May 27, 2026 • 10 mins
Love it or hate it, mayo achieves a creamy texture without any dairy thanks to the science of emulsions. Learn how it works -- and why it's not the real danger in potato salad -- in this episode of BrainStuff, based on this article: https://recipes.howstuffworks.com/food-facts/question617.htm Listen to the Savor episode about mayo here (or wherever you get your podcasts): https://omny.fm/shows/savor/mayonnaise-and-mayo-nays
See omnystudio.com/listener for privacy information.
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeartRadio, Hey brain Stuff,
Lauren Vogelbaum. Here here in the Northern Hemisphere, the weather
is getting warmer and thus cookout season approaches, promising a
rays of grilled foods and accompanying side dishes and salads
(00:22):
in lots of places. Some of those salads are bound
to be the type that consists of stuff bound by mayo.
Maybe a pasta salad or potato salad. Maybe eat sandwiches
with chicken, tuna, or egg salad. Mayonnaise is a thick
sauce or dressing that's yellowish white in color and tastes
creamy despite containing no dairy product. But how does that
(00:45):
work today? Let's look at the science and history behind mayonnaise.
In addition to being used as an ingredient in the
aforementioned cold mixed salads, mayo can show up as a
spread on sandwiches, onto itself, or as an ingredient in
casseroles or in dips alone or mixed with other sauces
or seasonings for veggies, French fries, and other dippable things.
(01:09):
It has a creamy mouthfeel and a mild, slightly zippy flavor.
That texture and flavor come from the fact that mayo
is made from some kind of acid like vinegar or
lemon juice, in an emulsion with a liquid fat like
olive oil or another vegetable oil. The emulsion is bound
together with something bindy that traditionally raw egg, yolk, and salt,
(01:33):
and various spices might be added for flavor. Emulsion is
the term for an even mixture of two liquids that
don't generally mix, like oil and water, or in this case,
oil and vinegar or lemon juice. If you put equal
parts of oil and vinegar in a jar and shake
them up, they'll beat up and appear to mix for
(01:55):
a minute or so, and then they'll start separating out again.
The molecules of water that the vinegar is primarily made
up of do not want to bind to the molecules
of fat in the oil, and the feeling is mutual.
It's like being at a party or maybe a school
dance where different social groups or genders are simply not mixing.
(02:18):
But there are plenty of molecules in nature that can
make oil and water play nice for our party. Metaphor
that might be I don't know. The snack table for
the molecules. It's more like the connective pieces in a
set of tinker toys. These connective molecules are emulsifiers. They'll
(02:38):
have one end that's a hydrophilic, meaning that it likes
connecting up with water, and another that's lipophilic, meaning that
it likes grabbing onto fats. The fats will still repel
against other molecules of water, but since they're also attached
to bits of water, they wind up dispersing themselves evenly
throughout the water. These physics are also Milk contains both
(03:01):
water and fats, but looks like a single homogeneous liquid.
Egg yolks contain a fatty molecule called lesse thin that
acts as an emulsifier. A bit of ground mustard seed
or prepared mustard is often added to homemade mayo because
mustard seeds contain a lot of mucilage, which is a
gluey protein that also acts as an emulsifier. But you
(03:25):
can't just pour vinegar, oil, and egg yolks together and
wind up with mayo. You need to encourage the molecules
to interact physically, so in a bowl or some kind
of electric mixer, you whip together egg yolks and your
acid of choice, and then continue whipping and slowly drizzle
in the oil. The physical action of the whip allows
(03:47):
the emulsifying molecules in the yolk to interact with and
grab up molecules of oil and water. Sometimes while you're
doing this, the mayonnaise will break, meaning it'll go lumpy
and runny the same time, in precisely the way that
mayo shouldn't well. When emulcifications break, the water and oils
that make them up go back to hanging out on
(04:09):
separate sides of the dance floor instead of mingling. This
happens in mayo when the amount of oil in the
mix overwhelms the connective molecules. But you can fix it
by restoring balance. You can do that by either adding
more connective molecules, more egg yolk, or by adding a
bit more of your acid or just plain water for
the oil to disperse itself through, and you have to
(04:33):
whisk to combine, otherwise those oils will resolutely hang out
by themselves. Chemically, emulsions are what's called colloids, which are
evenly balanced mixtures composed of tiny particles suspended in another
unmixable material. In other colloids, Solids, liquids, or gases can
(04:54):
be either the particles or the medium in which they're suspended.
