Ed Yong investigates the parasitic threat to Ghana’s cocoa trees, while SciShow lays down some tasty scientific facts about chocolate. Read more
There are few things sweeter in life than chocolate, which is probably why it’s one of the most popular flavors in the world. We can thank the cacao trees (Theobroma cacao) for this gift, which are only grown within a region known as the Cocoa Belt, 10° to 20° north and south of the equator . Chocolate is produced from the seeds of the pods that grow from the cacao trees; these seeds are better known as cocoa beans.
Chocolate is a complex flavor, containing over 200 different flavor compounds . While the type and mixture of cocoa beans that go into a chocolate bar play a role in determining the final flavor, chocolate is the kind of food where its taste is influenced by how it’s made rather than what it’s made of . The chocolate-making process varies among types of chocolate (milk, dark, bittersweet, etc.), but also depends on the style of the chocolate maker. So while the general principles and chemical processes at each step remain the same, chocolate-making is a delicious art form.
Straight off the trees, cocoa beans are bitter. When cacao pods are harvested, they are cracked open and left to sit for a couple of days, depending on the tree varietal. (5–6 days for forastero versus 1-3 days for criollo .) This allows the cocoa beans to undergo fermentation, a process that is carried out by naturally occurring yeast and bacteria. During fermentation, the microorganisms digest the pulp in the pods, which aids in converting the sugars in cocoa beans into acids. These acids decrease the overall bitterness of the beans. Notable flavor compounds, such as pyrazines, are also generated during fermentation, making the beans slightly more floral in aroma . After fermentation, the beans are scraped from the pods to dry. Drying releases certain molecules from the beans that would otherwise make chocolate taste smoky and sour .
The dried cocoa beans now taste nutty, bitter, and acidic; to drive out volatile (easily evaporating) acidic molecules, the dried beans are further processed by roasting. The elevated temperatures of roasting (120–150°C) also facilitate Maillard reactions that yield flavor molecules that are distinct to chocolate . These reactions are sensitive to both temperature and pH, so both the roasting temperature and bean acidity contribute to the final composition of flavor molecules that form during these Maillard reactions. Typically, milk and certain dark chocolates are made from beans that have been roasted at lower temperatures . The shells of roasted beans are then removed, leaving behind pieces called cocoa nibs. Depending on the chocolate-maker, cocoa nibs may undergo alkalization, whereby they are treated with an alkaline solution in order to further decrease their acidity. Alkalization also causes flavonoids to polymerize (link together), which reduces the astringency of the nibs .
The final phase in chocolate manufacturing is a two-step process known as conching. At this stage, the nibs have a gritty texture; the first step in conching turns this into a paste through grinding and heating. Acidic compounds and water are evaporated in this process. More importantly, many flavor compounds formed during fermentation and roasting that are responsible for astringent and acidic notes become oxidized during conching, which mellows the flavor of the final product . In the second step, cocoa butter and soy lecithin are added, decreasing the viscosity of the chocolate mixture to make it flow more easily.
Cocoa beans go through quite a long journey, from the cacao tree to the candy wrapper, where each step plays a role in producing the final combination of flavor molecules that makes chocolate such a beloved treat. This is just one of many reasons to savor your next taste of chocolate.
- “Cacaoweb.” About the Cacao Tree and Cacao Varieties. <http://www.cacaoweb.net/cacao-tree.html>.
- Afoakwa EO, Paterson A, Fowler M, Ryan A. Flavor Formation and Character in Cocoa and Chocolate: A Critical Review. Critical Reviews in Food Science and Nutrition. October 2008; 48(9): 840-857, DOI: 10.1080/10408390701719272.
- Schieberle, P. and Pfnuer, P. Characterization of Key Odorants in Chocolate. Flavor Chemistry: 30 Years of Progress. 1999: 147–153, DOI: 10.1007/978-1-4615-4693-1_13.
- Ziegleder G, Biehl B. Analysis of Cocoa Flavour Components and Precursors. Analysis of Nonalcoholic Beverages: Modern Methods of Plant Analysis. 1988; 8: 321-393.
Local grower Alex Weiser stopped by the 2013 Science & Food course discuss all things potatoes and parsnips. We heard all about Weiser’s experimental plant varieties (Laker Baker, anyone?) and even learned why parsnips always taste just a little bit better in the winter. Check out the highlights:
Astronauts grow veggies in space, while Earth-bound scientists uncover a genetic clue that could lead to tastier tomatoes. Read more
Alex Weiser of Weiser Family Farms is a grower of specialty fruits and vegetables in Kern and San Bernardino counties. You can find Alex and his produce at farmers’ markets across Southern California.
