The white pith just under the skins of citrus fruit is high in pectin. Any citrus fruit can be used, but choose ones that have a thick layer of white pith for good results with this recipe.

Most commercial pectins are from citrus fruit peels and are extracted ... by adding a simple HPP pre-treatment of fresh source material for pectin extraction," said Zhao. The research findings ...

High-pectin fruits include: blackcurrants, redcurrants, cooking apples, damsons, quinces, gooseberries and some plums. Low-pectin fruits include: blackberries ...