The secrets of Belgian chocolate

May 2012

Like a bonbon nestled snugly in a box of chocolates, Belgium sits between France, Germany, the Netherlands, and Luxembourg. With a land area of only about 30,528 square kilometers (11,787 square miles), Belgium produces 270,000 metric tons of chocolate each year and boasts more than 2,000 chocolate shops. Belgium’s chocolate obsession is fueled by a 150-year-old tradition of producing some of the world’s finest chocolate. But what is it about Belgian chocolate that makes it so smooth, flavorful, and melt-in-your-mouth irresistible? The secret lies in quality ingredients and expert processing, combined with a spirit of innovation that continues to refine Belgian chocolate even today.

The history of Belgian chocolate reaches back to the 17th century, when Spanish explorers brought cocoa beans from South America. The Spanish nobility, who then ruled Belgium, enjoyed cocoa as a luxury drink. However, chocolate did not gain popularity with the general public until the second half of the 19th century, when Belgian King Leopold II colonized the Congo. During the age of European imperialism, cocoa cultivation began to shift from the Americas to West Africa, which provided an ideal environment, as well as plentiful slave labor, for cocoa production.

In 1857, Jean Neuhaus opened a pharmacy in Brussels, Belgium, where, among more traditional remedies, he sold bars of bitter chocolate. Eventually, the bars became so popular that Neuhaus focused his efforts on chocolate making. In 1912, Neuhaus’ grandson, Jean II, invented the now-famous Belgian praline by filling hard chocolate shells with soft cream or nut pastes.

Today, the Neuhaus company continues to manufacture Belgian pralines (known as bonbons elsewhere in the world), joined by other large manufacturers such as Godiva, Leonidas, and Guylian. In addition, numerous small manufacturers and artisan chocolatiers attract loyal customers to their shops throughout Belgium. The country also supplies 20% of the world’s industrial chocolate (Dewettinck, K., The Secrets behind the quality and taste of Belgian chocolates, presented at the 103rd AOCS Annual Meeting and Expo, April 30, 2012), which food manufacturers use to create finished products such as bonbons, cookies, and ice creams (Belgian chocolates: the secrets of their quality and taste . Large producers of industrial Belgian chocolate include Cargill, Belcolade, and Barry Callebaut. The Barry Callebaut factory in Wieze, Belgium, is the largest chocolate-producing factory in the world, says Mark Adriaenssens, a native Belgian and the company’s director of research and development for the Americas.

From forest to factory

The story of Belgian chocolate, however, begins not in a factory but in the tropical rain forests of Africa, Central and South America, the Pacific islands, and Asia (Table 1). Cocoa trees (Theobroma cacao) thrive at altitudes of 30–300 m, with temperatures ranging 18–32 °C and annual rainfall 1–5 L/m². The trees bear yellowish, 15–30-cm-long by 8–10-cm-wide pods that contain 20–60 whitish-gray, almond-shaped seeds embedded in a white pulp. When the pods ripen, workers at cacao plantations harvest the pods by cutting them from trees with a curved knife on a long pole. Then, they split the pods open with a machete, remove the pulp and seeds, and place them on banana leaves on the ground or in boxes. After covering the cocoa pulp with more banana leaves, they let it ferment for about six days.

 

As the cocoa sits in the sun, three types of microorganisms sequentially consume and transform compounds in the pulp. Because the inside of the unopened cocoa pod is sterile, these microbes come from the cocoa pod surface, workers’ hands or knives, or elsewhere in the environment. The first microorganisms that act on the pulp are yeasts, which can grow under the anaerobic conditions found in the dense pulp. Yeasts convert glucose in the pulp into ethanol and produce pectinases that break down the pulp. The decreased pulp viscosity allows more air to penetrate, encouraging the growth of lactic acid bacteria. These bacteria convert fructose and citric acid in the cocoa pulp into lactic acid and acetic acid. Finally, when the yeast and lactic acid bacteria have consumed all of the sugars in the pulp, acetic acid bacteria convert the ethanol produced by the yeast into acetic acid. This reaction gives off heat, killing the microbes and ending the fermentation process. By this time, most of the pulp has liquefied and drained away.

