Take pectin, a soluble, non-starch polysaccharide that is extracted from citrus peel and membranes and used to thicken jams and jellies. A lot of pectin goes to waste, says Shan.

Pectin can hold pieces of fruit in suspension, but it must be combined with sugar and an acid (like lemon juice) in order to gel. The acid helps extract the pectin from the fruit while it's simmering.