Protein stabilization is the removal of proteins that can cause a protein veil – an opaque haze – in the wine. The wine is unstable because these proteins can start clumping when the temperature is raised or when the pH goes down. Protein instability does not correlate with total protein content, because especially chitinases and thaumatin-like proteins are responsible for the protein haze. Mannoproteins (glycoproteins derived from the cell wall of yeast cells) on the other hand, reduce the haze formation by heat-unstable proteins. In the wine making process proteins are often extracted from the wine with the aid of bentonite.