Measurement of micro-rheological properties of food structures

许多食物都是由小的（胶体）颗粒组成的。 有些只是颗粒的分散体（牛奶，奶油，蛋黄酱，奶油利口酒），必须保持在稳定的状态，直到他们被消耗。 另一方面，一些食品是通过使其组成颗粒变得不稳定而产生的，使得它们形成凝乳或凝胶或为消费者提供可接受质地的其他结构。 众所周知的例子是奶酪，酸奶和冰淇淋。 控制这些产品中基本颗粒的稳定性（或不稳定性）显然是相当重要的。 这些颗粒在食品的纳米工程中也很重要，可用于携带重要的食品成分，如必须防止分解（如氧化）的香料或营养重要分子。我们试图回答的问题是：不同类型粒子的稳定性是如何保持的，以及如何控制它？ 特别是，我们感兴趣的是如何像牛奶中的酪蛋白胶束颗粒可以可控地不稳定，给定义凝乳结构。 研究这一点的最新方法之一是扩散波光谱学（DWS）技术，它允许我们使用从胶体悬浮液散射的光来告诉我们粒子相互作用的方式。 使用该设备，我们可以观察凝胶形成的最早阶段以及颗粒之间的相互作用。 该技术还可以测量在这些早期阶段形成的非常弱的凝胶的强度。 正是在这个阶段，有可能进行干预以控制后续凝胶的性质。 如果我们能够理解在这些早期阶段发生了什么，我们就能够对最终食物的结构和性质进行迄今为止不可能的控制。 正是出于这个原因，我们希望改进我们现有的仪器，以便我们可以测量这些非常弱的凝胶，并更多地了解食品中凝胶化反应的机制和控制。

A great many foods are made up of small (colloidal) particles.  Some are simply dispersions of particles (milks, creams, mayonnaises, cream liqueurs) that have to be kept in a stable condition until they are consumed.  On the other hand, some foods are created by causing their constituent particles to become unstable, so that they form curds or gels or other structures that provide acceptable textures for the consumer.  Well-known examples of these are cheese, yogurts, and ice cream.  The control of stability (or instability) of the basic particles in these products is clearly of considerable importance.  The particles are also of importance in the nanoengineering of foods, and can be used to carry important food ingredients such as flavours or nutritionally important molecules that must be protected from breakdown (such as by oxidation). The question we are trying to answer is: how is the stability of different types of particles maintained and how can it be controlled?  Especially, we are interested in how particles like the casein micelles of milk can be controllably destabilized to give defined curd structures.  One of the newest methods of studying this is the technique of Diffusing Wave Spectroscopy (DWS), which allows us to use the light scattered from a colloidal suspension to tell us about the way in which the particles interact.  Using the equipment we can look at the earliest stages of gel formation and at the interactions between the particles.  The technique also has the possibility of measuring the strengths of the very weak gels that are formed in these early stages.  It is at this stage that it may be possible to intervene to control the properties of the subsequent gel.  If we can understand what is happening at these early stages, we may be able to exercise a hitherto impossible control over the structures and properties of the final foods.  It is for this reason that we wish to improve the instrumentation we have, so that we can measure these very weak gels and learn even more about the mechanisms and control of gelation reactions in foods.