of a phytosterol molecule that allows it to form an oleogel. Knowing the key structural features of optimum gelator molecules allows new gelators to be synthesised and tested in foods, leading to a wider range of sterol gelators and more widespread application to oily foods. Even with more efficient gelators the formulation of edible oleogels will be difficult. We will also look at the mechanisms of and control of gel formation using a range of experimental techniques, with the ultimate aim that we will use this knowledge to control oleogel structure, and eventually to demonstrate oleogel technology in food products. Successful formulation of edible oleogels will allow healthier oil-based foods that are reduced in saturated fats but maintain a desirable semi-solid or solid texture.