Proper fermentation is essential for producing high-quality chocolate, says Luc De Vuyst, food biotechnologist at the Vrije Universiteit Brussel. For one thing, the acetic acid produced by the microbes penetrates the cocoa seed and kills the embryo. If the embryo remained alive, it could start to grow, consuming the fat in the beans needed for chocolate production. In addition, acetic acid disintegrates membranes within the cocoa bean, releasing enzymes and substrates that mix and interact. “A whole series of enzymatic reactions takes place in the fermenting bean,” says De Vuyst. “The chemical products of these reactions contribute to the color and flavor of the final chocolate.”

Scientists used to think that the strains of yeast and bacteria responsible for fermentation varied with the cocoa-producing region, contributing to subtle flavor variations in cocoa from different parts of the world. However, when De Vuyst analyzed the microbes present in cocoa fermentations from Ghana, the Ivory Coast, Brazil, Ecuador, and Malaysia, he found that the microbial composition and fermentation process were everywhere the same, provided that the cocoa plantations observed good agricultural and operational practices (e.g., Food Microbiol. 2011, DOI 10.1016/j.fm.2011.06.003). In contrast, farms that harvested immature or fungus-infected cocoa pods, used defective equipment, or practiced poor hygiene showed variations in the fermentation process. “Under these conditions, a whole zoo of microorganisms can develop and destroy the fermentation process, delivering sour beans from which you make sour chocolate,” says De Vuyst.

Based on these findings, De Vuyst developed a fermentation starter culture consisting of strains of the yeast Saccharomyces cerevisiae, the lactic acid bacterium Lactobacillus fermentum, and the acetic acid bacterium Acetobacter pasteurianus. He found that adding this starter culture to newly harvested cocoa pulp shortened the fermentation process from six to four days (Food Microbiol. 2012, DOI 10.1016/j.fm.2011.12.021). Commercial use of the starter culture could enable faster and more uniform fermentation of cocoa beans. Furthermore, “By manipulating the microbial composition of the starter culture, we may be able to steer the fermentation process to generate certain flavors in the final chocolate,” says De Vuyst. He is currently working with the Barry Callebaut factory in Wieze to implement this controlled fermentation.

After fermentation, the beans have a rich brown color. Workers dry the fermented beans in the sun for 6–10 days, during which the chemical reactions in the beans continue. After drying, farmers or potential buyers can perform various tests to assess the quality of the beans. For example, in the grainage test they count the number of cocoa beans present in 100 g, which should be fewer than 100 beans. In the cut test, inspectors randomly select 100 cocoa beans and slice them in half lengthwise, looking for signs of mold, insect damage, shrinkage, germination, or a gray or violet color, all of which indicate lower-quality beans. In another test, inspectors weigh cocoa beans before and after removing their shells. If the mass percentage of the shells is greater than 14%, then the cocoa beans are too small or insufficiently fermented. With these tests, chocolate makers can ensure that the beans they purchase are of sufficiently high quality to produce good chocolate.

Making it Belgian

At this point, the cocoa beans are finally ready to leave the farm. Workers package the dried beans and ship them to factories, the sites of roasting and grinding. During roasting, flavor compounds develop through numerous chemical conversions collectively known as Malliard reactions. Carbonyl and amino groups of molecules formed during cocoa fermentation and drying react with each other, producing more than 600 flavor compounds that together give chocolate its characteristic taste and aroma. After roasting, a machine called a winnower cracks and deshells the beans. Then the deshelled beans, known as nibs, are ground into a thick paste called chocolate liquor. The chocolate liquor is pressed to extract cocoa butter, leaving behind a solid mass that is ground into cocoa powder.

Barry Callebaut produces its own chocolate liquor from cocoa beans, whereas other industrial chocolate makers purchase liquor from companies outside of Belgium to make their chocolate. According to the Belgian Chocolate Code, a measure introduced by the Royal Belgian Association of the Biscuit, Chocolate, Pralines and Confectionary (abbreviated Choprabisco) industry and agreed on by most major chocolate makers, products labeled as “Belgian chocolate” must be refined and molded in Belgium. However, the grinding of beans and production of chocolate liquor, cocoa powder, and cocoa butter may occur elsewhere.

