How Long Does Natto Last in the Fridge? Storage Tips for Maximum Freshness

An Introduction to Natto

Natto is a traditional Japanese food made from fermented soybeans. It has a distinct sticky, slimy texture and strong, cheese-like flavor. Natto originated in Japan over 1000 years ago and remains a staple of Japanese cuisine to this day. Its unique taste and texture takes some getting used to for many Westerners. However, natto is growing in popularity worldwide due to its many purported health benefits.

Natto is made by fermenting boiled soybeans with Bacillus subtilis, a beneficial bacteria found in the soil. This fermentation process produces the sticky substance and strong aroma that natto is known for. The fermentation also makes natto an excellent source of vitamin K2, which supports bone and cardiovascular health.

In Japan, natto is most commonly eaten mixed with rice for breakfast. It can also be mixed into noodles, used as a topping for sandwiches or toast, or incorporated into recipes like sushi rolls. Outside of Japan, natto can be found in many health food stores and Asian grocery stores.

How to Store Natto

Like many fermented foods, proper storage is important for maintaining the quality of natto. Here are some tips for storing natto:

Refrigerate Promptly After Opening

Always refrigerate natto immediately after opening the package. The fermentation process will continue at room temperature, causing the natto to become overly ripe and potentially spoiled. Keeping it refrigerated prevents further fermentation.

Store in an Airtight Container

Transfer any leftover natto from the original package into an airtight glass or plastic container. The airtight seal prevents air from causing oxidation and preserves freshness.

Keep Away From Other Foods

Be sure to keep natto sealed away from other foods in the refrigerator. Its sticky texture and strong aroma can easily transfer to nearby items. Store it on a shelf higher up or in a designated container.

Don't Freeze

Freezing is not recommended for storing natto. The freezing process damages the bacterial cultures that give natto its unique characteristics. Thawing will lead to a change in texture and decrease in beneficial bacteria.

How Long Does Natto Last in the Fridge?

When properly stored in the refrigerator, fresh natto will typically last for 7-10 days past the sell-by date printed on the package. However, there are several signs to look for to determine if your natto has expired:

Appearance

Fresh natto has a distinctly sticky, slimy appearance, while expired natto will become dried out. Its color also darkens from an off-white to yellowish brown upon spoiling.

Texture

The slimy tendrils of fresh natto become hard and dried up as it goes bad. Pressing a finger into it will leave an indentation rather than being slimy.

Smell

While natto always has a strong cheese-like smell, truly spoiled natto will have a particularly pungent rotten or ammonia-like odor.

Taste

Along with the stronger rotten smell, expired natto will also taste bitter rather than its typical nutty, cheesy flavor.

Mold

Finally, look out for the growth of blue, green or white mold. This is a sure indicator that the natto has spoiled and should be discarded.

How to Tell if Natto Has Gone Bad

Using your senses is the best way to determine if your natto has gone bad and needs to be thrown out. Here are some simple ways to check your natto quality:

Do a Visual Inspection

Take the natto container out of the fridge and inspect its appearance closely. Fresh natto should look mildly slimy and off-white in color. Dark yellow, dried out patches or fuzzy mold spots indicate spoilage.

Smell Check

Give the natto a sniff right when you open the container. A mildly cheesy and fermented scent is normal. A strong rotten, ammonia-like odor means it's no longer edible.

Feel the Texture

Gently poke a finger into the natto. It should still feel quite slimy. If it feels dried out or hardened, that's a red flag for spoiled natto.

Do a Taste Test

Finally, do a small taste test if it still seems borderline. Fresh natto tastes mildly nutty and fermented. Rancid, bitter flavors mean it's gone bad.

When in Doubt, Throw it Out

If there is any doubt after examining the natto's appearance, smell, texture and taste - do not eat it. Natto poisoning can cause gastrointestinal distress. It's better to be safe than sorry.

How to Keep Natto Fresh for Longer

Here are some tips to extend the shelf life of your natto and keep it fresh for as long as possible:

Buy Smaller Packages

Opt for single-serve or smaller natto packages rather than large batches. You are less likely to use up larger packages before the natto expires.

Seal Airtight After Use

Always transfer any leftovers to an airtight glass or plastic container, squeezing out excess air before sealing.

Use Within 7-10 Days

Try to finish consuming refrigerated natto within 7-10 days of opening for best quality. Write the date opened on the container as a reference.

Don't Return to Fridge Multiple Times

Take out only the amount of natto you plan to eat to avoid temperature fluctuations from continually opening the fridge.

Check for Mold Regularly

Inspect refrigerated natto every couple of days for any mold growth. This can happen even when sealed and requires immediate disposal.

What to Do if Natto Smells Bad

If you open up your natto and detect a rotten or ammonia-like odor, it unfortunately means it has gone bad and is unsafe to eat. Here is what to do:

Discard the Natto

When in doubt, throw it out! Spoiled natto can make you sick and should not be consumed.

Clean the Container Thoroughly

Make sure to wash the storage container with hot soapy water before reuse. This prevents any remaining spores from contaminating fresh natto.

Determine Why It Spoiled

Analyze how you stored the natto to see if any improper storage conditions caused it to spoil prematurely.

Check Other Packages

Inspect any other open natto packages you may have in the fridge for signs of spoilage as well.

Buy a Fresh Batch

Replace the spoiled natto with a fresh package, being mindful of proper storage going forward.

Frequently Asked Questions

Can I freeze natto?

Freezing is not recommended for natto, as the ice crystals can damage the bacterial cultures needed for fermentation, leading to changes in texture and taste.

What happens if I eat spoiled natto?

Consuming spoiled, rotten natto can potentially cause food poisoning symptoms like nausea, vomiting, and diarrhea. Always discard natto at the first signs of spoilage.

How can I make natto last longer?

Proper refrigerated storage in an airtight container and making sure to finish it within 7-10 days of opening will help natto stay fresh for as long as possible.

Is it OK to eat natto past the expiration date?

It can be safely consumed for up to 1 week past the sell-by date as long as it was promptly refrigerated and shows no signs of spoilage like mold, off-smells or texture.

Can natto be frozen after opening?

No, freezing is still not recommended for natto even after opening the package. The freeze-thaw process damages the bacterial cultures in it.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.