Pucker up, it’s time to talk pickles. Pickled peppers, cukes, onions, eggs, really anything that can be preserved by tossing it in a brine solution and letting nature take its course. In the case of pickling, its about establishing the right conditions for one group of bacteria to win out over another. The ones that proliferate give the food the flavors people like, and they preserve the food for the long haul (to the pantry or refrigerator… tough times). The ones that lose would have made the food taste off and can even make the food poisonous. It’s a rigged game that we don’t mind betting on.
Chemistry, as you might expect, is at the root of this. The brine solution makes conditions acidic, which the bacteria we want to thrive happen to prefer, and as they thrive, they generate lactic acid, making their surroundings even more to their liking. At the same time, the bacteria we want to fail prefer an environment on the other side of the pH scale. An ideal pickling solution ends up at a pH of 4.6, somewhere between tomato juice (4) and black coffee (5) in terms of acidity.
We have passed into the tenth week of the weekly, online, video series “Chemistry Now,” and the chemistry of the kitchen returns as a source of interesting video and lessons. As we’ve written before, please view the video, try the lessons, and let us know what you think.
Photo: T. Brown
Through the Chemistry Now series, NSTA and NBC Learn have teamed up with the National Science Foundation (NSF) to create lessons related to common, physical objects in our world and the changes they undergo every day. The series also looks at the lives and work of scientists on the frontiers of 21st century chemistry.
Video: “The Chemistry of Pickles” (one in a 6-part Cheeseburger Chemistry series) describes the role of fermentation, lactic acid, and pH in the process of pickling food to preserve it. (The Latin root of the word “preserve” is traced in a separate Word Root.)
Middle school lesson: the pH and Acidity Lesson Plan gives students an understanding of pH indicators, pH, and the acid/base properties of some common household mixtures.
High school lesson: the pH and Acid Content High School Lesson Plan helps students understand pH indicators, pH and properties of acids and bases, and titration of an acid.
You can use the following form to e-mail us edited versions of the lesson plans:
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