The Acids in Our Food

The Acids in Our Food 

Many foods have the ability to send the message “sour” to our brain when consumed. This is because of low pH levels that result from H⁺ ions reacting temporarily with molecules on the side of the tongue. This causes a change in shape, which sends the “sour” message to the brain. This entire process is due to the presence of weak acids. All citrus fruits contain citric acid and the overall flavor in these fruits is due in part to ascorbic acid. Ascorbic acid is also known as vitamin C. The pH levels of these fruits vary usually from 2 to 4, which correspond to H⁺ concentrations of 0.01 and 0.0001 moles per liter. This means that the level of hydrogen ions in things such as lemon and lime juice is 100 times greater than things like oranges and tomatoes. Wine also contains weak acid, usually at about 0.7%. Even milk contains an acid, known as lactic acid. Vinegar, which is produced by the fermentation of sugars when they are oxidized beyond the alcohol state, has a pH of about 3. It is a dilute solution in water of acetic acid. This process of oxidization is why some drinks become too sour to drink when exposed to air for a long period of time.

Unfamiliar terms:

• pH: a shorthand way of indicating H⁺ concentrations; the power of 10, without the negative sign, for the molarity of an H⁺-containing solution (G-8)  

As a child I liked the taste of anything sour and have even tried to eat lemons and limes all by themselves. It always seemed funny to me when others found this strange or did not like sour things as much as I did. While I do not know the reasons behind mine and other’s preferences, I found it interesting to learn about this odd taste. I did not know before about pH levels and that in the weak acids I consume these levels are usually low. While I had heard of citric acid before, I had not known about ascorbic acid, which is vitamin C. I also found it interesting that the level of hydrogen ions in lemon and lime juice is so much higher than those of oranges and tomatoes. After reading this section I also learned that the cola drinks I drink every day have phosphoric acid in them. Learning about these many different types of acids made me realize that I consume much higher levels of acid-containing foods and beverages than I previously knew. I love citrus fruits and drinks, and also drink soda on a regular basis. I will also have vinegar in my food as well as milk, which has lactic acid.

In the future, I wonder if there will be new discoveries as to how all of these different types of acids can be utilized. On the side note of this section it explains that washing your hair with an acidic substance such as vinegar makes it shiny. This is because the acidic substance shrinks the hair cuticles and hardens them, making them lie flat. I did not know about this trick, and would possibly try it if vinegar had a better smell. This section also states that vinegar can help dissolve soap scum, which increases the luster of hair. This means that vinegar can also be used to clean other things. Possibly in the future, chemists will be able to use the various acids found in our food and beverages and extract them for further use along the same lines as vinegar.

Baird, Colin. Chemistry in Your Life. W.H. Freeman & Company, New York. 2006. 429-430.