Have you ever been chopping onions with tears streaming down your face and suddenly thought, "why is this onion being so mean to my eyes?" Or eaten sambal terasi (shrimp paste chili sauce) that made your tongue feel like it was on fire, and wondered, "where does this spiciness actually come from?" Well, behind the kitchen ingredients we use every day, there are actually unique scientific facts we rarely realize. Not about the history of the food, but about why these ingredients behave the way they do. Let's uncover them one by one, while occasionally stopping by the classic kitchens of Bandung and the Indonesian archipelago.
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Why Are Chili Peppers So Spicy?
The spiciness of chili peppers isn't actually a "taste" in the true sense, but rather a burning sensation triggered by a compound called capsaicin. This compound attaches to the same nerve receptors that detect heat. So our brain gets "tricked" into thinking our mouth is really burning, even though the temperature is completely normal.
Interestingly, the spiciness level of chili peppers is measured using a unit called the Scoville Heat Unit (SHU). Bird's eye chilies, which we commonly use to make quick sambal, have an SHU of around 50,000-100,000, while sweet bell peppers have almost 0 SHU. If you love sambal so spicy it makes you sweat and tear up a little, that's a sign the capsaicin receptors on your tongue are working overtime!
Extra fun fact: plain water is actually not very effective at relieving spiciness. Milk or rice work much better, because their fat and casein content can "dissolve" capsaicin, which is oil-soluble rather than water-soluble.
Onions and Tears: There's a Chemical Reaction Behind It
When shallots or garlic are cut, their cells break down and release enzymes and sulfur compounds. This chemical reaction produces a gas called syn-propanethial-S-oxide, which, upon contact with air and reaching your eyes, immediately reacts with your tears to form a mild sulfuric acid. This automatically causes stinging eyes and a reflex to produce tears to "rinse away" the irritation.
Here are a few kitchen tricks you can try to avoid crying while slicing onions:
- Chill the onion in the refrigerator for about 30 minutes before cutting, since cold temperatures slow down the release of the gas.
- Use a truly sharp knife so the onion's cells aren't damaged as much all at once.
- Cut near a small fan or exhaust vent so the gas gets carried away by the airflow quickly.
Salt: A Simple Ingredient That Became a Natural Preservative
Salt has been used to preserve food for thousands of years, long before refrigerators were invented. The secret lies in salt's ability to draw water out of bacterial cells through a process called osmosis. Without water, bacteria struggle to multiply, allowing food to last much longer.
This also explains why salted fish, salted eggs, and dried meat (dendeng) can stay preserved for days or even months without needing refrigeration. In Bandung and the surrounding Priangan region, this salting technique is still commonly used to make jambal-style salted fish, as well as peuyeum, which is instead fermented with the help of yeast rather than salt—two different preservation techniques that are both cherished heritage from our ancestors.
Why Does Rice Left Overnight Taste Better for Fried Rice?
This is a fact that often escapes home cooks making fried rice. Freshly cooked rice has a high water content and a soft texture, so if you fry it right away, it tends to clump and turn mushy. Rice that's been left in the refrigerator overnight undergoes a process called starch retrogradation, in which the starch molecules rearrange their structure to become denser, reducing the water content.
As a result, the rice becomes drier, or "pera," meaning the grains stay neatly separated when fried, don't clump together, and can absorb the seasoning more evenly. So if you want to make authentic homestyle nasi goreng (Indonesian fried rice), don't use freshly cooked rice!
Why Can Bananas Make Other Fruits Ripen Faster?
Bananas, apples, and avocados are among the fruits that produce high amounts of ethylene gas during the ripening process. This gas acts as a natural "signal" that speeds up the ripening of nearby fruits. That's why if you store ripe bananas together with unripe mangoes in a closed plastic bag, the mangoes will ripen faster than usual.
This trick is often used by traditional fruit vendors and homemakers at markets in Bandung to "force" unripe fruit to ripen quickly without any added chemicals. Simple, natural, and practiced for generations.
Why Does Coconut Milk Curdle If Cooked Carelessly?
Coconut milk is a natural emulsion of water and coconut fat. If it's heated at too high a temperature or stirred while the temperature keeps fluctuating rapidly, this emulsion bond can break down, causing the fat to separate from the water—that's what we call curdled or "broken" coconut milk.
Here are some practical tips to keep coconut milk smooth while cooking, for example when making gulai (curry) or opor (coconut milk chicken stew):
- Cook over low to medium heat, never high heat.
- Stir slowly and consistently, especially once the coconut milk starts to simmer.
- Add thick coconut milk toward the end of cooking, not at the beginning, so it isn't exposed to high heat for too long.
Conclusion
It turns out the kitchen holds many fascinating scientific phenomena if we take a closer look. From the spiciness of chili peppers to the sting of onions in our eyes, to why overnight rice works better for fried rice—everything has a logical explanation behind it. Understanding these small facts doesn't just make us smarter in the kitchen, but also makes cooking more enjoyable because we know the "why," not just following habits blindly.
Go ahead and try one of the tips above the next time you cook, and see the difference for yourself! If you have any other interesting kitchen facts you've experienced, feel free to share them in the comments below!
