By the 19th century, sauces had been classified into four categories by Carême. One of his categories was "allemande", which was a stock-based sauce using egg and lemon juice. Escoffier replaced "allemande" with egg based emulsions, including "hollandaise" and mayonnaise in his list of the five mother sauces of haute cuisine. While many believe that a true hollandaise sauce should only contain the basic ingredients of eggs, butter, and lemon, Prosper Montagne suggested using either a white wine or vinegar reduction, similar to a Béarnaise sauce, to help improve the taste.