Ammonium bicarbonate

Ammonium bicarbonate, Vol. (NH4)HCO3

This is another white crystalline material. It is an extremely useful leavening agent for biscuits because it decomposes completely when heated, breaking down into carbon dioxide gas, ammonia gas and water and thus leaving no residue in the baked biscuit. The name "Vol", by which it is commonly known, derives from "volatile salt" because of this complete dissociation. It is readily soluble, but is very alkaline giving softer doughs which require less water for a given consistency.

Despite the strong smell of ammonia, both in solid form and in solution, only a small proportion of the available gas is lost when it is dissolved in water and held at normal temperatures. Even in solution for 24 hours, little of its potency is lost.

It is important that all of the ammonia is driven off during baking otherwise unpleasant tastes are encountered. Ammonium bicarbonate is therefore not suitable as a leavening agent in any products that leave the oven with more than 5% moisture, e.g. cakes and sponges.

In many cases, it has been found satisfactory and convenient to eliminate all acidulants in biscuit doughs and to use only Vol and soda. The soda is there primarily as a means of controlling the acidity of the baked biscuit.

Vol is purchased as a white crystalline solid in paper or plastic bags. It is prone to severe lumping even when stored in dry conditions. It should, therefore, be used as soon as possible after delivery. It may be best to dissolve the chemical in water before adding to the mixer.