What Determines Chocolate flavor?
Over 700 different compounds have been identified in cocoa, including fatty acids, amino acids, flavonoids, sugars, terpenoids, and more. Some are tasteless, but many contribute to the rich spectrum of flavors that we experience, ranging from delicate and nutty to tangy and fruity to woody and earthy.
The compounds responsible for the flavors in finished chocolate originate in the raw bean, and are determined by the genetics of the tree, management practices such as harvest time, and terroir, the unique local environment. Though management and terroir affect what compounds end up in the beans, the possibilities are ultimately bounded by the biochemical limitations of the plant. These compounds are modified significantly during drying, fermentation, roasting, and conching, which is why expert handling and processing are essential for good chocolate regardless of how good the beans are. The flavor can also be affected by conditions during transport and storage of the beans and the finished product, as odors from jute sacks, wooden crates, and truck exhaust can be absorbed by the beans. Continue reading for a more in-depth discussion of the determinants of chocolate flavor.
Cacao has been cultivated for thousands of years, and throughout this time varieties were selected for flavor as well as traits like adaptability to a range of growing environments in South and Central America. In recent times, intensive breeding efforts selected for high yields and disease resistance with little focus on flavor. Today, hundreds of different cultivars are grown around the world to meet diverse demands for flavor profile, yield, and hardiness. Though far from being the final determinant, the variety of cacao does determine the potential range of chocolate flavors. For example, Porcelana criollo cacao has light-colored beans and an inherently mild, delicate flavor. Its genes dictate production of a suite of flavor molecules and precursors with pleasant nutty flavors and fewer bitter and astringent compounds. It’s fine flavor could be ruined by poor handling, but the potential is there. On the other hand, CCN-51, a very high-yielding, disease resistant hybrid produces chocolate with a flavor that has been described as “acid dirt.” It could be handled and processed perfectly, but due to its genetics it will never taste like Porcelana. Other distinctive varieties include Ecuadorian Arriba Nacional, a handful of varieties formerly classified as forastero, such as Amelonado, and several other criollo strains.
The growing environment – soil, rainfall, temperature, season, and nearby crops – can significantly influence the flavor of the beans, as can the care they receive from farmers. We don’t yet fully understand how these factors shape the flavor of cacao, but there is at least some evidence that growing environment has significant effects on astringency, bitterness, fruitiness, and other flavors in processed cocoa beans. Different varieties of cacao may also be affected differently by the growing environment with regard to acidity, bitterness, and fruity, floral, and other flavors. Fermentation also reflects terroir, and the same cacao beans fermented at different locations may have distinct flavor profiles – perhaps due to differences in the local microbial communities.
For more information on terroir as it applies to cacao, see Evidence for applying the concept of “Terroir” in cocoa (Theobroma cacao L.) flavour and quality attributes, presented by Darin A. Sukha, Pathmanathan Umaharan, and David R. Butler at the 2017 International Symposium on Cocoa Research (ISCR), held in Lima, Peru from 13-17 November 2017. Download for free here.
Harvest timing is particularly important. Cacao needs to be harvested when ripe so that the sugar content is right for fermentation. Underripe cacao can taste sour, vegetal, and astringent, and overripe cacao can taste like overripe fruit. The pod needs to be opened carefully as well. If beans are cut or smashed, off flavors from damaged beans can affect the final flavor.
Fermentation is perhaps the most important processing step, arguably more important even than roasting. One can make chocolate with a good, though not fully developed flavor from well-fermented, unroasted beans (Raaka makes a nice selection of unroasted bars– I was pleasantly surprised) but you cannot make good chocolate from beans that were unfermented or poorly fermented regardless of how well they are roasted.
Fermentation takes place immediately after the beans are harvested and removed from the pods. Traditionally, beans are heaped up or placed in baskets and covered with banana leaves. On a larger scale, beans are often placed in wooden or plastic boxes, again covered with banana leaves or cloth. The materials used to hold the beans can affect the flavor, contributing woody, vegetal, or plastic flavors.
