The Science of Pickles

Step 1: Ingredients

The first step to making pickles is gathering your ingredients. You can pickle almost anything, but this is specifically for cucumbers. There are two main types of pickling methods you could follow. One is the traditional salt-brine method, which takes a long time but has a lot of funky science behind it. The other method, and the method for this particular demonstration, is vinegar pickling, which involves less cool science but only takes a few hours. Aside from fresh cucumbers you’ll need salt, a pre-made pickling spice like this one, or a blend of spices you mix yourself, a little bit of sugar, a sealable jar, and some water.

Step 2: The Jar

Our first scientific stop, is preparing the jar. In order to get a clean microbial slate for our pickles, we need to sterilize our jar. Since I’m using vinegar in my mixture, which has natural antibacterial properties due to its acidity, I’m not going the extra mile of boiling my jar, which you should definitely do if going the salt brine route, and probably in general but. Still, I’m washing my jar thoroughly with soap and some scorchingly hot water.

Step 3: Brine

Next, we want to prepare our brine. First I’m adding a cup of water and allowing that to come to a very small boil. Boiling the brine helps to combine all the flavors that we’ll be adding, as well as prevent any variable tap water conditions from effecting the pickling process. After that’s heated I’m adding a half a cup of apple cider vinegar. Then one tablespoon of salt. The brine should ideally have a salinity between 5-7%. This mixture is around 4.16%, so feel free to add a little more salt if you want. Then I add one teaspoon of sugar, and a little over a tablespoon of pickling spice. These last two ingredients are all for flavor, with little to no role in the actual fermentation process.

Step 4: The Cucumbers

While our brine simmers it's time to prepare our pickles. I cut mine into little wedges, you could do slices, whole cucumbers, the possibilities are endless. Afterwards just put them in your freshly cleaned jar and pour your brine in so that every last inch of the cucumbers are covered. Any area left exposed to oxygen escapes the antibacterial habitat of the brine and is vulnerable to mold and bacteria that causes spoilage. The length of time you leave out your pickles depends on the kind of pickle you chose to make. Vinegar pickles take anywhere from a few hours to 24 hours. Half sour pickles in a salt brine take around four days, but for full sour you’ll have to wait two weeks.

The Science!

Salt brine pickles undergo a lot of changes throughout those two weeks. Some of the changes you can observe without even eating one. Cucumbers are naturally a deep green, thanks to the presence of chlorophyll. Chlorophyll is a molecule that aids the photosynthesis process in plants. It absorbs energy from light, and in doing so absorbs almost every color within the light spectrum except for green, which is then reflected back, making the plant appear green to our eyes. Chlorophyll molecules contain magnesium atoms. In the process of fermentation, as well as the process of cooking any green vegetable, the magnesium atom in chlorophyll is replaced with a hydrogen atom. This change in the chemical make-up changes the natural bright color of the cucumber into a dull green.

Pickles don’t just change color though, they also shrink. This cause of this shrinkage, a process called osmosis, is also the reason pickles are crispy despite being soaked in water for weeks. Water molecules have a tendency to pass through semi-permeable membranes, which encase cells, in order to travel from an area with a high water density to an area with a lower water density. The water that naturally exists within cucumbers travels to the salt brine concentration, since it has a lower water density. This in turn makes the pickles crispier and smaller as they lose volume.

Now let’s talk about the heart of what makes a pickle a pickle: lactobacillus. Lactobacillus, or lactic acid bacteria, is a naturally occuring bacteria on the outside of many vegetables. The process of pickling is, at its core, helping this lactic acid bacteria win the war against all the other bad bacteria attempting to take over the cucumber. Like all bacteria, lactic acid bacteria have a favorite environment. For them, it’s a brine with a 5-7% salinity kept at around 70-75 degrees. By providing them with their ideal environment, we are giving the lactic acid bacteria a headstart in the bacteria race. From the outset they are able to out-reproduce and out-survive other bacteria that might cause the cucumber to mold or spoil. Bacteria rely on sugar for food, by having a larger population than other bacteria in the solution, lactic acid bacteria can monopolize the natural sugars in the cucumber, leaving no food for the rest of the bacteria who eventually die off. Lactic acid bacteria also kill off other bacteria themselves though. After eating sugar, they release something called lactic acid, the real star of pickling. Lactic acid consists of three carbon atoms, six hydrogen atoms, and three oxygen atoms. Lactic acid is naturally anti-some-bacterial, preventing both e. coli and salmonella. Aside from lactic acid, lactic acid bacteria also produce small amounts of alcohol and CO2, both of which can kill bacteria. Just the presence of lactic acid can make the brine less habitable to other bacteria. Cucumbers have a natural pH of 8, just right of neutral on the pH scale. Lactic acid, being an acid, lowers the pH of the cucumber. The pH of a pickle is around 4.6, which is pretty acid. Many bad bacteria cannot survive in such an acidic environment.

This acidity, and lactic acid bacteria in general, isn’t just important as a bacteria battler. It’s the reason pickles taste like pickles! Lactic acid is naturally sour, and its presence alters the flavor of the cucumbers to be more and more sour as time goes on and more of it is produced. Sour taste in any food comes from a molecule with positively hydrogen ions, like lactic acid, or citric acid, found in citric fruits. How sour the resulting flavor is depends entirely on how easily a molecule releases this hydrogen ion.

Vinegar pickles are unfortunately less exciting. Instead of harnessing the invisible power of lactic acid bacteria, the vinegar does all the work. It provides both the sour taste for the pickles, which comes from being soaked in the sour vinegar, and keeps bad bacteria at bay with its natural antibacterial quality.

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