- What hooked you on farming?
- Father and mother
- The coolest example of science in your produce?
- The creation of it from seed!
- The produce you find most fascinating?
- Romanesco cauliflower
- What scientific concept–food related or otherwise–do you find most fascinating?
- Your best example of a food that is better because of science?
- How do you think science will impact your world of food in the next 5 years?
- There will be a lot of new biological tools available to farmers
- One kitchen tool you could not live without?
- Toaster oven
- Five things most likely to be found in your fridge?
- Citrus, potatoes, butter, pickles, broccoli
- Your all-time favorite ingredient?
- Favorite cookbook?
- Santa Monica Farmers’ Market Cookbook
- Your standard breakfast?
- A large coffee and seasonal fruit
Given the popularity of cheese and the seeming ubiquitous goal towards eating less fat, it is no surprise that reduced- and low-fat cheeses have great market potential. Though as many cheese companies have discovered, reducing the amount of fat for the sake of fewer calories sacrifices that rich, bold, creamy flavor of cheese. Fat is a major contributor to taste and mouthfeel of foods, and many cheeses are considered high-fat foods. But how exactly does fat content influence cheese taste and texture?
In cheesemaking, the process of converting milk to cheese alters the structure and composition of milk, essentially reducing it to a concentrated form of milk fat and casein, a major milk protein. Casein forms a protein matrix that traps fat and water, giving cheese that soft, moist texture we expect . Full-fat cheeses typically have a casein-to-fat ratio of less than one, meaning there is a higher concentration of fat compared to casein in the cheese. Because fat is a nonpolar biomolecule, the greater fat content, locked within the casein network, gives rise to a predominantly nonpolar cheese matrix.
By definition, reduced-fat cheeses have at least 25% less fat than their full-fat counterparts and low-fat cheeses have 3g of fat or less per serving (21 Code of Federal Regulations [101.62b]), which is roughly around an 80% reduction or greater, depending on the type of cheese. To accomplish this, lower fat milks, such as skim milk, are used to produce the lower fat variants, which have a casein-to-fat ratio greater than one [1,2]. With less fat, the casein networks form a tighter matrix that gives rise to firmer cheese . To replace the fats removed from the cheese matrix and to soften the texture, water is typically added back into the cheeses . Water is a polar molecule, so by increasing the moisture this way, the cheese matrices of reduced- and low-fat cheeses are more polar, unlike the nonpolar matrices of the full-fat cheeses.
Comparing the casein-to-fat ratios of different cheeses gives insight into more than simply cheese composition—the ratios signify how we taste the cheese. When a piece of cheese is ingested, it increases in temperature in our mouth and dissolves with saliva, transforming from a semisolid to a liquid. In addition to textural changes, aromatic flavor compounds are also released during this phase change . The rate at which these compounds are released is determined by their partition coefficient, which is the concentration of the aromatic compound in its gas form compared to its concentration in its liquid form . Whether the flavor compound is in a polar versus a nonpolar matrix can influence the partition coefficient, altering the timing of their release and ultimately, our sensory perception of the flavor . Many flavor compounds found in cheeses happen to be fat-soluble, meaning they can mix with other nonpolar substances without separating into two layers. Considering that lower fat cheeses have prevalently polar matrices, the way the flavor compounds interact with the cheese matrices differs significantly enough to change flavor-release patterns. This is what causes some reduced- and low-fat cheeses to taste “off” compared to full-fat cheeses.
Fat reduction also modifies the cheese biochemistry. Through analysis of full-fat cheese versus 75% reduced-fat cheese, it was found that different sets of flavor compounds are critical for the cheesy flavor of the two types of cheese . When certain flavor compounds characteristic of full-fat aged cheddar were added to reduced-fat young cheddar, tasters scored the two cheeses similarly . So take heart, cheese-lovers. Reduced-fat cheeses certainly do have the potential to be healthy and delicious.
- Banks, J. M. (2004). The Technology of Low-Fat Cheese Manufacture. International Journal of Dairy Technology, 57(4), 199-207. doi:10.1111/j.1471-0307.2004.00136.x
- Impact of Fat Reduction on Flavor and Flavor Chemistry of Cheddar Cheeses. (2010). Journal of Dairy Science, 93(11), 5069-5081. doi:10.3168/jds.2010-3346
- Kim, M. K., Drake, S. L., & Drake, M. A. (2011). Evaluation of Key Flavor Compounds in Reduced- and Full-Fat Cheddar Cheeses Using Sensory Studies on Model Systems. Journal of Sensory Studies, 26(4), 278-290. doi:10.1111/j.1745-459X.2011.00343.x