There are two phases of fermentation, anaerobic (without oxygen) and aerobic (with oxygen). During the anaerobic phase, the juicy pulp surrounding the beans provides food for yeasts which convert the sugars into ethanol. Some anaerobic bacteria will convert ethanol into lactic acid. Over the course of the first day, the juice starts to drain away, allowing more oxygen into the beans. Turning or mixing the beans aids this process. By the second day, more aerobic bacteria will be active, converting the ethanol into acetic acid. If the beans tend to be very acidic, some of the pulp can be drained away before fermentation to reduce the amount of acetic acid produced. The beans can be turned multiple times to aerate the pile and increase aerobic microbial activity.
Fermentation also releases significant amounts of heat, which along with the acidity kills what was until that point a viable seed. This is essential for the development of the characteristic chocolate flavor, as it initiates a cascade of chemical reactions including enzyme activity, oxidation, and protein breakdown. For example, the caffeine content is reduced during fermentation, which makes the beans less bitter. Fermentation also decreases astringency, the sensation of dryness or roughness in your mouth. This is caused by chemicals known as tannins, found in foods like red wine, strong black tea, walnut skin, or unripe bananas in addition to cacao. Beans that were not fermented long enough can have lingering green, raw, bitter, and astringent flavors that persist in the final product. Over-fermented beans can have odd meaty and hammy flavors, overripe fruit and flower notes, or mold. Forastero variety beans, which tend to have stronger flavors, are typically fermented for 5-7 days, while criollo beans, with more delicate flavors, are usually fermented for 2-3 days.
Once the fermentation is complete, beans must be dried before they can be shipped or ground into cocoa mass. Some of the oxidation reactions that began during fermentation continue during drying, so the flavor will still be developing. Drying the beans too quickly, as sometimes happens in very warm, sunny climates or gas-powered driers, can result in a sour flavor. The acetic acid produced during the fermentation needs time to evaporate, and if the outside of the bean dries very fast, it can trap excessive amounts of acetic acid and lead to a sour bean. On the other hand, beans dried too slowly can develop musty flavors or even mold. Sometimes, in humid, rainy regions such as Papua New Guinea, beans are dried with heat from fires to avoid molding. This can have the adverse effect of imparting a smoky flavor to the beans. In other cases, beans are spread on less than ideal surfaces, such as asphalt roads, to dry. The beans can absorb tarry, petrol, and other unpleasant odors.
The best method is gentle sun drying, possible in warm climates without excessive rain. Beans can be spread on clean surfaces – tarps, tables, concrete patios – and left to dry for several days until the moisture content reaches 6-7%. If it is very hot, beans may be spread out in the morning, brought in during the peak midday heat, and returned to the drying area in the afternoon. This ensures that they dry quickly enough to avoid mold, but slowly enough to let acetic acid evaporate.
Sorting, Cleaning, and Grading
Inevitably, every batch of beans will end up with a few twigs, stones, or odd beans. Sorting is essential to ensure that anything other than top-quality cocoa beans is removed. Extraneous plant material can add undesirable woody and earthy flavors to the chocolate, or burn during roasting, leading to smoky, burnt flavors in the beans. The photo below (right) shows different beans from the same batch of Ecuadorian cacao. Clockwise from top left, you can see a range of bean sizes, a bean with white streaks indicating internal mold, two beans with desirable levels of fermentation, an over-fermented bean (note the very dark color) and a bean with a flat bean stuck to it. Sorting helps ensure standard sizes - the different sized beans here would roast unevenly - and remove beans with stuck-on material that can burn. Grading with a cut test (below left), a tool that slices a sample of beans neatly in half, allows the handler to determine the incidence of mold in the batch as well as the level and evenness of the fermentation.
Roasting is a key point for flavor development. Roasting temperatures between 240 and 280˚F allow for chemical reactions that develop flavor while preventing burning. Many types of flavor-forming chemical reactions can only occur at these temperatures – that’s why cooked food is, in general, more flavorful than raw food.
