|Liao, Ching Hsing|
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2007
Publication Date: April 1, 2007
Citation: Liao, C. 2007. Inhibitory effect on foodborne pathogens by native microflora associated with fresh peeled baby carrots. Journal of Food Science. 72(4):M134-M138. Interpretive Summary: Microorganisms present on the surfaces of fresh produce can affect the survival and growth of human pathogens, which may come in contact with produce before and after harvest. This study was undertaken to investigate the identity and composition of native microorganisms associated with fresh peeled baby carrot (designated as BG) and to determine their effect on the growth of four major foodborne pathogens (Salmonella enterica, Yersinia enterocolitica, E. coli O157:H7, and Listeria monocytogenes) in carrot juice and on green bell pepper disks. The growth of each pathogen in carrot juice or on green bell pepper disks was greatly inhibited in the presence of BG. At the end of incubation, the population of each pathogen on bell pepper disks that had been treated with BG was 100 to 10,000 times lower than that on control disks that had not been treated with BG, depending upon the initial number of BG applied. Coating the pepper disks with BG almost completely inhibited the growth of two cold-tolerant pathogens (L. monocytogenes and Y. enterocolitica) at the refrigeration temperature commonly used to store fresh produce. The potential of using BG as a biological control agent for use in control of foodborne pathogens on fresh produce or sprouts is under evaluation.
Technical Abstract: The inhibitory effect of fresh peeled baby carrot and associated microflora on the viability and growth of Listeria monocytogenes, Yersinia enterocolitica, Salmonella enterica, Escherichia coli O157:H7, and Pseudomonas marginalis in vitro and in situ was investigated. The population of viable L. monocytogenes was reduced by more than 2 log units following the dipping of sliced baby carrots in the bacterial suspension for 2 min. However, other pathogens in the suspensions subjected to the same treatment showed no reduction in the population. Filter-sterilized carrot homogenates exhibited antimicrobial activity and were able to support the full growth of each pathogen. However, the growth of each pathogen in carrot homogenates co-inoculated with native microflora from baby carrot (BG) was reduced by 2 to 3 log units. The growth of each pathogen on bell pepper disks was also inhibited in the presence of BG. After incubation at 20 deg C for 2 days, the growth of each pathogen on pepper disks was reduced by 2 to 4 log units depending upon the BG and pathogen ratio (1:1, 10:1, or 100:1) applied. After incubation at 8 deg C for 8 days, the population of L. monocytogenes or Y. enterocolitica on pepper disks increased from 103 to 107 cfu per disk in the absence of BG. However, in the presence of BG, the growth of either pathogen on pepper disks was completely inhibited. The inhibitory effect of baby carrots on pathogens is in part due to its antimicrobial activity and in part due to the antagonistic action of associated microflora.