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The science of flavour

In his debut book, 'Masala Lab', Krish Ashok decodes the science of ingredients, cooking procedures and taste perceptions

Representational image by iStockPhoto.
Representational image by iStockPhoto.

When you bite into pani puri, also called golgappa or phuchka, the dominant aroma of cumin and mint, the sour tang of the amchoor, the heat of the green chillies and the satisfying crunch of the puri contrasting with the soft and creamy texture of the filling (which varies by region) is what makes up the entirety of the pani puri experience. Flavour is a combination of taste, smell, mouthfeel, and to a smaller extent, sound and visual experiences. And despite the fact that 80 per cent of flavour perception happens in the nose, we tend to associate the tongue as being the Watson and Crick of flavour to the nose’s Rosalind Franklin.


Let’s start with taste. Our tongues have taste buds that can detect five primary tastes. Contemporary research tells us that the old picture of the map of the tongue, with distinct taste perception areas, is mostly wrong, and that while the tip of your tongue does have more taste buds dedicated to detecting sweet and salty flavours, it doesn’t mean that they cannot detect sourness or bitterness entirely. Taste bud specialization is reasonably well distributed. Sweetness and saltiness are detected rather quickly, while bitterness, which is mostly detected at the back of the tongue, takes a bit longer and tends to linger in the mouth. This explains the expression ‘bitter aftertaste’. Sourness tends to be detected more strongly on the sides of the tongue.

What kind of molecules tend to be sweet? Sugars, aldehydes, alcohols and certain amino acids taste sweet to varying degrees. Acids, such as tamarind, vinegar, yoghurt, juices of citrus fruits and many other organic acids in fruit juices taste sour and tart. Saltiness comes from, well, salts, of which sodium chloride tastes the saltiest, while other salts exhibit varying degrees. Bitter tastes come from substances called alkaloids such as caffeine (in coffee), theobromine (in chocolate), quinine (in tonic water), and so on. Our ability to detect bitterness comes from the need to identify poisons before we ingest them. Pure caffeine is deadly and poisonous, although a tiny amount as part of our morning coffee is typically safe. Umami is the fifth taste that has recently been added to this list. It is the savoury, lingering, meaty taste that comes from the presence of salts of a specific amino acid called glutamic acid. Food that is rich in glutamates has an intense, savoury and lingering flavour that feels very satisfying. Umami-rich foods do not need to be overly spiced or salted because of this lingering effect.

The perception of taste is also dependent on the concentration of the substance responsible for the taste, and different individuals have different thresholds for perceiving tastes. For instance, a lot of Indians will need salt at least at 1–1.5 per cent concentration by weight of the dish to taste acceptably salted. Many in the West will find that too salty, as they can perceptibly detect saltiness at much lower concentrations. In addition to traditional culinary habits, genetics also play a role. People with low thresholds for detecting the soapy, bitter taste of aldehydes will find coriander leaves unpalatable.

Fascinatingly, food scientists (and grandmothers and mothers) have figured out that there is a sub-threshold level of taste, which while not being individually detectable, can amplify or mute other tastes. For example, a tiny pinch of salt in your kheer can make it taste more intensely flavourful without being perceptibly salty, which no one would want. This is also why jaggery tends to be preferred when making Indian desserts, because it naturally contains a bit of salt. Likewise, a tiny pinch of sugar can mute saltiness without tasting perceptibly sweet. This is why a pinch of sugar is a good idea in any dish, because it balances saltiness. In fact, restaurants tend to take this effect to its logical extreme— adding lots of sugar allows you to add lots of salt to your dish. This combined effect is like turning the volume knob to 11, which is why restaurant food tastes more intensely flavoured than home-cooked food. And finally, a tiny pinch of salt can also mute sourness. This is why it’s common to add salt to extremely sour yoghurt in south India, where the local climate tends to supply crystal meth and cocaine to fermentation reactions, to make it palatable.

Temperature also impacts how you perceive taste. At lower temperatures, our tongues’ ability to detect tastes decreases. This is why melted ice cream tastes cloyingly sweet. It turns out that taste buds operate at their peak between 20 degrees Celsius and 30 degrees Celsius. This is why coffee is tolerable at 50–60 degrees Celsius, which is usually the temperature at which it is served, while it tastes bitter once it gets to room temperature, which tends to be the temperature range in which our taste buds operate at their peak.

The front cover of 'Masala Lab', published by Penguin Random House India.
The front cover of 'Masala Lab', published by Penguin Random House India.


Now, let’s talk about the most impressive, yet underrated, arsenal in our flavour-detection apparatus—the olfactory receptors in our noses. When you pick up that succulent piece of tangdi kebab, marinated in a ton of spices, tenderized by yoghurt and seasoned with salt, and bring it up to your mouth, the aroma molecules that escape the kebab enter your nose and hit these receptors, which then send out a message to the olfactory cortex that can recognize more than 10,000 unique flavours. But we are just getting started. You then bite into the kebab. Since saliva is mostly water, your tongue can only detect tastes coming from water-soluble flavour molecules. The gnashing of your teeth causes the release of more volatile flavour molecules that travel through the back of your mouth, into the nasal cavity, and hit the same receptors as you breathe out. What you smell before you eat is called orthonasal olfaction, and what you smell as a result of a ton of volatile flavour molecules hitting those receptors as you breathe out is retronasal olfaction. This, in my opinion, is the single largest contributor to taste, because the act of chewing releases the maximum amount of volatile aroma molecules from your food.

Excerpted from Masala Lab, with permission from Penguin Random House India.

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