Vacuum-Sealing Food in Jars: Do's & Don'ts
Fresh, plastic-free, and sustainable – vacuum sealing in glass jars is the clever method to keep food fresh longer. With our vacuum pump, you preserve the quality of your provisions, leftovers, or pre-prepared meals – completely without plastic and with full flavor. By removing oxygen, the natural oxidation and spoilage process is slowed down, preserving aromas, colors, and nutrients longer.
However, it's important to know: vacuum sealing food in glass jars does not mean making it permanently shelf-stable. Vacuum sealing does not replace canning or preserving and does not protect against risks like botulism in a vacuum. Therefore, ensure hygienic handling and continuous refrigeration – this way, you can safely and enjoyably benefit from your freshness in glass.
In this article, we explain step-by-step how vacuum sealing in glass jars works and what you should consider.
How to Vacuum Seal in Glass Jars – Step-by-Step Guide
When vacuum sealing in glass jars, oxygen is removed from inside the container. This slows down oxidation processes that are normally responsible for mold growth, discoloration, and loss of flavor. This way, you can vacuum seal your food in glass jars and keep it fresh significantly longer – completely without plastic and with full aroma.
For use: Place our vacuum pump on the plate that rests on the glass jar and press the pump head down several times. After a few pumping motions, a stable vacuum is created in the jar, which airtightly protects the contents. Depending on the jar size, the pump takes between 20 and 40 seconds.
The vacuum remains until you release it using the valve. To open, simply place the small opening tool under the side of the valve and gently pry it open. As soon as you hear a short hissing sound, the vacuum is released – the lid can now be easily removed, and your fresh provisions are ready to enjoy.
Which Foods are Suitable for Vacuum Sealing & Which are Not
Fruits & Vegetables
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Suitable: Berries, apple slices, vegetable sticks, herbs.
These products benefit from oxygen removal. They remain crisp and retain their color. Important: Dry fruits and vegetables beforehand – moisture shortens freshness time.
Conditionally suitable: Leafy greens – only if they are completely dry, as moisture forms condensation and makes the leaves soggy.
Not suitable: Fresh mushrooms – anaerobic bacteria, including Clostridium botulinum, can multiply in the absence of oxygen. Raw onions and garlic are also unsuitable as they produce gases.
Cooked Dishes & Meal Prep
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Suitable: Cooked rice, lentils, vegetable stir-fries, casseroles, curries.
Vacuum seal after cooling completely. The vacuum keeps them appetizing for 2-3 days longer in the refrigerator.
Conditionally suitable: Purees or hummus – store only in the refrigerator.
Not suitable: Very liquid soups or broths – risk of liquid being drawn into the valve. Cooked potatoes and garlic dishes should also not be vacuum sealed as they could pose a risk of botulism if stored incorrectly.
Dairy Products & Cold Cuts
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Suitable: Hard and semi-hard cheeses, cold cuts, tofu.
Under vacuum, the surface remains dry and mold growth is delayed. Always store in the refrigerator.
Conditionally suitable: Soft cheeses like Camembert or mozzarella – their high water content can change the texture.
Baked Goods
- Suitable: Cookies, crackers, crispbread – stay crispy.
- Conditionally suitable: Bread – possible for a short time, but the crust quickly loses its structure.
Fermented & Gas-Producing Foods
- Not suitable: Kimchi, sauerkraut, kombucha, water kefir, or yeast doughs – fermentation gases release the vacuum and can build up pressure.
Garlic and Onions in Oil
- Not suitable: Garlic or onions in oil must not be vacuum sealed or stored unrefrigerated. There is a risk of botulism in the absence of oxygen. Store only in the refrigerator for a few days or freeze.
How Long Does the Vacuum Last?
How long vacuum-sealed food stays fresh in glass jars depends on several factors – especially on cleanliness during filling, consistent refrigerator temperature, moisture content, and the type of food.
Rule of thumb for vacuum sealing in glass jars
Fresh foods like fruits, herbs, or cut vegetables stay fresh 2–3 times longer in a vacuum than without.
Cooked dishes or meal prep items usually last 3–5 days in the refrigerator if they were filled cleanly.
