Refrigerate or Leave Out? The Truth About Mayonnaise Storage
Commercial vs. Homemade Mayonnaise: Differing Risks
The distinction between commercial and homemade mayonnaise is significant when considering food safety:
- Commercial Mayonnaise: Typically contains pasteurized eggs and preservatives, making it less likely to harbor bacteria when unopened. Once opened, it must be refrigerated to maintain freshness and safety.
- Homemade Mayonnaise: Uses raw eggs and lacks preservatives. Experts recommend consuming it within a few days and keeping it refrigerated at all times.
According to the Food and Drug Administration (FDA), commercial mayonnaise’s acidity inhibits bacterial growth to an extent, but this does not make it fully immune from spoilage, especially after being opened.
Storage Guidelines: Expert Recommendations
Food safety authorities recommend storing mayonnaise under the following conditions:
- Unopened commercial mayonnaise: Store in a cool, dry place away from heat. The refrigerator is optional at this stage, but some prefer it for optimal freshness.
- Opened commercial mayonnaise: Always refrigerate after opening. Manufacturers typically recommend a temperature of 40°F (4°C) or lower.
- Homemade mayonnaise: Refrigerate immediately after preparation. Consume within 2–4 days.
Avoid cross-contamination by always using clean utensils and keeping the jar lid tightly closed. Never return unused mayonnaise from a plate or serving dish to the original container.
What Happens When Mayonnaise is Left Out?
Leaving mayonnaise out at room temperature increases the risk of bacterial growth exponentially. In temperatures above 90°F (32°C), spoilage occurs even faster. The USDA’s food safety guidelines state that perishable foods left out for more than two hours should be discarded. Signs of spoiled mayonnaise include:
- Change in color (yellowing)
- Separation or curdling
- Off or sour odor
- Bubbles or signs of fermentation
If any of these signs appear, do not taste to “check”—discard the product. Eating compromised mayonnaise can cause foodborne illness, most commonly presenting as nausea, vomiting, abdominal cramps, and diarrhea.
Global Food Safety Standards
International food regulatory agencies, including the European Food Safety Authority (EFSA), Australia’s Department of Health, and Canada’s Food Inspection Agency, follow similar recommendations regarding mayonnaise storage. Most emphasize refrigeration after opening and careful attention to expiration dates. The World Health Organization (WHO) includes guidelines for safe handling of egg-based products in its food safety campaigns.
