Fermented Happiness: The Fascinating Importance of Yeast
Years ago, one of my university lecturers asked me what my favourite living organism was. I have to admit, the first thing that popped to mind was Halle Berry, but realising the lecturer was probably looking for something a little more donnish, I paused and tried to look a bit more intelligent before answering him.
“Yeast” I answered. He nodded with an approving smile before telling me it was a good answer. I knew that it was as I had been reading about yeast the day before and had been fascinated by what I had learnt.
Yeast is a living organism, a single-celled fungus just 3 thousandths of a millimetre across. There are around 24 species of yeast used by humans but it is the one called Saccharomyces cerevisiae, which means “sugar-eating fungus,” which has changed our lives on this planet, for the better.
Turns out that much of what we depend on to live today would not be possible if it were not for yeast. I kid you not. Without it, there would be no bread, no biofuels, no insulin and perhaps more shockingly, no beer or wine. In fact, no alcohol at all. So, what would a world without yeast be like? In a word, sober. Probably sadder, too.
The first leavened bread loaves were thought to be made by Egyptians between 3,000-5000 years ago when beer foam was first added to bread dough. The chances of discovering accurate data for such events are on the anorexic side of slim. Leavened, or bread risen because of the addition of yeast, is now eaten in almost every culture on Earth.
Wine was recorded as first being made from vineyards in Tbilisi in Georgia, some 4000 years ago. Although some think that it has been around a lot longer, but was not farmed on such a large scale. Maybe it caused such bad hangovers that nobody felt like recording anything until one day, a Georgian picked up a stone and chiselled away details of what they drank at his stag do the night before.
Wines back then were made with wild yeasts found on the grape skins, but commercial wine today needs to have yeast added. It’s a simple process. A packet of wine yeast is opened and sprinkled directly on top of the grape juice. There is no need to stir as it will dissolve on its own. Once the yeast is added, they just let it be, as Lennon and McCartney would say.
So, how old is the oldest bottle of wine? An ancient, intact glass bottle of wine, dating back to the 4th century, was discovered during the excavation of a Roman nobleman’s tomb in modern-day Germany. It has not been opened but scientists believe it to still be drinkable. To the best of my knowledge, it’s still sitting in a museum somewhere, maybe waiting for someone to open it when the drinks run out at the staff Christmas party.
The oldest evidence of beer comes from forensic traces on fragments of 7000-year-old Iranian pottery. Beer was drunk regularly by most humans in ancient times as water was often dirty in those days and caused illnesses, whereas the alcohol in beer discourages bacteria from infecting the beer thus making it safer to drink.
With no leavened bread, our diets would be less dependent on crops like wheat and far more on root crops such as potatoes and imported foods like rice. Imagine no more toast, no more bacon or tofu sandwiches. Since the lockdown began in March 2020, we seemed to have turned into a nation of bread makers, and the prime riser of these must be the sourdough loaf.
Sourdough does not need any added yeast to get it going, but works with just the wild yeasts that are all around us, in our gardens, on fruit skins, on our computer keyboards etc.
Yeast cells are different from animal and plant cells, which is why they are not classed with them. They have a kingdom of their own. They start respiring carbon dioxide as soon as they come into contact with flour or sugar. These are the bubbles in your sourdough starter for example. They are actually expelled yeast fart bubbles!
As long as there is a supply of oxygen, yeasts crank out carbon dioxide and water as by-products. But if oxygen is scarce or sugars are available, the cells start a fermentation process, which causes them to spit out ethanol, more commonly known as alcohol.
Baking is a very aromatic process, with most of us loving the smell of freshly baked bread, and yeast is one of the causes of that delicious aroma. Estate agents know this only too well and often encourage anyone hoping to sell their house, to bake a loaf just before showing anyone around.
Whilst researching this article, I came across an unusual ingredient in bread making that was written about in ancient Rome. Pliny the Elder, the Roman naturalist and philosopher, was the first to suggest using dead wasps to help make bread!
It works because wasps get coated in wild yeast as they fly around searching for food, and this provides what is needed to make a loaf rise but please, don’t try this at home! All you really need to make a healthy sourdough starter at home is wheat or rye flour and water: the yeast and bacteria floating around your home will do the rest.
Fortunately for the human race, yeast is here to stay. In fact, it’s very hard to actually kill. You can starve it, dry it out and even freeze it, but if you give it a little sugar and some water… leave it for a bit and Wham Bam, you have the start of a party – booze n bread.
Written by Jerry Short
Jerry is a freelance writer, who has worked as a wildlife film producer for the BBC, a journalist, a musician and a narrator. He has a lifelong interest in science, has been stalked by lions, swum with sharks and is addicted to watching cookery programmes and is definitely a "foodie". His heroes are Douglas Adams and Charles Darwin.