|MadSci Network: Microbiology|
Actually, you are asking two questions. The "algae" in ice cream is really a processed form of algae ( alginates, etc.). These are used as thickening agents in many food products, mainly because they are stable at low (refrigeration and freezing) temperatures. We often use starch as a thickening agent in sauces and gravies, but the starch is usually not stable at low temperatures, and the sauce or gravy "break down" over time. You may see this at home if you place a gravy in the refrigerator for a few days; you often will see a separation of the water from the solids in the gravy.
The other question that you asked relates to microorganisms in foods. First, foods are not sterile. Every food that you eat contains microorganisms from the food itself, the environment, food contact surfaces (plates, glasses, etc.) and you. Every human being has bacteria on their skin, and no matter how much you wash, the bacteria are still there.
As far as microorganisms that are intentionally used in food processing, there is a category of bacteria referred to as lactic acid bacteria. These bacteria produce lactic acid as a by product. Lactic acid bacteria are very, very important, because without them, we would not have things like cheese, yogurt, pickles and some processed meats (pepperoni, summer sausage, salami). People have been using lactic acid bacteria, intentionally or unintentionally, to make these products for thousands of years. Many, many years ago, fermentation of milk to cheese and meat to summer sausage was used as a means of preservation. Before the advent of refrigeration, fresh milk would spoil quickly. Fermenting the milk to cheese preserved the nutritional qualities of the milk in a form that would not spoil as rapidly.
In the past several years, many researchers have begun to believe that the lactic acid bacteria also make compounds which improve the health of human beings. There are some interesting studies that suggest that people who eat lots of yogurt may live longer and healthier lives than those that don't. It is far from proven, but the current research is very interesting.
If you are really interested in this, look at the label of yogurt the next time you are in the store. Many of the major manufacturers of yogurt advertise "active cultures" or some similar term on the label. This indicates that, not only did the processor use bacteria to make the product, they went to great lengths to assure that the bacteria were still alive when they went to the consumer. Again, it may (and I emphasize may) have some beneficial health effects.
Yucky bacteria? Maybe. But a life without pepperoni pizza? Remember, we use yeast to make the crust and lactic acid bacteria to make the cheese and pepperoni. Mayb
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