Sensory compounds are, of course, not limited to cooling and tingling compounds. The breadth of tasteless, odorless chemicals that cause sensation is surprisingly wide and includes chemicals that cause feelings of warmth, pungency, heat, and astringency. Very few synthetic chemicals create the warming and heating sensations. Most of what I'm going to cover in this post comes from things like ginger, Szechuan pepper, chili pepper, mustard, horseradish, wasabi, cloves, and onions.


The first thing you're probably thinking is (maybe): well, warmth and heat are basically the same thing. This is not true in the complex world of sensory compounds. Warming compounds are generally considered to be more gentle (think: the comforting pleasure of vanilla) and heating compounds actually produce their sensation in the form of pain (think: one too many chili peppers). It does get a little confusing here since warm and hot compounds both typically contain "vanillyl moieties." Moiety was a new word for me, too, but it's a just another way to say that there's a structural component that resembles vanillin somewhere in the compound. It seems that the "warm" compounds tend to more closely resemble vanillin than the hot compounds. Most of these chemicals are also oleoresins - another great vocab word - meaning that they are oil-soluble extracts. This makes sense in context with many of the flavor and fragrance molecules being found in the essential oils of plants and naturally their sensory component isn't going to be too far away.

Vanillin
Wikimedia Commons

These warming and heating categories are really cool in all ways but the literal. I've heard a lot of arguments over the years about killing off your taste buds with spicy foods, or whether or not people in Thailand have genes that allow them to eat "Thai Spicy" curry, or if a food actually gets spicier the more of it you eat. Things like that. Science, as it often does, confidently answers these questions.

To answer a few urban unknowns:

Number 1. Desensitization at the nerve level does occur when eating spicy food, that is, something containing anything with a vanillyl moiety which can activate the VR1 or VRL-1 receptors in the mouth. These nerve channels will not activate as readily in a person who eats lots of spicy things compared to a person who does not. In short, no one's "killing their taste buds" with General Tso's Chicken, but they are acquiring something like an immunity to the sensation.

Number 2: This kind of blends into number 1, admittedly, but genetics does give one a sort of pre-determined threshold for spiciness. It's certainly not something that can't be overruled, however, by the above desensitization through regular exposure.

Number 3: Food doesn't technically get any "hotter" the more of it you eat, i.e. the chemicals I'm discussing here won't build on one another's presence. It might feel that the more chili you eat the hotter it gets as a result of repeated exposure to one of these sensory compounds (here, capsaicin) because the nerves simply haven't had time to recover from the prior exposure. Warming and heating compounds will cause the mouth to produce more saliva to "defend" itself against these irritating agents and help the nerves out but sometimes (I'm looking at you, wasabi) it's just not enough.

Hopefully that knowledge gives you a little insight into just how carefully crafted heating and warming compounds are in terms of their being additives in our food. Think about mild, medium, and hot salsas, for instance. Or muscle-warming lotions. Cosmetics are often considered more convincing and desirable from a consumer point of view if the user can feel the effects instantly, such as in products that enhance skin colors, like artificial tans. Maybe something about feeling a warming sensation causes the consumer to associate with lying on the beach? In any case, companies design use these compounds to enhance the flavors and smells of food, gum, mouthwash, lotion, liquor and more.

A kitchen staple? 

A current *hot* area of research, in fact, is finding synergies between these sensory compounds. What cooling, tingling, and warming compounds will enhance one another or create entirely new experiences for the consumer? Takasago International Corporation found that combining vanillin, a cooling agent, gingerone, and capsaicin created cool, warm and tingling effects all at the same time. This patent from von Borstel et al. on creating a better cigarette experience discusses throat feel, mouth sensation, and even reducing the nerve irritation caused by nicotine itself. Although I'm not sure what kind of product outside of cigarettes wouldn't overload one's mouth with all these nerve stimuli - gum, perhaps? - it's not an area of study that's likely to cool off anytime soon.


Ashley



1 Rowe, David J (ed.) (2005) Chemistry and Technology of Flavors and Fragrances. Blackwell Publishing: Poole. Ch.9.^↩