Carbohydrate molecules are made up of carbon, hydrogen and oxygen. Although all carbohydrates provide the same amount of energy (4 kcal/g), we can distinguish between two types of carbohydrates, which differ according to their size :
Simple carbohydrates, more commonly known as sugars, are found naturally in certain foods such as milk (lactose) and fruit (glucose, sucrose, fructose). Only simple carbohydrates have sweetening power. This is why they are used in sweet foods such as jam, fruit purees and flavoured dairy products.
Complex carbohydrates are found in cereals (wheat, rice, barley, maize, etc.) and cereal products (bread, etc.), root vegetables (potatoes), and legumes (lentils, beans, peas). The most common and well-known carbohydrate is starch.
In order to understand the difference between simple and complex carbohydrates, imagine two goods trains: the first - the sucrose train - having only two wagons while the second - the starch train - with a very large number of wagons.
Returning to the example of the apple pie, we already know that the sugar sprinkled on top contains carbohydrates, but so too do the apples and dough. This may seem obvious in the case of the apples, which are sweet without actually tasting of sugar. It is less obvious of the dough. Dough contains mostly complex carbohydrates (starch is the main component of flour), which does not have a sweet taste.