Food Composition and Taste

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Sulfur Dioxide in your Food?

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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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