To produce industrial chocolate, manufacturers mix chocolate liquor with sugar and varying amounts of cocoa butter, depending on the type of chocolate (Table 2). Since 2000, the European Union has allowed chocolate makers to substitute up to 5% of the cocoa butter in their chocolate with other vegetable fats such as palm oil or shea butter. However, Belgian chocolate makers pride themselves on using 100% cocoa butter, which enhances the quality and smoothness of the chocolate, says Bram Beheydt, research and development manager at Belcolade, in Erembodegem. Milk powder is added to milk and white chocolates. Lecithin acts as an emulsifier, producing a smoother chocolate.

Also crucial to obtaining the typical smooth Belgian chocolate is the refining step, in which sugar and cocoa particles are ground down to a size of 18–20 μm. “In Belgium, we’re very sensitive to having a fine chocolate—you will never have a grainy feeling in your mouth after eating our chocolate,” says Beheydt. In contrast, chocolate factories in many other countries consider particle sizes of 25–30 μm to be acceptable. “The secret is making the size of the particles smaller than the distance between the papillae of the tongue, so that when you eat a chocolate you cannot feel the particles on your tongue,” says De Vuyst. The papillae are the tiny bumps on the surface of the tongue that contain the taste buds. On the other hand, particles must not be ground too small, or they will produce a dry feeling in the mouth.

The precise conditions for the next step in chocolate making, known as conching, are a carefully guarded secret at most Belgian chocolate companies. In the conching stage, a shearing device heats and thoroughly mixes chocolate for up to 78 hours. Unwanted flavors, such as the acetic acid produced during the cocoa fermentation stage, are removed by evaporation. Chocolate passes through three phases during the conching stage: dry, pasty, and liquid. “Belgian chocolate has become famous by the optimization of conching to drive off flavors we don’t want in the final chocolate,” says Adriaenssens. “The balance between dry and liquid conching develops the particular caramelized flavor of a good Belgian chocolate.”

Different conching procedures help distinguish the typical flavors of Belgian chocolate from those of its major competitor, Swiss chocolate. “Swiss milk chocolate is conched very liquid—they use almost no dry conching,” notes Adriaenssens. “That’s what makes Swiss chocolate milkier, less caramelized, and with a different body than Belgian chocolate.”

After conching, the chocolate is finally ready to be solidified into its final form, such as chocolate bars or chips. But to achieve chocolate that melts in the mouth and has a smooth, glossy finish, a crisp snap, and a long shelf life, chocolate makers must heat and cool the chocolate in a process known as tempering. At the microstructural level, chocolate consists of particles of sugar and cocoa solids embedded in a cocoa butter matrix. The cocoa butter can exist in six different crystal forms, designated by the Roman numerals I–VI. Each crystal form has a different melting temperature. Tempering forces the cocoa butter to adopt form V, which has the optimal melting temperature of 34–36°C. As a result, form V crystals remain solid at room temperature but melt in the mouth.

Tempering conditions depend on the type of chocolate, tempering equipment, and application, but in general the process involves cooling liquid chocolate from 45–50°C to about 25°C while stirring, bumping the temperature up to 30¬–32°C, and then cooling to the temperature at which the chocolate is poured into a mold and solidified. The first cooling step initiates mass crystallization of the cocoa butter. Then, by raising the temperature slightly, the less stable crystal forms melt, leaving primarily form V crystals. In the final cooling step, the form V crystals act as seeds or templates to drive further form V crystallization. As a result, the molded chocolate will consist mainly of form V crystals, which confer the desired textural and melting properties.

The fine art of pralines

After this lengthy processing from farm to factory, Belgian chocolate is finally ready to be packaged and sold. Belgian chocolatiers purchase chocolate bars and other products from industrial manufacturers such as Belcolade and Barry Callebaut, melt the chocolate, and retemper it. Then, they form it into pralines or other chocolates in a variety of shapes, from simple squares to hearts, seashells, and birds.

