Making fruit jellies is a real science, so thought I'd get the ball rolling on some good tips for beginners. There are some really involved scientific resources out there on the web, but let's keep it simple and practical!
1. Making sure the damn thing sets
1.(a) Make sure you're using the right fruit
Fruit should be picked when it's only just ripe if you want it to contain the best pectin (which makes the jelly set!). It's a balance between being unripe enough to contain the most pectin vs ripe enough to have fully developed its flavour.
Some types of fruit have naturally high or low levels of pectin:
High levels: apples, crab apples, quinces, plums, citrus fruits, cranberries, gooseberries, and sour blackberries and boysenberries.
Low levels: cherries, ripe blackberries, grapes, melons, peaches, pears, figs, apricots, elderberries, strawberries, raspberries, guava, and pomegranates.
Apparently kiwifruit and papayas also contain an enzyme that inhibits the effect of gelatine.
You can use fruit with low levels of pectin to make jelly so long as you either follow a recipe or add shop-bought pectin.
1(b) Altering recipes
Many recipes can be altered or completely made up, but you've got to have a pretty good idea of the mechanics of jelly setting to do so. If you're worried, stick to the recipe. If it fails, you can always buy some pectin and reboil your mess. Common recipe alterations are omitting shop-bought pectin or reducing the amount of sugar, either of which is doable but risky if you don't know what you're doing. If your fruit is low in pectin (see list above) or you're altering a recipe/making one up, here are some guidelines:
- Often it's the skin and seeds of a fruit that contain the most pectin, so always include them while boiling!
- You can add fruit with high pectin content (or just the seeds and peelings) to improve the chances of setting.
- Sugar is important for making the jelly set, and preserving it from nasty pathogens. It can be hard to tell if the amount of sugar in the recipe is really needed, or if the person writing it just had a sweet tooth/was being careful. Experiment, but not too much.
- Boiling the mixture for longer.
1.(c) Testing for setting point
- Coat the back of a spoon in the mixture, wait a few minutes, then run your finger through it and see if it has set.
- Drip the mixture onto a cold saucer and see if it sets after a few minutes.
2. Straining the jelly through muslin
Traditionally, great pride was taken in the clarity of the final jelly. If you want jelly of stained-glass clarity, the juice must not be forced through the muslin. That might mean:
- adding the mixture to the muslin in smaller batches to prevent the weight of the fruit pulp pushing the juice at the bottom through the muslin, and removing the pulp in between additions.
- Definitely no squeezing the bag! Leave the muslin bag/muslin-lined sieve to drip overnight.
- If you stir the pulp to let the juice move through the pulp, make sure you don't scrape the bottom or sides of the muslin.
Of course, that can equate to a lot of time and effort, leave you with less juice to make jelly with and I don't particularly care whether my jelly is clear or not. I squeeze the bag. However, if you squeeze the bag too thoroughly, you can force through too much fine pulp which will affect the texture and jellylike-ness of your jelly.
3. What to do with the leftover pulp?
Making jelly (or juicing for that matter) can seem rather wasteful, with all the leftover pulp. Also, there is a lot of fibre and nutrient loss that comes from separating the juice. You can't really use the pulp to make anything else because you've gone and taken out all its flavour.
You can either stick to making jams and chutneys, or settle with composting the pulp.