melanoid

Melanoidins, often referenced in the literature as melanoidin polymers, are brown, nitrogen-containing polymers formed during browning reactions in foods and biological systems. The most studied class arises from the Maillard reaction, a chemical process between reducing sugars and amino compounds that occurs with heating, aging, or processing. Melanoidins are the end products of complex polymerization and carbonization reactions and are typically heterogeneous in composition and molecular weight.

Formation and properties: Melanoidins form progressively as heating continues and contribute color, aroma, and flavor to many processed foods. Their structure is not fully defined, but they are generally high-molecular-weight, polymeric compounds that can be soluble or partially insoluble depending on their origin and processing conditions. They often contain nitrogenous moieties and aromatic rings derived from sugars and amino acids.

Occurrence and significance: In foods such as coffee, bread crust, baked or roasted goods, cocoa, beer, and dairy products, melanoidins impart brown color and may influence taste. They can contribute antioxidant activity in some contexts, but their exact health effects remain a topic of research. They are relatively resistant to digestion and can reach the colon, where they may interact with gut microbiota.

Terminology and distinctions: The standard term used in most literature is melanoidin (plural melanoidins). The adjective melanoidal or melanoid may be encountered as a shorthand, but melanin is a different pigment produced by organisms and should not be confused with melanoidins.