Should Mayonnaise Taste Sour?

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Key Takeaways:

  • Mayonnaise getting a sour taste could indicate it has gone bad.
  • Sourness comes from breakdown of oils and proteins into acids.
  • Using old or spoiled acidic ingredients also causes sourness.
  • Bad eggs produce sulfur compounds that make mayo taste sour.
  • Small taste test can verify if mayo tastes “off” and should be discarded.

Introduction: Why is it important to know if mayonnaise should taste sour??

Mayonnaise is a versatile condiment used in many dishes and sandwiches. Its rich, creamy taste comes from egg yolks and oil emulsified into a thick, smooth texture. When fresh and made properly, mayonnaise has a mild, slightly nutty and eggy flavor. However, mayonnaise can go bad after a period of time. One of the first indicators of spoilage is a sour taste. So is a sour taste normal, or a sign to throw out the mayo?

This article will provide a comprehensive analysis of the reasons why mayonnaise can develop a sour flavor. Key factors such as ingredient breakdown, acidic components, egg quality, and storage conditions will be evaluated. The objective is to help readers understand what causes sour mayonnaise and how to tell if it is unsafe to eat. With food safety being paramount, the ability to identify bad mayonnaise is an important skill for consumers.

Having clear guidance on sour mayonnaise can prevent foodborne illness. The in-depth information presented here will enable readers to confidently determine if their mayonnaise has gone bad due to its sour taste. Being able to make this assessment empowers consumers to discard spoiled mayo and protect themselves and their families from potential food poisoning.

Should Properly Made Mayonnaise Have a Sour Taste?

The simple answer is no – mayonnaise that has been recently made with fresh, high-quality ingredients should not taste noticeably sour. Acidity is needed to make mayonnaise, but well-balanced mayo has a mild, creamy flavor.

What Causes Mayonnaise to Taste Sour?

There are a few reasons why mayonnaise can develop a sour flavor over time or if certain ingredients have gone bad:

Breakdown of Fats and Proteins

Mayonnaise contains egg yolks and vegetable oil, which are rich in fats and proteins. As mayonnaise sits over time, these compounds slowly break down into fatty acids and amino acids. This process releases lactic acid and acetic acid, which give mayonnaise a sour taste.

Spoiled Acidic Ingredients

Ingredients like lemon juice, vinegar, and mustard provide acidity needed to emulsify mayonnaise. But if these acidic components have become old, rotten, or fermented, they introduce excess acidity. This can make fresh mayo quickly taste sour.

Bad Eggs

Since egg yolks are a key ingredient, bad eggs can ruin a whole batch of mayonnaise. As eggs go bad, the proteins break down and create sulfur compounds that have a very distinct rotten smell and sour taste.

Bacterial Growth

If mayonnaise is kept too warm or left out too long, bacteria can grow rapidly. Many harmful bacteria produce acids as they multiply, lowering the pH and causing sourness.

How to Tell if Mayonnaise Has Gone Bad?

Look for these signs that may indicate it is time to throw out sour-tasting mayonnaise:

Color Changes

Fresh mayo should be rich yellow. Grayish, brown, or greenish tints likely mean oxidation and spoilage.

Texture Changes

Properly emulsified mayo is thick. Runny, watery, or excessively gloopy texture is suspicious.

Sour Odor

Smell the mayonnaise. Rancid, vinegary, or rotten smells mean it is no longer fresh.

Mold Growth

Check thoroughly for white, blue, green, or black fuzzy mold spots, which signal spoilage.

Taste Test

If appearance and smell seem fine, confirm with a small taste on a clean finger. Spit out immediately if an off or sour flavor is detected.

How Long Does Mayonnaise Last Before Going Bad?

With proper storage, mayonnaise can retain quality and flavor for:

  • Unopened mayo: 2-3 months past the “best by” date.
  • Opened mayo: 2-3 months in the refrigerator.
  • Homemade mayo without preservatives: 1 week in the fridge.

Once opened, mayonnaise quality declines faster. Check frequently and rely on smell and taste – not just dates. Discard immediately if any sourness or spoilage is detected.

What Are Signs of Spoiled Mayonnaise?

Aside from sour flavor, look for these indicators mayonnaise has spoiled and should be discarded:

  • Thin, watery texture instead of thick and creamy
  • Gray, yellow, green, or brown discoloration
  • Rancid odor like vinegar or rotten eggs
  • Mold growth – may look fuzzy or slimy
  • Unnatural taste that is bitter, sharp, or “off”
  • Wheezing or popping sound when first opened

Trust your senses. If mayonnaise shows visual, smell, taste, or textural signs of spoilage – do not eat it!

Can Spoiled Mayonnaise Make You Sick?

Yes, consuming rancid mayonnaise that contains pathogenic bacterial growth or toxins can cause food poisoning symptoms:

  • Nausea, vomiting, diarrhea
  • Abdominal pain and cramping
  • Fever, headache, weakness
  • Dehydration

Severe cases may even require hospitalization. Food poisoning from spoiled mayo can occur within hours after eating and lasts around 1-3 days.

How to Prevent Mayonnaise From Going Bad?

Practice proper hygiene, storage, and handling:

  • Use only fresh, refrigerated eggs and oil. Never use rotten or old ingredients.
  • Keep unopened mayo refrigerated at 40°F or below.
  • Store opened mayo in a clean, sealed container in the fridge.
  • Keep cooking utensils and bowls extremely clean when making homemade mayo.
  • Never leave mayo out at room temperature more than 2 hours.
  • Check for signs of spoilage regularly before use.
  • Consume within recommended time limits.

