Food Composition and Taste

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Sulfur Dioxide in your Food?

The process of food preservation can be dated back about 5000 years ago in ancient Mesopotamia. The process of food preservation can be found in the history of many civilizations for it is an essential tool for successful population growth. Preservation usually involves the means of preventing the growth of bacteria, fungi, and other microorganisms. Traditional food preservation includes drying, refrigeration, freezing, salting, curing, sugar, smoking, pickling, canning and bottling, and etc. Although the processes described above indeed contain elements of chemistry, there are a lot more chemistry involved in the preservation of food today, since chemical additives are now being added for stronger and more prolonged effects.

Chemical preservatives are essential for modern day food industries and human health concerns. Chemical preservatives are not meant to fully substitute processes such as commercial sterilization, which annihilates all enzymatic and bacterial activity. Therefore, chemicals are more effective when used to slow spoiling and maintain the population of microorganisms. Chemical preservatives can be categorized into three general types: antimicrobials; antioxidants; anti-enzymatic. Antimicrobials prevent the development of bacteria, yeasts or molds on food. Antioxidants slow air oxidization of fats and lipids, which eventually can lead to rancidity. Finally anti-enzymatic inhibits the natural ripening and enzymatic processes that would naturally occur after harvest.

One great example of a chemical additive that serves all three functions is Sulfur dioxide. Sulfur dioxide or SO2 (figure 1) can be found in many household items such as sundried tomatoes, dried fruits, vinegar, juice, and syrup. Sulfites are also commonly found in wine preparation to prolong the life of fruit juice, which will allow the process of fermentation to carry-on for a greater amount of time. According to Hassan Gourama, an associate professor of food science at Pennsylvania State University, sulfites are able to react with the energy currency of the cell, adenosine triphosphate to inhibit metabolic pathways. By blocking cellular transport systems within the cells of the food, Sulfur dioxide greatly prolong the enzymatic processes of the cells, and minimalize the development of bacterial colonies.

Fig. 1 Molecular structure of SO2

From left to right, the difference between using commercial food preservatives, Sulfur Dioxide, and just letting it dry…

 

Author: David Zhang

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All About Soda

Every once in a while we all like to take a sip of our favorite beverages to quench our thirsts. One of the most famous types of beverages would be the fizzy drink known as soda. This fizzy bubbly sensation is produced by adding pressurized carbon dioxide gas into the beverage. Therefore sodas are also known as carbonate water.

Soda water is basically created by adding pressurized carbon dioxide through water. As we know from Henry’s law, high pressure increases the solubility of a certain solute. Therefore high pressure allows an abnormally high amount of carbon dioxide to be dissolved in the water, causing the water to be supersaturated with carbon dioxide. This is also why when you open up can of soda pop, all of the gas would rise to the top and try to escape. Therefore if you build up more pressure in the can by shaking it, the soda will blast out of the can when you open it.

The biting texture of soda is due to the result of effervescence. Effervescence is the escape of gas from an aqueous solution. The pressurized dilute solution of carbonic acid in water releases gaseous carbon dioxide during decompression, the lowering of pressure, when one opens the can of soda. The carbon dioxide escaping the water also creates the fizzy sounds and bubbling in the soda.

A common question concerning sodas might be: Why is soda harmful to the body aside from the artificial ingredients and sugar? The answer is: When carbon dioxide is introduced to the water, carbonic acid is created H2O + CO2–>H2CO3(figure1). Salts like sodium bicarbonate (NaHCO3) are needed in order to reduce the acidity.  And other metallic salts are introduced to the solution to neutralize the acidic flavor. Despite all of these salty cover ups of soda’s acidity, soda is still acidic, therefore over consumption is detrimental to the body.

figure 1

Here deep explanation of how the process of carbonation works:

Author: David Zhang

Sources:

http://humantouchofchemistry.com/the-science-behind-soda-water.htm

http://chemistry.wikia.com/wiki/Carbonation


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Hello world!

This is Jennifer, Jonathan, and David!

Our very first post! This is just an introductory message to our blog. We will be discussing the chemical composition behind our favorite thing on earth, food! Do you like our play on the word “food” in our title? For those who do not get it, it’s the lewis dot structure of O2. Hope you enjoyed that.

Happy blogging and remember to visit frequently for more interesting posts!