What is mayonnaise?

Mayo is an emulsion - a mixture of two liquids that normally can't be combined. So how do these ingredients come together? Tune in to learn how oil, egg yolks and acid combine to form one of the world's most popular condiments.

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from house Stuff Works dot com
where smart happens. Hi Am Marshall Brain with today's question,
what is mayonnaise? And this question comes up because lots
of people have no idea what mayonnaise is. You know,

(00:21):
if you look at butter, most people know that you
can make butter out of cream. And if you look
at catchup or something like that, most people know that
it's made out of a thick tomato sauce. But mayonnaise,
what what is it? Is it made out of milk
because it's white? Is it some other substance? If you
look at the label, you can see that it has
a lot of fat in it. Some mayonnaises have as
much as nine fat. So let's take a look at

(00:44):
where this stuff comes from. It turns out that mayonnaise,
and here we're talking about real mayonnaise, the kind of
mayonnaise you could make at home if you wanted to,
is made out of at least three things, and those
are oil, a lot of oil, egg yolks, and some
kind of acid, either lemon, juice or vinegar. There might
also be some kind of seasonings in there, like salt,

(01:05):
and maybe something else. But mayonnaise itself is just the
three things oil, egg, yolks, and lemon juice or vinegar.
The obvious question is, how are you going to get
oil and lemon juice to mix together? Because lemon juice
is water based and oil is oil based, obviously, so
when you try to mix them together, they're not going
to mix. Oil and water don't mix. And the magic

(01:28):
of mayonnaise and mayonnaise really is kind of magic, is
that the egg is there to act as an emulsifier
and to make those two things that normally wouldn't combine
able to combine together to create the unique taste of mayonnaise. Therefore,
we say that mayonnaise is an emulsion, which is a
mixture of any two liquids that normally can't be combined chemically.

(01:52):
Mayonnaise is also known as a colloid. A colloid is
a mixture composed of tiny particles that are suspended in
another or immiscible or unmixable material. These particles are usually
larger than molecules, but less than one one thousand of
a millimeter in size. Small particles like this don't settle

(02:14):
out or don't rise to the top, depending on their nature,
and they will pass right through filter paper. One really
good example of a colloid that we see all the
time is homogenized milk. In homogenized milk, they've taken the
cream and they've broken it up into such tiny particles
that it remains mixed in with the watery milk. And

(02:34):
it's the size of the particles that allows that to happen.
So that's a mechanical colloid, a colloid that was created
mechanically by breaking those cream particles up into such small,
tiny spheres. Chemically, you can also create an emulsion, so
you use chemicals of some sort to break the particles
up and get them to suspend in a liquid. So

(02:57):
to make mayonnaise, you start with the lemon juice and
to that you add some egg yolk eggs, which contain
an emulsifier called less than bind the ingredients together and
prevent them from separating. So you add the eggs and
the lemon juice, and those are going to combine together fine.
Then you add the oil in a tiny bit, like

(03:18):
just a few drops at a time, and whisk that
together with a fork or with an actual metal whisk
to get the oil and water emulsion started. If the
chef messes up with this initial mixing step, the whole
batch isn't gonna work. You have to start very slowly
with the oil and get the emulsion to start, and

(03:40):
then you can add more and more oil more quickly
because the process accelerates as the mayonnaise thickens. Then, if
you want to add in any seasonings to make flavored mayonnaise,
you add them in at the end of the process.
Since homemade mayonnaise isn't cooked, you need to be sure
to use the freshest eggs possible, and you need to

(04:00):
be pretty sure that they're free from salmonella. You also
want to use it quickly. You can store it in
the refrigerator for two or three days, but after that
you really should throw it out rather than letting it
hang out for a week or two. Commercial mayonnaise, which
is the kind of mayonnaise you buy at the store
in a jar, will last up to six months in
the refrigerator. It contains by US law at least oil

(04:24):
by weight, except for reduced fat and fat free mayonnaises.
The standard of Identity law also requires that all commercial
real mayonnaise use only egg as the emulsifier. Reduced fat mayonnaise,
which isn't considered real mayonnaise anymore, usually contains modified food starts,
cellulose gel, and other thickeners and emulsifiers. Once you have

(04:48):
your mayonnaise, you can use it straight up on something
like a bacon lettuce tomato sandwich, or you can use
it as a base for other sauces like tartar sauce
or a Thousand Islands salad dressing. Be sure to check
out our new video podcast, Stuff from the Future. Join
how staf work staff as we explore the most promising
and perplexing possibilities of tomorrow. The hou stef Works iPhone

(05:12):
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