Dry provisions like nuts, coffee, or grain products remain aromatic and crisp for several weeks to months.
Important: Even if you can keep food fresh longer by vacuum sealing it in glass jars, this does not replace refrigeration or preservation. Perishable products always belong in the refrigerator – this way, your freshness in glass remains safe and enjoyable.
Safety & Botulism – What to Consider When Vacuum Sealing in Glass Jars
Botulism in a vacuum is rare but can be dangerous. The disease is caused by the bacterium Clostridium botulinum, which can grow in the absence of oxygen – including in vacuum-sealed foods, if conditions are ideal. There is a particular risk with moist, protein-rich, or oily products if they are not sufficiently refrigerated or stored for too long.
To ensure you stay safe when vacuum sealing food in glass jars, remember:
Only vacuum seal completely cooled foods. → Warm foods promote condensation and create an ideal breeding ground for bacteria.
Always store in the refrigerator. → Vacuum sealing does not replace refrigeration – it only slows down spoilage.
Consume food promptly. → Even in a vacuum, fresh foods should be eaten within a few days.
Do not vacuum seal oily mixtures with garlic or onions. → There is a particular risk of botulism in a vacuum here.
If gas formation, bloating in the jar, or an unusual smell occurs: Discard immediately.
This way, you combine freshness in glass with food safety – and use vacuum sealing in glass jars to keep your provisions fresh longer, sustainably and plastic-free, without health risks.
Frequently Asked Questions About Vacuum Sealing
Is the vacuum pump suitable for screw-top jars?
No, the vacuum pump is not compatible with conventional screw-top jars or other lid systems. It works exclusively with our Lieblingsglas Mason Jars – in Regular Mouth and Wide Mouth sizes – and the corresponding lid plates.
This means:
You cannot reuse old jars (e.g., from jam or supermarket products) as they do not create an airtight vacuum seal.
Only in combination with our Mason Jars and the matching plates will a consistently stable vacuum be created. You can find the vacuum pump as a set with suitable jars here.
How much longer do foods stay fresh under vacuum?
This depends heavily on the food and its storage – so we don't provide exact timeframes. Generally, the vacuum ensures less oxygen reaches the food. This slows down oxidation processes, and freshness, taste, and aroma are preserved for longer.
Can I vacuum seal soups or liquid dishes?
Yes, that works – but only for thick dishes like stews, cream soups, or curries. Clear liquids such as broths or very thin soups should not be vacuum sealed, as they can easily be drawn into the valve or pump. It is also important that the food is completely cooled and that you leave enough headspace.
Can I vacuum seal ferments or preserves?
No – active fermentations must not be vacuum sealed.
During fermentation, gases are produced that need to escape. A vacuum would block this process, build up pressure, and in the worst case, cause the jar to overflow or burst.
For preserves:
- Already canned, sealed foods do not require an additional vacuum.
- However, after opening, you can vacuum seal them to maintain aroma and quality.
What foods should not be vacuum sealed?
Fresh mushrooms, fermented foods, garlic or onions in oil, and very liquid soups or broths. These can form gases or be drawn into the valve.
How long does the vacuum last?
With clean, dry jars and cool storage, the vacuum can remain stable for several weeks. Moisture, dirt, or temperature fluctuations can shorten its duration.
How do I open a vacuum-sealed Lieblingsglas jar?
Use the opening tool to gently pry up the valve on the side until a soft hissing sound is heard. The lid can then be easily removed.
You can find the detailed instructions for opening the vacuum-sealed jar here.
How long does vacuum sealing take?
Depending on the jar size, the pump takes between 20 and 40 seconds. Pumping pressure: -60 kPa (negative pressure during suction).
Inspiration & Recipes
Conclusion for Freshness in a Jar
With the vacuum pump, freshness in a jar can be easily extended – completely without plastic or complicated technology. Whether vacuum sealing meal prep, pantry items, or snacks: those who store food consciously keep it fresh longer, save time and money, and reduce waste.
It remains important to work hygienically, store chilled, and enjoy consciously. This way, freshness in a jar remains visible, palatable, and guaranteed safe.
