BICARBONATE OF SODA OR BAKING POWDER? Bicarbonate of soda and baking powder are two kinds of chemical leavener or raising agent. When bicarbonate of soda (sodium bicarbonate) is combined with moisture and an acidic ingredient (e.g. cider vinegar, yoghurt, soured cream, chocolate, buttermilk, honey) the resulting chemical reaction releases carbon dioxide bubbles that expand in the oven and help your bakes to rise. This will start to happen as soon as you mix the bicarbonate of soda and the acid together in a batter, so try to get it into the oven quickly. Baking powder is a blend of acid (cream of tartar) and alkali (sodium bicarbonate). Although the acid and the alkali are already combined, they will only start to fully react when exposed to the heat of the oven. Which of the two leaveners you should use will depend on your other ingredients: bicarbonate of soda needs an acid to balance it (and to react with) so it’s best used in a recipe containing an acidic ingredient – if you ever accidentally substitute bicarbonate of soda for baking powder in a recipe with no acid ingredient to balance it, you will notice a very bitter, soapy taste. Baking powder has a more neutral flavour. Don’t try to substitute one for the other without adapting the rest of the recipe. In most cases, if a recipe asks you to use both, the baking powder is likely to be acting as the main leavener, while the bicarbonate of soda will be there to neutralise an excess of acid from the other ingredients. NOTE: Measure chemical leaveners carefully; a little goes a long way. As a general rule you should use 1 teaspoon of baking powder or ¼ teaspoon of bicarbonate of soda per 130g of plain wheat flour.
IF YOUR OVEN IS TOO HOT the edges of the cake will crust before the middle has a chance to fully bake, leaving a soggy centre full of gases that continue to expand late in the baking process and cause your crust to crack. IF YOUR OVEN IS TOO COLD the fat will melt, releasing its air and leavening gases before the other elements in the batter set to hold them in place, and the cake won’t rise. COOLING You should generally leave a cake to cool in the tin for at least 10 minutes after removing it from the oven, placed on a wire rack so that air can circulate. Cakes are softer and more fragile before they are fully cooled – the cooling process allows the flour’s gelatinised starch to gel and firm up the cake, and if you try to remove it too soon, it will likely stick to the tin. If you leave the cake in the tin too long, the steam it releases will be trapped and make it soggy. After 10 minutes, remove it from the tin and leave it on the wire rack to cool. It’s best to wait until the cake is completely cool before peeling away any baking paper, otherwise you might take chunks of cake off with it. STORING Cakes generally keep well at room temperature for a few days, thanks to the moisture-retaining properties of the butter and sugar they are made with. Icing a cake will help to preserve it for longer, as less of the cake is exposed to the air. Putting cakes into the fridge tends to dry them out, but you can freeze most cakes. Just wrap the un-iced cakes tightly in a thick layer of clingfilm and defrost at room temperature.
CAKES MADE WITH WHIPPED EGGS
OCCASIONALLY a recipe will call for whipped egg whites, and in this case the cake batter is getting some or all of its leavening from air trapped in the beaten whites. This process requires beating the whites to a rich white foam, filled with air bubbles. These expand in the oven until the egg sets and seals the air in place. When it comes to whipping egg whites for a cake the rules are strict, but don’t be put off – it’s actually very simple and you’ll probably nail it first time. As with making meringues, you need to use room temperature eggs and separate them carefully, as fat from the yolks will spoil the process | see page 20 for how to separate eggs |. In fact any fat or grease is your enemy here, so make sure everything is really clean.
WHIPPING EGG WHITES Ideally use a stand mixer with the whisk attachment or hand-held electric whisk to beat egg whites, and a mixing bowl large enough to hold up to eight times the volume of the whites you start with. Add a pinch of salt and start beating on a medium speed, gradually increasing to high as the whites start to foam. The beating time will vary depending on how many whites you are using so keep a close eye on them. The whites are ready when they reach ‘stiff peaks’ stage – they should be smooth, moist, shiny and the tips will stand up straight as you lift the beaters out of the bowl. NOTE: Add a pinch of cream of tartar or a drop of lemon juice to the mix to help increase volume and stability. FOLDING WHITES INTO A BATTER When the whites are beaten to stiff peaks, you need to fold them carefully into your batter right away – as soon as you stop beating they will start to lose air. A metal spoon or rubber spatula is best for doing this. Start by making a well in the centre of your batter or dry ingredients. If it’s a wet batter, stir a small spoonful of whites in, just to introduce it to the mix. Now spoon the whites into the centre – use your spatula to cut through the middle, scoop up towards the edge of the bowl and ‘fold’ back over the top of the whites. Turn the bowl slightly and repeat until all the foam is incorporated. It may look like it’s never going to happen, but it will. Just keep folding. Your aim here is to preserve as much of the trapped air as possible while incorporating the foam evenly. Try to handle gently and be patient.