Glucono Delta-Lactone (GDL)
What it does
Slow acid release (tofu, cured meats).
How it's made
Made from glucose.
Glucono delta-lactone, or GDL, is a mild acidifier with a special trick: it is not very acidic when first added, but slowly turns into gluconic acid when dissolved in water, releasing acidity gradually. This makes it ideal for jobs that need a slow, even set or acidification, such as setting tofu, curing certain sausages and leavening some baked goods.
It is made from glucose, usually derived from corn starch. The glucose is oxidised to gluconic acid, most often by fermentation with the mould Aspergillus niger or with enzymes, in a controlled reaction. Under the right conditions the gluconic acid forms its lactone — a ring-shaped version of the molecule — which is the stable, slow-release form sold as GDL.
The lactone is crystallised out and dried into a white, food-grade powder that stays inactive until it meets moisture. Once in a watery food it gently converts back to gluconic acid over minutes to hours, which is exactly the slow, controllable souring that makes GDL so useful.
Possible reactions
Generally safe.