Food and the Senses (Part 7)

 “Love is a burning thing, and it makes a fiery ring”, goes the lyrics of Johnny Cash’s 1963 country hit. Fun fact, the original version was recorded a year earlier by Cash’s sister Anita Carter. The closest thing we get to a ring of fire in the culinary world is heat or pungency from ingredients like chillies, wasabi, ginger, mustard and black pepper.

Cash’s analogy is more appropriate than you realise. Anyone who has bitten into a green chilli is aware of the burning sensation; some people actually start sweating after eating too much wasabi at a sushi restaurant. Yet people keep coming back for more, and spicy food is an integral component of a lot of cultures, like Sichuan Chinese, Mexican and our very own Indian cuisine.

It’s hard to imagine, but before Vasco da Gama landed in India in 1498, the primary source of heat in Indian food was black pepper and ginger. The chilli, which is now somehow intricately linked with Indian food in people’s minds, is a relative newcomer to the Indian kitchen’s arsenal. The chilli actually comes from the New World. When Columbus landed in the Americas in 1492, he thought that he had reached India, the land of spices, especially the coveted black pepper. There, he sampled some spicy fruits and mistook them for a variety of pepper. But of course, they weren’t; they were chillies. Yet the name “chilli pepper” stuck and this culinary misnomer is used to this very day.

What exactly is heat or pungency? It’s definitely not a taste, because there are no taste buds for pungency, and although wasabi burns our nose as many unfortunate beginners in sushi restaurants will vouch for, it’s not an aroma either. More importantly, why is it called “heat” when the food itself is not literally hot, temperature-wise? It turns out, pungency is sensed by receptors which are analogous to those which sense heat elsewhere in our body. In other words, chillies feel hot because they stimulate actual heat receptors on our tongue.

The TRPV1 receptor, also called the capsaicin receptor, detects and regulates body temperature, and provides a sensation of scalding heat or pain. On the opposite spectrum is the TRPM receptor which is stimulated by menthol and produces a cooling sensation. In our mouths however, TRPV1 receptors can be triggered by a compound in chillies which leads to the same response, producing a sensation of heat (hence the sweating), and pain. That compound is what gives these receptors its name: capsaicin.

Capsaicin is an oily compound present in chillies which provides them their heat. The amount of capsaicin varies widely across chillies, and can be measured by the famous Scoville scale, which basically measures the number of times a solution of the capsaicinoids extracted from a chilli needs to be diluted before the heat becomes undetectable. Bell peppers rate lowest on the scale at zero, and topping the list right now is the Carolina Reaper at a whopping 2.2 million.

There are other receptors of the TRP family that play similar roles. Wasabi, horseradish and mustard, all members of the cabbage family, contain a compound called allyl isothiocyanate, which is detected by a receptor called TRPA1. Unlike the TRPV1 receptors which are abundant in our mouths, TRPA1 is more abundant in our noses. Moreover, allyl isothiocyanate is more volatile than capsaicin and tends to drift up to the nose. And this explains why wasabi and horseradish tends to burn our nose while chillies burn our mouths. Pepper contains piperine which floats up to the nose and irritates it, making us sneeze.

Well, if chillies and wasabi cause such an unpleasant sensation, why do people all over the world crave it? Functional MRI or fMRI scans have revealed that eating a chilli makes the limbic system of the brain light up like a Christmas tree; it triggers both the pain and pleasure centres of the brain simultaneously. Which means that although it hurts, we tend to enjoy it.

Many people enjoy really spicy food. And even for those who don’t like the uninhibited punch of chilli, heat still plays a key role in a balanced eating experience. Think of a cool cucumber raita served alongside a spicy pork vindaloo or lamb rogan josh. The pseudo-heat of the curry is neutralised by the actual coolness of the raita.

Sichuan cuisine is dominated by the use of chillies and the famous Sichuan peppercorns. Dishes like dan dan noodles or mapo tofu are known for their intense heat and mouth-numbing , tingly sensation called“málà“, caused by a compound called hydroxy-alpha-sanshool present in Sichuan peppercorns. This is balanced out by fresh, crunchy, cooling pickles, which are abundant in Sichuan cuisine. The famous smashed cucumber salad called pai huang gua, flavoured with Chinese black vinegar and toasted sesame oil, is the perfect foil to all that heat and spice. Like the yin and yang, food is all about the balance.

That brings us to the end of this series. Over the past few months we’ve come to realise why food is so much more than mere sustenance; it is a world unto itself. Throughout this series we’ve taken passing glimpses at a lot of things, which we’ll take a better look at in future articles. Till then, appreciate the complex flavour of a glass of orange juice, the crunch of a potato chip as it gently crumbles on your tongue, the sinus-cleansing burn of a dollop of wasabi, and a whole lot more. Happy eating!