Kitchen Science Quiz

Answer: Cutting its cells releases a sulphur gas that irritates the eyes. By breaking the onion's cells, the knife brings enzymes into contact with sulphur compounds. This forms a volatile gas, the "lachrymatory factor", which reaches the eyes. The tear glands react to wash it away.

Answer: The pressure makes water boil at about 120 °C instead of 100 °C. By trapping the steam, the pressure cooker raises the pressure: water only boils at around 120 °C. Those extra 20 degrees often cut cooking times by half or two-thirds.

Answer: An enzyme oxidises the flesh in air, and lemon's acidity slows it down. Cutting the apple brings oxygen from the air into contact with an enzyme and compounds in the flesh: new brown pigments appear. Lemon's acid greatly slows the enzyme. Avocados and bananas react the same way.

Answer: The fibres relax and the juices redistribute, so less runs out when carved. Straight out of the oven, the fibres are contracted and the juices are pushed towards the centre. A few minutes' rest allows a more even spread: the meat stays juicier on the plate, and the centre finishes cooking gently.

Answer: The cold damages its leaves, which quickly turn black. A plant of tropical origin, basil tolerates low temperatures poorly: its cells are damaged and the leaves turn brown. It is best kept like a bunch of flowers, stems in a glass of water, at room temperature.

Answer: Some beetroot pigments aren't destroyed by digestion. This harmless phenomenon, called beeturia, affects part of the population. Betalains, beetroot's red pigments, pass through the body without being broken down. Surprising the first time, but harmless.

Answer: The Maillard reaction. Described in 1912 by the French chemist Louis Camille Maillard, it occurs between sugars and amino acids at high heat. It creates hundreds of aromatic molecules: it is what makes a grilled steak so appetising.

Answer: An iron and sulphur compound, from overcooking. With prolonged cooking, sulphur in the white reacts with iron in the yolk to form iron sulphide. It is harmless but unappetising. To avoid it: about 9 to 10 minutes' cooking, then a plunge into cold water.

Answer: Menthol activates the mouth's cold receptors. Menthol "tricks" the nerve sensors that detect cold: the brain feels coolness although the temperature has not changed. Conversely, chilli's capsaicin activates the heat sensors. These discoveries earned a Nobel Prize in 2021.

Answer: Kikunae Ikeda. Intrigued by the taste of dashi, a Japanese kombu broth, Ikeda isolated glutamate from it and named its taste umami, "delicious taste". Long ignored in the West, it was only fully recognised after specific receptors were found on the tongue.

Answer: A genetic variant in their sense of smell makes them sensitive to certain aldehydes in the plant. Genetic studies have linked this aversion to an olfactory receptor gene. The proportion of "haters" varies between populations. For them it is not a whim: they really do perceive soapy notes.

Answer: Some sulphur compounds pass into the blood and are breathed out through the lungs. One of garlic's compounds is not broken down by digestion: it enters the bloodstream, then escapes with every breath for hours. One study showed that raw apple, lettuce or mint help neutralise these molecules.