How Do Microbes Help Make Some Of The Food We Eat?

Imagine a hamburger with blue cheese on a sourdough baguette. Alongside is a tall glass of beer. And for dessert, have some healthy yogurt with a drizzle of chocolate sauce. Or maybe you would prefer sausage topped with Swiss cheese and sauerkraut. In either case, your entire meal relies on microorganisms, also called microbes. Fungi microbes, called yeast, make the beer and the bread. Bacteria microbes are responsible for the cheese, yogurt, chocolate, sausage and sauerkraut.

Yogurt

Two bacteria create the tang and thickness of yogurt, Lactobacillus bulgaricus, or sometimes Lactobacillus acidophilus, and Streptococcus thermophilus. Yogurt producers add these bacteria to milk at just the right temperature, about 50 degrees C. The bacteria produce lactic acid, which begin what might be called digestion of the milk, turning it to yogurt. Another word for yogurt's bacteria is probiotics, or live microbes. Some yogurt makers also add prebiotics when making yogurt that provide food for the bacteria. These prebiotics may include carbohydrates, fiber or sugar.

Yeast Breads, Beer and Wine

As the single-celled yeast fungi eat sugar and starch from bread flour or beer hops, they produce carbon dioxide and alcohol. In the process, bread rises and the air holes from the carbon dioxide bubbles create an airy texture in the bread. Makers of beer and champagne need both the alcohol as well as the sparkling effect the carbon dioxide produces. Both bread-making and alcohol production need just the right amount of moisture, food and warm temperature for the yeast to grow.

Cheese

All cheese-making relies on bacteria called rennin, or chymosin. These bacteria, originally from enzymes from the stomach of a cow or calf, convert milk into solids, called curds, and liquid, called whey. The curds turn into cheese once they are dried and salted. After 1990, manufacturers began making cheese with genetically modified chymosin, which then produces the rennin needed for the cheese-making process. For blue cheese, the cheese-maker injects penicillium bacteria, gathered from another blue cheese, into any cheese when it is still in the curds-and-whey stage. Holes poked in the curd with a sterilized poker provide the bacteria with the air it needs to grow and form the distinctive color and flavor of blue cheese.

Chocolate

Chocolate illustrates the principle that bacteria exist everywhere. Chocolate begins with cacao seeds that are exposed to bacteria from splitting tools, workers' hands, carrying boxes and anything else they come into contact with. When the seeds are split, heaped into covered piles and left for five to seven days, they begin to warm, and the bacteria, as well as fungi and yeasts, begin to grow and ferment on the pulp that surrounds the cacao beans. During this process, the cacao seeds turn dark brown and develop their chocolate flavor. Once the beans dry and are roasted, all traces of bacteria and yeast disappear.