Mayonnaise
Mayonnaise is a thick, creamy sauce or dressing that is made of
oil, egg yolks, lemon juice or vinegar, and seasonings. It's not the same as
salad dressing, which doesn't contain egg yolks and is generally sweeter than
mayonnaise.
Mayonnaise is an emulsion, which is a mixture two
liquids that normally can't be combined. Oil and water is the classic example.
Emulsifying is done by slowly adding one ingredient to another while
simultaneously mixing rapidly. This disperses and suspends tiny droplets of one
liquid through another.
However, the two liquids
would quickly separate again if an emulsifier were not added. Emulsifiers are
liaisons between the two liquids and serve to stabilize the mixture. Eggs and
gelatin are among the foods that contain emulsifiers. In mayonnaise, the
emulsifier is egg yolk, which contains lecithin,
a fat emulsifier.
Chemically, emulsions are
colloids, heterogeneous mixtures
composed of tiny particles suspended in another immiscible (unmixable)
material. These particles are larger than molecules, but less than one
one-thousandth of a millimeter (.001mm). Small particles like this do not
settle out and will pass right through filter paper. The particles in a colloid
can be solid, liquid or bubbles of gas. The medium that they are suspended in
can be a solid, liquid or gas (although gas colloids cannot be suspended in
gas).
Emulsions are
liquid-liquid colloids, tiny liquid droplets suspended in another liquid.
Emulsions are usually thick in texture and satiny in appearance.
Emulsions are used in
many different ways:
- by pharmacists, as a
vehicle for medication
- in photography, to coat
plates, film and paper
- in explosives, paints,
coatings, make-up and detergents
- in food, including baked
goods and confectionery products
Mayonnaise is made by combining lemon juice or vinegar with egg
yolks. Eggs (containing the emulsifier lecithin) bind the ingredients together
and prevent separation. Then, oil is added drop by drop as the mixture is
rapidly whisked. Adding oil too quickly (or insufficient, rapid whisking) will
keep the two liquids from combining (emulsifying). But, as the sauce begins to
thicken, oil can be added more rapidly. Seasonings are whisked in after all of
the oil has been added. Blenders, mixers and food processors make it easy to
make homemade mayonnaise, which many gourmets feel is far superior in taste and
consistency to commercial mayonnaise.
Since homemade
mayonnaise is uncooked, be sure to use the freshest eggs possible, and ones
that you are reasonably sure are free from salmonella. Homemade mayonnaise will last three to four days in
the refrigerator.
Commercial mayonnaise,
which will last up to six months in the refrigerator, contain (by
Procedure
To make mayonnaise you will need the following ingredients:
6 large egg yolks 9 tablespoons of lemon juice ¾ tablespoons of salt 3 pinches of white pepper 3 cups of olive oil
Put the yolks, lemon juice, salt, and pepper into a
mixing bowl and whisk until smooth and light. Then whisk the oil in a few drops at a
time into the mixture. Make sure the
mixture is smooth and well integrated before adding the next few drops of
oil. Whisking will suspend the oil
into the yolk mixture and adding oil a little at a time will keep the
mixture in an emulsified state.
After 1 cup of oil has been whisked in, you can speed
up the pouring a bit. Make sure the
mixture remains in an emulsion before pouring any more oil. Once all the
oil has been whisked in, you have mayonnaise. †Because handmade mayonnaise is mostly egg yolk, the
mayonnaise will be a yellow color.
The mayonnaise should be placed in a covered/sealed jar and
refrigerated immediately.
* Repeat the process again except, substitute 3 cups of extra virgin olive oil
for the 3 cups of olive oil.
-After 3 days of refrigeration, view each sample and check for any signs of separation. If either sample shows signs of separation, note which one.
Questions
1.) What are some other common food products are identified as emulsions? What emulsifier(s) bind them together?
2.) Did either mayonnaise sample show signs of separation? Would one sample be more likely to separate over the other, why?
3.) Assuming white and black pepper provide the same amount of flavor, what why would white pepper be used instead of black pepper?
4.) What process ensures that the mayonnaise is reasonably safe to eat, even though it contains uncooked eggs?
References
Franco, J.M.; Munoz, J.; Gallegos, C.; Berjano, M.;
Guerrero, A.. 1995. Flow behavior and stability of light mayonnaise containing a mixture of egg yolk
and sucrose stearate as emulsifiers. Food hydrocolloids v. 9 (2), p.
111-121
Mistry, B.S.
1993. Shelf life of mayonnaise and salad dressings. Developments
in Food Science v.33, p.409-450
Whiting, R.C. 1997. Development of
a quantitative risk assessment model for Salmonella enteritidis
in pasteurized liquid eggs. International Journal of Food Microbiology v.
36(2/3), p. 111-125