🧪 Kitchen Chemistry

Baking soda (sodium bicarbonate) reacts with acids in the batter (buttermilk, yoghurt, brown sugar, cocoa) to produce carbon dioxide gas. These bubbles are trapped in the batter's gluten network and expand in the oven's heat, causing the batter to rise and giving the cake a light texture. Too little baking soda produces a dense cake; too much leaves a soapy or metallic aftertaste.

The Maillard reaction is a chemical reaction between amino acids (from proteins) and reducing sugars (glucose, fructose) that occurs above about 140°C. It produces hundreds of flavour, aroma, and colour compounds — the brown crust on bread, the seared crust on a steak, roasted coffee aroma. It is not caramelisation (which involves only sugar) and requires both protein and sugar to be present.

Water is polar (molecules have separated positive and negative regions) and forms hydrogen bonds; oil is nonpolar. Polar and nonpolar molecules do not mix because the energy cost of disrupting their respective bonding networks exceeds the gains from mixing. Mayonnaise holds together because egg yolk contains lecithin, an emulsifier with a water-loving head and oil-loving tail that sits at the oil-water interface, stabilising tiny oil droplets in water.

Yeast in bread dough ferments sugars, producing carbon dioxide and ethanol. The CO₂ is trapped by gluten (a network of wheat proteins developed by kneading), causing the dough to expand and develop a light, airy texture. The initial rise (bulk fermentation) and second rise (proofing) allow the gluten network to relax and the yeast to generate enough CO₂ for good texture. Heat in the oven kills the yeast and sets the structure.

Raw egg white contains proteins (ovalbumin, ovotransferrin, lysozyme) folded into compact 3D structures. Heat (above ~60–70°C) provides enough energy to break the weak bonds holding these structures together, causing proteins to unfold (denature) and then randomly tangle together, forming a solid network that traps water. This is irreversible — you cannot uncook an egg — because the protein network is stabilised by new disulphide bonds and hydrophobic interactions.