Confectionery and Chocolate Engineering

Principles and Applications

Ferenc A. Mohos

• Publisher: Wiley-Blackwell
• Year: 2010
• Print ISBN: 9781405194709
• eBook ISBN: 9781444396195
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Confectionery and chocolate manufacture has been dominated by large-scale industrial processing for several decades. It is often the case, though, that a trial and error approach is applied to the development of new products and processes, rather than verified scientific principles.

The purpose of this book is to describe the features of unit operations used in confectionary manufacturing. In contrast to the common technology-focused approach to this subject, this volume offers a scientific, theoretical account of confectionery manufacture, building on the scientific background of chemical engineering. The large diversity of both raw materials and end products in the confectionery industry makes it beneficial to approach the subject in this way. The industry deals with a variety of vegetable based raw materials as well as milk products, eggs, gelatin, and other animal-based raw materials. A study of confectionery and chocolate engineering must therefore examine the physical and chemical, as well as the biochemical and microbiological properties of the processed materials. By characterizing the unit operations of confectionery manufacture the author, who has over 40 years' experience in confectionery manufacture, aims to open up new possibilities for improvement relating to increased efficiency of operations, the use of new materials, and new applications for traditional raw materials.

The book is aimed at food engineers, scientists, technologists in research and industry, as well as graduate students on relevant food and chemical engineering-related courses.

Part I: Theoretical introduction

Chapter 1

Principles of food engineering

1.1 Introduction

1.1.1 The peculiarities of food engineering

Food engineering is based to a great extent on the results of chemical engineering. However, the differences in overall structure between chemicals and foods, that is, the fact that the majority of foods are of cellular structure, result in at least three important differences in the operations of food engineering – the same is valid for biochemical engineering.

(1) Chemical engineering applies the Gibbs theory of multicomponent chemical systems, the principal relationships of which are based on chemical equilibrium, for example the Gibbs phase rule. Although the supposition of equilibrium is only an approximation, it frequently works, and provides good results. In the case of cellular substances, however, the conditions of equilibrium do not apply in general, because the cell walls function as semi-permeable membranes, which makes equilibrium practically possible only in aqueous media and for long-lasting processes. Consequently, the Gibbs phase rule cannot be a basis for determining the degrees of freedom of food engineering systems in general. For further details, see Section 1.3.2.

(2) Another problem is that cellular substances prove to be chemically very complex after their cellular structure has been destroyed. In the Gibbs theory, the number of components in a multicomponent system is limited and well defined, not infinite. The number of components in a food system can be practically infinite or hard to define; in addition, this number depends on the operational conditions. Certainly, we can choose a limited set of components for the purpose of a study – and this is the usual way – but this choice will not guarantee that exclusively those components will participate in the operation considered.

Therefore, interpretation of the degrees of freedom in food engineering systems causes difficulties and is often impossible, because the number and types of participants (chemical compounds, cell fragments, crystalline substances, etc.) in food operations are hard to estimate: many chemical and physical changes may take place simultaneously, and a small change in the conditions (temperature, pH, etc.) may generate other types of chemical or physical changes. If we compare this situation with a complicated heterogeneous catalytic chemical process with many components, it is evident that in food engineering we struggle with complex tasks that are not easier, only different.

Evidently, comminution plays a decisive role in connection with these peculiarities. However, in the absence of comminution, these two peculiarities – the existence of intact cell wall as barriers to equilibrium and the very high number of operational participants – may appear together as well; for example, in the roasting of cocoa beans, the development of flavours takes place inside unbroken cells. In such cases, cytological aspects (depot fat, mitochondria, etc.) become dominant because the cell itself works as a small chemical plant, the heat and mass transfer of which cannot be influenced by traditional (e.g. fluid-mechanical) means. This problem is characteristic of biochemical engineering.

(3) The third peculiarity, which is a consequence of the cellular structure, is that the operational ‘participants’ in food engineering may be not only chemical compounds, chemical radicals and other molecular groups but also fragments of comminuted cells.

In the case of chemical compounds/radicals, etc., although the set of these participants can be infinitely diverse, the blocks from which they are built are well defined (atoms), the set of atoms is limited and the rules according to the participants are built are clear and well defined.

In the case of cellular fragments, none of this can be said. They can, admittedly, be classified; however, any such classification must be fitted to a given task, without any possibility of application to a broader range of technological problems. This is a natural consequence of the fact that the fragments generated by comminution, in their infinite diversity, do not manifest such conspicuous qualitative characteristics as chemicals; nevertheless, they can be distinguished because slight differences in their properties which occur by accident because of their microstructure may become important.

This situation may be understood as the difference between discrete and continuous properties of substances: while chemical systems consist of atoms and combinations of them, to which stoichiometry can be applied, the systems of food engineering can not be built up from such well-defined elements. This stoichiometry means that well-defined amounts by mass (atomic masses or molecular masses) may be multiplied by integers in order to get the mass fluxes in a reaction. However, in the recipes that are used for describing the compositions of foods, the mass fluxes are treated as continuous variables, contrary to the idea of stoichiometry.

1.1.2 The hierarchical and semi-hierarchical structure of materials

Although foods also consist of atoms in the final analysis, it is characteristic of food engineering that it does not go to an elementary decomposition of the entire raw material; however, a certain part of the raw material will be chemically modified, another part will be modified at t...

Table of contents

• Cover
• Halftitle page
• Dedication
• Title page
• Copyright page
• Preface
• Acknowledgements
• Part I: Theoretical introduction
• Part II: Physical operations
• Part III: Chemical and complex operations: Stability of sweets
• Part IV: Appendices
• References
• Index