Emulsions are liquids suspended in liquid. Emulsions are usually thick
in texture and sort of satiny in appearance. They can
be used in lots of different ways outside of making mayo,
like by pharmacists, as a vehicle for medication, in anything
that needs to stay stable, from paints to detergents to
(05:16):
make up to explosives, and in other food products, including
in similar dressings that are made without eggs or with
less oil and thus generally can't be labeled mayonnaise. The
US Food and Drug Administration and other governing bodies irregulate
foods that are labeled and sold to make sure that
consumers know what they're getting and to keep manufacturers from
(05:40):
cutting corners by using too many fillers in their foods.
In the case of mayo, its rules lay out how
much acid and oil the product should contain by weight,
plus what kinds of acids, oils, and egg products may
be used, plus what optional flavorings and texture modifiers are allowed.
This is why you might see products on a shelf
(06:03):
next to mayonnaise labeled salad dressing or sandwich spread. Some
of them lower the oil content and therefore the fat content,
by swapping some out for other texture modifiers like sugar
or food starch. These products, like the brand Miracle Whip,
can taste a bit sweeter than mayo. For this reason,
(06:24):
others swap out the egg for a plant based product
to make a dressing suitable for vegans. The emulcifiers found
in egg yolks can be derived from lots of other stuff.
For example, soybeans contain a lot of less than and
seaweed a lot of mucilage. A mayonnaise as we know
it today developed in France sometime in the late seventeen
(06:44):
to early eighteen hundreds, though exactly where, when and how
is debated. Legend says it may have been prepared by
a chef for a victory feast at Port Mahone, hence mayonnaise,
but evidence is scant. Further north, in Germany and England,
other creamy dressings developed around the same time, though because
(07:08):
olive oil would have been an expensive imported product back then,
but dairy was widely available, these dressings incorporated ingredients like butter, milk,
or sour cream. You can see these influences in boiled
dressings in the American South, which aren't boiled but rather
simmered gently in a pan over boiling water. Products like
(07:30):
these started getting manufactured and bottled around the nineteen twenties. Today,
mayo is the best selling condiment in the United States,
with more Americans more likely to have it on hand
than even ketchup or peanut butter. As of twenty fourteen,
of the eight billion eggs produced every year in the States,
(07:50):
about one percent eight million went directly to making mayo,
which is impressive and brings us to one last question.
Are mayo based sides and salads the culprits behind summer
cookout food poisoning. The answer is maybe, but the mayo
isn't actually the problem here. Mayo contains a lot of acid,
(08:14):
which prevents bacterial growth. Commercially bottled mayo is especially safe
because the egg yolks in it are pasteurized. The CDC
has never reported an incidence of food borne illness associated
with commercial mayo. However, the other things in these salads chicken, potatoes, eggs,
fresh vegetables, are bacterial playgrounds at room temperature. If that
(08:40):
salad is allowed to sit out between the temperatures of
forty and one hundred and forty fahrenheit, otherwise known as
four point four two sixty celsius, otherwise known as the
danger zone. Any bacteria that have found their way into
it can multiply really fast, like double their population every
twenty minutes. This is why it's always a good idea
(09:03):
to serve chilled foods in a shaded area on ice
if you can. If cold foods are not kept chilled,
it's safest to not eat them if they've been sitting
out for more than two hours, and if the ambient
temperature is above ninety degrees fahrenheit or thirty two celsius. Well,
first of all, I'm sorry, and b you should produce
(09:24):
that non chilled time to just one hour. Today's episode
is based on the article what is Mayonnaise on HowStuffWorks
dot com and on an episode of my other podcast
Saver devoted to the topic. Brain Stuff is a production
of iHeartRadio in partnership with how Stuffworks dot Com, and
it's produced by Tyler Klang. Four more podcasts my heart Radio,
(09:48):
visit the iHeartRadio app, Apple Podcasts, or wherever you listen
to your favorite shows,
Welcome to brain Stuff, a production of iHeartRadio, Hey brain Stuff,
Lauren Vogelbaum. Here here in the Northern Hemisphere, the weather
is getting warmer and thus cookout season approaches, promising a
rays of grilled foods and accompanying side dishes and salads
(00:22):
in lots of places. Some of those salads are bound
to be the type that consists of stuff bound by mayo.
