Combined effect of hop resins and sodium hexametaphosphate against certainstrains of Escherichia coli

The combined antimicrobial effects of hop resins with sodium hexametaphosph ate, glycerol monocaprate, and lysozyme were investigated aiming to make an effective agent against Escherichia coli. When they are used separately, t he antimicrobial activity against E. coli was minimal. However, the combina tion of hop resins with sodium hexametaphosphate exhibited strong antimicro bial activity against E. coil, but no effect was found in combinations of h op resins with the other agents. The activity was strongest when the combin ation was added at the beginning of growth of the bacteria, resulting in a prolonged lag phase. However, when the antimicrobials were added during the log phase, growth was depressed considerably. By addition of these materia ls, cell components with absorbance near 260 nm were leaked out. This possi bly may have resulted from damage to the cell membranes of the bacteria. Th e combined effect was also detected in model food systems such as mashed po tatos. The use of hop resins and sodium hexametaphosphate in combination ma y thus be useful for controlling E. coli.