Following safe food handling procedures reduces the risk of mayonnaise harboring dangerous bacteria and tasting sour.

Can You Save Sour Mayonnaise?

Unfortunately, there is no way to save mayonnaise once it starts tasting sour. The chemical breakdown of fats and the bacterial contamination cannot be reversed. Any attempts to modify the flavor of sour mayo could still leave toxic substances.

The only safe option is to discard the entire batch of mayonnaise at the first signs of spoilage. Sour mayo smells, looks, and tastes bad because it has the potential to cause foodborne illness. It should never be consumed or used in recipes.

What Is the Best Substitute for Spoiled Mayonnaise?

If you need to toss sour mayonnaise, suitable replacements to use instead include:

  • Fresh mayonnaise – Open a new jar or make a new batch.
  • Plain yogurt – Provides tangy creaminess.
  • Sour cream – Similar texture and rich flavor.
  • Buttermilk – Brings a creamy, thick taste.
  • Hummus – Great for spreads and dips.
  • Guacamole – For sandwiches or toppings.
  • Oil and vinegar – Recreate the base flavors.

Get creative with combinations of acids, oils, eggs, and dairy to replicate mayo’s flavor profile.

Can You Make Your Own Mayonnaise?

Absolutely! Making your own mayonnaise at home is simple. Here is a basic recipe:


  • 1 egg yolk
  • 1 tbsp lemon juice
  • 1 cup vegetable oil
  • 1/4 tsp salt
  • 1/2 tsp Dijon mustard


  1. In a blender or food processor, combine the egg yolk, lemon juice, salt, and mustard. Blend for 10 seconds.
  2. With the motor running, slowly drizzle in the oil and blend until emulsified, about 2-3 minutes.
  3. Transfer mayonnaise to an airtight container and refrigerate up to 1 week.

Tips for best homemade mayo:

  • Use the freshest ingredients possible.
  • Drizzle oil very gradually so the emulsion holds.
  • Add herbs, garlic, spices, or vinegar to customize flavors.
  • Make sure all equipment is extremely clean to prevent bacterial contamination.

With this simple DIY approach, you can avoid spoiled mayonnaise and control exactly what goes into your healthy handcrafted condiment.

FAQs About Sour Mayonnaise:

Why does my fresh mayo taste sour?

If mayonnaise tastes sour right after being made, the likely causes are:

  • Old eggs were used. As eggs age, sulfur compounds develop that have a Rotten or sour taste.
  • The lemon juice or vinegar was past its prime. Spoiled acidic ingredients introduce extra sourness.
  • Equipment wasn’t sanitized properly. Bacteria added during prep can produce acids.
  • Too much acid such as lemon juice or vinegar was added. Proper balance is key for flavor.

Is it safe to taste test mayonnaise?

It is generally safe to do a small taste test of questionable mayonnaise by following these precautions:

  • Use only a tiny amount on the tip of a clean spoon or finger.
  • Do not swallow the mayonnaise. Simply lick it and immediately spit it out.
  • Rinse mouth thoroughly afterwards with water.
  • If an off or sour taste is detected, discard the entire batch of mayo.
  • When in doubt, throw it out. Never taste mayo with visible mold.

How can you tell if homemade mayo is spoiled?

Homemade mayonnaise should be discarded if it shows any of these signs of spoilage:

  • Watery texture – properly emulsified mayo is thick.
  • Light brown, gray, greenish color – should be pale yellow.
  • Rancid, vinegary, eggy, or sulfurous smell.
  • Mold growth, even just a few spots.
  • Unnatural taste that is bitter, harsh, or rotten.
  • Wheezing or popping when first opened.

Trust your senses. If homemade mayo looks, smells or tastes off – do not eat it. When unsure, err on the side of caution.

Can expired store-bought mayo still be used?

It’s not recommended to use store-bought mayonnaise past its expiration date, even if unopened.

  • Quality and safety decline over time after bottling.
  • Dates indicate maximum freshness, not when it becomes inedible.
  • Opened mayo spoils faster than unopened due to oxygen exposure.
  • An unopened jar can last up to 3 months past its date if refrigerated.
  • However, the microbiological risks increase over time.

For optimal food safety, it’s advisable to discard expired store-bought mayonnaise even if it looks okay. Using fresh mayo minimizes the risks of foodborne illness.


Mayonnaise should not taste sour when freshly made with quality ingredients. A sour flavor is a warning sign that it has spoiled and should be discarded. Sourness in mayo can stem from chemical breakdown of fats and proteins, contamination with bacteria, or the use of old acidic ingredients in the recipe. Consuming rancid mayonnaise poses a real risk of food poisoning. Always inspect mayo carefully for visual and smell cues of spoilage in addition to an unnatural sour taste. With this knowledge, you can determine if your mayonnaise is still safe to enjoy or requires being thrown out to avoid a nasty bout of illness.

Mayonnaise has a relatively short shelf life and needs refrigeration after opening. But armed with the information provided in this article, you can better prevent your mayonnaise from going bad and evaluate possible sourness issues if they arise. Stay vigilant against foodborne illness by knowing what signals spoiled mayo and when it’s time to toss it. Then switch to a fresh container or whip up a new homemade batch for creamy, non-sour flavor to spread on sandwiches with confidence

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