Bioactive high molecular mass component induced in barley grain by roasting process

Some beverages and foods protect dental surfaces against oral bacteria colonization; in particular the adhesion of Streptococcus mutans to tooth surfaces is a crucial step in the initiation and development of dental caries. The present work shows that barley coffee (BC), a beverage obtained by a roasting process, interferes with the S. mutans and other oral streptococci adsorption to hydroxyapatite (HA). Two experimental approaches were followed to evaluate the effects of sub-lethal concentrations of BC (sub-MICs) on the adherence of S. mutans to saliva-coated HA beads: streptococci were pre-treated with BC before the addition of bacteria (A); BC and bacteria were added to HA simultaneously with the HA beads (B). The treatments caused a statistically significant, dose-dependent inhibition of bacteria with regards both to sucrose-dependent and sucrose-independent adherence to HA. Dialysis and gel filtration chromatography fractioned the BC components. A component with high MM, which consists of a brown potent antioxidant melanoidin, showed to be responsible for most of the anti-adhesive properties found for BC. This high MM melanoidin does not occur in the natural barley, indicating that it originates in barley grains during the roasting process. These results suggest that BC consumption might influence the colonization of tooth surfaces by cariogenic bacteria.