Purpose: The present study was conducted to determine the antimicrobial effect of cinnamaldehyde, a plant-based extract, against E. coli O157:H7 and Salmonella enterica in refrigerated carrot juice (CRJ) and blackberry juice (BBJ).
Methods: Carrot juice (pH 6.25, 8.5°Brix) and BBJ (pH 3.59, 12.3°Brix) with added cinnamaldehyde (0.25, 0.5, and 1.5 μl/ml) were inoculated with a 5-strain cocktail of E. coli O157:H7 or S. enterica to give an initial viable count of 5.0 log CFU/ml. Inoculated juices without cinnamaldehyde served as control. Survival of pathogens in the juices (4°C) for 24 hours was monitored by surface plating diluted (10-fold) juice samples on sorbitol MacConkey agar (E. coli O157:H7) and xylose lysine tergitol 4 agar (S. enterica) and counting bacterial colonies on agar media following incubation (35°C, 48 h).
Results: No growth of the pathogens was observed in juices with or without added cinnamaldehyde. Numbers of viable pathogens in control juices were reduced by about 1.0 to 1.4 log CFU/ml at 24 h. Both pathogens were less sensitive to the lethal effects of cinnamaldehyde in CRJ compared to BBJ. At 24 h, initial viable counts of S. enterica and E. coli O157:H7 in CRJ with 2.0 μl/ml cinamaldehyde were reduced by ~4.5- and 5.0 log, respectively (P < 0.05). In contrast 1.5 μl/ml cinnamaldehyde in BBJ resulted in a 5-log reduction of S. enterica and E. coli O157:H7 as early as 2 and 8 h, respectively (P < 0.05).
Significance: Cinnamaldehyde has good potential for use as a natural antimicrobial to decrease the viability of bacterial pathogens in refrigerated fruit and vegetable juice blends.