Each type of bean and even different batches of the same variety can have different ideal roasts to bring out the best flavors. Proper roasting develops the satisfying deep chocolate and coffee-like roasted notes and enhances the more delicate fruit and nut flavors without destroying them. Slight over-roasting will result in one-dimensional, bitter flavors, and serious over-roasting will just taste burnt. On the other hand, under-roasted beans can taste raw, vegetal, and astringent.
One of the reasons many people don’t like dark chocolate is that mass-market dark chocolate is usually over roasted and bitter. This is done partly on purpose to hide defects in poor quality beans and is partly inevitable because different varieties of beans with different ideal roasts are all mixed together, so some end up over-roasted. You might be surprised at the lack of bitterness in properly roasted high-quality dark chocolate, even those with a cocoa content over 75%!
Once cocoa beans are roasted, they can be ground to make cocoa mass, also known as cocoa liquor. This thick paste can be sweetened to make a coarse-textured chocolate or put in a conching machine or melangeur for further refining. These machines work by very gently heating the cocoa mass and grinding the particles to an extremely fine texture over a long period of time – at least eight hours and as long as 72. Typical conching times are around 24 hours. Conching can help evaporate any remaining acetic acid, mellow out other flavors, and create a smooth texture. However, conching for a very long time can result in the loss of interesting nuances and chocolate that is blander, albeit very smooth and generally agreeable. Think Swiss milk chocolate.
Sugar is usually added during the conching step to ensure that it is ground to a smooth texture. The flavor of the sugar and any imperfections in it will be transmitted to the chocolate. Pure refined cane or beet sugar provide sweetness with nearly no additional flavors. Unrefined cane sugar can impart a molasses-like flavor or a grassy taste. Less common sweeteners like maple sugar or coconut might be chosen to complement the flavor of the chocolate.
Cocoa butter is commonly added to decrease the viscosity of the melted chocolate, which makes it easier to work with. A small amount of good cocoa butter may have a minimal impact on the final flavor, but it can also dull the flavors of the chocolate and poor-quality cocoa butter can add a stale cardboard flavor.
The milk powder used in milk chocolate can add pleasant milk, cream, and buttery flavors, as well as stale or rancid flavors if it is of low quality. Non-traditional milk powders such as goat’s milk can add a pleasant tanginess.
Vanilla is a common addition to chocolate and is usually not a good sign. Vanillin, a synthesized version of the main flavor molecule of vanilla, is often added to cover up poor flavor in cheap chocolate. Some high-quality chocolates add real vanilla to complement the cocoa, and while it is a nice combination most craft chocolatiers leave the cocoa beans as pure as possible. My feeling is that great chocolate should be left to speak for itself.
Mass-market chocolate often has other ingredients added to stretch the cocoa beans and hide flavor defects. Small amounts of soy lecithin (0.5 – 1% ) are added to reduce viscosity and make melted chocolate easier to work with. Some experts say that it can dull the flavors of the chocolate and high-quality chocolates rarely contain it. Non-cocoa fats such as vegetable oil, shortening, or butter oil may be used as cheap substitutes for cocoa butter. The texture is inferior and seeing these ingredients on a package is a sure sign that the cocoa beans are too. Some products may also contain 'natural and artificial flavors,' which is an insult to cacao.
Transport and Storage
At any point in the supply chain, cocoa beans or finished chocolate can be contaminated with flavors or odors from shipping containers, water that gets though jute bags, exhaust fumes from transport vehicles, mold from improper storage conditions, or strong smells from other food stored nearby. Cocoa beans and chocolate are high in fat, which tends to absorb flavors and odor well – think of unwrapped butter in the fridge. Cocoa beans need to be transported carefully and stored at the appropriate temperature and humidity, and finished chocolate should be sealed against air and moisture and eaten soon after production.
As you can see, many factors impact the final flavor of chocolate. Genetics, fermentation, and roasting are particularly important, with major effects from drying, proper handling, and conching as well. Understanding the determinants of chocolate flavor will help you better appreciate them and the expertise of growers and makers of fine chocolate.