Microbes help to produce a huge range of food, from cheese, bread, beans and pulses, chocolate and vinegar as well as many drinks. For lots of other foodstuffs they even play an indirect role, like helping plants to grow and then breaking food waste down. Without them, we’d go hungry and be surrounded by waste!
Humans have been using microbes to generate food for thousands of years, long before we even know microbes existed. Alongside domestication of plants and animals for food production, spontaneous fermentation was used as a beneficial process to preserve foodstuffs, increase nutritional value and reduce pathogenic bacteria. It also resulted in improving the taste of many food products. Many of the same basic processes are still used to this day. The chemical reactions for fermentation vary slightly between different microbes, but essentially convert a carbon source, like glucose into pyruvate. By-products of the reaction are then exploited for making the different types of food.More Information
Bread-making is one of the oldest food production processes known, and cereal cultivation dates back to ~ 10,000 BC. Records of beer and wine-making also date back several thousand years. Yeast is an important microbe, and probably best known for these fermentation processes. In bread making yeast ferments sugars in the cereals to generate gas, making bread rise, whereas the sugars from cereals or grapes are converted into alcohol in beer or wine production. The fermentation process of making bread doughs rise can also be carried out by other microbes called lactic acid bacteria, which are found in sourdoughs. Yeasts are eukaryotic microbes and belong to the same group as fungi, whereas lactic acid bacteria belong to a separate kingdom and are classed as prokaryotes.
Fermentation of dairy products is another ancient process. It was mainly used to preserve products that have a very short shelf-life. The low pH generated by the process helps to reduce pathogenic bacteria like Shiga toxin-producing Escherichia coli that can’t grow well under these conditions. The main microbes involved in the process are lactic acid bacteria, and although they are essentially the same, thousands of different types of cheeses and many different types of yoghurt drinks are produced. The same process is also used to preserve vegetables, such as sauerkraut or kimchi.More information
Chocolate is made from coco beans. Microbes ferment cocoa beans to give chocolate its flavour. Yeasts, lactic acid bacteria, and acetic acid ferment the pulp surrounding the bean. After fermentation, the beans are dried and roasted before being processed into a liquid and finally into raw cocoa bars.
Vinegar is a well-known addition to fish and chips. But why is vinegar so strong and what has it got to do with microbes? The French meaning of the word is ‘sour wine’, describing that strong smell. Vinegar can be made from fruit juices or from alcohol, like wine or cider. It is made by the microbial process of fermentation, converting alcohol (ethanol) into acetic acid, and carried out by a specific group of acetic acid bacteria that function in aerobic conditions (i.e. in the presence of oxygen). Traditional methods of producing vinegar can take quite some time, where the alcohol is left to ferment in wooden barrels for several months. Lots of different types of vinegar can be made, each one with different flavours depending on what was used to make it.
Marmite isn’t a fermented product, but is a by-product of fermentation, made from brewers yeast. After the brewing process of making beer, yeast cells are collected and undergo a natural chemical process where they release enzymes that break down their own cells and proteins (autolysis). This extract is concentrated and undergoes a further process that gives marmite its very distinct taste.
Soil is a mixture of inert, mineral particles (clay, silt, sand and stones) and organic matter, termed humus. Topsoil, the part in which plants grow, contains an unimaginable number of microbes – more in a teaspoon of soil than the number of people on earth. Compost is made through natural microbial processes that break down plant material to one of the main components of humus.More information