Evidence for the formation of maillardized insoluble dietary fiber in bread: A specific kind of dietary fiber in thermally processed food

Bakery products are rich in insoluble dietary fiber (IDF), and Maillard reaction products (MRP), which are commonly studied as two independent constituents. The aim of this work was to elucidate whether IDF contains MRP as an intrinsic constituent, as well as to check the possible contribution of polyphenols to MRP in bread. It was found that MRP contribute to the increase in IDF from wheat flour to bread; indeed, 8% of furosine (a common indicator of MR) is associated with IDF. Also, ferulic acid and (-)-epicatechin got incorporated to MRP in a model system. This work provides evidence for the existence of a complex DF-protein-MRP-polyphenols, named maillardized IDF, in bakery products, a term applicable to other thermally processed food. Moreover, the present results strengthen the concept that MRP are formed not only from reducing sugars and amino acids, but also from phenolic compounds, including phenolic acids and flavonoids. (C) 2013 Elsevier Ltd. All rights reserved.