Food browning

Browning has many important implications on the food industry relating to nutrition, technology, and economic cost.

It begins with the oxidation of phenols by polyphenol oxidase into quinones,[4] whose strong electrophilic state causes high susceptibility to a nucleophilic attack from other proteins.

[4] These quinones are then polymerized in a series of reactions, eventually resulting in the formation of brown pigments (melanosis) on the surface of the food.

A variety of approaches are used to prevent or slow down enzymatic browning of foods, each method aimed at targeting specific steps of the chemical reaction.

[8] Much research has been conducted regarding the exact types of control mechanisms that take place when confronted with the enzymatic process.

For instance, ion exchange filtration or ultrafiltration can be used in winemaking to remove the brown color sediments in the solution.

Melanoidins are commonly present in foods that have undergone some form of non-enzymatic browning, such as barley malts (Vienna and Munich), bread crust, bakery products and coffee.

[4] Enzymatic browning affects the color, flavor, and nutritional value of foods, causing huge economic loss when not sold to consumers on time.

These apples, engineered by Okanagan Specialty Fruits Inc, are a result of applying gene splicing, a laboratory technique that has allowed for the reduction in polyphenol oxidase.

The browning of shrimp, which is actually referred to as melanosis, creates a great concern for food handlers and consumers.

[7] Recent studies have found a plant extract that acts as an anti-melatonin polyphenol oxidase inhibitor serves the same function as sulfites but without the health risks.

Browning Fuji apple - 32 minutes in 16 seconds (video)
Example of a general reaction of polyphenols by polyphenol oxidase (PPO) that catalyzes enzymatic browning. The production of quinones undergoes more reactions which eventually form brown pigments on the surface of the food.
Irradiated guava
Aged white wine with brown color
The crust of brioche bread, which is golden-brown due to the Maillard reaction
Example caramelization of table sugar (sucrose) caramelizing to a brown nutty flavor substance (furan and maltol)
Overview of the mechanism of non-enzymatic Maillard reaction in foods. The Schiff base loses a CO 2 molecule and adds to water. Notice the interaction between the amine group of the amino acid (asparagine here) and the carbonyl carbon of the sugar (glucose). The end product is acrylamide . For more information, visit Maillard reaction .