For the preparation of the stock solution of the regular and
decaffeinated coffee extracts the lyophilized powder was resuspended in sterile Milli-Q water at a final concentration ranging
from 100 to 350 mg/ml for all the antimicrobial activity assays
For
the caffeine stock a solution was prepared dissolving 150 mg of
caffeine powder (SigmaeAldrich, St. Louis, MO) in 1 ml sterile MilliQ water at 80
C