The Science of Chocolate leads the reader to an understanding of the complete chocolate making process and includes the ways in which basic science plays a vital role in its manufacture, testing and consumption. Originally based upon a talk to encourage school children to study science, the book is now widely used within industry and academia.

The third edition of this international best seller has been fully revised and updated. The author has now included methods of sensory evaluation, designing and modifying chocolate flavour to suit the product and the history and manufacture of some well-known confectionery products. Fat, calorie and sugar reduction are also covered including a review of patents in this area. In addition, the section on why chocolate might be good for you has been updated to include some more recent research results. Three new experiments have been added, so there are now twenty of them, which use simple materials and apparatus to demonstrate the scientific and mathematical principles found in the rest of the book. Most are easily adapted to suit different student abilities.

This book will appeal to those with a fascination for chocolate and will be of specialist interest to those studying food sciences and working in the confectionery industry.

Extracts from reviews of 2^nd Edition:

...I found this to be an interesting read, and I think the book would be useful to graduates thinking of a career in the food industry (and not just the chocolate industry specifically), to schoolteachers looking for some interesting experiments, and to lecturers (Chemistry, Biochemistry, Botany, Food science) looking for interesting facts to enliven their lectures.

Bioscience Education, Volume 12, 2008, E J Wood.

...very well written and complete book for everyone who wants to learn more about chocolate and its production process.

Crystallography Reviews, Volume 15, 2009 - Issue 4, pages 275-277, Henk Schenk.

The easy reading style of the book makes it valuable not only to school and university students, but also to those who are new to working with chocolate or those needing a good summary of chocolate science.

Chemistry World, for the Christmas Books

BSc (Durham) D.Phil (York) in physics. 8 years research into asbestosis, followed by over 27 years working in the chocolate industry, with Rowntree then Nestlé. Chairman of Solingen Confectionery School, Chocolate Technology Conference Committee (Germany). Now retired from Nestlé, and currently a director of Sporomex, an encapsulation research company.

The Science of Chocolate

The Royal Society of Chemistry

Contents

The History of Chocolate

Chocolate is almost unique as a food in that it is solid at normal room temperatures yet melts easily within the mouth. This is because the main fat in it, which is called cocoa butter, is essentially solid at temperatures below 25 °C when it holds all the solid sugar and cocoa particles together. This fat is, however, almost entirely liquid at body temperature, enabling the particles to flow past one another, so the chocolate becomes a smooth liquid when it is heated in the mouth. Chocolate also has a sweet taste that is attractive to most people.

Strangely chocolate began as a rather astringent, fatty and unpleasant tasting drink and the fact that it was developed at all is one of the mysteries of history.

1.1 Chocolate as a Drink

As early as 1900 BC cocoa was being used as a beverage by the Mokaya people in Mexico. Cocoa plantations were grown by the Maya in the lowlands of south Yucatan about 600 AD and cocoa trees were being grown by the Aztecs of Mexico and the Incas of Peru when Europeans discovered Central America. The beans were highly prized and used as money, where its actual value varied according to quality and type. There was even a special currency variety called quauhcacaoatl. Counterfeit beans filled with wax have been discovered.

The main use of cocoa beans, however, was to produce a drink known as chocolatl. The beans were roasted in earthenware pots and crushed between stones, sometimes using decorated heated tables and mill stones, similar to that illustrated in Figure 1.1. They could then be kneaded into cakes, which were added to cold water to make a drink. Vanilla, spices or honey were often added and the drink whipped to make it frothy. The Aztec Emperor Montezuma was said to have drunk 50 jars of this beverage per day.

Christopher Columbus brought back some cocoa beans to Europe as a curiosity, but it was only after the Spaniards conquered Mexico that Don Cortez introduced the drink to Spain in the 1520s. Here sugar was added to overcome some of the bitter, astringent flavours, but the drink remained virtually unknown in the rest of Europe for almost a hundred years, coming to Italy in 1606 and France in 1657. It was very expensive and, being a drink for the aristocracy, its spread was often through connections between powerful families. For example, the Spanish princess Anna of Austria introduced it to her husband King Louis XIII of France and the French court in about 1615. Here Cardinal Richelieu enjoyed it both as a drink and to aid his digestion. Its flavour was not liked by everyone and one Pope in fact declared that it could be drunk during a fast, because its taste was so bad.

