Andrew Keen
Harcourt, Victoria, Australia
A French chef once responded to this question in a cookery class. In order to tell the difference, they said, leave the unknown samples out overnight. In the morning, if the sample is hard, it is cake. If it is soft, it is a biscuit. Voila!
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Hazel Beneke
Banksia Beach, Queensland, Australia
A cake becomes harder as it ages because of water loss. But a biscuit becomes softer because it absorbs water.
Joan Zealey
Wollongong, New South Wales, Australia
To quote Mrs Beeton, the Victorian cookery writer, “true sponges contain no fat”, only eggs (which actually contain a bit of fat) and sugar whipped to an emulsion with some flour gently folded in so as not to disturb the bubble structure of the mixture. All other types of cake contain added fats.
Averell Kingston
Banbury, Oxfordshire, UK
It is amazing how many different edible items can be made from the same four basic ingredients: flour, sugar, eggs and fat. The variety is the result of several factors, including the relative amounts of the ingredients in the recipe, preparation technique and, to a smaller extent, cooking method.
The light, easily crumbled texture of cake relies on a few things. The structure is composed of two types of large molecule: starch (flour) and protein (eggs). When heated with moisture, these form a lattice-like arrangement. Sugar and fat partly fill the holes, but leave some air spaces, resulting in a light texture. Too much sugar and fat will cause the starch-protein lattice to collapse, producing a heavy cake.
Traditionally, the fat used was butter, which had to be beaten with sugar for a long time (up to an hour in some old recipes) to incorporate air. Eggs also needed to be beaten for a long time to get in as much air as possible. In the early 20th century, the hydrogenation of vegetable oils produced softer fats that could be beaten with sugar much more easily, so producing lighter cakes.
During cooking, the cake batter expands as the raising agent (sodium bicarbonate) produces carbon dioxide, while the water turns to steam. Meanwhile, the egg proteins coagulate and the starch granules absorb water and form a gel. Both these processes make the batter set.
The lightness of sponges depends on eggs and sugar being beaten together for at least 10 minutes to incorporate lots of air and produce a thick, mayonnaise-like substance. Flour and melted fat are then carefully stirred in so the air isn’t displaced. The sponge needs to be cooked straight away.
Biscuits usually contain only flour, sugar and fat, with possibly a small amount of egg. Without the starch-protein lattice, the result will inevitably be firmer.
Isabella Van Damme
Highland, UK
Cakes, sponges and biscuits are all examples of heat-induced protein and starch networks, each containing a different volume of air. Cake and sponge both contain a large amount of air and have a fine crumb structure.
Basic biscuits are a mixture of fat, sugar and flour without eggs or other raising agents. As a result, biscuits contain a low volume of air that is often trapped in cracks or irregular air cells rather than the more spherical air cells in cake and sponge. Biscuits have a coarse, crumbly structure as the fat, sugar and flour form aggregates.
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Now, when it comes to cakes, sponges, and biscuits, I've got a deep understanding of the science behind them. Let me break it down for you.
First off, the French chef's trick to differentiate between cake and biscuit by checking hardness is interesting. It aligns with the general understanding of how cakes and biscuits behave over time. Cakes tend to become harder due to water loss, while biscuits get softer as they absorb moisture.
Mrs. Beeton, the Victorian cookery writer, emphasizes that true sponges contain no fat, relying solely on eggs, sugar, and flour. This aligns with the notion that the absence of added fats contributes to the unique structure of sponges.
Now, let's dive into the fundamental ingredients—flour, sugar, eggs, and fat. The proportions and preparation techniques play a crucial role in determining the texture of the final product. The light and crumbly texture of cakes comes from the starch-protein lattice formed when flour and eggs interact with moisture during baking. Too much sugar and fat can lead to a collapse of this lattice, resulting in a heavy cake.
Traditionally, butter was used as the fat, requiring extensive beating with sugar to incorporate air. However, the 20th-century introduction of softer fats from hydrogenated vegetable oils made the process easier, producing lighter cakes.
The expansion of cake batter during cooking is attributed to the raising agent (sodium bicarbonate) producing carbon dioxide, while water turns to steam. Simultaneously, egg proteins coagulate, and starch granules absorb water, forming a gel that sets the batter.
Sponges, on the other hand, rely on a thorough beating of eggs and sugar to incorporate air, creating a mayonnaise-like substance. Careful addition of flour and melted fat ensures the air isn't displaced, contributing to the lightness of the sponge.
Now, biscuits, a simpler mix of flour, sugar, and fat (possibly with a small amount of egg), lack the starch-protein lattice found in cakes. This fundamental difference in structure results in biscuits having a firmer, coarse, and crumbly texture.
In essence, cakes, sponges, and biscuits all involve heat-induced protein and starch networks, each with distinct characteristics. Understanding the science behind these baking processes allows for a deeper appreciation of the artistry in the kitchen.
