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Misconceptions
When I first learned about making mayonnaise, let alone letting it sit out, I will admit I was a little off-put. These were my misconceptions:
- After all, food containing store-bought mayonnaise is one of the worst offenders for sickening people at picnics…isn’t it?
- Letting homemade mayo sit out for 72 hours? Ewe!!!! Won’t acid kill germs at refrigeration temperatures?
- Is it fermentation?
…and then came the flip side
- I’ve seen countless bloggers say that homegrown eggs have very little risk of being contaminated with salmonella. Woohoo, raw cookie dough here I come! Store-bought mayo is for chumps. If “everyone” says so, it must be true…
- There are tons of recipes out there for egg-based dressings, even very mainstream ones, so they must be very safe… No?
The funny thing is, it never dawned on me to do further research until I had already blindly followed the advice of some of my favorite bloggers. Feeling unsettled one day, I decided to indulge my curiosity and research a step deeper. What I found kinda blew my mind.
Commercial mayo study
When food has been properly prepared and handled, mayo can actually slow or even stop the growth of harmful bacteria! here’s a review of one study that I found that looks at commercial mayo’s strong ability to destroy harmful microbes.
Why homemade mayonnaise rocks
Most of us by now have heard of Sally Fallon Morell’s book (Affiliate link) “Nourishing Traditions: The Cookbook that Challenges Politically Correct Nutrition and the Diet Dictocrats“. (And if you haven’t, I highly recommend you get a hard copy for your kitchen). This has been the backbone of my traditional cooking lifestyle.
About 10 years ago I came across the “Nourishing Traditions” mayonnaise recipe. I was drawn in by the words:
“Homemade mayonnaise imparts valuable enzymes, particularly lipase, to sandwiches, tuna salad, chicken salads and many other dishes…”
Wow, something that makes meat and veggies taste better, aids digestion and keeps me thin deserves some attention! I decided to give it a go.
As I mentioned above, after making this a few times, our lucky breaks didn’t shake my safety concerns. I decided to poke around and do more research.
Questioning authority
Now I hope that I don’t come across as bashing anyone here. I have lots of appreciation for Alton Brown, and I think most of us can agree that he is a source of reliable information on food. An Authority really. His recipe for homemade mayonnaise on foodnetwork.com has a warning that eating raw eggs may increase the risk of foodborne illness. Raw eggs have been a source of salmonella and other harmful bacteria that have been known to make people very sick. In severe cases, they can even cause death. I get it. The writers have to protect themselves from a lawsuit.
Unfortunately, Alton’s recipe, like most, does not include the instructions below that have been shown in scientific studies to kill salmonella. A few little changes would surely make his recipe, and others like his, much safer.
Sally Fallon Morell is another one of my personal food heroes so I wanted to shout out to the world that her recipe is perfect. It could be deemed a little closer to the mark if you opt for the fermented version since it involves leaving it out longer than most recipes, however, I was unable to find any studies to confirm that the length of time recommended is truly enough.
So what you’re saying is there’s a chance😜
Rather than point anymore fingers, I think it’s safe to say that there are a plethora of recipes on the webs that don’t make any mention of any risk of getting sick from their raw egg recipes. Some even go as far as to say that there is no need to be worried about raw eggs whether store-bought or home-grown. Hmmm…
I’m sure you’ve seen the statistics being passed around, stating that the chances of contracting salmonella from an undercooked or raw egg are somewhere around 1/30,000. Ok so if this is true, the chances are very small. But there’s a chance. (I realize I run the risk of reminding you of a scene from “Dumb And Dumber” so I’m just going to run with it.)
My burning need to find a better way to make mayo stems from a friend’s horrible experience. She got violently ill for a week after eating raw cookie dough that was made with store-bought eggs. If you’re blissfully unaware of the risks, I dare you to Google “salmonella outbreaks from mayonnaise“. Outbreaks do happen. The ones I’ve seen all came from homemade mayo, not commercial. The odds are very low but what I’m going to share with you may eliminate risk all together.
Sour is safer
Thankfully, THERE IS A THOROUGHLY RESEARCHED and EASY WAY to make homemade mayonnaise and other egg based dressings with a greatly reduced risk! It’s as simple as the right amount of acid, and the right amount of time at room temperature to let the acid kill harmful bacteria. Unfortunately, I’ve never seen a mayo recipe with these crucial instructions!
The acid needed to kill salmonella is also a bit more than you’ll find in most mayo recipes online. Yes, it will mean a tangier mayo. For my family, that is not a problem. For those that want a less tangy option, fermenting may be just the ticket.
Acid or Fermentation?
If you prefer a less tangy mayo, fermentation may reduce the need for quite so much acid, and is said to have the added benefit of increasing the shelf life considerably. Unfortunately, I couldn’t find any studies that offer specific recommendations on making it safely this way. Personal experience with the recipe in “Nourishing Traditions” says it works, but as of yet, I don’t know how much of a risk I’m taking.