The first chocolate drinking meeting place was established in London in 1657 and was mentioned in Pepys' Diary of 1664 where he wrote that "jocolatte" was "very good". In 1727 milk was being added to the drink. This invention is generally attributed to Nicholas Sanders or Sir Hans Sloane, founder of The British Museum. Their recipe was purchased and used by the Cadbury family. During the eighteenth century, White's Chocolate House became the fashionable place for young Londoners, while politicians of the day went to the Cocoa Tree Chocolate House. These were much less rowdy than the taverns of the period. It remained, however, very much a drink for the wealthy.

One problem with the chocolate drink was that it was very fatty. Over half of the cocoa bean is made up of cocoa butter. This will melt in hot water making the cocoa particles hard to disperse, as well as looking unpleasant because of fat coming to the surface. The Dutch, however, found a way of improving the drink by removing part of this fat. In 1828 Van Houten developed the cocoa press. This was quite remarkable, as his entire factory was manually operated at the time. The cocoa bean cotyledons (known as cocoa nibs) were pressed to produce a hard "cake" with about half the fat removed. This was milled into a powder, which could be used to produce a much less fatty drink. In order to make this powder disperse better in the hot water or milk, the Dutch treated the cocoa beans during the roasting process with an alkali liquid. This has subsequently become known as the Dutching process. By changing the type of alkalizing agent, it also became possible to adjust the colour of the cocoa powder.

1.2 Eating Chocolate

Having used the presses to remove some of the cocoa butter, the cocoa powder producers were left trying to find a market for this fat. This was solved by confectioners finding that "eating" chocolate could be produced by adding it to a milled mixture of sugar and cocoa nibs. (The ingredients used to make dark chocolate are shown in Figure 1.2.) If only the sugar and cocoa nibs were milled and mixed together they would produce a hard crumbly material. Adding the extra fat enabled all the solid particles to be coated with fat and thus form the hard uniform bar that we know today, which will melt smoothly in the mouth.

Almost 20 years after the invention of the press in 1847, the first British factory to produce a plain eating chocolate was established in Bristol in the UK by Joseph Fry.

Unlike Van Houten, Fry used the recently developed steam engines to power his factory. Interestingly, many of the early chocolate companies, including Cadbury, Rowntree and Hershey (in the USA), were founded by Quakers or people of similar religious beliefs. This may have been because their pacifist and teetotal beliefs prevented them from working in many industries. The chocolate industry was, however, regarded as being beneficial to people. Both Cadbury and Rowntree moved to the outside of their cities at the end of the 1890s, where they built "garden" villages for some of their workers. Fry remained mainly in the middle of Bristol and did not expand as quickly as the other two companies. It eventually became part of Cadbury.

With the development of eating chocolate, the demand for cocoa greatly increased. Initially much of the cocoa came from the Americas, with the first cocoa plantation in Bahia in Brazil being established in 1746. Even earlier, however, the Spaniards took cocoa trees to Fernando Po (Bioko), off the coast of Africa, and this soon became an important growing area. In 1879 a West African blacksmith took some plants home to the Gold Coast (now Ghana). The British governor realised its potential and encouraged the planting of trees, with the result that Ghana has become a major source of quality cocoa. Other European powers also encouraged the growing of cocoa in their tropical colonies, e.g. France in the Ivory Coast (Côte d'Ivoire), which is now the world's largest producer of cocoa.

