Series on Molecular Cuisine – Pt. 3

December 15, 2015

Molecular Cuisine: Considering the Chemical Senses in Culinary Practice

Pt. 3 – All in Good Taste

 

While olfaction contributes considerably to flavor perception, gustation’s contributions obviously cannot be dismissed. The five, possibly six, different taste qualities serve to signal the health benefits (or lack thereof) contained in different foods. For instance, sweet tastes are evoked by mono- and disaccharides and therefore signal high calorie foods. Animals prefer specific concentrations of salt that optimally maintain osmotic balance, electrical conductance of neural and muscular circuits, and other homeostatic and physiological processes. Umami (savory) tastes are evoked by L-amino acids, which may signal the presence of protein. Animals typically avoid sour and bitter tasting foods due to their potentially harmful pH levels and alkaloidal toxins, respectively (St. John & Boughter, 2008). Molecular chefs are striving to better understand the functionality of taste and its relation to the chemical composition of foods. This knowledge allows them to effectively customize diners’ taste perceptions from the ground up.

 

Umami, the so-called “fifth taste,” has long interested chefs and neuroscientists alike. It was previously thought of as a “taste modifier” rather than a taste in itself, as it intensifies saltiness and sweetness while weakening bitterness and sourness. It has since been found to be detected by a specialized G-protein coupled taste receptor. This receptor detects both basal and synergistic umami, signaled by the amino acid glutamate and nucleotides, respectively. Glutamate is present in some fresh foods but is more known for forming during protein degradation. Fish sauce, marmite, miso, prosciutto and other foods manufactured through processes of fermentation and aging are subsequently very high in umami (Adams, 2015). Many molecular chefs experiment with fermentation in a quest to draw the most umami from their ingredients as possible. Noma, the restaurant named “world’s best” four years out of the last six (World’s 50 Best Restaurants), dedicates a large portion of its research lab to fermentation experiments. The facility is outfitted with precise climate controls which allow for the tightly regulated fermentation of peas, egg yolks, fennel, vinegars, beef trim, grasshoppers, and any number of other ingredients. Noma’s goal in this is to discover new sources of umami to utilize in dishes (Dixler, 2014).

 

Food scientist Akira Kuninaka discovered how to add umami to foods outside of processes of fermentation. He found that the interaction between glutamate and various nucleotides is responsible for the deep umami sensation elicited by certain foods. Specifically, the interaction of glutamate with adenylate, guanylate, and inosinate intensifies the umami taste of food dramatically. Umami can therefore be enhanced through a methodology of food pairing. Dishes simply need to be structured around pairing glutamate-rich food with foods rich in adenylate, guanylate, or inosinate. For example, cooked potatoes are high in both glutamate and guanylate. When paired with seafood, which is rich in inosinate and adenylate, boiled potatoes can be transformed into an incredibly savory broth (Adams, 2015).

 

In their quest for umami, molecular chefs try to greatly enhance a perceived taste quality by altering a food’s chemical composition. Along a similar yet opposite vein, some chefs are trying to reduce certain taste qualities inherent in foods by the same methodology. Here we return to the labs of Noma, where they are developing a process to “de-bitter” foods. To reiterate, alkaloids elicit bitter sensations via G-protein coupled receptors. Bitterness often initiates aversive or negative hedonic reactions, as many toxins are alkaloids. In de-bittering foods, researchers at Noma are attempting to balance the pH of bitter foods to achieve a more pleasant taste perception. They have generated results using a Native American technique for cooking maize called “nixtamalization.” In this process, corn is cooked in a highly alkaline solution of ash and water. This breaks down the corn’s cell walls, releases nicotinic acid (vitamin B3) and other nutrients, and reduces the number of mycotoxins significantly (World Heritage Enclyclopedia). Noma chefs successfully de-bittered yeast extract and endive juice using this alkaline solution and are looking to apply it to other products (Williams, 2012).

 

While olfaction has stronger influence over taste perception than vice versa, gustation does have the ability to enhance congruent olfactory percepts. In a study by Pam Dalton and colleagues, participants were asked to sniff a cherry-almond scented solution. When holding a sub-threshold concentration of saccharin on their tongues, the participants rated the intensity of the solution to be significantly higher. This increased intensity was not reported by participants holding glutamate on their tongues. This can be attributed to cherry-almond scent often being paired with sweet tastes, and therefore the sensation of one increases perception of the other. In later studies, these congruency effects were found to correlate to superadditive activation of the orbitofrontal cortex, where olfactory and gustatory projections terminate. The activation of the OFC is related to hedonic and food reward values and is therefore very important to the enjoyment of food. Molecular chefs take advantage of this neurally coded relationship with taste/smell pairing strategies as described previously.

 

There was a second aspect to Dalton’s study, however, that molecular cuisine has yet to adequately take into account. The study contained a significant cross-cultural angle which demonstrated the importance of associative learning in flavor perception. While western participants showed perceptual enhancement in the saccharin condition, Japanese participants did so in the glutamate condition. The Japanese participants were accustomed to consuming almonds more often in savory, pickled dishes and so perceived glutamate-taste and almond-scent as congruent. There is evidence that this type of perceptual learning begins in utero, crafting diners’ flavor preferences, perceptions, and expectations before they even exit the womb (Spence, 2015). This means that, even if a molecular chef deliberately designs every chemical component of a dish, each individual who eats it will have a totally different sensory experience.

 

It will be a continual challenge for molecular chefs to take this information into account as they craft menus for their diners. This challenge falls under a larger umbrella of challenges facing molecular cuisine. Molecular chefs have begun to understand how chemical stimuli are detected by our senses and perceived by higher cognitive centers. Now, they must consider their diners’ hedonic responses to those stimuli. Congruency effects represent a facet of this task. The phenomenon of sensory specific desire (SSD) is another element to consider. SSD is related to sensory adaptation, where the neural response to a constant stimulus changes over time. In this instance, neural response to a specific taste quality decreases while responses to other tastes remain robust. For instance, after consuming a sweet food to satiation, adults’ desires for sweet foods decrease (Olsen et al, 2011). Understanding SSD could help molecular chefs plan their menus, in such that each dish’s taste qualities could be enjoyed to their full potential.

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