Mixing technology An introduction

Table of contents Introduction 17 Understanding key mixing challenges 3 Mixing – a key process with complex demands 4 An overview of powder properties 4 Understanding common stabilizers 5 Solubility limits of powders 6 Two types of mixtures and their unique properties Mixtures – Suspensions 8 Suspensions and their properties 8 Flocculation, suspension and sedimentation 9 Achieving efficient wetting and preventing fish eyes 10 How to make a stable suspension 17 Air incorporation and foaming 19 Lump formation 19 Clogging The right solution conquers mixing challenges 20 Preventing air incorporation...

Introduction Mixing – a key process with complex demands Mixing is the process of dissolving, emulsifying or dispersing powder and liquid ingredients into a liquid medium. Mixing, a common operation in food processing, aims to efficiently achieve a smooth, homogenous product with consistent quality. Food processors, and consumers, insist on a perfect product every time. To achieve this, food processors must stay in complete control of every aspect of their production from beginning to end. Mixing is a highly complex operation and often takes place early on in the process of food production. Thus,...

Powders An overview of powder properties The handling of ingredients in powder form has many advantages. Powder ingredients have longer shelf life and are smaller, lighter and more convenient to transport and store. This has lead to an increase in powder ingredient use. Certain powders, such as pectin, do not deliver their functional properties unless they have reached the correct temperature. Pectin, for example, needs to reach 80°C in order to be activated so that it protects the proteins in, for example, a milk-juice beverage. A wide range of ingredients are available in powder form, including...

Solubility limits in powders There are physical limitations on how much powder it is possible to dissolve into a liquid. Some common examples where the limits of solubility are important to consider are aspartame, lactose, and stabilizer ingredients. In some powders, such as aspartame, pH affects solubility. For example, a citric acid solution of 10% and with a pH of 2 can accommodate a 5 to 8% solution of aspartame while a non-acidic solution can only accommodate a 1% solution of aspartame. Temperature also affects the solubility of aspartame. Higher temperatures allow more aspartame to be dissolved...

Mixtures Two types of mixtures and their unique properties Continuous phase Solid Liquid Dispersed phase Solid Liquid Solid Gel Suspension Continuous phase Dispersed phase This section describes two main types of mixtures handled in the mixing process. The first type of mixture is a suspension, defined as a mixture of solids and liquids. The second type of mixture combines liquids with other liquids to create an emulsion. Classifications of mixtures This document will focus on suspensions and emulsions, which are the mixtures most commonly used in the food industry.

Mixtures Suspensions Suspensions and their properties A suspension is when denser par ticles are evenly dispersed in a less dense liquid. The goal in mixing suspensions is to achieve stability. This is achieved by counteracting their naturally unstable nature. To achieve a stable suspension, it is important to understand the properties of a powder as well as what happens when powder and liquid meet. This understanding enables food processors to determine the most efficient way to introduce it into a liquid. When powder is introduced to a liquid, the liquid penetrates through the pores of the...

Achieving efficient wetting and preventing fish eyes Faster wetting prevents lumping and increases the overall efficiency of the mixing process. However, when a high-viscosity powder such as guar gum is added to a liquid too quickly and in too large amounts, the viscosity of that solution increases and the dissolution rate slows, hindering the thorough wetting of particles. The product then risks the formation of fish eyes, lumps of dry powder with an outer gelling layer. How much shear force is required to prevent fish eyes and achieve a stable suspension depends on a number of factors including...

Mixtures Suspensions How to make a stable suspension Stoke’s law describes the separation behaviours of particles in suspensions. The main types of separation in suspensions are flocculation and sedimentation Creaming d 2 (p1 - pfl) V= g 18n The settling velocity (V) is influenced by the particle diameter (d), the particle density (p1), the density of the solution (pfl) and the viscosity of the solutions (n); (g) describes the acceleration due to gravity. According to Stoke’s law, food processors may improve suspension stability by: 1. Decreasing the difference in density between the particles...

Mixtures Emulsions Emulsions and their properties Emulsions are mixtures containing two liquid phases that do not naturally mix, one of which is dispersed in the other as droplets. There are two types of emulsions in the food industry – oil-in-water emulsions and water-inoil emulsions. In oil-in-water emulsions, the oil phase is the dispersed phased and water phase is the continuous phase. This is the most common type of emulsion and examples include mayonnaises, dressings, soups, and sauces. In water-in-oil emulsions, which include margarines and spreads, water is the dispersed phase and oil/...

Emulsions components Oil phase The oil phase (fats and oils), provide the main flavour of a product since fat carries a large amount aroma and flavour. Water phase The water phase includes water and water-soluble ingredients such as sugar, mustard seeds, proteins, vitamins, minerals, and some thickening agents. Emulsifier Emulsifiers are the compounds that make emulsions possible by stabilizing the dispersed phase and the continuous phase. They reduce the interfacial tensions between the two phases. An emulsifier has one lipophilic tail, which loves the fat phase, and one hydrophilic head, which...