Maybe a pasta salad or potato salad. Maybe eat sandwiches
with chicken, tuna, or egg salad. Mayonnaise is a thick
sauce or dressing that's yellowish white in color and tastes
creamy despite containing no dairy product. But how does that
(00:45):
work today? Let's look at the science and history behind mayonnaise.
In addition to being used as an ingredient in the
aforementioned cold mixed salads, mayo can show up as a
spread on sandwiches, onto itself, or as an ingredient in
casseroles or in dips alone or mixed with other sauces
or seasonings for veggies, French fries, and other dippable things.
(01:09):
It has a creamy mouthfeel and a mild, slightly zippy flavor.
That texture and flavor come from the fact that mayo
is made from some kind of acid like vinegar or
lemon juice, in an emulsion with a liquid fat like
olive oil or another vegetable oil. The emulsion is bound
together with something bindy that traditionally raw egg, yolk, and salt,
(01:33):
and various spices might be added for flavor. Emulsion is
the term for an even mixture of two liquids that
don't generally mix, like oil and water, or in this case,
oil and vinegar or lemon juice. If you put equal
parts of oil and vinegar in a jar and shake
them up, they'll beat up and appear to mix for
(01:55):
a minute or so, and then they'll start separating out again.
The molecules of water that the vinegar is primarily made
up of do not want to bind to the molecules
of fat in the oil, and the feeling is mutual.
It's like being at a party or maybe a school
dance where different social groups or genders are simply not mixing.
(02:18):
But there are plenty of molecules in nature that can
make oil and water play nice for our party. Metaphor
that might be I don't know. The snack table for
the molecules. It's more like the connective pieces in a
set of tinker toys. These connective molecules are emulsifiers. They'll
(02:38):
have one end that's a hydrophilic, meaning that it likes
connecting up with water, and another that's lipophilic, meaning that
it likes grabbing onto fats. The fats will still repel
against other molecules of water, but since they're also attached
to bits of water, they wind up dispersing themselves evenly
throughout the water. These physics are also Milk contains both
(03:01):
water and fats, but looks like a single homogeneous liquid.
Egg yolks contain a fatty molecule called lesse thin that
acts as an emulsifier. A bit of ground mustard seed
or prepared mustard is often added to homemade mayo because
mustard seeds contain a lot of mucilage, which is a
gluey protein that also acts as an emulsifier. But you
(03:25):
can't just pour vinegar, oil, and egg yolks together and
wind up with mayo. You need to encourage the molecules
to interact physically, so in a bowl or some kind
of electric mixer, you whip together egg yolks and your
acid of choice, and then continue whipping and slowly drizzle
in the oil. The physical action of the whip allows
(03:47):
the emulsifying molecules in the yolk to interact with and
grab up molecules of oil and water. Sometimes while you're
doing this, the mayonnaise will break, meaning it'll go lumpy
and runny the same time, in precisely the way that
mayo shouldn't well. When emulcifications break, the water and oils
that make them up go back to hanging out on
(04:09):
separate sides of the dance floor instead of mingling. This
happens in mayo when the amount of oil in the
mix overwhelms the connective molecules. But you can fix it
by restoring balance. You can do that by either adding
more connective molecules, more egg yolk, or by adding a
bit more of your acid or just plain water for
the oil to disperse itself through, and you have to
(04:33):
whisk to combine, otherwise those oils will resolutely hang out
by themselves. Chemically, emulsions are what's called colloids, which are
evenly balanced mixtures composed of tiny particles suspended in another
unmixable material. In other colloids, Solids, liquids, or gases can
(04:54):
be either the particles or the medium in which they're suspended.
