Why do you have to sterilise bottles?

Whether you are making homemade pickles, sauerkraut, ginger beer, water kefir or kombucha, having clean bottles, jars and brewing equipment is a fundamental step to maintaining the quality, consistency, and safety of your ferments. By ensuring a clean brewing environment you can protect them from spoilage, weird flavours, and potential health risks. 

Cross-contamination is the transfer of microorganisms or contaminants from one bottle to another, which can compromise an entire batch of ferments. This happens when sterilisation equipment or techniques are not adequately maintained or when proper sanitation practices are not followed, so it’s essential to follow good sanitation practices like

• Thoroughly clean the bottles before sterilisation to remove any visible dirt or residue
• Use clean and sanitised sterilisation equipment
• Ensure that work surfaces are properly sanitised
• Handle sterilised bottles with clean hands or sanitised tools
• Avoid touching the inside or rim of sterilised bottles with unclean hands or objects

Following these practices can minimize the chances of cross-contamination and help ensure the health and safety of your ferments. But let’s talk a little more about the differences between the different levels of cleaning we need to do for our ferments.

Clean, Sanitise or Sterilise

In the world of fermentation and homebrews, there’s a difference between washing your bottles, sanitising them or sterilisation. Here are the key differences:

Cleaning

• Removes visible dirt, residue, and contaminants from the jar’s surface.
• Typically involves washing with hot water and soap or a mild detergent.
• Aims to improve the overall hygiene of the jar and remove organic matter that could support microbial growth.
• Does not guarantee the elimination of all microorganisms.

Sanitising

• Reduces the number of microorganisms on a surface to a safe level.
• Helps eliminate or significantly reduce bacteria, yeast, and other microorganisms that could cause contamination or spoilage.
• Methods include chemical sanitisers or heat sanitisation with hot water.
• Creates a clean environment for fermentation but does not completely eliminate all microorganisms.

Sterilising

• Aims to eliminate or kill all microorganisms, including bacteria, yeast, moulds, and spores.
• Achieves a higher level of microbial reduction compared to sanitising.
• Involves more rigorous methods such as boiling, pressure cooking, or heat sterilisation in an autoclave.
• Creates a completely sterile environment, reducing the risk of contamination by undesirable microorganisms.
• Preferred when starting a new batch or using a sensitive or controlled fermentation process.

The choice between sanitising and sterilising jars depends on the specific fermentation process, your desired outcome, and your personal preference. Following the recommended guidelines for your particular fermentation recipe or method ensures the cleanliness and success of your fermentation.

When it comes to fermentation, sterilisation is often preferred, especially when starting a new batch or using a sensitive or controlled fermentation process. 

The goal of sterilisation is to create a completely sterile environment inside the jar, free from any bacteria, yeast, or other microorganisms that could impact the fermentation process. Sterilizing jars helps ensure a clean and controlled environment for fermentation, minimizing the risk of contamination or undesirable flavours.

Sterilizing jars helps create a completely sterile environment, reducing the risk of contamination by undesirable microorganisms and providing an optimal setting for the growth of specific beneficial microorganisms.

However, it’s important to note that in some cases, such as certain types of wild fermentation or when using specific strains of bacteria or yeast, complete sterilisation may not be desired. In these cases, sanitisation may be sufficient to create a clean environment while still allowing for the growth of desired microorganisms.

Fermentation itself involves the growth of specific microorganisms, such as yeast or bacteria, which convert sugars into alcohol or carbon dioxide. But, unwanted microorganisms can also find their way into the fermentation process, leading to contamination. Sterilising bottles helps eliminate these unwanted microorganisms, ensuring that only the intended fermentation microbes are present and preventing spoilage. 

Plus, if you are using your bottles and jars for a pickle and then use it for a ginger beer without cleaning it properly you may be in for some funky flavours. The king of fermentation Sandor Katz’s motto is “cleanliness, not sterility,” but when you’re starting out on your own fermentation journey, I feel it’s important to learn all the “correct” processes. This you’ll know what to expect if something goes wrong and how to fix them.

Different methods

There are different methods you can use to sterilise bottles and jars for fermentation. The most common methods include boiling, chemical sanitisers, and heat sterilisation. Some methods may be more effective for certain types of fermentation, so it’s important to know the requirements of your specific fermentation process. Here are the most common techniques for home fermentation

Boiling

To prevent glass jars from breaking when boiling them in a pot, you can line the pot with a few layers of kitchen towels or a silicone trivet. These materials act as a barrier between the glass jars and the direct heat of the pot, helping to distribute the heat more evenly and reducing the risk of thermal shock. Trust me, you don’t want to skip this step if you love your jars.

