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Why Our Food Rots: Part III

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Welcome back for part three of this food preservation saga! I am right now looking at my can of Diet Coke. It contains carbonated water, caramel color, aspartame, phosphoric acid, potassium benzoate, natural flavors, citric acid and caffeine.

This drink I like a lot. One reason I like it is because it tastes better than water. This beverage also gives me the caffeine that helps me make it through long and arduous days of discussing the finer points of grading tests for medical students.

A couple of the ingredients of the drink are purely for enjoyment. The carbonation, natural flavors and aspartame give Coke the tingle, taste and sweetness I desire in a beverage. However, it has been shown that the carbonation does inhibit microbial growth.

But what about the other ingredients? Why is phosphoric acid, citric acid and potassium benzoate in my drink? These three ingredients have dual purposes. The citric acid gives the tart taste Coke drinkers expect. The phosphoric acid helps lower the pH of the drink so the potassium benzoate can prevent growth of fungi and bacteria in a can of Coke. The potassium benzoate is a food preservative that prevents microbial growth by destroying the microbes' ability to make energy. No energy, and microbial death is certain to follow.

Fortunately, potassium benzoate does not have any known effects on humans. Very small amounts of this preservative are used in drinks. Unfortunately, it only works at killing microbes when at acidic or low pH's. Potassium benzoate is commonly used in fruit juice, carbonated drinks, pickles, and preserves (jams and jellies -- it keeps mold from growing on the top).

To help in preserving other foods, there are alternative preservatives that have been developed. Without these preservatives food costs would increase. Day-old bread would be moldy old bread. Most people would be shocked a the terrible appearance of our food if all preservatives were eliminated tomorrow.

There are basically five different classes of food preservatives. This is using the strict term for food preservative as something that inhibits microbes from growing. They are:

• Benzoates
• Sorbates
• Propionates
• Nitrates
• Sulphites

Sorbates are compounds like potassium sorbate, calcium sorbate or sodium sorbate. Another name for these compounds is sorbic acid. These compounds prevent the growth of mold on/in cheeses, jelly, cake, syrup, dried fruits and wine. Sorbic acids are naturally found in plants and have been found to be safe for human consumption. They inhibit microbial growth in the same way that benzoates do.

Propionates also inhibit microbial growth by inhibiting energy production. However, they do not require low pH's to inhibit the microbes. Compounds like sodium propionate and calcium propionate are placed in bread, biscuits, cakes, pastries and other flour products to prevent that ubiquitous mold from destroying them. As a result, bread does not have to be purchased every day to keep the mold monsters away.

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