Sugar is the primeval essence of biological energy. All life forms on Earth are built on a foundation of sugars. Plants convert sunlight and carbon dioxide into glucose, which then forms the building blocks of their very being. Pectin, cellulose and hemicellulose (that give plant cells their rigid structure, which is why vegetables and fruits tend to be fibrous and crunchy) are all built by constructing long chains of glucose. The starch in grains like rice, wheat and corn is similarly made up of chains of sugars, designed to feed a growing plant embryo, and, thanks to the agricultural revolution, also us. All animals use glucose as the energy currency. It is the US dollar of the biological universe.
Glucose, transported by blood, is what keeps every cell in our body ticking. When there’s too much or too little of it in the blood, it’s a problem. When you are unwell, glucose is pumped straight into the bloodstream, sparing your body the complex effort of breaking down carbohydrates in your food into glucose. Even carnivores like the cheetah, whose diet is largely just protein and fat, converts them to glucose to fuel those powerful leg muscles to attain speeds upwards of 100 kmph.
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Evolution has not just given us the ability to detect the taste of glucose (and other simple sugars), but also a dedicated brain apparatus to get addicted to it. We crave sugars because in the deep past, being able to get even a little bit of it meant the difference between survival and death. And for most of our history, the only way to get sugar was to consume ripe fruits or honey. Fruits contain the sweetest of basic sugars—fructose; honey contains both fructose and glucose. Mammalian milk has lactose, a sugar that does not taste as sweet as fructose or glucose. Unfortunately, fruits have always been expensive, honey came with the risk of angering a large number of bees, and most adult humans lose the ability to digest lactose. So sugar was an expensive luxury item for most of our history.
Most sugar in the modern world is made from the sugar-cane plant, whose juices contain a large amount of sucrose (made of one molecule each of glucose and fructose). When this juice is heated, water evaporates, leaving behind a sticky brown substance that used to be called sharkara in Sanskrit, a word that is the origin of both “sugar” and “jaggery”. When this is refined, we get crystalline white sugar, and when the Europeans discovered this, it changed the world, and not for good.
A luxury good in the Middle Ages, the trans-Atlantic slave trade and colonisation made sugar cheap and affordable for all Europeans, and life horrendous for the enslaved and colonised. It also set in motion a permanent shift in our diets—our addiction to sugar makes it hard for us to say no to it, and it has found its way into almost everything we eat nowadays.
Sucrose, typically in the form of crystalline white or brown sugar, does more than just make food taste sweet. It helps cut bitterness and balances sourness. It also enhances the perception of aromas. While salt makes a dish less bland and acids add more dimensions to a dish, sugar amplifies the entire package.
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A teaspoon of sugar in your dal will significantly elevate flavour without adding any perceptible sweetness. Try eating some cardamom raw and then with some sugar—you will smell the cardamom more intensely when your brain detects sweetness on your tongue.
Sugar’s ability to dissolve in water makes it an excellent preservative. Like salt, sugar molecules bind with water molecules and don’t make them available for bacteria and fungi. Sugar syrup is simply equal parts by volume white or brown sugar dissolved in water. Bringing water to a simmer before adding the sugar quickens the process. And by the way, “brown sugar” is simply white sugar with molasses added back to it during the manufacturing process, so don’t be fooled by the “natural” or “healthy“ labels.
Sugar reacts with amino acids in protein at temperatures above the boiling point of water to produce a range of aromatic, delicious molecules in a complex series of chemical interactions called the Maillard reaction. Some of these molecules lend the brown colour characteristic of deep-fried or grilled food. When sugar is directly heated to high temperatures, typically well above 180 degrees Celsius, it breaks down into smaller molecules with some remarkable properties. An otherwise odourless and colourless white substance turns into “caramelised” sugar, with hundreds of intensely aromatic molecules with buttery, milky, flowery, fruity and liquor-like tones.
There is now consensus among scientists and health professionals that reducing the intake of sugars in all forms is strongly correlated with better health outcomes and longevity. There is a common misconception that the sugars in fruits and honey are “healthier”. This is not true. They are chemically the same thing, though you may personally prefer the richer flavour of jaggery or honey.
The global rise of type 2 diabetes has spawned an entire industry of alternatives: Sugar alcohols (like sorbitol and mannitol), which take longer to digest and thus release glucose more slowly into the bloodstream, and intensive sweeteners like aspartame or stevia, molecules that trick our sweet tastebuds into thinking that it’s glucose but do not add too many calories to our food. As Wilfred G, Oakley, pioneer in the clinical care of diabetes, once said: “Man may be the captain of his fate, but he is also the victim of his blood sugar.”
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Krish Ashok is the author of Masala Lab: The Science Of Indian Cooking.