Is homemade mayo safe to eat? (How to avoid contamination)

In this brief article, we are going to answer the question “Is homemade mayo safe to eat?”. We will also discuss how homemade mayonnaise can get contaminated and how to properly store it.

Is homemade mayo safe to eat?

It depends on the recipe, some mayo recipes are intrinsically safe while others are not. An unsafe recipe used with raw eggs to prepare mayonnaise has a very high risk of getting contaminated and causing food poison.

While pH levels can be used to assess the microbiological safety of mayonnaise, it’s often impractical for home cooks and caterers to apply these criteria due to limited kitchen facilities.

There have been numerous reported cases of food poisoning, particularly Salmonella outbreaks, associated with the consumption of homemade mayonnaise. It’s possible that in most cases can be attributed to the use of unsafe recipes in mayonnaise preparation.

Eliminating intrinsically unsafe recipes from use could potentially lead to a significant reduction or even the elimination of food poisoning outbreaks associated with homemade mayonnaise consumption. (1)

How can eggs get contaminated?

Salmonella can be present on the oute­r shells of eggs. This usually occurs when birds lay their eggs or when the e­ggs come into contact with bird feces after being laid. It is worth noting that handling eggs purchased from a groce­ry store is not a common source of illness.

The eggs undergo thorough washing before they are made available in stores. Salmonella can penetrate e­ggs as they are being forme­d inside the chicken, e­ven before the eggshell is fully deve­loped. Some mayonnaise produce­rs incorporate dried egg products in their recipes.

The drying process effectively e­liminates a significant number of bacteria that were originally present in liquid e­ggs. Once the product reache­s its dried state, the microbiological population stabilize­s, and any decline in quality occurs gradually over time­.

During the drying process, the number of Salmonella bacteria can be greatly reduced. However, Salmonella can still pose a challenge in dried egg products. (2-4)

How can homemade mayo get contaminated?

Major risk factors contributing to foodborne disease outbreaks include improper storage at non-recommended temperatures, extended periods of inadequate storage, lapses in hygiene practices, and the potential for cross-contamination and recontamination.

While eggs can become contaminated with Salmonella through various means, such as infections in reproductive organs or penetration of the eggshell and membranes, this pathogen is more likely to reach harmful levels, often leading to illness, when mayonnaise is stored under unsuitable conditions (5)

What is the role of acidity in homemade mayo safety?

From a microbiological perspective, it is recommended that a minimum of 60 ml of vinegar per whole egg, 40 ml per egg white, or 20 ml per egg yolk (with a 6% w/v acetic acid content) is necessary to create Salmonella-free mayonnaise in a home setting.

It has been observed that the pH level of mayonnaise is primarily influenced by the ratio of egg to vinegar, and it decreases as this ratio decreases.

Even though egg yolk, egg white, and whole egg have distinct pH values, their impact on the pH of mayonnaise is the same when the ratio is less than 2.5.

Additionally, the presence of salt and sugar tends to decrease the pH of mayonnaise, while oil, mustard, and pepper have the opposite effect. A mayonnaise recipe can be considered safe only when the ratio of egg to vinegar is equal to or less than the established safe ratio. (1, 6)

How to store homemade mayo safely?

For safe storage of homemade mayo, it’s important to maintain a pH level of 4.1 or lower. It’s recommended to initially incubate the mayo at room temperature (18-22°C) for 24 hours before refrigeration. This room-temperature incubation is advised as low-temperature incubation affords some protection to the salmonellas against the antimicrobial effects of organic acids.

After that period, homemade mayo should be stored in a refrigerator at 4°C. When handling eggs, it’s crucial to exercise caution. Whenever possible, use fresh eggs and avoid cracked ones. For catering purposes, it’s advisable to prepare mayonnaise using pasteurized liquid eggs.

It’s essential not to mix any unused mayo with fresh batches. Adding other foods to mayo can impact its antimicrobial properties, so this should be considered during preparation. (7)

What are the symptoms of food poisoning?

The majority of individuals who contract Salmonella experience symptoms such as diarrhea, fever, vomiting, and stomach cramps. These symptoms typically manifest within a window of 6 hours to 6 days after infection and typically persist for 4 to 7 days.

Most people recover without requiring antibiotics; however, these medications are essential for patients who are severely ill or at risk of becoming severely ill. Individuals with diarrhea should make a point of increasing their fluid intake. In rare cases, Salmonella can enter the bloodstream and result in a potentially life-threatening infection. (2)


In this brief article, we answered the question “Is homemade mayo safe to eat?”. We also discussed how homemade mayonnaise can get contaminated and how to properly store it.

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