Molecular Cuisine: Considering the Chemical Senses in Culinary Practice
Pt. 2 – Tasting – with your nose?
In order to understand the techniques molecular chefs use to develop flavor, “flavor” must be properly defined. In laymen’s terms, “taste” and “flavor” are considered interchangeable. Such is the same in traditional cooking. In neuroscience and molecular cuisine, however, these terms are distinct. “Taste” involves only the stimulation of taste receptors and their subsequent projections to higher processing. Taste receptors detect the sweet, sour, bitter, salty, umami (savory), and possibly, fatty qualities of different stimuli. In contrast, “flavor” is a unitary perception deriving from all the sensory modalities, though primarily olfaction and gustation (St. John & Boughter, 2008). “Taste” therefore functions only as a contributor to greater “flavor” perceptions, and not even the main contributor at that.
Most of what people generally label as “taste” is actually contributable to our sense of smell. This relationship becomes apparent when your food seems bland when you come down with a cold. The confusion arises from the assumption that the sense of smell detects only chemicals in our external environment, while taste encompasses all the sensations that take place in the mouth. In actuality, smell operates in two modalities. The more readily recognized modality is orthonasal olfaction, which occurs when volatile chemicals reach the olfactory receptors via the action of sniffing. Retronasal olfaction, contrastingly, occurs when volatiles are delivered to the olfactory receptors via the nasal passages at the back of the mouth. Retronasal olfaction is the modality key to flavor perception and often confused with taste (Noble, 1996) This is because olfaction’s dual modalities operate under different neural pathways. Orthonasal olfaction is consequently associated with the external environment and retronasal with the internal, though the volatiles being detected might be the same (Rozin, 1982). Additionally, taste-aroma interactions only occur in conjunction with retronasal olfaction, resulting in unitary flavor percepts that are mistakenly attributed to taste (Noble, 1996).
Molecular chefs use retronasal olfaction as a means to enhance the flavor of their dishes. They use various techniques to aromatize their food, including one called “vaporization.” This is a method of distilling essential oils from foods in order to capture their characteristic scents. Vaporizers heat food gently through the controlled application of hot air. Volatile compounds evaporate quickly and are less dense than non-volatile compounds, and so are released and rise as the food is heated. The “pure aromas” are then captured in a holding receptacle like a bag or balloon (Sosa Ingredients). Chefs use vaporization to infuse foods and beverages with flavor. They might do this to supplement a flavor that is lost in cooking a product, to avoid introducing displeasing textures to a dish, or to emphasize an easily overpowered flavor. They can envelop foods in vapors while they cook or bubble vapors through liquor and stocks. With the help of egg white protein and Xanthan gum, they can even craft bubbles of vapor to be suspended in syrups and juices (Vaporization, 2012).
Studies have found that retronasally perceived scents enhance the perception of congruent tastes. For example, strawberry scent enhances sweet tastes while peanut butter scent does not. Vaporization techniques can therefore be used to enhance certain taste qualities within a dish (Noble, 1996). Depending on what volatiles are applied, the same dish could be perceived as either a savory main course laden with umami or a tantalizingly sweet dessert. An opportunity exists to disrupt diners’ expectations of flavor by pairing this concept of congruency with a dish’s visual presentation. Imagine being presented a dish that appears to be a savory side of roasted parsnips. Unbeknownst to you, however, the parsnips have been infused with the volatiles of apricot and guava. The scents emphasize the sweetness of the parsnips, and you therefore perceive the dish as a fruity, sweet dessert. This juxtaposition of expectation and reality helps create a much more stimulating dining experience (Vegetable Desserts, 2015).
Rotary evaporators (known recreationally as “rotovaps”) perform a similar distilling function to vaporizers in that they separate food compounds based on their volatilities. Rather than keeping the essential volatiles in a vapor state, however, rotovaps condense them back into liquid form. This device is able to distill solvents efficiently without applying enough heat to alter their chemical composition. The solvent is placed in a heated bath in a rotating flask, which increases its surface area. This promotes speedy, even evaporation. In addition, the distillate is removed to its cooling chamber via a vacuum, effectively lowering the solvent’s boiling point and reducing the heat needed to evaporate it (Arnold). Molecular chefs use rotovaps to capture the “pure flavors” of food in order to apply them without using the food itself. They often use this technology to craft their own custom food extracts and essences, which tend to be much more concentrated than commercially produced products.
As the aromatics extracted during this process tend to be hydrophobic, they are more apt to vaporize when distilled in water. Consequently, chefs often use alcohol when using rotovaps, as the hydrophilic ethanol retains the infused aromatics more effectively than water (Matson, 2011). Thanks to this practice, rotovaps are very popular in “molecular mixology.” For example, influential molecular chef Dave Arnold uses a rotovap in making his signature take on a gin and tonic, which takes the G&T’s classic flavors and concentrates them a thousand fold (Allen, 2008). Todd Maul of the restaurant Clio uses a rotovap to infuse vodka with the aromatics usually found in gin, such as juniper, coriander, and angelica root (Mennies, 2011).
One of the most exciting applications of rotary evaporators, vaporizers, and similar technologies is infusing flavors into products where they previously couldn’t exist. For instance, the flavor of chili can now be applied to dishes without its accompanying burn of capsaicin. Perhaps most compelling, though, is that the aromas of non-foods can now be applied to dishes. The signature dish at El Celler de Can Roca, “mar y montaña” (“sea and mountain”), applies this methodology. In this dish, oysters float in a sauce made by thickening a distillate of soil with xanthan gum. Described as a “modernist surf n’ turf,” this dish brings the familiar scent of the earth into new context and pairs it with a familiar flavor from the sea (Villeneuve, 2011). The application of non-food aromas to food can serve to deepen a diner’s sensory perceptions of a meal, exciting more and different neural pathways than the food could alone. Olfactory projections to higher processing centers, namely those downstream of the piriform cortex (or “primary olfactory cortex”), are highly associated with memory and affective learning. The application of particular odorants to food can therefore elicit recollection of experiential or emotionally arousing memories. These memories create a context for the dish, thereby elevating the dining experience beyond flavor perception and propelling it into the realm of storytelling (Gottfried, 2010).