Effect of barley coffee on the adhesive properties of oral streptococci.

Some beverages and foods protect tooth surfaces against Streptococcus mutans colonization.
Adhesion of S. mutans is a crucial step in the initiation and development of dental caries. In this
study, we showed that barley coffee (BC), a beverage made from roasted barley, interferes with
S. mutans adsorption to hydroxyapatite (HA), and we identified its antiadhesive components. The
effects of sublethal concentrations (sub-MICs) of BC on the adhesion of S. mutans to saliva-coated
HA beads were assessed using three experimental approaches: (A) Beads were pretreated with BC
before adding bacteria, (B) BC and bacteria were added to the beads simultaneously, and (C)
streptococci grown in the presence of sub-MICs of BC were added to the beads. All treatments induced
variable but significant inhibition of S. mutans sucrose-dependent and -independent adherence to
HA. Similar results were obtained with other oral streptococci. BC components were fractioned by
dialysis and gel filtration chromatography; the <1000 Da molecular mass (MM) fraction, which contains
polyphenols, zinc, and fluoride ions, and the >1000 kDa MM fraction, which consists of a potent
brown antioxidant, melanoidin, both displayed antiadhesive properties. High-MM melanoidin was not
detected in unroasted barley, indicating that it forms during the roasting process. Results suggest
that BC consumption may influence the colonization of tooth surfaces by cariogenic bacteria.