1. Choose a pot large enough for the bottles and jars you want to boil, and make sure it has a lid that fits securely.
2. Place a few clean kitchen towels at the bottom of the pot. You can fold the towels to fit the pot’s size or use a silicone trivet instead.
3. Set the glass jars on top of the towels or trivet, ensuring they are evenly spaced and not touching each other or the sides of the pot.
4. Fill the pot with water, making sure the water level covers the jars by at least one inch.
5. Place the pot on the hob and turn on the heat. Gradually bring the water to a boil.
6. Once the water reaches a rolling boil, reduce the heat to a gentle simmer. This will help maintain a steady and controlled temperature throughout the boiling process.
7. Allow the jars to boil for the required time. The recommended boiling time can vary depending on specific fermentation recipes, but a general guideline is to maintain a rolling boil for about 10 to 15 minutes.
8. Once the boiling time is complete, turn off the heat.
9. It’s essential to handle the jars with care when removing them from the boiling water. Use jar lifters or tongs to safely remove the jars from the pot.
10. Place them on a heat-resistant surface or a kitchen towel to cool.

You should always follow the specific instructions provided in the recipe or fermentation process you are following. Some recipes may require longer boiling times or other sanitation methods, such as chemical sanitisers, to ensure proper sterilisation.

Chemical Sanitisers

When using chemical sanitisers for fermentation jars and bottles, follow these general steps:

1. Select a suitable sanitiser that’s recommended for food contact surfaces and safe for use with your particular fermentation process. Common sanitisers include iodophor, Star San, and sodium metabisulfite.
2. Each sanitiser will have specific instructions provided by the manufacturer. Read the instructions carefully to understand the proper dilution ratio, contact time, and any safety precautions.
3. Prepare the sanitising solution according to the manufacturer’s instructions. This usually involves diluting the sanitiser with water to the recommended concentration. Use clean water, preferably distilled or filtered, to avoid introducing additional contaminants.
4. Before sanitising, ensure that the jars or bottles are thoroughly cleaned. Remove any visible dirt or residue using hot water and a bottle brush. Rinse them well to remove any cleaning agents.
5. Submerge the cleaned jars or bottles in the prepared sanitising solution, ensuring they are fully immersed. Follow the recommended contact time specified by the manufacturer. This can vary depending on the sanitiser used but typically ranges from a few minutes to several minutes.
6. Once the contact time is complete, remove the jars or bottles from the sanitising solution and allow them to drain. Avoid rinsing them with water, as the sanitiser residue left behind can help maintain the sanitising effect. Let the jars or bottles air dry upside down on a clean surface.
7. After drying, cover the sanitised jars or bottles with clean aluminium foil, plastic wrap, or sanitised lids to protect them from contaminants until they are ready to be filled for fermentation.

Remember to always follow the specific instructions provided with the sanitiser you are using, as different sanitisers may have slightly different procedures and requirements. 

Dishwasher

If your dishwasher has a high-temperature or sanitising cycle, you can place the bottles in the dishwasher and run them through the appropriate cycle. This can effectively sterilise the bottles, but be sure to remove any labels or caps that may not be dishwasher safe.

Once the bottles are sterilised, it’s crucial to handle them carefully to maintain their sterility. Avoid touching the inside of the bottles or the inner surface of the caps. If you’re not using the bottles immediately, you can cover them with clean aluminium foil or plastic wrap until they are ready to be filled.

If you are using bottle caps or other closures, ensure that they are also properly sterilised. Boil the lids along with the bottles or soak them in the sanitising solution, following the same procedures.

My method

Personally, I use the dishwasher to sterilise my bottle jars, tongs, funnels, sieves, and spoons. I let them fully dry in the dishwasher, and then I put the lids on or place the jars/bottles upside down so nothing can get inside. Before I use them, I will rinse them out with non-chlorinated water. For my other equipment, that I don’t use all the time, I will clean them in the dishwasher, and then run boiling water over them and allow them to come to room temperature right before I use them. 

Chlorinated water should never be used to clean your tools as this can kill your ferments, and boiling water is an effective way to remove chlorine and other potential contaminants.  This method may not be effective for chloramines, however, which are chlorine compounds with a longer-lasting residual effect.

If you don’t have filtered water and you don’t want to boil water, you can fill a container with tap water and let it sit uncovered for 24 to 48 hours. The chlorine will naturally dissipate as it evaporates and then you’ll have dechlorinated water for your fermentations. 

This was a method I used for more than a year before I got a British Berkefeld.

Preferred method for common ferments

Here is a list of common sanitisation or sterilisation methods preferred for various types of common ferments:

TYPE	METHOD
Fermentation vessels, jars, and equipment	Sanitising solution, Boiling, Heat sterilisation
Water-based ferments (kombucha, water kefir)	Sanitising solution, Boiling
Fermentation airlocks and lids	Sanitising solution
Brewing and winemaking equipment	Sanitising solution, Heat sterilisation

Handy Tools

Here are a few tools that I use or want to use for cleaning my bottles. If you live in a small space like me, some of these don’t make sense unless you’re making large batches often, but if you have the space these can make your fermenting life easier. I may receive a small commission when you click the links and make a purchase. Thank you!

Bottle brush

Bottle drying rack

Bottle RINSER