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Look at the title picture of the two jars of preserved gherkins. Apart from the herbs, can you see any difference? I dare say no. Same green cucumbers, same briny liquid—so what gives?  The answer is that the gherkins in the left jar are preserved with vinegar, and the ones in the jar on the right are fermented. While they appear to be alike – and are often generally referred to as “pickles” – there is a difference between fermentation and pickling.

First of all, they differ in taste. The pickled gherkins taste bright and acidic, while the fermented ones have a tangy and more complex flavour. Additionally, they contain numerous beneficial probiotics, which have a positive impact on health.

Let’s have a closer look at pickling and fermentation and compare them.

Quick Overview

Fermentation

Fermentation is a biological process where beneficial bacteria convert sugar and starch in the food into lactic acid. This happens naturally when vegetables are submerged in salt water or when salt is added directly to them.

To start fermentation, we make a salt brine or add salt to the goods we want to ferment. The salt creates an environment where the good bacteria (for example, lactobacilli) thrive while harmful ones can’t survive.

After a few days, we can watch little bubbles in the jar. The lactobacilli have started converting carbs (sugar and starch) into lactic acid and carbon dioxide (CO₂). The latter displaces oxygen from the jar by pressing it out of the jar (sometimes even together with some brine). That’s great because lacto-fermentation needs an anaerobic environment (that is, an environment without oxygen) to work properly.

The fermentation process needs temperatures between 18 and 22 °C (64 – 72 °F). Not only does it form lactic acid and thus preserve the food, but it also increases the content of vitamins and micronutrients and creates probiotics, which have a positive effect on gut health.

After 1 – 4 weeks, depending on the food and the taste we like to acquire, we transfer the ferment to a cool place, for example, the fridge to stop – or rather, slow down – fermentation.

Fermented vegetables have a salty-fresh, complex, tangy flavour.

Examples of fermented goods are sauerkraut and kimchi, sourdough, kombucha and yoghurt.

Pickling

Pickling, on the other hand, is a chemical process where food is preserved in an acidic solution, usually vinegar. The acid (here: acetic acid) creates an environment that’s too harsh for harmful bacteria to survive.

To pickle vegetables, we make a brine from water, vinegar, salt (and sometimes sugar), heat it and pour it over the vegetables in a jar. During cooling, the jar forms a vacuum, which is an environment with low oxygen. That and the acid from the vinegar and the salt kill any harmful bacteria.

Unlike fermentation, pickling doesn’t affect vitamin levels or create probiotics.

Pickles are ready to eat within a very short time, usually a few hours to a few days. They are usually kept in a cool, dry place (usually the fridge), unless you preserve them additionally in a water bath canner. The canning makes the low-oxygen environment in the jar into a no-oxygen (that is, anaerobic) environment. That way, you can store it at room temperature for up to 2 years.

Pickled vegetables have a bright, sharp, fresh flavour.

Typical pickles are pickled gherkins, onions and zucchini.

The role of salt in preservation and texture

Understanding these basic differences leads us to a crucial component in both processes: salt.

Salt plays multiple crucial roles in fermentation, but also in pickling, working through several different mechanisms:

Preservation Through Osmosis

Salt not only draws water out of the vegetables, but also any pathogens that may be present. This dehydration effect concentrates the remaining liquid into a high-sodium environment where most spoilage bacteria cannot survive. The salt essentially “pickles” the gherkins at a cellular level, creating an inhospitable environment for decomposition.

Selective Bacterial Environment

While salt kills bad bacteria, it also encourages beneficial bacteria, which are more salt-tolerant than pathogens. The right salt ratio (typically 2 – 5 % by weight) is therefore essential to create a selective environment where only the bacteria we want can thrive and produce lactic acid.

Texture Preservation Through Cell Structure

Apart from its preserving benefits, salt also firms the vegetable texture by drawing moisture from cell walls and then allowing them to reabsorb the salty brine. This process replaces the vegetable’s natural water content with salt water, which helps maintain the crispy texture of the cell walls. The salt also breaks down pectin enzymes that would otherwise soften the vegetables over time.

During fermentation, this happens automatically when the vegetables are covered with brine, but we also use this effect to keep gherkins crisp when pickled. This is why many pickle recipes call for pre-salting (brining) the vegetables for several hours before the final pickling – it jump-starts this firming process and results in crunchier final pickles.

Concentration Matters

Too little salt won’t provide adequate preservation or firming, while too much can make pickles inedibly salty and overly firm. The optimal range depends on your method – quick pickles typically use less salt since vinegar provides the primary preservation, while fermented pickles rely more heavily on salt concentration for both safety and texture.

This dual action of preservation and texture enhancement makes salt the cornerstone ingredient that separates successful pickles from mushy, spoiled failures.

Acidity levels and food safety

Acidity levels are absolutely critical for safe pickle making – they’re the primary defence against dangerous pathogens, particularly botulism:

The pH Safety Zone

For safe home pickling, your final product must have a pH of 4.6 or lower. This acidic environment prevents Clostridium botulinum (the bacteria that cause botulism) from growing and producing toxins. Botulism is especially dangerous because it can be fatal, and the bacteria can survive in low-oxygen environments like sealed jars.

Understanding Acetic Acid Percentages

What we can do, now, to ensure the right pH of the finished product is to use a vinegar with the right amount of acid. Most pickling recipes call for vinegar with at least 5% acetic acid. This isn’t arbitrary – it’s the minimum concentration you need to reliably acidify your brine so that it’s safe when combined with water and vegetables. Using weaker vinegar can create unsafe conditions.

When you want to modify recipes, use different vinegar types or work with vegetables with varying natural acidity levels, you may want to test the pH level of your pickles. Testing strips or digital meters can give you a definitive confirmation of the pH.

Proper Brine Ratios

The standard safe ratio for vinegar and water is typically 1:1, which means one part of vinegar to one part of water. This can vary, however, based on other ingredients like salt and sugar. Never reduce the vinegar content in tested recipes without understanding the pH implications. Adding too much water, vegetables with high pH, or alkaline ingredients can push your pickle into the danger zone above pH 4.6.

Summary

While both are preserving methods, fermentation and pickling differ in the way they approach preservation: fermentation is a biological process that uses salt to create an environment ideal for beneficial bacteria, usually lactobacilli that convert carbs into lactic acid.

Pickling, on the other hand, is a purely chemical process that uses acidity, typically from vinegar, to also create an environment where harmful bacteria can’t survive.

Fermentation takes longer (usually several weeks) and enhances vitamins and creates probiotics, while pickles can be eaten almost immediately but have no altered nutritional content.

Also, the flavours differ: ferments have a more complex and tangy flavour while pickles taste more bright and acidic.

Neither is better than the other, though, both methods produce delicious results! They are just two different ways to preserve food. I happily use both, fermentation and pickling, to make our food last through winter, and I recommend the same for you!

Ready to try both methods? Start with quick pickles, such as zucchini or pickled gherkins, if you want immediate results, or begin a fermentation project (for example, fermented gherkins) if you’re interested in the health benefits.