Processbeginnerdraft
Setting with pectin
Also searched as: jam, marmalade, jam sugar, pectin
In short: from fruit forms a gel, but only with enough sugar and acid. That is why jam needs both.
Picture it
Like a lock with three keys: pectin, sugar and acid. If one is missing, it stays runny.
Level 3 · Pectin chains in fruit juice≈ 10 nm
Simplified model
What happens
Pectins are long chains from fruit cell walls. Sugar draws water away from them, and acid takes away the charge that makes them repel each other. Then they can link into a network. Apples, quinces and redcurrants have a lot of pectin, strawberries little.
Why it matters
Explains why jam with little sugar does not set and why lemon juice belongs in it.
Rules of thumb
- Setting test: a dollop on a cold plate should form a skin after a minute.
- Combine low-pectin fruit with apples or jam sugar.
- Lemon juice helps with mild fruit.
Levers
Amount of sugartoo little → stays runny
pH (acidic to alkaline)acidic → sets better
Related entries
Sources
- Harold McGee: On Food and Cooking (2004), Kapitel Milch, Zucker, Schokolade