Chocolatiers continue to refine the art of making pralines, the Belgian specialty. The two classic methods for praline production are molding and enrobing. In molding, chocolatiers use a mold to create a hollow chocolate shell, insert a soft filling through an opening in the shell, and then cover the opening with a layer of chocolate. Although some chocolate makers continue to produce their molded pralines by hand, modern “one-shot processing” machines enable the simultaneous extrusion of the chocolate mass and filling into the mold. However, the filling must be viscous enough that it won’t mix with the chocolate shell during cooling. Praline manufacturers can temporarily increase the filling viscosity during processing by adding pregelatinized starch and malt extract to the filling. The starch thickens the filling during molding, whereas the malt extract contains starch-cleaving enzymes that make the filling more liquid during storage.

Enrobing is typically used for firmer fillings. In this method, a slab of filling is dipped in melted chocolate, coating the filling. Enrobing machines exist, but some artisan chocolate makers still prefer to enrobe their chocolates by hand. Although time-consuming, handmade Belgian chocolates fetch a premium price. Also contributing to a high-quality praline is the use of couverature chocolate for molding and enrobing. Couverture chocolate contains a higher percentage of cocoa butter (32–39%) than regular chocolate and is thus shinier, snaps more firmly when broken, and has a mellow, creamy flavor.

Praline fillings have evolved considerably since Neuhaus’ first simple creams, nougats, and ganaches. Traditional favorites such as caramels and hazelnut creams remain popular, but they have been joined by a dazzling array of flavors ranging from the expected (fruit, coffee, and flower essences) to the exotic (chili peppers, tomato-basil, and wasabi). Indeed, as a counterpoint to the traditionally sweet praline fillings, savory fillings with flavors of cheese, tomato, wine, even goose liver and seafood, are gaining popularity among praline-savvy Belgians.

Yet for many Belgian praline makers, the flavor of the chocolate itself remains the paramount consideration. Such is the case for Geert Decoster, artisan chocolatier and owner of Centho Chocolates in the village of Duisburg, near Brussels (Fig. 1).

Twelve years ago, Decoster was among the first to embrace an up-and-coming trend in the chocolate world: making chocolates with cocoa beans from one region, or sometimes even one plantation. Such “single-origin” chocolate has subtle flavors that reflect the unique cocoa tree variety and growing conditions of that particular region. In contrast, most industrial chocolate contains a mixture of beans, typically from countries in West Africa. Blending beans from different geographical regions ensures taste consistency and compensates for a bad growing season in any one region.

However, Decoster believes that blending sacrifices the unique character of cocoa beans from different regions. For example, Ecuadorian beans produce a fruitier-tasting chocolate, whereas beans from Papua New Guinea confer hints of mushroom and tobacco flavors. Decoster enjoys concocting praline fillings that perfectly complement the flavor of each origin chocolate. “The chocolate from Vanuatu, with hints of licorice and cinnamon, pairs well with a filling of good Scotch whiskey and pear jam,” he explains. Other tempting pralines from Centho’s large assortment include spicy Peruvian chocolate paired with a violet and raspberry filling, and earthy Ugandan chocolate harmonized with wild Tuscan fennel flowers and blood oranges.

For Decoster, chocolate making is a family affair. His business name, “Centho,” comes from the first three letters of his children’s names: daughter Centa and son Thomas. His small factory has only two employees, in addition to him and his wife, Els, who manages the retail shop. Nevertheless, Centho pralines have made their way into some of the finest restaurants and hotels in Europe, including London’s Ritz and Savoy hotels. “The reason we supply all the beautiful restaurants is because after dinner, there’s nothing as nice as a good praline,” says Decoster. “And when you have a small praline like ours, you can taste more than one.” At 8 g, Centho’s square-shaped pralines are diminutive compared with many of their competitors. “Here in Europe, the time of eating one big chocolate and then having enough is going away,” he says. “I see the young people loving a large assortment of smaller pralines.”

