What happens to proteins when they are tested with ethanol?

When proteins are tested with ethanol, they generally precipitate out of solution. This is due to ethanol's ability to disrupt the interactions that keep proteins soluble in water. Ethanol decreases the solubility of proteins by altering their hydrophilic and hydrophobic balance, leading to the aggregation and formation of a precipitate.

The emulsion formation mentioned in the chosen answer does not apply here. A visible emulsion typically involves dispersing one liquid in another, which usually applies to certain types of lipids rather than proteins. In the context of proteins and ethanol, the expected response is precipitation, not emulsion formation, which suggests that the correct understanding of protein behavior in ethanol leads to precipitation rather than remaining solubilized or forming an emulsion.