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The chemical properties of flavonoids (i.e. epicatechin) not only make them unique with respect to their bioactivity but also as reactants during thermal processing (flavor development).  Previous studies by our research group have shown that epicatechin (EC) influenced flavor generation pathways (Maillard-type) in model systems and food products. 

The study focuses to gain an insight into the chemical mechanistic pathways by which epicatechin alters the generation Maillard reaction products (MRP).

Six model Maillard reaction systems comprising of glucose-glycine (control) with the addition of either epicatechin or di-tertiary-butyl-o-benzoquinone in phosphate buffer (350ml, 0.1M, pH7.0) were heated (Parr reactor) at 125 ºC for two time intervals (15 and 30min).  All reactants were at 0.01M. Glucose-glycine reactions were also conducted under anaerobic conditions by flushing N₂ gas through the mixtures for 1 and 13 hours prior to the thermal treatment.  The MRP’s were extracted by diethyl ether analyzed by gas chromatography-mass spectrometry.  The non-volatile components were analyzed using liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS).

Volatile analysis of the MRP indicated that the addition of epicatechin to glucose–glycine reaction completely inhibited the formation of 2,3-butanedione and 2,5-dimethyl pyrazine, while the addition of quinone inhibited the pyrazine formation by 80% but accelerated the formation of 2,3-butanedione by 15%.  Furthermore, 2,3-butanedione production was reduced by 23% in the N₂ enriched system.  The LC-ESI-MS analysis tentative identified an EC-N,N′-dimethyldihydropyrazine adduct (M⁺-1=427) in the glucose-glycine plus epicatechin reaction mixture and suggested the possible quenching of N,N′-dimethyldihydropyrazine free radical ion by epicatechin may explain the noted reduction of the MRP’s in the EC containing systems. 

The results suggest that EC reduced the occurrence of pyrazine and sugar degradation products formed during Maillard reaction via radical chemistry pathways.  Understanding how flavonoids behave as reactants in food systems will aid in controlling flavor quality of processed food products.