Rise Up – A History of Leavening; Potash
In an earlier post I mentioned that the English translator of one of the earliest cookbooks known made a fairly big deal on her blog about the fact that the cookbook contains Arabic recipes for sandwiches from the 9th and 10th century. It is a neat connection showing how few things in food are really unique to one place or time but to me there is a bigger surprise in al-Warraqs tenth-century cookbook; a possible source of leavening.
There are two broad forms of leavening in baked goods. You can use yeast to biologically produce carbon dioxide gas or you can use chemical leavening to produce gas through an acid base reaction. Note that I didn’t specify carbon dioxide gas when dealing with chemical leavening. Practically all of the acid base reactions used do produce carbon dioxide but there are some reactions that produce ammonia gas also though the use of baker’s ammonia (ammonium carbonate). While they have been important in the past particularly in Northern Europe and Scandinavia (and still have some use) I’m going to ignore them for now and concentrate on reactions that produce only carbon dioxide.
Chemical leavening of the carbon dioxide kind relies on reacting a base containing carbon and oxygen (carbonate or bicarbonate) with an acid. If you remember high school chemistry that means you also have a random hydrogen (from the acid) and something that forms the positive ion on the base. Hydrogen isn’t a problem and goes into forming water but you need to find a water soluble cation that is safe to have in the body. For cooking that pretty much means sodium, potassium, and calcium.
Calcium carbonate might well be the oldest of these chemicals used in food. However most of it’s use is for counteracting acidity. While it can produce carbon dioxide people don’t tend to think of it as leavening. Yet one of the known uses of chalk, calcium carbonate, in cooking is as an additive to poor wheat because it will help a yeast bread rise even with poor wheat in it. The problem is that chalk is cheaper and heavier than bread flour. Chalk isn’t harmful to the body in small quantities but it isn’t nutritious either but the economics of the situation push towards increasing using cheap, poor quality flour and “improving” it with cheaper chalk. However calcium carbonate is the active ingredient in antacids. If you add more than a little amount to the flour you will have unreacted base reacting with the stomach acids which is not a good thing. So it comes down to sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. Most of the time people state that these chemical leavening agents weren’t used as leavening until the 18th century but that is a simplification.
Humans have been using potassium carbonate for thousands of years in the form of lye. Soaking ashes from a hardwood fire in water generates a very alkaline solution of potassium carbonate. If you don’t use it up making soap or other more industrial uses such as fertilizer, glass making, or dyeing you can let it evaporate to get potash – potassium carbonate plus other impurities. I haven’t tried using it but mostly people claim that it has a smokey taste. In English pearlash refers to a refined or purified potash that removed the smokey taste. It is often described as the first leavening agent and it was the first commercially sold one in the 19th century.
It might have an even longer history. There are sources that point to potash as a guild secret ingredient used by bakers in the Netherlands to make a fluffy gingerbread in the 14th century. Potash has also been used in Chinese noodles especially in the northwestern regions near the Gobi desert. In noodles it isn’t a leavening agent really as there is no acid to lead to the production of carbon dioxide. Instead it provides an elasticity and yellow color (also seen in Japanese ramen). Yet if you did combine it with an acid including the lactic acid in sourdough you would gain a leavening effect. While the Dutch can lay the first recorded claim to leavening it is tempting to think that it has been used to at least some extent as a helper to make sourdough rise better for even longer.