One of my favorite ‘on-the-side’ vegetables are cucumbers, pickled or fresh. They fit well in salads, as a side to pasta or rice dishes or just as an afternoon snack. They’re very versatile. And even though the pickled version tastes very different, they start out very similarly. A lot of fascinating processes happens durnig the pickling process that cause the cucumber to lose its bright green colour, lose its crispiness and become slighlty translucent.
Ever wondered what really happens when making a pickled cucumber or how to make some at home yourself? We did!
What is pickling?
Pickling is one of many ways to preserve fresh produce. It’s another alternative besides making jam, candying or freezing. Suitable vegetables tend to be those that are crunchy naturally, especially since pickling them will soften them, you don’t want them to turn into mush. You can pickle most vegetables (e.g. red onions), but we’ll focus on pickling cucumbers here.
When you pickle you use either a salty brine or a an acidic brine to ‘pickle’ your produce. The pickle will help preserve the cucumber and it changes its colour, bite and structure.
In the case of the acidic brine, you place your cucumbers in an acidic liquid such as vinegar. By either leaving it in their for several days (depending on the size of your cucumber) or heating it, the acid will transform the cucumber.
The other method uses salt. You place your cucumber in a salty brine. The saltiness prevents the growth of most micro organisms, except for a few desirable bacteria, mostly lactic acid bacteria. These bacteria convert the sugars inside the cucumber and, if added, in the brine, into acids. So over time these pickles turn acidic as well.
Why is your pickle yellow/green?
Cucumbers change colour when they are being pickled. They change from a dark strong green into a lighter, more yellow/brownish green colour. This is because of a chemical reaction occuring in the cucumber. The colour green of a cucumber is caused by chlorophyll. Chlorophyll is what makes most of the plants out there green, it is just about everywhere! However, chlorophyll isn’t very stable in produce once it’s been harvested or processed. Old broccoli florets turn yellow, as does lettuce for instance. All of this is because of the chlorophyll losing its green colour.
This also happens in pickles. In pickles the acid (and heat if used) displaces an important ion in the chlorophyll molecule: magnesium. Without this ion, which sits at the center of chlorophyll, the green colour disappears.
Why is your pickle less crunchy?
Compared to a fresh cucumber, a pickle is less crispy. This again is because of acid (and heat if you used it). The acid soften and breaks down the cell walls between cells in the plant. Remember how important turgor is to help a vegetable maintain its bite? By softening the cell walls, moisture can escape from these walls. As a result the plant loses its turgor, and they can’t be as firm anymore as a fresh cucumber was.
How pickles are made
Any (cucumber) pickle starts with freshly harvested cucumbers from the field. After cleaning and sorting them, they go into the production process. The fresher the produce, the crunchier the pickle. Over time, cucumbers turn softer and lose some of their bite and as a result the pickle would too. So, if you’re making pickles at home use fresh, super crunchy, cucumbers!
Size of your pickle
During pickling the brine, whether it’s salty or acidic, needs to penetrate the whole cucumber that you put in. If your cucumber is very small, that happens a lot faster than when you’re using a large thick cucumber. You can overcome this long wait but cutting your cucumber into pieces, slices or sticks for instance. This also has the advantage that the skin is cut, which is a bit of a barrier for the brine to penetrate through and soften.
Fresh acidic pickles
If you’re making acidic pickles the cucumbers are packed into their acidic brine pretty much right after it’s been prepped. This brine contains mostly vinegar (or other acid) with maybe some sugar and spices (more on those later). The brine needs to have a pH-value below 4.5. At this value micro organisms that make you sick cannot grow anymore, so your pickles are protected.
If you make these pickles at home, you can now place the cucumbers in the fridge for several days until they have transformed into juicy pickles. However, these pickles cannot be kept forever. A few weeks at most. This is because, despite the low pH-value, some micro organisms, especially yeasts and moulds can still grow. As a result, if given enough time, they will spoil you pickles. It depends on the exact recipe how long this will take.
This is why commercial manufacturers pasteurize their pickles after they’ve put them in their brine and closed the lids on top. During pasteurization the freshly made cucumber pickles are heated between 80-82C to a set amount of time to ensure all micro organisms are killed off. Pasteurization does not kill everything, but the micro organisms that might survive this generally can’t grow anymore in this acidic brine!
The video (in German) below shows how these pickles are made. You will notice that the colour of the pickles has changed as soon as they’ve gone through the pasteurization unit. This is because the heat has a similar effect as the acid has, it helps break down and soften the cucumbers skin and cells.
Instead of placing your pickles into an acidic brine you can also ferment your cucumbers. Instead of adding acid, you will add salt. The salt solution (at least 10% in weight) will prevent the growth of most undesirable micro organisms, but allows the growth of those you actually want: mostly lactic acid bacteria. These bacteria convert the sugars inside the cucumber into acid, lactic acid, due to a process called fermentation. It is very similar to the process used to make beer, sauerkraut or bread!
After several days or weeks, depending on the size of your cucumbers, the cucumbers will have transformed. They will have turned sour, less green and softer, just like the acid brine pickles.
Manufacturers of these pickles will then rinse of the salt of the pickles, since they can be really salty at this point (up to 15% in weight). That said, they do want to maintain some, both for flavour and because it helps maintain the pickle crunchy. After that, they’re ready for packaging and distribution.
The video below (in English) shows both the fermented pickle as well as the fresh pickle production process.
While your pickles are soaking in their final brine in the jar, they will take over the flavour of the brine. This is why you will often find spices and other flavourants in the bottom of your pot of pickles. Mustard seeds as well as garlic are commonly used, but you can use pretty much anything. The pickles do need some time to absorb the flavours (again, how long depends on how large they are) so a little bit of patience is helpful.
There is a good reason why you will find a lot of pickles packaged in glass jars. Of course, it allows you to see the beautiful pickles. But glass is also very resistant against acids. A lot of packaging materials cannot handle the acidity of a pickle, glass has no problems. The lids themselves also need a special coating to ensure they can withstand the sourness!
Susan Featherstone, A complete course in canning and related processes – Volume 3 Processing Procedures for Canned Food Products, 2015, p. 352, link
Hyfoma, Augurken, link
Jyoti Prakash Tamang, Fermented foods and beverages of the world, 2010, p. 174-177, link
Gary S. Tucker, Food biodeterioration and preservation, 2008, p.12-14, link