Emulsions are liquids suspended in liquid. Emulsions are usually thick
in texture and sort of satiny in appearance. They can
be used in lots of different ways outside of making mayo,
like by pharmacists, as a vehicle for medication, in anything
that needs to stay stable, from paints to detergents to
(05:16):
make up to explosives, and in other food products, including
in similar dressings that are made without eggs or with
less oil and thus generally can't be labeled mayonnaise. The
US Food and Drug Administration and other governing bodies irregulate
foods that are labeled and sold to make sure that
consumers know what they're getting and to keep manufacturers from
(05:40):
cutting corners by using too many fillers in their foods.
In the case of mayo, its rules lay out how
much acid and oil the product should contain by weight,
plus what kinds of acids, oils, and egg products may
be used, plus what optional flavorings and texture modifiers are allowed.
This is why you might see products on a shelf
(06:03):
next to mayonnaise labeled salad dressing or sandwich spread. Some
of them lower the oil content and therefore the fat content,
by swapping some out for other texture modifiers like sugar
or food starch. These products, like the brand Miracle Whip,
can taste a bit sweeter than mayo. For this reason,
(06:24):
others swap out the egg for a plant based product
to make a dressing suitable for vegans. The emulcifiers found
in egg yolks can be derived from lots of other stuff.
For example, soybeans contain a lot of less than and
seaweed a lot of mucilage. A mayonnaise as we know
it today developed in France sometime in the late seventeen
(06:44):
to early eighteen hundreds, though exactly where, when and how
is debated. Legend says it may have been prepared by
a chef for a victory feast at Port Mahone, hence mayonnaise,
but evidence is scant. Further north, in Germany and England,
other creamy dressings developed around the same time, though because
(07:08):
olive oil would have been an expensive imported product back then,
but dairy was widely available, these dressings incorporated ingredients like butter, milk,
or sour cream. You can see these influences in boiled
dressings in the American South, which aren't boiled but rather
simmered gently in a pan over boiling water. Products like
(07:30):
these started getting manufactured and bottled around the nineteen twenties. Today,
mayo is the best selling condiment in the United States,
with more Americans more likely to have it on hand
than even ketchup or peanut butter. As of twenty fourteen,
of the eight billion eggs produced every year in the States,
(07:50):
about one percent eight million went directly to making mayo,
which is impressive and brings us to one last question.
Are mayo based sides and salads the culprits behind summer
cookout food poisoning. The answer is maybe, but the mayo
isn't actually the problem here. Mayo contains a lot of acid,
(08:14):
which prevents bacterial growth. Commercially bottled mayo is especially safe
because the egg yolks in it are pasteurized. The CDC
has never reported an incidence of food borne illness associated
with commercial mayo. However, the other things in these salads chicken, potatoes, eggs,
fresh vegetables, are bacterial playgrounds at room temperature. If that
(08:40):
salad is allowed to sit out between the temperatures of
forty and one hundred and forty fahrenheit, otherwise known as
four point four two sixty celsius, otherwise known as the
danger zone. Any bacteria that have found their way into
it can multiply really fast, like double their population every
twenty minutes. This is why it's always a good idea
(09:03):
to serve chilled foods in a shaded area on ice
if you can. If cold foods are not kept chilled,
it's safest to not eat them if they've been sitting
out for more than two hours, and if the ambient
temperature is above ninety degrees fahrenheit or thirty two celsius. Well,
first of all, I'm sorry, and b you should produce
(09:24):
that non chilled time to just one hour. Today's episode
is based on the article what is Mayonnaise on HowStuffWorks
dot com and on an episode of my other podcast
Saver devoted to the topic. Brain Stuff is a production
of iHeartRadio in partnership with how Stuffworks dot Com, and
it's produced by Tyler Klang. Four more podcasts my heart Radio,
(09:48):
visit the iHeartRadio app, Apple Podcasts, or wherever you listen
to your favorite shows,
BrainStuff News
Host
Lauren Vogelbaum
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