How Long Does Kewpie Mayo Last?

Kewpie mayonnaise has become a pantry staple for many over the years. With its distinctly tangy, umami flavor and ultra-smooth and creamy texture, it’s easy to see why Kewpie has earned such a cult following. But if you’ve ever found an ancient bottle tucked away in the back of your fridge, you may have wondered – how long does Kewpie mayo last?

In this article, I’ll break down everything you need to know about properly storing Kewpie mayonnaise to maximize its shelf life, spot signs of spoilage, and ensure your jar tastes fresh from beginning to end.

Background on Kewpie Mayo

Before diving into proper storage, it’s helpful to understand what gives Kewpie mayo its uniquely velvety texture and rich, eggy flavor. Kewpie mayonnaise contains only five simple ingredients – soybean oil, eggs, vinegar, salt, and sugar. The eggs and oil are emulsified into an incredibly smooth blend.

The vinegar helps stabilize the emulsion while adding a tangy note, and the salt enhances overall flavor. This simple ingredients list means no thickeners or stabilizers are needed.

Knowing the ingredients can provide hints about Kewpie mayo’s shelf life. The vinegar acts as a preservative, while the eggs make it more perishable. Finding the right balance of storage conditions lets you enjoy the irresistible flavor of Kewpie for months.

How Long Does Unopened Kewpie Mayo Last?

Let’s start with a factory-sealed, unopened jar of Kewpie mayonnaise. Kewpie does not use preservatives, but the vinegar acidity and salt help prevent bacterial growth. The packaging also protects the mayo from contamination, air exposure, and other factors that reduce shelf life.

An unopened jar of Kewpie will typically last 1 year past the printed “best by” date if stored properly in the pantry or fridge. The vinegar and salt keep it safe for a while, but the eggs still make mayo a perishable product. For best flavor and texture, try to use Kewpie mayo by its best by date.

Over time after the date, you may notice the texture thinning slightly or the flavor becoming a touch less vibrant. But the mayo should still be usable for a while if it has been sealed and stored properly. Just be sure to look for any signs of spoilage before using old mayo.

How Long Does Kewpie Mayo Last In The Fridge?

Once you twist off that Kewpie jar lid for the first time, exposure to air and microbes reduces the shelf life compared to an unopened jar. An opened jar of Kewpie mayo will last 2-3 months in the fridge if stored properly.

To help your Kewpie mayo survive that long after opening:

  • Keep it refrigerated at all times, at a temperature between 35°F-41°F.
  • Seal the lid tightly after each use to limit air exposure.
  • Store in a clean container if not using the original packaging.
  • Keep it away from cross-contaminants like raw meat juices.

The vinegar and refrigeration temperatures help slow bacteria growth. But over time, the quality still diminishes. For the best flavor and texture, try to finish Kewpie mayo within 2 months of opening.

After 2-3 months in the fridge, it’s best to discard any remaining mayo instead of taking a chance on using it.

Best Practices for Refrigerated Storage

To maximize that 2-3 month fridge life after opening, be meticulous with your Kewpie mayo storage habits. Here are some best practices:

  • Refrigerate at 35-41°F consistently. Fluctuating temperatures cause condensation and quality issues. Keep the mayo toward the back where temps are most stable.
  • Store in the original container or transfer to an airtight non-reactive container like glass or plastic. Metal can react with the mayo.
  • Avoid storing in the fridge door, where the temps fluctuate more as the door opens.
  • Seal extremely tightly after each use to limit air exposure. This slows chemical breakdown.
  • Wipe up any drips or spills immediately to prevent cross-contamination.
  • Keep away from raw foods like meat, poultry, and eggs, which can cross-contaminate.

Following these tips religiously can help your Kewpie mayo last a full 2-3 months after opening.

Early Signs Your Kewpie Mayo Is Spoiling

To determine if your opened Kewpie mayo has gone bad before the 2-3 month mark, check for these signs of spoilage:

  • Mold spots – You may notice fuzzy mold spots growing on the surface, which signals bacteria growth. Discard immediately.
  • Watery texture – A runny consistency or oil/vinegar separation means emulsification is breaking down.
  • Sour or rancid smell – An unpleasant or smell that’s “off” indicates spoilage bacteria.
  • Discoloration – Darkening from cream to yellow or grey hue signals deterioration.
  • Expired “best by” date – The date is a good guideline for discarding.

If you notice any of these warning signs, don’t risk tasting the Kewpie mayo – when in doubt, throw it out!

Effects of Improper Storage

Storing your Kewpie mayo improperly after opening accelerates bacteria growth and chemical breakdown, shortening its fridge shelf life. Watch out for these consequences of poor storage:

  • Rapid bacteria growth leading to faster spoilage
  • Increased risk of foodborne illness if you consume spoiled mayo
  • Changes in texture – runny, thickened, lumpy, watery separation
  • Strange flavors – rancid, bitter, sour, “off” tastes

By following proper refrigeration and sealing techniques, you can avoid these undesirable effects.


No one wants to run the risk of foodborne illness from consuming spoiled mayonnaise. My guidance is: if in doubt, throw it out!

Don’t taste test Kewpie mayo that shows signs of spoilage or is way past its prime. Discard immediately, and open up a fresh jar to enjoy that irresistible tangy Kewpie flavor you love. A new jar is inexpensive peace of mind.

With proper refrigerated storage and careful monitoring for any signs of spoilage, a jar of Kewpie mayonnaise can maintain optimal flavor and texture for 2-3 months after opening. Keep it refrigerated at all times, sealed tightly, stored properly, and away from contamination.

Use by the “best by” date on an unopened jar, and within 2 months of opening. Taking these precautions allows you to safely enjoy the velvety richness of Kewpie mayo without worrying about foodborne illness!

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