The chocolate made by Fry was initially a plain block and it was only in 1875 that the first milk chocolate was made by Daniel Peter in Switzerland. Chocolate cannot contain much moisture, because water reacts with the sugar and turns melted chocolate into a paste rather than a smoothly flowing liquid (see Project 5 in Chapter 13). As little as 2% moisture can give a product a poor shelf life as well as an inferior texture. This meant that Daniel Peter had to find some way of drying the plentiful supply of liquid milk that he found in his own country. He was helped in this by the recent development of a condensed milk formula by Henri Nestlé. This meant that he had much less water to evaporate, and he was able to remove the remaining amount using relatively cheap water-powered machines. In most countries milk chocolate products are now much more popular than plain chocolate ones. In the early 1900s Daniel Peter was challenged to prove that he did in fact invent milk chocolate, so he took his original notebook to the lawyer to get it stamped. The original page together with the lawyer's mark is reproduced in Figure 1.3. Currently many manufacturers add the milk in the form of milk powder. See Figure 1.4.

At this time most of the milk chocolate-like bars were still used to make drinks. Figure 1.5 shows an early 1900s' advertisement for Peter's company. He made a triangular bar, which was known as Peter's Delta chocolate. It was made so that it could easily be broken into smaller triangular pieces, each of which would dissolve in a cup full of hot water.

In order for the chocolate to feel smooth on the tongue when it melts in the mouth, the solid non-fat particles must be smaller than 30 microns (1000 microns=1 mm). The chocolates made by Fry and Peter were ground using granite rollers, but still had a gritty texture. This was because of the presence of some large particles and some groups of particles joined together to form agglomerates, and also because the fat was not coating the particles very well. In addition, the chocolate tended to taste bitter because of the presence of some acidic chemicals (see Chapter 4).

In 1879 Rodolphe Lindt, in his factory in Berne in Switzerland, invented a machine that produced a smoother, better tasting chocolate. This machine was known as a conche, because its shape was similar to the shell with that name (Figure 1.6). It consisted of a granite trough, with a roller, normally constructed of the same material, which pushed the warm liquid chocolate backwards and forwards for several days. This broke up the agglomerates and some of the larger particles and coated them all with fat. At the same time moisture and some acidic chemicals were evaporated into the air, producing a smoother, less astringent tasting chocolate. A schematic diagram of the chocolate making processes is shown in Figure 1.7. In the 1890s about half the world's eating chocolate was manufactured in Switzerland.

1.2.1 Chocolate Crumb

In the early part of the twentieth century the milk used to make chocolate had poor keeping qualities. This caused problems for the chocolate industry, whose major sales were at Christmas, a time of the year when there was a very limited supply of fresh milk. In the UK and some other countries this lead to the development of an intermediate ingredient called "chocolate crumb". (See Figure 1.8.)

The cocoa nibs contain substances known as antioxidants (see Chapter 12). These restrict the breaking up of the fats, which would normally make the milk fat turn sour. In addition, sugar was known to extend the shelf life of foods (it is used in jams etc.). The chocolate manufacturers therefore added sugar and cocoa to the milk and dried them together. This produced chocolate crumb, which had a shelf life of at least a year. Milk produced during the spring peak could then be used to make chocolate the following Christmas. The drying process, however, introduced some cooked flavours into the chocolate and it is for this reason that many UK milk chocolates taste different from some continental European ones, which are made from milk powder.

1.2.2 White Chocolate

Nestlé white chocolate was sold in 1936 with the Galak brand advert using the strapline "tout blanc". It was made from sugar, full cream milk powder and cocoa butter (see Figure 1.9). The preserving qualities of the cocoa antioxidants are mainly in the dark cocoa material. This means that white chocolate does not keep as well as milk chocolate, and also that it should be kept in a non-transparent wrapper, as light will speed up the decomposition of the milk fat.

1.3 Development of the Chocolate Industry

Table 1.1 shows the year of first sale of some well-known chocolate products. By dividing the products into five different types it is possible to see definite trends over the years. Not many manufacturing industries have brands over one hundred years old.