In 2009, Decoster brought a sampling of his chocolates to the Summer Fancy Food Show in New York City. “Everybody was crazy about our chocolates,” recalls Decoster. “Our chocolates were completely new for them because in the States, people are used to a bigger chocolate that is very sweet.” But even in Belgium, Centho chocolates are unique. “Everyone has two or three single-origin chocolates in his assortment, but we’re the only ones to have 40 different types of single-origin chocolates,” he notes.

Decoster’s innovative approach is typical for a country not prepared to rest on its chocolate-covered laurels. New technology now allows researchers to probe the science of chocolate making, with the potential to dramatically improve quality and shelf life. In 2009, the University of Ghent inaugurated the UGent Cacaolab, a small-scale experimental chocolate and fillings production facility (Fig. 2).

According to AOCS member Koen Dewettinck, food scientist and director of the facility, UGent Cacaolab researchers partner with industry to create innovative chocolate products, improve chocolate-making processes, and stimulate the export potential of Belgian chocolate. Current projects at UGent Cacaolab include efforts to improve the microbial resistance of water-based praline fillings, adjust the flow behavior of chocolate, and develop sugar-free dark chocolate. Another important focus of UGent Cacaolab is extending the shelf life of Belgian pralines, which are susceptible to a phenomenon known as fat bloom. This is a whitish-gray coating that forms on the surface of chocolate, typically after several months’ storage. Fat bloom is unattractive and gives chocolate a waxy texture.

According to AOCS member Dérick Rousseau, food chemist at Ryerson University in Toronto, Canada, fat bloom in chocolate occurs for three main reasons: improper tempering, temperature fluctuations during storage or in the hands of the consumer, and the migration of fats from a praline’s filling through its chocolate shell. At the microstructural level, fat bloom is associated with the transformation of form V crystals of cocoa butter into the undesirable, but more stable, form VI crystals.

“Regardless of how well you temper your chocolate, eventually the chocolate will transform to form VI because it’s the most stable,” says Rousseau. However, the consumer can hasten this process by subjecting the chocolate to temperature fluctuations, for example, storing chocolate in the freezer or moving it from an air-conditioned store to a hot car.

Rousseau has used scanning electron microscopy to show that the needle-like fat bloom crystals can grow from imperfections on the surface of the chocolate (Soft Matter 2008, DOI 10.1039/b718066g). This observation led Rousseau to hypothesize that channels in the chocolate serve as conduits for lower-melting triglycerides to rise to the surface of the chocolate and recrystallize, primarily into form VI. Therefore, minimizing surface imperfections on chocolate may help control fat bloom, he says.

Pralines are more susceptible to fat bloom than unfilled chocolates because their fillings often contain higher concentrations of specific triglycerides than their chocolate shell. As a result, these fats diffuse to the chocolate surface, transforming into form VI crystals. Because fat bloom is a major impediment to long-term storage, and thus export, of Belgian pralines, the UGent Cacaolab is working to produce fat bloom-resistant chocolates.

The early results are promising. Dewettinck’s group found that storing pralines at a cold temperature (4ºC or –20ºC) immediately after production decreased oil migration and fat bloom during later storage at a higher temperature (Eur. J. Lipid Sci. Technol. 2009, DOI 10.1002/ejlt.200800179). Cold storage therefore may cause favorable fat crystallization that leads to permanent microstructural changes.

Thus, the secrets of Belgian chocolate lie in a mix of quality ingredients, expert processing, centuries-old tradition, and a willingness to embrace new technology. But the importance of Belgians’ passion for chocolate cannot be underestimated. “Ever since I was a kid, I knew I wanted to make chocolate,” says Decoster. “I’m always thinking of chocolate. My brains are chocolate,” he jokes. Such dedication gives chocolate lovers the world over cause to celebrate—and what better way than with a fine Belgian chocolate?

Laura Cassiday is a freelance science writer and editor based in Hudson, Colorado, USA. She has a Ph.D. in biochemistry from the Mayo Graduate School and can be contacted at lauracassiday@yahoo.com.