Mayonnaise is a popular condiment made from oil, egg yolks, and an acid like vinegar or lemon juice. It has a creamy, thick texture and is used to add flavor and moisture to sandwiches, salads, burgers, and more. But when it comes to storing mayonnaise, people often wonder if it needs to be refrigerated or if it can be kept at room temperature. Here is a comprehensive look at whether or not mayonnaise requires refrigeration.
The Ingredients in Mayonnaise
To understand mayonnaise’s refrigeration requirements, it helps to look at what ingredients are used to make it. The main components are:
- Oil – Most mayonnaise is made with soybean oil, canola oil, or a blend.
- Eggs – Egg yolks are a key ingredient that give mayonnaise its texture.
- Vinegar or lemon juice – An acidic liquid is needed to stabilize mayonnaise and prevent the oil and water from separating.
- Water – Added to thin out the texture.
- Salt and other seasonings – Small amounts of salt, sugar, mustard, and other flavorings are also common.
The egg yolks and oil are the two main factors that determine how perishable mayonnaise is. The eggs provide protein and moisture – things bacteria need to grow. And the oil does not have natural antimicrobial properties like acids found in foods like vinegar.
Does Mayo Contain Raw or Uncooked Eggs?
Raw, uncooked eggs can pose a salmonella risk. But commercially made mayonnaise sold in jars and bottles does not contain raw eggs. The eggs used in mayo are pasteurized to kill any potential bacteria. Pasteurization involves heating the eggs to a high enough temperature for a period of time to destroy pathogens.
Homemade Mayonnaise and Raw Eggs
If you make mayonnaise at home using raw, unpasteurized eggs, there is a risk of salmonella. The CDC recommends using pasteurized eggs for any recipe calling for raw or undercooked eggs like homemade mayo, Caesar dressing, mousse, and more. Or an alternative is to use pasteurized liquid egg products.
With store-bought mayo, the pasteurization process makes it safe in terms of salmonella risk. However, its perishability due to the eggs and oil is still a factor for refrigeration.
Does Mayonnaise Need to be Refrigerated When Unopened?
When mayonnaise is unopened in a new, sealed jar or bottle, it does not require refrigeration. The packaging creates a closed environment that protects the mayonnaise from contamination, light exposure, and oxygen exposure.
An unopened mayonnaise product can be kept in the pantry at room temperature without going bad. The length of time it stays safe before opening will depend on the best by date, which is usually 1-2 months from the manufacturing date.
The key is keeping the mayonnaise properly sealed. If the lid or bottle cap becomes loose or falls off, it is best to move it to the refrigerator.
Can Unopened Mayonnaise be Kept at Room Temperature Indefinitely?
While keeping unopened mayonnaise in the pantry is generally safe, it should not be kept indefinitely at room temperature. Make sure to check the best by or expiration date and follow that for maximum freshness and safety.
The quality of the oils in the mayonnaise can degrade over time at warm room temperatures. The texture and flavor start to decline even though it may not necessarily be unsafe to eat.
An open jar of mayonnaise has a shorter shelf life and refrigeration is recommended.
Does Mayonnaise Need Refrigeration After Opening?
Once a jar or bottle of mayonnaise has been opened, it does require refrigeration. The introduction of oxygen and light exposure speeds up the breakdown of the mayonnaise.
Leaving opened mayonnaise at room temperature for more than 2 hours is not recommended. It provides an environment for bacteria to multiply quickly.
To keep opened mayonnaise safe and shelf stable, it should be stored in a closed container in the refrigerator. Properly stored, refrigerated mayonnaise will maintain quality and fresh taste for 2-3 months after opening.
Can You Leave Mayonnaise Out Overnight?
It is not recommended to leave mayonnaise out on the counter overnight once the jar or bottle is opened. Bacteria starts multiplying rapidly between 4-6 hours when left at room temperature.
Leaving opened mayo unrefrigerated for 8-12 hours or more allows even more growth of bacteria. And general food safety guidelines recommend throwing out perishable foods left overnight at room temp.
How to Tell if Mayonnaise Has Gone Bad
When stored properly in the fridge, mayonnaise lasts 2-3 months after opening. But there are some signs that opened mayonnaise has gone bad and should be discarded:
- Change in color – Fresh mayonnaise should be creamy white. Yellowish gray, brown, or darkening colors indicate spoilage.
- Texture changes – Mayo naturally thickens over time but curdling, separation, or becoming very thin are undesirable changes.
- Sour smell and taste – Rancid odors and unpleasant tangy, bitter, or cheese-like tastes mean mayonnaise is spoiled.
- Mold – Presence of visible mold is a sign mayonnaise should be thrown away.
- Sliminess – A gummy, slimy texture when mayo is usually smooth and thick is a red flag for bacteria growth.
When in doubt about the freshness, it is best to discard opened mayonnaise after 2-3 months. Using fresher mayonnaise will provide the best flavor.
Does Refrigerating Mayonnaise Affect Quality?
Refrigerating mayonnaise after opening maintains safety but it can impact the quality and taste over time. The cold temperature causes a few changes:
- Texture – Mayonnaise thickens up and becomes more dense in the fridge.
