I was wondering if there is a way to make jam without going through a gelatin type product. There is no real motive behind that question, except for curiosity
- Use a mixture of 3/4 ripe and 1/4 under-ripe high-pectin fruits. Under-ripe or just barely ripe fruit contains the most pectin.
- Cook the fruit with cores and peels to add extra pectin (but do remove stems or pits). Put through a sieve before adding sugar and spices.
- Citrus peel contains lots of pectin, so consider adding some of it to your mixture.
Fruits low in pectin: apricots, blueberries, cherries, peaches, pears, raspberries, and strawberries. That's not saying you can't make jam/jelly/butter from these without added pectin. It just may be a little more difficult than, say, using apples. In fact, as an example, here's a pear butter recipe w/o pectin.
I'm not sure if you can with all fruits, but some fruits, like fruits like apples, blackberries, gooseberries, crab apples, cranberries, and grapes are naturally high in pectin and might produce the desired effect without extra help.
You can simply simmer off enough liquid until any fruit is thick. For example, I make a blueberry sauce for pancakes and blintzes by just putting some blueberries, sugar, and a pinch of salt in a saucepan, bringing to a boil, and then reducing heat to low until it is as thick as I want. When cooled in the fridge, it will be pretty jammy. (This isn't a canning recipe, it only keeps a few days).
I am rather shocked by the question and the presumption something like gelatine is added to fruit and sugar to make jams and jellies. Jams and jellies are fundamentally made without gelatine or any such product. The fruit contains pectin naturally, and it is this that makes the jam set. Manufactured jam, jellies and marmalades sometimes contain commercially produced pectin, which is labelled as E440.
Fruits with HIGH in pectin include: Blackcurrants, Cranberries, Damsons, Plums, Gooseberries, Redcurrants, Cooking Apples and Quince.
Fruits with MEDIUM pectin content: Apricots, Greengages, Loganberries, Raspberries and early Blackberries.
LOW pectin content fruit includes: Cherries, Elderberries, Medlars, Pears, Rhubarb, Strawberries and late Blackberries.
Fresh fruit contains more pectin than stored fruit. It deteriorates or breaks down as the fruit ages. That is why it is best not to use really ripe fruit for making jams and jellies, but firm slightly unripe or barely ripe is preferable.
I have never made jam using gelatine and would not really care to try either. All my jams are made using one part fruit to one part sugar and jellies are made using a pound of sugar to each pint of juice. If I want to make a jam or jelly with a fruit really low in pectin (so it would not set on its own) for example marrow, I add lemon juice and rind and use jam sugar which contains commercially produced pectin made from citrus peel (which contains a whopping 30% pectin).
Low sugar jams and jellies which do not have a long shelf life are not part of my repertoire. Neither would I care to make jams from fruit which would need commercially produced pectin adding to make them viable.