INSIDE (Paula): A short pithy post on what’s inside pips and peel.
My marmalade is made from three ingredients, ruby grapefruit, sugar and water.
As a jam maker and scientist, I’m aware that pectin is the ingredient that helps my jam to set. But where does it come from and how does it work?
Pectin is found inside plant cell walls. It’s involved in helping neighbouring cells bind to one another. From a chemist’s perspective, pectin is a polymer – a long chain molecule composed of smaller repeating subunits. It’s also a polysaccharide as the repeating subunit is a sugar molecule.
When making marmalade, I take advantage of the fact that citrus fruits have high concentrations of pectin, particularly in the peel and the pips, and that pectin is water soluble. My recipe tells me to collect the grapefruit pips and soak them with the sliced fruit. The next day, I boil them together until the fruit softens. This method helps extract the maximum pectin out of the pips and peel. Then as I add sugar to the softened fruit mixture and keep the pot simmering, the sugar, acid (from the grapefruit) and heat work together to change the chemical structure of the pectin molecules. They slowly form a suspension that will gel as it cools. It’s this transformative process, this kitchen chemistry, that makes my jam set.
If you’d like to ‘see’ that there’s pectin in citrus pips, put a spoonful of pips into a small amount of water and leave overnight. The next day, the water will taste bitter and feel viscous.
through a science lens 