The Foodpairing® team has developed a system for classifying scents based on aroma types and their descriptors. With this ‘language of scent,’ we can describe and create visualizations for the aroma profiles of all the ingredients and products we encounter in our daily lives.
From 10,000 different aroma molecules to 14 aroma types and 70 descriptors
To visualize the aromatic links between different odorants, we created a virtual three-dimensional space to model the connections between all 10,000 aroma molecules in the Foodpairing® database. The dense perceptual web reveals striking similarities between certain clusters of molecules, some of which we split into separate groupings such as green and vegetal. Altogether, we have identified 14 separate categories of aroma types that we use to describe the broad range of scents found in the aroma profiles of different ingredients.
These aroma types have been further divided into subcategories of descriptors according to the base scent of each molecule.
Every aroma molecule has its own distinct base scent. For instance, pineapples contain methyl-hexanoate, an odorant with a base scent that smells like the fruit. After analyzing an ingredient, we look at which volatile compounds register above the odor recognition threshold and then identify the base scents of the various aroma molecules so that we can assign the individual molecules to the appropriate descriptor groups. The descriptor labels tell us about the base scent of an aroma molecule. So when we use the label ‘pineapple’ as a descriptor, it means that all of the molecules within that descriptor group have a distinct pineapple smell. Within the fruity aroma type, you’ll find descriptors like ‘pineapple,’ apple,’ ‘banana’ or ‘tropical.’ Altogether we have identified a total of 10,000 aroma molecules that we’ve classified into 14 different aroma types and 70 descriptors in the Foodpairing® database.
Fruity: Esters play a key role in the aroma profiles of many fruits such as strawberries, bananas, pineapples and other tropical fruits. Depending on the concentration, lactones can have a peachy or coconut smell and are found in fruits, milk, cheeses and other dairy products.
Citrus: Lemons, limes, grapefruit and gooseberries contain mostly citrusy notes, which are also present in other less obvious ingredients like coriander seed, lemongrass and lemon balm.
Floral: Beta-damascenone, beta-ionone and (Z)-1,5-octadien-3-one are responsible for the intoxicating fragrances of roses, violets and geraniums, while also lending their floral notes to ingredients like apples, pears, raspberries and sweet potatoes.
Green: Green descriptors can range in smell from cucumber-ish to fatty (olive oil), like freshly mown grass or even waxy (orange peel), depending upon the specific concentration of aldehydes. Metallic:Epoxides like trans-(E)-4,5-epoxy-2-decenal give seaweed its metallic flavor. Milled grains also contain green volatile compounds that smell like oat flakes.
Vegetable: Pyrazines, 1-octen-3-one and methianol are largely responsible for the vegetal odors of bell peppers, mushrooms and potatoes, respectively. Alliums (e.g. onions, garlic, leeks, etc.), cabbage and other Brassicaceae contain a separate category of sulfurous volatile compounds. However, the process of cooking vegetables, seafood and even meat creates new sulfurous, potato and mushroom-scented aroma molecules that form as the Maillard reaction occurs.
Herbal: Menthol and thymol give fresh mint and thyme their distinct herbal notes.
Caramellic: Compounds like furaneol, maltol and sotolon are characterized by the sweet caramellic smell of caramelized sugar and maple syrup.
Roasted: The Maillard reaction causes new volatile compounds to form that smell roasted or popcorn-like. Some roasted descriptors smell malty or coffee-like, whereas pyrazines and geosmin have more of an earthy scent.
Nutty: Benzaldehyde is the character impact compound in almond extract, while the intoxicatingly sweet hay-like fragrance of tonka beans comes from coumarin. Ketones provide hazelnuts with their distinctive smell.
Spicy: Many of the warm notes in spices come from aroma molecules like cinnamaldehyde, cuminaldehyde, eugenol (cloves) and vanillin, whereas camphor and estragole (anise) offer more refreshing notes.
Woody: Some ingredients contain woody-scented terpenes and pinenes (pine). Using wood to grill meat, fish or any other ingredients will impart the same woody, smoky flavors, whereas the process of cold-smoking fish or meats infuses their flesh with phenolic compounds.
Cheesy: Cream, butter and ripe cheeses all contain cheesy notes. Vinegars and fermented dairy products like yogurt, buttermilk and sour cream contain other cheesy and acidic volatile compounds.
Animal: Descriptors like meaty, fishy and animal-like describe the strong odors associated with meat-based stocks and ingredients like venison, cooked liver and fish. Liver contains the aroma molecule, indole, which can smell animal-like, fecal, earthy, phenolic, perfumy or even floral, depending on the intensity. Skatole has a similar animal-like odor that is often described as smelling fecal or like a civet.
Chemical: Burnt, musty, petroleum, soapy and solvent (e.g. paint or glue) are some of the descriptors used to describe the undesirable off-odors that develop as a result of improper storage or poor packaging.
Aroma wheel visualization
The Foodpairing® aroma wheels are visual representations of different ingredients’ unique aroma profiles. Below you’ll see an aroma wheel of Bourbon vanilla.
The aroma wheel consists of 2 separate rings. The inner-circle shows all 14 aroma types. From here, the present aroma descriptors show the aroma profile of the ingredient in the outer circles. If an aroma type is not found in the profile, it will be grayed out.
The width of the band in the outer circle indicates the intensity of that particular descriptor in the flavor profile. The distance between a certain aroma type and its associated descriptors, connected by a wavy band, reflects the intensity of this particular aroma type in the aroma profile.
In the case of vanilla, vanillin is the key aroma molecule determines the aroma of the spice. In most cases the profile looks much more complex, like the strawberry pictured below. At least five groups of aroma molecules contribute to the fruity fragrance of strawberry: coconut-smelling lactones, fruity esters, aldehydes with a green scent, caramellic furanones and cheesy acids.
In the aroma wheel above, we see that the fruity aroma type is the most important type in strawberry. They are therefore furthest away from the inner circle. The green, nutty and citrus aroma type follows in rank. Within the fruity aroma type, the descriptor tropical has the highest intensity (thickest band), followed by fruity and pineapple.