Food preparation

Enzyme – Buffering and Browning

 

 

Buffering

Proteins have the unique ability to behave as buffers, compounds that resist extreme shifts in pH. The buffering capacity of proteins is facilitated by their amphoteric nature.

Browning

Proteins play a very important role in the browning of foods through two chemical reactions: the Maillard reaction, which does not require an enzyme, and enzymatic browning, which, as the name implies, does.

KEY TERMS

Amphoteric

Capable of acting chemically as either acid or base.

Maillard reaction

The reaction between a sugar (typically reducing sugars such as glucose/dextrose, fructose, lactose, or maltose) and a protein (specifically the nitrogen in on amino acid), resulting in the formation of brown complexes.

Enzymatic browning

A reaction in which an enzyme acts on a phenolic compound in the presence of oxygen to produce brown-colored products.

CHEMIST’S CORNER

The amino groups on the amino acids act as bases (accept 1-1* to yield -NH3*), while the carboxyl groups act as acids (donate Fr to yield —000-). When the amino and carboxyl groups are equally ionized (neutralized), the protein’s isoelectric point is reached. Isoelectric points range between pH 4.5 and 7.0 for most proteins. Each protein has a different isoelectric point, which allows proteins to be separated by electrophoresis, the use of an electrical field to cause proteins to move through a buffered gel.