Gellability of fruits or fruit juice

The pectin content is critical for gellability. This varies, depending on the ripeness of the fruit used and on the species of fruit. 

As a general rule, the more acid and less ripe the fruit is, the higher is the pectin content. 

Fruit of species with a high pectin content does not normally need any additional gelling agent, but a gelling agent has to be added in the production of jam from low-pectin fruit. 

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