Chocolate-Team 12

INTRODUCTION & HISTORY

From snacks to drinks to spicing up meals, chocolate is a versatile product that has been introduced to many different parts of the world. The chocolate journey starts from the cacao tree, Theobroma cacao, that originated from the continents of Central and South America (1). Dating back to 500 A.D., it was recorded that the Mayans and Aztecs were the first to use the fruits of the cacao plant in a variety of forms. For example, cocoa beans would be used for offerings in rituals as they were thought to hold spiritual powers (1). They also functioned as either currency to trade for goods or be ground up and put into drinks that contained a variety of spices such as chilis (2). These drinks made by the Mayans and Aztecs were not the sweet hot chocolate drinks we are familiar with in Western society. Instead, these drinks were often bitter and sometimes spicy due to the variety of spices that were added to them; like wine, it had a taste that one had to grow accustomed to (2). The sweet hot chocolate drink was only founded after Christopher Columbus brought the cocoa beans back and introduced them to European culture. Spain was where the first sweet chocolate drink first emerged. They had opted to substitute the strong spices for sugar in order to create the sweet drink we know and love as hot chocolate.

Coenraad Johannes van Houten, a dutch chemist, is the genius behind the first steps leading into the discovery of the chocolate bar (3). Eventually, the bar form of chocolate came into existence around the mid 1800’s and since then has evolved to the many different flavours and textures such as milk and dark chocolate, and bars with nuts or dried fruits mixed in. Due to the global appreciation for this product, the chocolate bar was discovered by multiple people around the world; as a result, there is no one true inventor of the chocolate bar.

WHY DID TEAM 12 CHOSE CHOCOLATE?

Our group decided to investigate chocolate due to its versatility in regards to how it can be consumed. For instance, we can cook with chocolate to create a milky texture and taste in curries or we can create rich frothy hot chocolates if we melt it with milk. We also wanted to investigate the similarities in the processing steps between the three main types of chocolate: white, milk, and dark, as well as the differences that create the different flavours and textures of the three types of chocolates. Of course, chocolate is also a food item that we all enjoy on a regular basis despite our different backgrounds and upbringings.

FROM GROWTH TO FACTORY

Cocoa trees grow in hot, rainy tropical areas within 20° of the latitude from the equator. Since the weather in these areas is pretty stable throughout the year, cocoa production is not restricted to a certain time period and is usually over several months and in many countries at the same time of year. Many farmers use pesticides in order to combat pests and to fight black pod disease.(2)

Cocoa beans grow in pods, these cocoa pod have a rough and leathery rind, which is approximately 3cm thick. Each pod is filled with about 30 to 50 large seeds, which are fairly soft and a white to pale lavender colour. The pods which are about the size of a football, is the place coca seeds grow. Unlike most fruiting trees, the cocoa pod sprouts directly from the trunk or a large branch of a tree rather than the end of the branches. The immature cocoa pods have a variety of colours but are most often green, red or purple and as they ripen they turn towards yellow or orange. When the pods have ripened harvesters with machetes hack pods gently of the trees. The advantage of having the pods grow directly from the trunk or at the beginning of the branches is that it makes harvesting by hand much easier since most of the pods will not be up in the higher branches. Also the process is done manually because it is said that machines may damage the tree and the clusters of flowers. Therefore the workers that harvest the pods do it by hand using short, hooked blades mounted on long poles to make sure they reach the highest fruit. However care must be taken when cutting the stem of the pod to avoid injuring the junction of the stem with the tree, because that is where the future pods will grow. Not all pods ripe at the same time therefore there harvesting usually occurs 3 to 4 times weekly during harvest season. All cocoa beans are recollected, the pods are taken to be processed.(2)

The pods are split open and cocoa beans are removed. There can be about 50 cocoa beans in each pod. The fresh cocoa beans taken out from the pods are not brown at all and they do not taste like the sweet chocolate they will eventually produce.(2)

Then these beans undergo the fermentation process in which they are either placed in large, shallow, heated trays or covered with large banana leaves. If the climate is adequate they may be heated by sun dried. However, the workers must come periodically and stir the cocoa beans out so they are all equally fermented. Fermentation of cocoa beans is when the beans turn brown; this process may take five or eight days.(2)

After the fermentation has been completed, the cocoa seeds must be dried before they are scooped into sacks and shipped to chocolate manufacturers. The workers taking care of the cocoa beans simply spread the fermented seeds on trays and leave them to sun dry. This process takes about a week, resulting in seed weight decreasing to half of their original weight.(2)

TEMPERING OF CHOCOLATE:

Before chocolate can be processed from a liquid into a solid, it must be tempered. Tempering is the controlled crystallisation of cocoa butter to produce the most stable finished product possible. It is a necessary step because chocolate is polymorphic- it has the ability to crystallise into six different crystal configurations. Most of these crystal configurations are unstable and therefore undesirable because they will affect the surface appearance of the chocolate and also reduce the shelf life. The six forms differ in the way the glyceride molecules are arranged in the fat crystal, which affects not only stability, but also melting point and volume of the solid product. As we move from one form to the next, they become increasingly stable, have higher melting points, and a lower volume (because the crystal structure is more compact). The fifth crystal state, Form V, is the most desirable for high quality chocolate.

Form I is made from rapid cooling, is the least stable form, and has a melting point of 17⁰C. Because it is so unstable, it does not last long and quickly morphs into Form II, which has a melting point of 21⁰C. Form II, also being quite unstable, typically changes into Form III and then Form IV. Form IV is the configuration most likely to be produced if chocolate does not undergo tempering, or undergoes inadequate tempering. Though more stable than the previous three, it will still result in a chocolate surface appearance that quickly degrades, and a shorten shelf life. Finally, Form IV morphs into Form V which is the desired crystal structure of chocolate. After a lengthily storage time, form V can transition into form VI, usually recognised by fat bloom on the product. The goal of tempering is to ensure the finished product is composed of mostly, if not completely, form V crystals

The tempering process starts by completely melting the chocolate, usually done at about 50⁰C. It is important to ensure all of the chocolate is in a liquid state before moving on. The next step is to cool the chocolate to a temperature where crystallisation can occur. At this point, both stable and unstable crystal configurations will be created- in other words, Forms I-V will be present sporadically in the mixture. Now, the chocolate is reheated, only enough so that the unstable crystals, forms I-IV, will melt (because the less stable configurations also have a lower melting point). The result is mixture that contains mostly the desired form V crystals. There are no exact temperatures for the steps of the tempering process. It has been found that dark chocolate requires a couple degrees higher than milk chocolate, but the precise temperature depends on the recipe used and the desired end product.

The original way of tempering chocolate was to heat it in a pot, and then pour it onto a cold metal slab and work it with a flexible spatula until it cooled and crystallised. The chocolate was then poured into a warm pot to melt away the unstable crystals before the moulding process. Chocolatiers that produce small quantities of high quality chocolate still prefer this method. There are now tempering machines, though, that carry the chocolate through the various temperature stages automatically.

The degree of temper can be measured using the ‘cooling curve’ of the product. A device has been designed specifically to determine this. It consists of a metal tube connected to a cup at the top where a chocolate sample is placed. A cap then fits snugly over the cup, with a thermometer probe that attached to the centre that protrudes into the chocolate sample. The long metal tube is placed in a flask with water and ice, which will cool the chocolate. As it cools, the device records the changes in temperature to create a graph, or cooling curve, of the tempered chocolate. The shape of the curve will tell the manufacturer if the chocolate has been tempered adequately- chocolate that has been tempered properly will have a ‘Z’ shaped cooling curve.