Changes in antioxidant activity of dehydrated onion and garlic during storage

The effect of the Maillard reaction evolution on the overall antioxidant activity (AA) of stored dehydrated onion and garlic has been studied. Extent of the reaction was followed through the determination of the Amadori compounds, measured as 2-furoylmethyl-amino acids (2-FM-AA), and colour development whereas AA was evaluated by the ORACFL assay. Dehydrated garlic exhibited a very slow progress of the Maillard reaction which did not lead to any noticeable change in its AA upon storage. However, a substantial increase of AA was observed in dehydrated onion samples, in agreement with a major Maillard reaction evolution. Moreover, a positive correlation between colour and antioxidant properties was observed during the storage of dehydrated onion at 50 °C, suggesting the predominant role of the advanced stages of the Maillard reaction over the AA. In conclusion, this study demonstrated that, although the Amadori compounds might exert a moderate effect on the AA, the advanced Maillard reaction products are the major contributors to this property.