Protease
The enzyme for protein stains, and the reason a hot pre-wash makes blood and egg permanently worse.
In detail
A protease is an enzyme that cuts protein chains into fragments small enough to dissolve and rinse away. In a laundry product it is the component that deals with blood, egg, milk, gravy, grass and perspiration — the stain family that ordinary surfactancy handles badly because the protein is not oily and does not simply lift. The practical consequence is the temperature rule that surprises people. Heat denatures protein and sets it into the fibre, and it also destroys the enzyme that would have removed it. So the correct first move on a protein stain is cold water, and the enzyme's working range is warm rather than hot. Enzymes are one of the classes a detergent label must declare irrespective of concentration, though the label says 'enzymes' and not which ones.
Why
- Protease is explained by Enzymes in cleaning
- Protease is explained by Protein denaturation
- Protease is explained by Heat-set stains
Sources for this page
Sources
Regulation (EC) No 648/2004 on detergents, Annex VII — labelling and ingredient data sheet
European Parliament and Council, as retained in UK law (legislation.gov.uk), 2004 · Government or regulator
Relied on for: That the class must be declared on a detergent label irrespective of its concentration. (states this directly)
Handbook of Detergents (Surfactant Science Series)
CRC Press / Taylor & Francis · Reference work
Relied on for: That proteases hydrolyse protein soils into soluble fragments and are formulated into laundry detergents for protein-based stains. (background and mechanism only)