Antimicrobial activities of high molecular weight water‐soluble chitosans against selected gram‐negative and gram‐positive foodborne pathogens

Summary Antimicrobial activities of high molecular weight water‐soluble chitosans ( HMWWS ) against selected Gram‐negative and Gram‐positive foodborne pathogens (initial inoculation of ca. 6.5 Log CFU  mL −1 ) were evaluated. Chitosans with 789  kD a and/or 1017  kD a were dissolved in aspartic acid ( AS ) to obtain 1–4% w/v solutions. Among HMWWS , only 4% 789 kD a AS chitosan reduced E. coli counts by 2 Log CFU  mL −1 from 7.33 at 0 h to 5.16 Log CFU  mL −1 at 96 h, and they were not effective against S . Typhimurium. Depending on the concentrations, HMWWS completely inhibited V. cholerae, V. vulnificus and V .  parahaemolyticus as well as B. cereus and L. monocytogenes after 48 h or 96 h of incubation. Compared with the control (no HMWWS ), 2% or 3% 1017  kD a AS chitosans showed about 3 Log CFU   mL −1 lower (4.72–4.86 vs. 7.71) for S. aureus at 96 h of incubation.