Protein adsorption and protein fouling can cause major problems in the food industry (particularly the dairy industry) when proteins from food adsorb to processing surfaces, such as stainless steel or plastic (e.g. polypropylene). Protein fouling is the gathering of protein aggregates on a surface.  This is most common in heating processes that create a temperature gradient between the equipment and the bulk substance being heated.  In protein-fouled heating equipment, adsorbed proteins can create an insulating layer between the heater and the bulk material, reducing heating efficiency.  This leads to inefficient sterilization and pasteurization.  Also, proteins stuck to the heater may cause a burned taste or color in the bulk material.  Additionally, in processes that employ filtration, protein aggregates that gather on the surface of the filter can block the flow of the bulk material and greatly reduce filter efficiency.