Crystallization

Crystallization is a dissolved solid returning as a solid you can feel. In kitchen work the usual culprit is Sugar in a kettle. Candy-stage temperatures vary with the sugar system and the desired texture.

Jam that grits #

Ohio State’s failure list for cooked spreads includes crystals from sugar that never fully dissolved, or from overcooking ¹. Undissolved grains are seeds. A pot you scrape down carelessly throws those seeds back in. Over-concentration drives water off until sugar has nowhere to stay dissolved — Evaporation gone too far.

Observe: stir until no grit remains on the spoon before the hard boil. Look at the jar days later: a sandy layer is sugar, not pectin sand. Weeping jelly is often too much acid, a different failure ¹. Application: Jam and Jelly.

A thermometer cue for concentration is a hint, not a crystal law. Pectin-added jams often finish by a timed boil instead; use the test that belongs to the formula.

Salt is a different crystal #

FAO salting is dry salt or brine, not a jam defect ². Coarse grains dissolve slower on a curd; they can pock a surface if they sit. That is a cheese-salting observation. Salt is the substance.

What this is not #

Ash in flour is inorganic residue after combustion, a bran indicator — not sugar crystal. Ice in a freezer is water’s crystal; it wrecks vegetable texture when it grows large, which is why blanch-and-freeze is a different process. Do not treat freezer burn as jam grit.

Action: dissolve completely, avoid seeding, stop concentrating when the gel test says stop. Quality failure, not a canning-safety failure.