pH changes cause protein denaturation in food,
as the pH influences the charge of the amino acids within a protein
molecule, which in turn affects the shape, stability, and function of
the protein.
When proteins in food are exposed to acidic conditions, the protein
molecules unfold and coagulate. This process is used in dairy
production. In the first step, milk is acidified by using lactic acid
bacteria, which convert lactose to lactic acid. The pH of milk decreases
as the lactic acid concentration increases, causing the casein proteins
to coagulate and to form curds. The process (production of yoghurt) can
be manipulated by careful monitoring of the coagulation temperature and
duration.
Similar tactics are also used in processing panner, an Indian type of cheese that is acidified by adding lime juice or vinegar.
Another process that can be used to induce protein denaturation and gel formation is the addition of salts, which increase the ionic strength
in the solution, thereby causing protein denaturation and aggregation.
This is e.g used in processing certain meat products as well as in tofu
making.
