Mayonnaise (ˌmeɪəˈneɪz), colloquially referred to as "mayo" (ˈmeɪoʊ), is a thick, cold, and creamy sauce commonly used on sandwiches, hamburgers, composed salads, and French fries. It also forms the base for various other sauces, such as tartar sauce, fry sauce, remoulade, salsa golf, ranch dressing, and rouille.
Mayonnaise is an emulsion of oil, egg yolk, and an acid, either vinegar or lemon juice; there are many variants using additional flavorings. The color varies from near-white to pale yellow, and its texture from a light cream to a thick gel.
Commercial eggless imitations are made for those who avoid chicken eggs because of egg allergies, to limit dietary cholesterol, or because they are vegans.
Mayonnaise is a French cuisine appellation that seems to have appeared for the first time in 1806. The hypotheses invoked over time as to the origin(s) of mayonnaise have been numerous and contradictory. Most hypotheses do however agree on the geographical origin of the sauce, Mahón, in Menorca, Spain. Other theories have been dismissed by some authors as being somewhat a retrospective invention aiming to credit the sauce as an invention of south-western France, when most likely, its origin can be found in the port city of Menorca.
According to Émile Littré, it may have come from Mahón, capital of Menorca, in the Balearic Islands, Spain, occupied by the British at the time and then conquered by the Duc de Richelieu in 1756. His cook would have presented him with this sauce, called the "mahonnaise", made with the only two ingredients he had: egg and oil. Nevertheless, this sauce was starting to be described a little before this event while several versions of similar sauces existed in France and in Spain.
Mayonnaise sauce may have its origins in the ancient remoulade. Another hypothesis is that mayonnaise is derived from aioli. Finally, the process of emulsifying egg yolk was known for a long time to pharmacists, who used it to prepare ointments and salves.