How long can jam sit out?

Jam is a delicious and versatile way to enjoy fruit. It can transform toast, scones, and other baked goods into a sweet treat. However, because jam contains sugar and fruit, it also carries a risk of spoilage if left unrefrigerated for too long. So how long can jam sit out safely at room temperature before it goes bad? Here is a comprehensive guide to jam storage and food safety.

Quick Answer

The quick answer is that an unopened jar of commercial jam should not sit out at room temperature for more than 2 weeks. Once opened, the jam should be refrigerated and used within 3-4 weeks. Homemade jam generally lasts 1-2 weeks unrefrigerated.

How Long Can Unopened Jam Sit Out?

An unopened jar of store-bought jam can be safely stored in the pantry for up to 1 year past the “best by” date on the label. Over time, it may lose some flavor and texture quality, but it will remain safe to eat if the seal has not been broken.

Once opened, jam should not sit out at room temperature for more than 2 weeks before being discarded. Even if mold is not apparent, harmful microbes could be growing in the jam and pose a food poisoning risk.

Here are some general jam storage guidelines for unopened jars:

Type of Jam Pantry Refrigerator
Commercially sealed jar 12 months past best by date 24 months past best by date
Homemade jam 1-2 weeks 2-3 months

How Long Can Opened Jam Last Unrefrigerated?

Once opened, the shelf life of jam is drastically reduced. Exposure to air and microbes limits the time it can safely sit out to just a few weeks. Follow these jam storage guidelines after opening:

– Refrigerate after opening and use commercial jam within 3-4 weeks.

– Homemade jam or jam with less sugar should be refrigerated and used within 1-2 weeks.

– Do not leave jam out more than 2 hours at room temperature.

– Never return jam to the pantry after refrigeration. Keep refrigerated.

– Watch for signs of spoilage like mold, off smells, bubbles, or texture changes. Discard if any are present.

– To extend the shelf life, store jam in the freezer for up to 1 year.

What Happens If Jam Sits Out Too Long?

There are a few risks associated with leaving jam out too long unrefrigerated:

Mold growth – Jam left out offers an ideal breeding ground for mold. Mold spores in the air can land on the sticky surface and grow rapidly.

Bacteria – Bacteria growth is also likely, particularly in homemade jams with lower sugar content. Salmonella, E. coli, and other harmful bacteria can grow and cause foodborne illness.

Fermentation – Prolonged exposure to air can cause the natural yeasts in the jam to multiply and produce gas or alcohol resulting in off tastes and bulging lid.

Texture changes – The jam can thicken, crystallize, weep, separate, or become runny if left out too long.

While jam that smells or looks abnormal should always be discarded, harmful microbes can grow with no visible signs. So it’s best to follow the recommended timelines for refrigeration. If in doubt, throw it out.

How to Tell If Jam Has Gone Bad

Watch for these signs that indicate your jam has spoiled and should be discarded:

– Mold growth on the surface or within the jam
– Unpleasant odors like sourness or yeastiness
– Separation of liquid or hardening of texture
– Popping, bubbling, or foaming when the jar is opened
– Cloudiness or haziness
– Changes in color like darkening or graying
– Crystallization on the lid or rim of the jar
– Metal lid that has popped up or is bulging

Tips to Keep Jam Fresh Longer

Here are some tips for maximizing the shelf life and safety of your jam:

– Use clean utensils and containers when making and storing jam.
– Opt for full sugar jams over low sugar versions. The extra sugar acts as a preservative.
– Use jam within a year of purchase for best flavor, even if sealed.
– Refrigerate after opening and never return to the pantry.
– Keep the lid tightly sealed when not in use.
– Always use a clean knife when portioning out jam.
– Store in smaller containers rather than one large one to limit air exposure each time.
– Freeze for extended storage. Thaw in the refrigerator before use.
– When refrigerated, store jam towards the back, not in the door where temperature fluctuates.
– If mold forms, discard the entire contents of the jar – washing may not remove hidden spores.

Can Jam Be Frozen?

