Why Homemade Lacto Fermented Pickles Get Fizzy

Written by Michael Grant in Lacto Fermented Vegetables

This post contains affiliate links.

When you first start making lacto fermented pickles you will find that a few days into the process if you are using a sealed jar it will start to pressurize and need to be burped (opening the lid momentarily to release CO2).  This is a natural part of the lacto fermentation process and nothing to be worried about.

Lacto fermentation is a process where lactic acid bacteria (LAB) consume sugar producing lactic acid and CO2.  Pickles will become fizzy because of the active LAB in and around the cucumbers during fermentation.  The action of the LAB will slow as the sugar is depleted or when refrigerated.

Lacto Fermented pickles are made in a variety of ways but all of them require the action of LAB which acidifies the cucumbers by using the simple sugar found in the cucumbers for energy.

Fizzy brined pickles have not gone bad

Do not be concerned if your lacto fermented pickles go through a fizzy stage.  This is perfectly normal and to be expected when lacto fermenting pickles.  It is a sign that the LAB are doing their job of acidifying the pickles and in the process releasing some CO2 gas.

It is the CO2 that makes your lacto fermented pickles fizzy.  Cucumbers naturally have LAB on them when they come from the field and like any living thing need energy to live.  In their case they consume the simple sugars which are found in the cucumbers.  As the LAB consume the sugar in the cucumbers they break it down into metabolic energy usable for the cell, lactic acid and CO2. 

The CO2 is just a byproduct of the fermentation process and exists in all forms of fermentation including all methods of lacto fermentation. 

The cucumber fermentation process

The process a cucumber goes through to become a pickle requires specific environmental conditions which protect the cucumber from spoilage while allowing the LAB to multiply and acidify its environment.

Lactic acid bacteria need an anaerobic environment for fermentation

LAB are anaerobic bacteria which means they grow best without access to oxygen (anaerobic conditions) so when you start your lacto fermented pickles you need to have a sealable container such as:

  • Repurposed food grade glass jar
  • Food grade plastic container
  • Swing top glass jar
  • Mason jar
  • Fermenting crock
  • Wooden pickle casks

Any of these are acceptable choices and each will give your pickles a different taste.  Ensure you match the size of the container with the amount of pickles you want to make.

When packing the container ensure the cucumbers are under the liquid.  This can be done using one of these options

  • Specially designed Weights
  • Stones
  • Glass beads
  • Plastic covers

When using a sealed container such as a mason jar or other sealable glass container it is important that you release the pressure from the jar every few days.  Otherwise the jar may explode as the pressure increases which can cause serious injury as well as a big mess. 

You can release the pressure from your container in a number of ways:

  • Burping the container daily
  • using plastic bags filled with water
  • using an air lock
  • using a hose into a cup of water

If you have access to a crock then sealing the top requires adding some water to the groove where the lid sits.  This will prevent air from going in but will allow pressure out of the jar.

Keep the temperature cool

LAB have a wide temperature range where they like to grow but they will grow slower when kept cool.  This is what you want when fermenting cucumbers as it helps the pickles to be crisp and flavorful.  If you ferment you pickles in warmer temperatures the LAB get a chance to break down the structure of the cucumber making which can make them mushy.

A temperature between 13-18˚C. during the first three weeks of fermentation the cooler the better.  If you store them at cooler temperatures they will take longer to ferment but will be nice and crisp.  Be aware that storage temperatures slow the fermentation process down considerably, up to five to 6 weeks.

Molds and yeast need to be inhibited from growth

The main method of reducing yeast and mold growth is by the addition of a salted brine to the fermentation container.  LAB are salt tolerant microorganisms whereas yeast and mold are not.  With the addition of the salt the yeast growth is inhibited giving the LAB the upper hand.

The amount of salt you need to add depends on the weight of the contents of the jar.  To ensure your pickles do not spoil before the LAB dominate the culture and acidify it enough to inhibit mold growth it is recommended to have a 3.5% salt concentration. 

How to calculate how much salt is needed:

  • Weigh the container you are using
  • Pack the container you are using with cucumbers
  • Add filtered water to cover the cucumbers with at least an inch of headroom
  • Weigh the full container
  • Multiply the result by .035
  • Pour out the water and mix the salt into the water until dissolved
  • Fill the container up with the brine and cover

LAB must be able to reach its food source

LAB live in the surface of most vegetables throughout their growth stages but they cannot penetrate the skin on thick skinned vegetables like cucumbers.  To aid the growth of the LAB in your fermentation pierce the cucumbers several times.

This does two things:

  • It helps the salt draw out the sugars in the cucumber where the LAB have easy access to it
  • It allows the LAB easy access to the inside of the cucumber
  • LAB must be given enough time to acidify the cucumbers into pickles

LAB grow slower when kept in cool temperatures so it takes time for them to get into the cucumber and consume the sugar in them.  Especially if you are making whole dill pickles because it is harder for the LAB to enter the cucumber while it still has skin on all sides. 

Sliced cucumbers will ferment faster than whole ones but they still take at least 3 weeks to properly acidify.

Safety aspects of lacto fermentation

Lacto fermentation is considered one of the safest methods of food storage.  In fact fermented vegetables of any type are safer to eat then fresh.  That said there are some precautions you should take when making lacto fermented pickles

  1. Start with clean containers and utensils
  2. Wash all cucumbers under clean running water before packing then into a container
  3. Cover the container to prevent contamination during the pickling process
  4. Refrigerate once the pickles are to your liking or seal them and place them in cold storage

How to tell if your fermented pickles are bad

Lacto fermented pickles will last a long time if they are stored in a cool place in covered containers but like all foods they do not last indefinitely.  Pickles which have gone off are easy to spot and should be thrown away.

Signs of contaminated pickles:

  • Mold growth on the surface
  • Rancid smell coming from the container
  • Slimy or mushy pickles

Can I eat my pickles while they are fermenting?

Of course!  There is not time which your pickled cucumbers go through a stage which they are unsafe to eat.  As the pickles age they will get tangier and less sweet so depending on what you want your pickles to taste like they may not be to your liking but they are not bad or contaminated.

This is how food was preserved before such things as refrigerators.  At the end of the growing season cucumbers were packed into casks and brined to preserve them.  Then the casks were stored in the cellar or some other cool location.  When they were needed or wanted they were retrieved from the cask and consumed.  As the winter progressed the pickles would get tangier and less like the cucumbers which were packed into the cask.

Michael Grant

Mike has been an enthusiast of fermentation for over ten years. With humble beginnings of making kombucha for himself to the intricacies of making miso, vinegar and kefir. He makes a wide variety of fermented foods and drinks for his own consumption and family and friends. Being a serial learner he began experimenting with a wide variety of fermented products and learning widely from books, online from content and scientific studies about fermentation, its health benefits, how to use fermented food products in everyday life and the various techniques used to produce them both traditionally and commercially. With a focus on producing his own fermented products in an urban environment with little access to garden space he began Urban Fermentation to help others who want to get the benefits of fermentation in their lives. He provides a wide variety of content covering fermented drinks like kombucha and water kefir, milk kefir and yogurt, vinegar production and lacto-fermentation such as pickles, sauerkraut for those who have to rely on others for food production. With an insatiable hunger to know more about fermentation from all nations and cultures he also has learned to make natto, miso and soy sauce, with more to come as the body of knowledge about fermentation is constantly expanding and becoming more popular as time passes.

Recent Posts

Urban Fermentation is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. We also participate in other affiliate programs which compensate us for referring traffic.