Proteins (e.g. ovalbumin, cooked fish meat, vegetable proteins) are broken down (hydrolysed) into their building blocks (ultimately amino acids) under the action of water. Often, simple boiling in water is not sufficient for hydrolysis.
In these cases, concentrated mineral acid (generally hydrochloric acid) or concentrated alkaline solutions (e.g. potassium hydroxide solution) are used to start the hydrolysis, if necessary by heating (to accelerate the process sufficiently, the temperature must usually be above 100 °C; if necessary, the pressure is increased additionally). In hot caustic potash solution, hydrolysis is already successful at normal pressure. This form of hydrolysis can be used to break down hair proteins, for example.
Enzymatic hydrolysis: Highly effective (and at room temperature) are proteases which are contained e.g. in gastric juice or in the pancreatic enzyme mixture (exoproteases). In the case of proteases there is a dependence of the respective enzyme reaction on the pH value.