During the Second World War, prisoners held by the Japanese in an internment camp in Dutch Indonesia subsisted primarily on dry bread they made themselves in a camp bakery. But when their captors stopped supplying them with yeast, it became impossible to keep making the bread — until some of the inmates who were trained chemists figured out it was possible to use urine as a yeast substitute.
In the video above, Pieter Wiederhold, who was held in the camp as a boy with his father, discusses this urine bread. He gives a longer account of it in his book, The Soul Conquers
Our bread was baked in ovens in the camp kitchen. This task required a large staff of kitchen personnel that came mostly from the Chinese contingent, many of whom were former restaurant cooks. The bread was as tasteful as one could expect considering the few ingredients that were available. After a few months the Japanese stopped supplying the needed yeast, so bread could no longer be made. This meant that the available flour could only be used to make a kind of unappetizing gruel or we would get extra oebi or ketella.
The absence of bread was most disappointing. Some creating chemists in our camp got together to think about an alternative way to make yeast. After much discussion and some experimentation, they came up with a solution. They would make yeast using urine. When I heard about it I was surprised but not particularly disturbed. After all, I had eaten frogs and lizards that had been cooked in our soup and I had drunk filthy water from a toilet on the train. Why would it kill me if I ate bread that was made with yeast derived from urine? When he heard about it Father smiled. "As long as I have something to eat to stay alive," he said.
In order to provide the entire camp with bread, a large volume of urine was needed every day. A number of large drums were placed in several locations around the camp and each carried a sign:
"Do your Duty. Think of the yeast factory.
By 8:00 AM we must have at least two
full drums or there will be
no bread tomorrow."
Some internees were given the job of collecting the filled urine drums and replacing them with empty ones. They made the rounds using a two-wheeled cart with handlebars like the one I had used for my moving tasks in the women's camp. The drums were taken to the bread kitchen where they were put on large wood-burning firest to cook. Nitrogen had to be kept inside the urine, which was then transformed to ureum, which in turn converts to ammonia carbonate. The nitrogen was then removed. The resulting residue could be used as a substitute for yeast. The project was directed by someone who we called the "chief urinist."
The first time I received my allocated piece of this bread I was pleasantly surprised. It did not look much different from the way it was before, and bringing it to my nose I did not detect any unusual smell. It tasted OK, although we were so hungry that almost everything seemed palatable. The uniqueness soon wore off and no one gave it any further thought. The bread was baked in this manner throughout the rest of our internment in Cimahi.
In Life of Pee: The Story of How Urine Got Everywhere
, author Sally Magnusson explains the chemistry:
The secret is ammonium carbonate, formed when the urea in stale urine combines with water. It can be distilled, as the Dutch internees found, in a simple cooking pot. Ammonium carbonate decomposes to form ammonia and carbon dioxide, and it's these gases that cause the pockets or bubbles of air that make the dough rise. When the dough is then baked, the air pockets set, giving the bread its soft and spongy texture.