Yes, jam can be successfully frozen to extend its shelf life. Here are some freezing tips:

– Store jam in freezer-safe containers leaving 1/2-inch headspace to allow for expansion.
– Portion jam out into smaller containers rather than freezing the entire jar to limit freezing time.
– Use within 1 year for best quality and safety.
– Let frozen jam thaw overnight in the refrigerator before use.
– Do not refreeze jam once thawed.
– Jam may lose some texture after thawing but remains safe to eat.

Freezing stops the growth of mold and bacteria. With proper thawing and storage, jam can be safely frozen for up to a year after opening.

Can Jam Be Canned Again?

Previously opened jam should not be re-canned at home. The canning process requires specific conditions to destroy bacteria and prevent spoilage that cannot be safely replicated at home.

However, you can freeze jam in an airtight freezer-safe container. Commercial jam producers sterilely re-can products after opening, but the conditions are challenging to mimic at home. Freezing is the safest option.

Is Moldy Jam Safe to Eat if I Cut the Mold Off?

No, jam with mold should be completely discarded. It is unsafe to scoop out the mold and eat the rest.

Mold can send invisible filaments called mycelia deep into the jam that could contaminate areas that appear mold-free. Mycelia can also produce toxins that spread throughout the jam. These mold toxins can cause illness if consumed.

So even if you don’t see mold beyond the surface, the entire jar should be thrown away if mold is present. Don’t risk getting sick – it’s better to be safe and start with a fresh jar of jam.

Can I Make Jam Last Longer With Preservatives?

You can extend the shelf life of homemade jams and jellies with lemon juice, vinegar, or commercial pectin products. These work by increasing the acidity of the jam to inhibit bacteria growth. Sugar in a jam recipe also helps preserve it.

Here are some common preservatives for home jam making:

– Added lemon juice or vinegar – The extra acid helps control bacteria and yeasts.
– Pectin – Derived from citrus peels or fruits. It thickens jam and allows you to use less sugar.
– Ascorbic acid – An antioxidant that enhances pectin gelling.
– Honey – Contains hydrogen peroxide which helps jam keep longer.
– Sugar – High sugar jams last longer thanks to sugar’s preservative properties.
– Salt – A small amount of salt inhibits bacterial growth.
– Spices – Some spices like cloves or cinnamon can extend freshness.

When canning jam, always follow established recipes and procedures carefully to prevent spoilage. Avoid adding too many unproven preservatives that could change the pH and compromise the canning safety.

What Are Signs of Fermented Jam?

Jam that has become fermented will exhibit some of these possible signs:

– Bubbles or foam visible when you open the jar
– Bulging lid, popped lid, or rust around the rim
– Gassiness, fizzing, or hissing sounds
– Strong unpleasant odors like alcohol or yeast
– Increased tart or vinegary taste
– Layer of film, bubbles or haze over the jam’s surface
– Liquid separating or fluid at the top of the jam

These can indicate yeasts, harmless fermentation, or more concerning spoilage microbes. Do not taste fermented jam, the toxins can make you sick. Check for these warning signs and discard jam that shows evidence of fermentation.

Can I Test Jam Acidity to Check Freshness?

Yes, you can use a pH test strip to test the acidity level of your jam. The optimal pH for safe canned jam is 2.7-3.5.

Here’s how to test the pH of your jam:

1. Purchase pH test strips online or from a brewing supply shop. Look for a 0-6 pH range.

2. Open the jar and remove a small jam sample on a clean spoon.

3. Dip the pH strip into the jam, ensuring it is coated. Compare the color change to the guide on the package.

4. The ideal pH is 3.3 or lower. Higher readings may indicate spoilage.

5. Repeat with fresh samples from different parts of the jam.

If the pH is above 3.5, it indicates the jam may be spoiled or poorly preserved. Fermented jam will show a pH over 4.0. Discard the jam if the pH is off.


To maximize freshness and prevent foodborne illness, limit the time jam sits out unrefrigerated. Store unopened jam in the pantry, refrigerate after opening, and freeze for long-term storage. With proper jam making, handling, and storage, you can safely enjoy its fruity deliciousness!

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