Mayonnaise is an emulsion of oil, egg yolks, and an acid like vinegar or lemon juice. Egg yolks contain lecithin, which stabilizes the mixture. Commercial mayonnaise usually adds preservatives and pasteurized eggs, which extend its shelf life. Homemade mayonnaise lacks these safeguards, making it more prone to spoilage.
Acidity in mayonnaise slows bacterial growth, but it’s not foolproof. Leaving it out at room temperature for too long can still be risky.
Why Temperature Matters
Temperature plays a critical role in mayonnaise safety. At room temperature, bacteria multiply quickly. Refrigeration slows this growth, keeping the mayonnaise safe longer. For best results, store mayonnaise below 40°F (4°C).