1.3.1 Chocolate Bars

In the late 1800s most eating chocolate was manufactured by French or Swiss companies, with factories in other countries, e.g. Cadbury and Rowntree, mainly producing drinking cocoa or chocolate. Then suddenly at the turn of the century, three companies in three different countries produced three very different tasting bars, i.e. Hershey Bar, Milka® and Cadbury Dairy Milk®. Each one remains the principle selling bar in its launch country.

Technological innovation was then required to make a product that was easily distinguished from these three and in 1935 a method was found of putting air bubbles into chocolate and Aero® appeared on the market. The following year Galak® (Milky Bar®), with its novel colour, texture and flavour started being sold.

The development of faster and finer grinding of the ingredients enabled a smoother chocolate to be launched in 1960 and sold as Galaxy®.

1.3.2 Chocolate Boxes

Alongside the bars, boxes of chocolates with a variety of centres were produced. In the 1920s some of the boxes became a work of art in themselves and were very expensive. As early as 1915, however, Cadbury started selling boxes of Milk Tray® in a simpler box, but with individual sweets side by side on a tray. In the 1930s, chocolate became more readily available and other similar boxes such as Black Magic® and Terry's All Gold® appeared.

Each sweet had to be placed by hand into its allotted place in the tray, which was expensive and time consuming. To get around this, sweets were individually wrapped and then put randomly into a box. Quality Street® and Cadbury Roses® are good examples from 1930s.

Traditionally sweets were single centred often with fondant or caramel. In the 1990s several companies made selections of miniature versions of their own countlines.

1.3.3 Countlines

A countline is an individual unit (bar) normally purchased and eaten by the consumer as a snack or treat. Very often these are a cheaper centre coated by more expensive chocolate. They can therefore be made less expensively than a solid bar. The choice of centre varies strongly with the market for both countlines and boxed chocolates. Peanut butter is very popular in the USA, but seldom used in Europe. In the UK, there are many sweets with sugar fondant centres, e.g. After Eight® and orange and coffee crème. These in turn are regarded as cheap in some countries of Continental Europe, where pralines (usually ground nuts and sugar) are preferred. These have relatively recently become widely available in the UK.

The 1930s were once again a time of major innovations that are still important brands today, such as KitKat® and Mars Bar®. At the same time products also became known under a brand name rather than that of the manufacturer. Some companies, like Cadbury, tended to give both equal prominence.

1.3.4 Multi Small Pieces

A typical example is Hershey Kisses®, which has a large number of similar small sweets sold in a bag, in particular to children. Kisses® were first marketed in 1907. They were followed in the early 1930s by multicoloured sugar coated chocolate centres under the name of Smarties® or M&Ms&®. Traditionally in the UK only the orange Smartie® is flavoured.

1.3.5 Novelty

Chocolate sales are seasonal, peaking at cooler times of the year and for special occasions such as trick or treat (Hallowe'en) and Easter. Some products such as chocolate eggs were made to capitalise on this. Others are for special eating occasions, for example After Eight® mints were advertised to be consumed after a main meal, whilst Cadbury Flake® is uniquely added to ice-cream sold in a wafer cone.

1.3.6 Changes in Manufacturing Scale

Until the 1970s many factories processed their own cocoa and chocolate. Then there were a lot of company takeovers that resulted in about six multinationals using most of the world's supply of cocoa. Smaller companies tended to buy in chocolate and cocoa liquor (ground cocoa nibs) from specialist suppliers.

Relatively recently there has been a big increase in the number of artisan chocolate sweet makers. Although most buy in their chocolate, some make it from cocoa liquor and a very few process from bean to bar. This enables them to use beans from special growing areas, often in bars with a high cocoa content.

1.3.7 National Chocolate Consumption

Cooler countries tend to consume a relatively higher amount of chocolate per head (see Figure 1.10) although a long history of making it is also important. Switzerland meets both criteria and is normally regarded as having the world's highest consumption per head of population, although some is taken home or eaten by visitors. In addition, what is recorded as chocolate, particularly regarding biscuits, can vary from country to country.