Protein adsorption refers to the adhesion of proteins to solid surfaces.  This phenomenon is an important issue in the food processing industry, particularly in milk processing and wine and beer making.  Excessive adsorption, or protein fouling, can lead to health and sanitation issues, as the adsorbed protein is very difficult to clean and can harbor bacteria, as is the case in biofilms.  Product quality can be adversely affected if the adsorbed material interferes with processing steps, like pasteurization.  However, in some cases protein adsorption is used to improve food quality, as is the case in fining of wines.