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 degree Celsius 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. 巧克力堪称独一无二的食品，在室温下是固体但却入口易化。这是由于它内含的称为可口脂的主要脂肪，在25摄氏度以下就是固体，能将糖粒和可口粒固化在一起，而温度升高到体温时，这种脂肪几乎完全是液体，使得上述颗粒可以流动交融，于是巧克力在口中受热后便成为滑溜的液体，并且有着令大多数人难以拒绝的甜美口味。
The first known cocoa plantations were established by the Maya in the lowlands of south Yucatan about 600 AD. Cocoa trees were being grown by the Aztecs of Mexico and the Incas of Peru when the Europeans discovered central America. The beans were highly prized and used as money as well as to produce a drink known as chocolate.The beans were roasted in earthenware pots and crushed between stones, sometimes using decorated heated tables and mill stones,similar to those illustrated in Figure1.1. They could then be kneaded into cakes, which could be added to cold water to make a drink. Vanilla, spices or honey were often added and the drink whipped to make it frothy(Note1). The Aztec Emperor Montezeuma was said to have drunk 50 jars of this beverage per day.
Christopher Columbus bought 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 favours, 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 favour 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 was established in London in 1657 and it 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(Note2).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 alkalising 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.
Unlike Van Houten, Fry used the recently developed steam engines to power his factory. It is interesting to note that 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 1990s, 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 (Biyogo), 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 (Cote dIvoire), 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 12). 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 Nestle. 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.
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, 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). 为了使巧克力在嘴里融化时舌头感觉滑溜，非脂肪固体颗粒必须小于30微米。夫瑞里和皮特生产的巧克力都是用花岗石辊磨粉的，可是仍有砂砾感。这是因为还存在一些大颗粒和结团成块的颗粒，也因为脂肪在颗粒上覆盖得不太好。另外，由于含有某些酸性化学品，这种巧克力尝起来比较苦（参见第四章）。
In 1880 Rodolphe Lindt, in his factory in Berne in Switzerland, invented a machine which 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 1.5). 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 1.6. 1880年，鲁道夫·林特在其瑞士伯恩的工厂里，发明了一种更顺滑口味更佳的巧克力机器。这种机器以海螺巧克力精炼机闻名于世，因为它的形状和海螺壳相似（图1.5）。它由一个花岗岩槽和一个通常是相同材料的滚筒组成，后者将暖乎乎的巧克力流体来回辗压数天时间。这就把团块和大颗粒打散，并且完全裹上脂肪。同时，水分和部分酸性化学品蒸发到空气中，产生更顺滑、更少涩味的巧克力。图1.6是一张巧克力制程示意图。