Vegetables And The Science Of Pickling

Introduction

Everyday vegetables are transformed into pickles using a combination of salt and acidity; these halt spoilage and impart big flavors and a crisp texture. There are two basic categories of pickles: In vinegar pickles, a vinegar brine works to stave off harmful bacteria. In fermented pickles, a salt brine encourages fermentation and the growth of good bacteria.

Salt is Key

Layered salad ingredients in mason jars with fresh basil

Salt plays three important roles in pickling: It creates an inhospitable environment for bad microbes, it seasons the pickles, and it gives them their texture. This all happens through the scientific principle of diffusion.

Fruits and vegetables are made of millions of individual cells. These cells allow certain molecules to flow in and out to keep things in balance. Small molecules, like salt, will naturally move from an area of greater concentration to one of lesser concentration by a process called diffusion. The salt in pickle brine is more concentrated than that inside the cells of the vegetable, so the salt diffuses into the cells and causes their walls to soften. Larger flavor molecules (such as those in garlic, dill, and vinegar) slowly make their way into the vegetables as well, providing depth and complexity. As the cell walls continue to soften over time, it becomes easier for the flavors to move into the pickles; for this reason a number of our recipes sit in brine for an extended period of time. Learn more aboue the topic advanced canning techniques for optimal texture and flavor.

Acidity as a Preservative

Person preparing vegetables for pickling with fresh greens around

The other key to preservation through pickling is acidity. Bad microbes can’t thrive in a high amount of salt and are also vulnerable to highly acidic environments. Vinegar pickles and fermented pickles differ in the source of acid used to lower the pH of the solution; vinegar pickles quite simply call for the addition of vinegar as a main ingredient in the brine, while the process of fermentation requires the help of good bacteria, and the right conditions, to create the proper acidic environment to produce pickles.

Fermentation

Fermentation relies on the cultivation of beneficial bacteria, naturally present on the produce. These good bacteria outcompete harmful bacteria for food and resources—therefore preventing their growth. The good bacteria are anaerobic, meaning they thrive without oxygen (such as below the surface of a brine). They consume sugars present in the ingredients being pickled and the brine, and they produce byproducts. These byproducts include alcohol, lactic acid, acetic acid, carbon dioxide, and other flavorful compounds. While the production of acid (mostly lactic) is what is “pickling” our ingredients, the other byproducts play equally important roles. They act to inhibit the growth of bacteria and the enzymatic activity that creates spoilage. They also provide a fascinating variety of flavors and sensations. Get more information on preserving wild foraged foods through fermentation and canning.

Balancing Salt and Temperature

A saltwater brine serves to support the growth of good bacteria and protect against the bad. If there is not enough salt, other microbes can take over. However, if the salinity is too high, fermentation is slowed to a halt, and other microbes spoil the product. In each of our recipes, we determined a salt content that promoted adequate fermentation without becoming unpalatably salty.

The temperature at which a pickle is fermented affects the speed of the process. We found the ideal range for the growth of beneficial bacteria to be between 50 and 70 degrees Fahrenheit. Warmer temperatures promote faster fermentation because the desired microbes are highly active and metabolize more quickly. The products fermented above 70 degrees became pungent and broke down too quickly. Much warmer, and beneficial bacteria can’t survive. Colder environments slow the microbes’ metabolism and retard the process: While fermentation can take place in the refrigerator, it occurs at a much slower rate and often doesn’t create an acidic enough environment to be safe. We found 65 degrees to be the best temperature for creating a balance of complex flavors. In addition, we noticed a trend of unique flavor profiles present in pickles fermented at warmer temperatures compared to cooler temps, ranging from boozy to cheesy and buttery to pleasantly fishy.

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