My version of “Nourishing Traditions” (revised second edition) only recommends setting the mayo out for 7 hours, and only if you have added whey (not protein powder whey, but the liquid you can drain off yogurt, or that’s produced when making certain types of raw cheese). The lactobacilli in whey fight pathogens and produce more food preserving acid. This is not quite the same as letting the acid alone in the lemon juice or vinegar work.
Here’s a preliminary study on whey’s effectiveness at killing pathogens. It looks like the whey they used is just as effective as chlorine when used in a 75:25 (v/v) whey to water ratio.
Unfortunately, with no definitive studies on what types of whey, temperatures, or amounts needed to be effective, we don’t really know what kind of risk we’re taking making fermented mayo. And I’m not even really sure what is being fermented if oil can’t ferment. Personally, if I do make fermented mayo I will use the acid ratios in my conclusions below, and let it sit out the required time to make sure all the bad bugs are gone.
What studies say about homemade mayo
This review looks at 15 studies from all over the world. Not only does it show the effectiveness of vinegar in the right concentrations at the right temperature for the right amount of time, This review also explores the effectiveness of other substances such as garlic, olive oil, and oregano essential oil to name a few. Surprisingly, contrary to the older articles below, the jury is still out as to whether vinegar or lemon juice is more effective at killing Salmonella.
This older article concludes that vinegar is more effective against germs than lemon juice. Different oils and types of vinegar had different effectiveness. They recommended that mayonnaise is prepared with vinegar to a pH of 4.1 or less. The addition of garlic or mustard to mayonnaise at certain concentrations results in an increase in the death rate of Salmonella. SALT, on the other hand, HAS A PROTECTIVE EFFECT ON SALMONELLA! Whaaaa? I guess I’ll be waiting to salt my mayo until after it has been properly prepared and set out for a sufficient amount of time. This article also says that refrigeration protects Salmonella from the acids. Ahhh, so letting it sit at room temp IS necessary…
Here is another study that plays around with different pH levels and temperatures. This study also concluded that vinegar was more effective at killing Salmonella than lemon juice. What we can be sure about is that both acidic mediums are MORE EFFECTIVE AT ROOM TEMPERATURE and ineffective at killing pathogens at refrigerated temperatures.
According to this study, mayonnaise made with lemon juice can be made safe as long as the pH reached 3.30 or below. To achieve this, they recommended that 20–35 ml (~4-7 tsp.) pure lemon juice per egg yolk should be used, and that the prepared mayo SHOULD BE HELD at 71.6 °F for AT LEAST 72 HOURS. For a shorter wait of at least 48 hours, 35 ml lemon juice per egg yolk should be used. I’ve made it with 4 tsp. per yolk and left it out for 72 hours, and for me that was plenty tangy but reasonable. I haven’t tried 7 tsp. per yolk, but I think that would be some pucker inducing mayo. This is a good reason to plan ahead!
A word on home-grown VS. commercial eggs
I couldn’t find a single study on salmonella risk of homegrown vs. commercial eggs. The general consensus among scientists (and homestead bloggers) is that chickens that are raised in crowded cages are much more likely to contract salmonella than chickens raised in a clean free-ranging environment.
{Fermenting the feed can go a long way to reducing your risk of salmonella in your flock. I’ll be sure to write more about that someday.}
It is wise to keep in mind that homegrown eggs do sometimes get contaminated with salmonella. Symptoms of salmonella are not always visible in a flock. You can have your birds tested by a vet, but if you have rats and other vectors that may spread diseases, they could get infected after being tested.
Calculated risks
Do I worry terribly about the safety of my homegrown eggs? Not really. I enjoy fried eggs with a runny yolk several times a week. I’m not a total prude ;). And despite my friend’s experience, I also eat raw cookie dough on occasion (gasp), but only with my home-grown eggs that have been produced with care. That’s a calculated risk I’m willing to take. 😉
Since the steps to reducing the risk of making dangerous mayonnaise are so incredibly easy I’ll cut a percentage of my risk there where it’s easy. Plus I can enjoy having no reservations about making a big bowl of potato salad with homemade mayo for our next pot luck.
Pasteurized eggs
You can even buy pasteurized eggs to make your mayonnaise, but for me, buying special eggs when you’ve got laying hens just feels silly. I’ve seen methods for pasteurizing eggs yourself without coagulating them, however, I haven’t been able to verify if it really works.
My conclusions
- Vinegar and lemon juice are both fine.
- Temps must be at least 68° F or 20°C in order for the acid to kill bacteria. {Good to know if using vinegar to clean up outside after processing animals!}
- Use at least 4 tsp (20 ml) lemon juice or vinegar per egg yolk if setting out for 72 hours. If you only have 24 hours to set out the mayo, use 7 tsp (35 ml ).
- Properly fermented mayo may last a lot longer, and provide another option that won’t be overly tangy. Do this at your own risk though.
- I would NOT add salt or vegetable material to the mayo until after it has sat at room temp for 72 hours. Who knew that salt in concentrations that taste good in mayo could actually protect the bad guys, salmonella?! Vegetable material, such as dill or other herbs, absorb citric acid, so wait until it has sat for the full-time before adding it in.