- Flavor – Notes of vinegar and citrus diminish while tastes become more bitter.
- Appearance – Color lightens over time.
- Separation – Water droplets can start to separate from the oil emulsion.
These changes are natural but affect the fresh flavor of mayonnaise. Using mayo quickly after opening provides the best texture and taste.
Tips to minimize changes after refrigeration:
- Use clean utensils when scooping to avoid contamination.
- Make sure the lid is tightly sealed.
- Keep mayonnaise towards the front top of the fridge where temperature is most consistent.
- Gently stir before use if separation occurs.
Should You Keep Mayonnaise in the Fridge Door?
It is better to store mayonnaise inside the main refrigerator compartment rather than the door. The temperature fluctuations that occur from frequent opening of the door can accelerate quality decline. A stable temperature inside the fridge helps mayo maintain its texture and taste longer.
Can You Freeze Mayonnaise?
Freezing is not an ideal way to store mayonnaise long term once it has been opened. The freezing and thawing process causes undesirable changes to the texture and emulsion.
When thawed, mayonnaise can become extremely runny or separated with the oil and water splitting. It also tends to have a grainy, gritty mouthfeel when frozen.
However, if you have leftover mayonnaise that needs using up, freezing can prolong storage life for 1-2 months. Keep the following tips in mind:
- Freeze in an airtight container leaving headspace to prevent container breakage.
- Stir after thawing to redistribute ingredients.
- Use thawed mayonnaise for cooking rather than spreading.
- Do not refreeze after initial thaw.
Does Commercial, Sealed Mayonnaise Need Refrigeration?
Commercially made mayonnaise that is properly sealed in its original airtight packaging does not require refrigeration before opening. Large jars, bottles, or individual packets of mayonnaise can be kept at room temperature.
Commercial manufacturing conditions are regulated for safety. The packaging prevents contamination, light exposure, and oxygen exposure to maintain stability.
The Mayonnaise Shelf Life Studies conducted by researchers at Virginia Tech and Tennessee University concluded commercially prepared mayonnaise has a substantial shelf life of 4-5 months when unopened and kept below 75°F.
Once opened, commercial mayonnaise then requires refrigeration. And as with all foods, it is important to follow the expiration or use by date on the label when storing unopened mayonnaise.
How Long Can Sealed Packets of Mayonnaise be Left Unrefrigerated?
Individual serving packets of mayonnaise from restaurants or cafeterias can also safely be left unrefrigerated until opened. The packets protect the mayonnaise similarly to jars or bottles. Unopened mayo packets maintain quality for several weeks when kept in cool, dry storage.
However, any packets that were not properly sealed should be discarded. And opened packets that have been exposed to air should be used immediately or refrigerated.
Can Homemade Mayonnaise be Left Out at Room Temperature?
Homemade mayonnaise has a shorter shelf life and less stability at room temperature compared to commercial products. It requires more diligent refrigeration.
It is risky leaving homemade mayonnaise out more than 2 hours before refrigeration. The fresh ingredients and lack of preservatives create an environment for bacteria to grow rapidly if left unrefrigerated.
To enjoy homemade mayonnaise safely:
- Make only what you plan to consume within a couple weeks.
- Refrigerate immediately after making – within 1 hour.
- Keep refrigerated until ready to serve.
- Discard after 1 week.
Does Vegan Mayonnaise Need to be Refrigerated?
Vegan mayonnaise substitutes also need refrigeration after opening. Products made without eggs are more shelf stable unopened. But refrigeration is still required to maintain safety and quality once exposed to air.
Substitutes like soy milk and pea protein are not as perishable as raw eggs. But the vegetable oils, moisture content, and potential for contamination still make refrigeration important.
Check packaging of vegan mayo substitutes for any specific storage instructions. But follow general opened mayonnaise guidelines to refrigerate within 2 hours after opening.
Key Points
To summarize key points on mayonnaise refrigeration:
- Unopened mayonnaise can stay at room temperature in the pantry.
- Refrigerate mayonnaise within 2 hours of opening.
- Don’t leave opened mayonnaise unrefrigerated overnight.
- Store opened mayonnaise in the refrigerator for 2-3 months.
- Check for signs like smell, texture, and appearance to determine spoilage.
- Freezing mayo can help prolong shelf life but affects quality.
- Homemade and vegan mayonnaise also require refrigeration after opening.
The Bottom Line
Mayonnaise contains egg yolks and oils that can go rancid at room temperature. Once a jar or bottle is opened, oxygen and light exposure speed up spoilage. So opened mayonnaise must be refrigerated for food safety and to maintain flavor quality.
Unopened, properly sealed mayonnaise can stay stable at cool room temperatures for a few months. But the priority should be refrigerating mayonnaise within 2 hours of opening. Proper refrigeration temp and storage helps prevent bacterial growth as well as separation of ingredients.
Checking the expiry date, smell, color, and texture can help determine if mayonnaise is still fresh. Keeping mayonnaise refrigerated and using within 2-3 months of opening provides the best taste and safety.