Whether to add pectin
Updated
What changes
Adding pectin changes almost everything about how a batch runs: the cooking time, how much boils off, the yield, and how much room you have to get it wrong. It is not an ingredient decision so much as a decision about which process you are running.
| Without added pectin | With added pectin | |
|---|---|---|
| Fruit choice | Constrained by pectin content | Open |
| Ripeness | Matters, and differs for jam and jelly | Matters less |
| Cook time | Longer, to concentrate | Short, often a minute at a boil |
| Doneness test | Temperature, sheet or refrigerator test | By the clock, per the pectin |
| Yield | Lower, water has been driven off | Higher |
The honest case for each
Both are legitimate and the published guidance covers both, so this is a choice rather than a standard to meet. What differs is where the risk sits: one puts it in judgment at the stove and the other puts it in following a schedule exactly.
Without added pectin the product is fruit, sugar and acid, the yield is lower and the flavor is more concentrated because you have boiled water off to get there. With added pectin the yield is higher, the batch is faster, and the result is more repeatable, which matters more as the number of jars goes up.
The thing to avoid
The failure mode is mixing the two approaches, which is easier to do by accident than it sounds and produces a batch neither method would have produced. Pick one, follow it through, and write down which one you used, because the two look identical in a finished jar and nothing else will tell you later.
Taking a no-pectin recipe and adding pectin to it, or the reverse. The two routes have different sugar quantities and different cook times, so a hybrid is a batch nobody has a doneness test for. Follow one set of instructions through.