Note: I don’t use egg whites because they contain high amounts of avidin when raw. Avidin binds to biotin and depletes it from the body. Cooking deactivates avidin so no worries eating the whites of the eggs when cooked. TIP: Set aside and freeze the whites until you have enough for coconut macaroons! Yes, they should still whip up nice!
Ingredients
- 1 egg yolk
- 4 tsp. lemon or vinegar
- 1-2 tsp. mustard
- *1 TBSP whey (only if fermenting)
- 1 cup avocado oil
- 1/2 tsp. salt (save for after set out time is complete)
Instructions
- Add yolk, lemon or vinegar, and mustard to a wide mouth mason jar. *If fermenting add in your whey. Blend with a stick blender until ingredients are well blended. Slowly drizzle in oil in a very thin stream. blend until the mayo thickens. Let sit at room temp. (at least 68º F or 20º C) for 72 hours. If you need it faster (24 hours) no worries! You can use 7 tsp. lemon or vinegar per yolk. Just be prepared for a very tangy mayo. Once the mayo has set out for the full length of time, you may add the salt and any herb seasonings you wish. Refrigerate and enjoy!
So there ya have it! The secret tricks to make homemade mayonnaise safer. Doesn’t it make you wonder why you haven’t heard of this before? Me too.
I hope you enjoyed the read. Please comment below if you have any questions, corrections or personal experiences to share!
Sources and further reading:
The fate of Salmonella enteritidis PT4 in home-made mayonnaise prepared with citric acid
I just love the whey 🙂 that you not only do the research that helps to keep us safe; but you also share your sources. Thank you for all your hard work Liz.
Thank you so much Donna!🌺
Thank you for your article. I just started making mayonnaise and it is the first article I read about how I should reduce the risk of salmonella infection. You summed it all up nicely. And thank you for referencing that book. I’ll be sure to read it sometime.
Thank you Yuri!
Dear Liz, could you perhaps also write at the end of the article how long you can keep the selfmade mayonnaise in the fridge after waiting the needed 72 hours? Thank you!
From what I can gather it looks like the homemade mayo will last 3 days in the fridge unless whey is used. I’ve seen people suggest a week for mayo that is made by fermenting it with whey. I couldn’t find any studies to substantiate those claims but that seems to be the consensus among bloggers.
If you use pasturized eggs do you still need to leave the mixture at room temperature for 72 hours? Also if you use pasturized eggs can you use the egg whites? Thank you.
Hi Amanda, if you use pasteurized eggs, there’s no need to let the mayo sit out. I’ve never used pasteurized eggs so I’m not sure how the egg whites would behave with different uses, but it sounds like you can still separate them. I’m just not sure if they will still whip up as nice as unpasteurized eggs. If you try this please let me know how it turned out for you.
I live in a rather hot climate (nowadays it’s around 30C inside the home). I would think that the fermentation process might happen faster at that temperature… any cues to know when it has fermented enough? I checked it today after 24 hours of fermentation and it was very bubbly, almost fluffy texture… very surprising for mayo! Should I still let it ferment for 48 more hours?
Hi Uma,
Yes you are right, fermentation happens faster in warmer temperatures. You won’t have to wait very long for your ferments to complete at that temperature. The studies I refer to all seem to have controlled temperature. So I can’t safely say much about adjusting the time and temperature. Generally I would just go by the taste and smell, but for mayo I would be more careful. I don’t know if it would be safe to eat if it’s getting fluffy. Mine always gets some bubbles but never fluffy. How does it smell?
One of the reasons that store bought eggs cause Salmonella is that many of the hens are carriers and it enters the egg from them. In Europe the hens are vaccinated by law for this, not in the US.
I had to check that out. Sure enough! From what I read it’s in a spray on form so very easy to administer. I wonder if there are any downsides?
Is there any harm in leaving the mayo out of the fridge an extra day? The temperature gets below 68 degrees in the evenings where I live and I’m tempted to leave it out in the sun one extra day.
Hi CK, that sounds pretty reasonable to me. I don’t know how the sun might effect the ferment though.
Hi I am new to this and I am wondering when you leave the mayo out for the 72 hours is it covered tightly in the mason jar are open?
Hi Yvette, great question. I keep an airtight lid screwed on tight for making Mayo since the process is not so much about gas producing fermentation and more about letting the acid kill germs. For true fermentation such as using a starter to ferment sauerkraut the lid needs to be fingertip tightened so it’s tight enough to keep air out but loose enough for gasses to escape.
Can you use bottled lemon juice or does it need to be fresh?
Thanks for the article, it was very well researched and written and made me feel better about homemade mayo!
Thank you so much Leena! And great question. I believe bottled will work since the pH is often more acidic while fresh can vary wildly but still seems to work.
Could you ferment the yolks and culture alone to a safe pH, and then continue with the recipe, adding oil etc.? With this method, it seems it would be easier to get the acid concentration necessary, without a too-tangy flavor.
That’s a really great question and honestly I don’t know for sure but it would make sense to me. I’ll see if I can find some research on that!