Why Does Orange Juice Hate Toothpaste?
Orange juice and tooth brushing are both part of the morning routine of millions of people around the world. At some point in our life we all have experienced the change in taste of orange juice right after tooth brushing. It transforms the flavor from a sweet enjoyable drink, to a gruesome bitter one. What interaction between toothpaste and orange juice is causing that terrible flavor?
The quick answer is sodium lauryl sulfate (SLS), a widely used chemical that makes toothpaste foamy. This molecule is amphipathic, meaning that it can attract both polar and non-polar molecules. It is also a surfactant meaning that it helps lower the surface tension between water and fats. These chemical properties and its inexpensive cost of production, make it a very popular detergent in different personal care products including toothpaste. When SLS has contact with the tongue two main changes occur. First, it binds to sweet receptors in your taste buds making it harder to detect this taste in your food. Also, because of its detergent properties, SLS binds to phospholipids that normally block the bitter receptors, making it easier to detect bitterness in food.
With the sweet receptors blocked, and the bitter receptor more exposed than usual, the food you eat right after brushing your teeth will not taste as pleasant as you would expect. The sweetness will barely be detected, and the bitterness will be more prominent than usual. It is also interesting to notice that it is not orange juice in particular what goes bad after the dental cleaning routine, but it is the most common beverage people drink in the morning. However, because citric juices are highly sweetened, the effect of SLS on your taste buds can be more noticeable with this kind of beverages.
REFERENCES
· Allison, A.M.A. and Chambers, D.H. 2005. Effects of residual toothpaste flavor on flavor profiles of common foods and beverages. Journal of Sensory Studies. 20: 167–186.
· University of Wisconsin-Madison. 2007. Why does orange of grapefruit juice taste so nasty after I brush my teeth? UW-Madison News. Extracted November 15, 2015. http://www.news.wisc.edu/14477
· U.S. Department of Energy. Orange juice and toothpaste. http://www.newton.dep.anl.gov/askasci/chem00/chem00216.htm