melanoidin

{{Short description|Polymers formed from sugars and amino acids in certain conditions}}

Melanoidins{{efn| From Greek melas, black, dark [also gives rise to melanin]; eidos, resembling, like [also gives rise to sarcoid, coracoid]; and a common suffix in biochemistry used for chemicals -in [as in protein, keratin]. Overall the word refers to "a dark colored chemical, which looks like melanin".}} are brown, high molecular weight heterogeneous polymers that are formed when sugars and amino acids combine (through the Maillard reaction) at high temperatures and low water activity.{{Cite journal | doi = 10.1016/j.foodchem.2011.03.075| title = Melanoidins produced by the Maillard reaction: Structure and biological activity| journal = Food Chemistry| volume = 128| issue = 3| pages = 573–584| year = 2011| last1 = Wang| first1 = He-Ya| last2 = Qian| first2 = He| last3 = Yao| first3 = Wei-Rong}} They were discovered by Schmiedeberg in 1897.

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. They are also present in the wastewater of sugar refineries, necessitating treatment in order to avoid contamination around the outflow of these refineries.

Dietary melanoidins themselves produce various effects in the organism: they decrease Phase I liver enzyme activity and promote glycation in vivo, which may contribute to diabetes, reduced vascular compliance, and Alzheimer's disease.{{medcn|date=October 2024}} Some of the melanoidins are metabolized by the intestinal microflora.{{Cite journal |pmid = 15926141|year = 2005|last1 = Somoza|first1 = V.|title = Five years of research on health risks and benefits of Maillard reaction products: An update|journal = Molecular Nutrition & Food Research|volume = 49|issue = 7|pages = 663–72|doi = 10.1002/mnfr.200500034}}

Coffee is one of the main sources of melanoidins in the human diet,{{Cite journal |pmid = 22584883|year = 2012|title = Coffee melanoidins: structures, mechanisms of formation and potential health impacts|journal = Food & Function|issue = 9|doi = 10.1039/c2fo30048f | last1=Moreira | first1=Ana S. P. | last2=Nunes | first2=Fernando M. | last3=Domingues | first3=M. Rosário | last4=Coimbra | first4=Manuel A. | volume=3 | pages=903–915 }} yet coffee consumption is associated with some health benefits and antiglycative action.