Why do flavors feel warming or cooling?

Ioana Weber

PhD Student, AG Tarabykin

Why is Pumpkin Spice a Warming Flavor?

As October draws near, I brace myself for the flooding of popular and social media with Pumpkin Spice-flavored Everything. Yes, this happens even in a country such as Germany, which doesn’t have that US-grade historical craze fondness for cucurbitaceae. So what is it in pumpkin spice that makes us feel all warm and fuzzy inside? Moreover, why do we, in general, consider some flavors warming whereas we think of others as refreshing?

Flavor = taste + smell 

Before we delve into warm vs cool flavors, let’s lay some groundwork on what flavor actually is. Many of us use “taste” as a synonym for flavor (myself included in an earlier draft of this story). However, flavor is a much more complex biochemical business. At the most basic, flavor is composed by the substances in food that trigger our taste buds (the basic sweet, salty, sour, bitter, savory/umami) plus the volatile compounds that waft from the mouth into the nasal cavity. In more simple terms, flavor is a mix of taste and smell. Yet on top of that, we perceive other sensations, such as textures or irritants of the mouth’s mucosa. According to Cooking for Geeks [1], the brain combines all of these cues, for instance, “the tiniest bit tangy on the tongue, sweet, but not too much, fruity-fresh odor, medium water content and firmness”, and concocts a unitary experience which we then call “strawberry flavor”.

True Heat, or “What’s in a tingle?” 

Hot and cold feelings on the tongue are intimately intertwined with sensations induced by chemicals other than those involved in the five basic tastes. For instance, we perceive menthol as being cooling not just because its evaporation leads to a local decrease of temperature on the tongue, but also due to its binding to TRPM8 [2]. TRPM8 is a calcium channel in pain-sensing nerves (nociceptors) that also responds to pain in, say, frostbite. Therefore, the brain perceives a “true” chill. Conversely, the “true” hotness of chillies and wasabi is given by the components capsaicin and allyl isothiocyanate, respectively, which bind to yet another calcium channel, TRPV1 [3]. This, in turn, leads to the opening of the channels, the efflux of calcium and thereby the depolarization of the neuron and transmission of an action potential, processed as pain in the brain [4]. Since the same calcium channels also respond to high temperatures, we tend to associate the pain from chiles and other spices with heat. 

Cooling/refreshing: foods that trigger “cold pain” sensation (peppermint), lemon and other sours (astringent tastes), tannin-containing bitter foods and drinks – think gin tonic, iced tea with little to no sugar, cucumbers (the peel is almost always slightly bitter). Yoghurt and other milk products counteract effects of capsaicin very well, so can be considered cooling too (think of an Indian cucumber raita)

Hot/warming: foods that trigger “hot pain” sensation (chillies, wasabi, radish), but also sweet tastes (cinnamon, cloves, nutmeg, anise, carrots, beets,…) and savory/umami tastes (mushrooms, meats, soy sauce…)

Heat & Associates

An astute observer will now point out that many spices do not trigger the same pain response that hot peppers do. This begs the question: why are these other spices, such as nutmeg or ginger, perceived as warming? Straightforwardly, much of our taste in food relies on learned associations. We mentally and emotionally connect certain spices with dishes served on specific celebrations or occasions. Ginger, for instance, is a wintry spice for most Westerners due to its association with gingerbread for Christmas. However, in other cultures, ginger is considered a cooling palate cleanser. The classic example being Japan, where pickled ginger is paired with (cold) sushi and eaten, of course, all year long. It is interesting to note, though, that these associations are not purely randomly dictated by the flora and fauna of a particular region and the culture it birthed. Like basil and tomato, local ingredients have been historically paired based on how certain of their flavor molecules fit together. More specifically, matches made in heaven are not different from good partnerships: each partner brings out the best in the other. According to Gail Vance Civille in Cooking for Geeks [1], in the case of basil and tomato, basil quenches certain not-so-savory elements of the tomato flavor and makes the dish more fresh. Much of the pairing process can be tweaked these days with hard science: based on the flavor profiles of ingredients, as measured by mass spectrometry.* For instance, as shown by foodpairing.com [6], pumpkin goes well with ciabatta, which is why I chose it to accompany my recipe for pumpkin soup.

The Spicy End

So, what have we learned so far? Well, the pumpkin taste is probably not warming by itself, but we believe it to be so due to our common association of it with Thanksgiving (when the weather is already colder in many parts of the US) and with perceived warming spices such as ginger, nutmeg and cinnamon. This is precisely the combination that the popular coffee places exploit in order to draw you inside on chilly autumn mornings. And why do we care so much about warming flavors anyway? It turns out that, just like with any other pain, food hotness induces the release of endorphins, and also leads to a reduction in blood pressure due to the dilation of blood vessels, both in proximity of the “hot” stimulus and at a wider range in the body [5]. If you would like to reap the benefits of that heartwarming pumpkin flavor mix without the sugar rush from any beverage of the green mermaid café chain, give my pumpkin cream soup recipe a try. If you aren’t blessed with a fireplace of your own, this is as close as you’ll get to that luxurious warm glow that puts a smile on your face when it’s cold outside.

Sources

[1] Porter, J. 2011. Cooking for Geeks.

[2] Pan et al., European Journal of Physiology, 2017

[3] https://bit.ly/2m2B1Rv

[4] https://bit.ly/2ml56M2

[5] Yang et al., Cell Metabolism, 2010

[6] https://www.foodpairing.com/en/home (first 50 pairings are free, offers seasonality filters for ingredients)

Photo by Valeria Boltneva from Pexels

*This QR code will take you to a scientific paper on flavor pairing: Ahn et al., Sci Rep, 2011 

This article originally appeared in the Charité Neuroscience Newsletter

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