Surface Character and Integrity of Multi-Component Systems During Spray Drying

食品粉是一种商品，在世界范围内构成了食品配料的重要类别。它们通常是通过喷雾干燥方法产生的，在该方法中，将溶液或悬浮液喷入室内，并与热空气接触，以干燥雾化的液滴并形成颗粒。这些商品产品的利润率非常低，这使得通过改变其散装成分来改善此类粉末的性能在经济上是困难的。然而，对于许多性质(如粘性和润湿性)来说，粉末的表面是重要的，因为它是与环境最直接相互作用的表面。拟议的访问研究员吉姆·琼斯博士发现，含脂肪的喷雾干燥粉末的表面组成可以受到工艺条件(主要是出口空气温度)变化和少量表面活性剂添加的影响。这可能提供了一条途径，通过以相对较低的成本对粉末进行表面裁剪，从而为粉末提供附加值。这项建议旨在更好地了解在干燥过程中食品成分如何在主体和粉末表面之间分配(或分配)的机制，以及改变工艺条件和使用少量添加剂如何影响这一点。这将通过实验和数学建模相结合的方法来实现。建模将设法估计液滴内循环流动的规模，这可能有助于或阻碍成分的分配。然后，所有的实验和建模结果将被用来产生干燥过程中组分的分配的机械模型。该项目将由新西兰梅西大学化学工程系的Jim Jones博士与拉夫堡大学化学工程系的Andy Stapley博士和Chris Rielly教授合作，为期七个月，作为访问研究员。该项目将研究以食品为基础的悬浮液的喷雾干燥，该悬浮液含有少量但可变的增稠剂和增塑剂(可改变粘度)和表面活性剂。琼斯博士将利用该联谊会进行一系列实验，改变原料组成和出口温度，并使用拉夫堡提供的各种表征技术分析产品材料(特别是表面组成)。他将与斯塔普利博士合作设计实验并开发机械模型，他们都将与里利教授合作，后者将执行计算流体动力学(CFD)建模。首先进行CFD建模，以计算整个喷雾干燥器内的流场，以评估作用在液滴表面的力。然后，这些信息将被用作单独的模拟的输入，该模拟将模拟干燥液滴内的循环流动。获得的信息将有助于评估液滴内的再循环是有助于还是阻碍了分配。一旦了解了这一点，就将开发出一种分配的机械模型，并最终为制造商提供操作建议，以制造设计的粉末表面。

Food powders are commodity products which constitute an important category of food ingredients worldwide. They are typically produced by the spray drying method in which a solution or suspension is sprayed into a chamber and contacted with hot air to dry the atomised droplets and form particles. These commodity products are made with very low margins, which makes it economically difficult to improve the properties of such powders by changing their bulk composition. However, for many properties (such as stickiness and wettability) it is the surface of the powder that is important as it is the surface that interacts most directly with its environment. The proposed Visiting Researcher, Dr Jim Jones, has found that the surface composition of spray dried powders containing fats can be influenced by changes in processing conditions (chiefly outlet air temperature) and the addition of small amounts of surfactants. This potentially offers a route by which added value can be given to powders by tailoring the surfaces at relatively modest cost. This proposal described here aims to acquire a greater understanding of the mechanisms determining how food components distribute (or partition) themselves between the main body and the surface of a powder during drying, and how this can be influenced by changing process conditions and using small amounts of additives. This will be achieved by a combined experimental and mathematical modelling approach. The modelling will seek to estimate the scale of recirculating flows within droplets which may help or hinder the partitioning of components. All the experimental and modelling results will then be used to produce a mechanistic model for the partitioning of components during drying. The project will involve Dr. Jim Jones of the Department of Chemical Engineering of Massey University in New Zealand working in collaboration with Dr. Andy Stapley and Prof. Chris Rielly at the Department of Chemical Engineering at Loughborough University for a period of seven months, as a Visiting Researcher. The project will study the spray drying of food-based suspension-emulsions containing small, but variable, amounts of thickeners and plasticisers (which alter the viscosity) and surfactants. Dr Jones will use the Fellowship to perform a set of experiments whereby feed composition and outlet temperature are varied, and the product materials (particularly surface composition) are analysed using a variety of characterization techniques available at Loughborough. He will collaborate with Dr Stapley in the design of the experiments and in the development of a mechanistic model, and they will both collaborate with Prof Rielly who will perform computational fluid dynamics (CFD) modelling. The CFD modelling will first be performed to calculate the flow fields within a whole spray dryer to assess the forces acting at the surfaces of droplets. This information will then be used as input to separate simulations which will model the circulating flow within drying drops. The information gained will help to assess whether recirculation within droplets helps or hinders partitioning. Once this is understood a mechanistic model for partitioning will be developed, and ultimately provide operational recommendations for manufacturers to make designer surfaces for powders.