When the base of a hollandaise sauce is colder than the butter to be emulsified, what will the chef notice?

When the base of a hollandaise sauce is colder than the butter that is being added to create the emulsion, the chef will likely notice that the sauce will break. Hollandaise sauce is an emulsion, which means it combines fat (from the butter) with liquid (the base made from egg yolks and lemon juice or vinegar). For successful emulsification, both the base and the fat should be at a similar temperature.

If the base is colder, the contrast in temperature can hinder the incorporation of the fat into the liquid. The cold base makes it difficult for the fat to disperse evenly. Instead of creating a smooth and cohesive sauce, the fat can separate and result in a broken sauce. This breaking happens because the emulsifying agents (like the proteins in the egg yolk) are unable to effectively stabilize the fat globules at lower temperatures. Thus, achieving the desired emulsion becomes challenging, leading to a failed hollandaise sauce.