Why are stewed Apples a mustardy colour?
Oxidation, in cooking, is the reaction of a food with oxygen. This explains why apples, and other fruits and vegetables, go brown when cut and left exposed for long periods of time. It is speeded up when the apple is exposed to light and / or heat. In fact, for every 10’C increase in temperature the speed of oxidation doubles! So, although apples will naturally change colour when cooking, the best thing to do is to add something acidic (lemon juice is perfect in this case) and I find covering the food also helps. I add a few squeezes of lemon juice and then take a piece of baking parchment, crumple it up and the unfold it. I then lay that directly ontop of the apples to stop them being exposed to air, and keep the temperature nice and low so they cook slowly. Crumpling the baking parchment before putting it ontop of the apples makes it easier to work with. It’s also a great way to stop skin forming ontop of custard!
