glass of
water
mug of
beer
| This project is especially good for students of history and literature. |
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glass of water | History of Safe Drinks | mug of beer |
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SIGNIFICANCE & BACKGROUND Significance: "We wouldn't be here had this not happened." Going back to times prior to Pasteur and what is called "germ theory", eating and drinking were rather risky daily activities as one never knew whether sickness or death lurked in the what one ate or drank. What must have been found very early - long before the early Sumerians long prior to Babylon - was that fermented juices and solid foods rarely led to illness. This knowledge was widespread across the face of the ancient world. Apparently, only the North American native tribes were not familiar with the products of alcoholic fermentation. Fermented grains was called beer, while fermented milk was kifir, and that of fruit juices was wine. Three common fermented solid foods are sauerkraut, pickles and the many cheeses.
Not only did the fermentation tend to assure safety, but also it allowed the food source to be stored for long periods of time such as over winter and also for long journeys.
There are three well known types of food fermentation:
Comments made by Shakespeare and others said that beer was often "stretched" by diluting it with [questionable] water. This suggests that there was enough alcohol in the beer to "do the job" of making it safe to drink. Dilution of course was for two purposes - to economically extend the supplies, and to allow the drinking of more water without getting tipsy from it. (And remember that even small children were given beer to drink in the Middle Ages.) How much water was allowed to be added to the beer before it became unsafe? That is the question that can be answered with the following experiment.
WHAT TO DO
General overview of procedure: you want to make a model system using milk, which contains what might be called the "dairy bacteria," These bacteria are in that half of all bacteria that are Gram-positive. You will further add some E.coli to the milk to represent the other group of bacteria - namely, Gram-negative. Dairy bacteria and the E.coli will be your "tool" bacteria because they are harmless relatives of many of the "bad" or pathogenic bacteria. The idea is for you to be able to do the experiment without getting yourself sick, and if and when these bacteria are killed, it will indicate conditions at which the pathogens would also be killed.*
Once the bacteria are all in the milk and mixed thoroughly, you will make the milk more and more alcoholic and test it for viable bacteria. At some point the alcohol content ought to become lethal to the bacteria. It is above that point that you would say the milk is probably safe to drink because the bacteria are dead and thus cannot cause disease.
The particulars of how to do the experiment:
Materials and Equipment Needed:
* The dairy bacteria consist of various forms of streptococcus, and lactobacillus species. These are non-sporeforming Gram-positive bacteria, and can represent the organisms that cause scarlet fever, childbirth fever, rheumatic fever, and strep throat. The E.coli will be representing a number of Gram-negative bacteria that cause devastating gastrointestinal problems such as typhoid, dysentery, and cholera.