Moisture Content
Moisture content is how much water is trapped inside a food or material.
A dry sponge is a stiff block with no water inside it. A wet sponge holds tiny drops of water trapped in all its small holes. The more water fills those holes, the heavier and softer the sponge feels. Moisture content measures how much of that space inside is filled with water.
Explaining moisture content by grade level
An orange is heavy because it holds a lot of water inside. You can find out how much by weighing it before and after it dries out. The water part is the moisture content. Most fruits have more water in them than you might guess.
Projects that explore moisture content
This experiment changes the moisture content of popcorn kernels in two ways. Soaking kernels in water adds moisture. Drying them in an oven removes moisture. You then pop each batch and count the unpopped kernels to see how moisture content affects the result.
Fruits hold a surprising amount of water inside, and drying one reveals exactly how much. You weigh a whole orange, slice it thin, and spread the slices on paper-covered aluminum foil. A desk lamp and fan speed up evaporation until the slices are completely dry. When you weigh them again, the difference is striking — in this experiment the orange lost about 81 percent of its weight. Almost all of that lost weight was moisture hidden inside the fruit.