|Zhang, Xuejie - Chinese Academy Of Agricultural Sciences|
|Solaiman, Daniel - Dan|
|Liu, Zengshe - Kevin|
|Yan, Ruixiang - Chinese Academy Of Agricultural Sciences|
|Ashby, Richard - Rick|
Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2015
Publication Date: 7/23/2015
Citation: Zhang, X., Fan, X., Solaiman, D., Liu, Z., Yan, R., Mukhopadhyay, S., Ashby, R.D. 2015. Inactivation of Escherichia coli O157:H7 in vitro and on the surface of spinach leaves by biobased surfactants. Food Control. doi: 10.1016/j.foodcont.2015.07.026. 60:158-165.
Interpretive Summary: Chlorine is commonly used by the fresh produce industry to wash fresh fruits and vegetables. However, potentially harmful chemical by-products may be produced during the washes. Effective and safer interventions are needed to enhance the microbial safety of fresh and fresh-cut fruits and vegetables. This study was conducted to evaluate the effectiveness of eight bio-surfactants on the populations of Escherichia coli O157:H7 in suspension and on spinach leaves. Results showed that sophorolipids and thiamine dilaurylsulfate may be potential sanitizers in inactivating human pathogens such as E. coli O157:H7. This information could help the industry to consider the use of bio-based active compounds to enhance microbial safety of fresh produce.
Technical Abstract: This study was conducted to evaluate the effect of biosurfactants on the populations of Escherichia coli O157:H7 in suspension and on spinach leaves. Eight surfactants including four soybean oil-based biosurfactants, sodium dodecyl sulfate (SDS), polyoxyethylene sorbitan monooleate (Tween 80), sophorolipid (SO) and thiamine dilaurylsulfate (TDS) at concentrations of 0.1%, 0.5% and 1.0% were tested in bacterial suspension, and the most effective biosurfactants were applied on spinach leaves. Results showed that the soybean oil-based biosurfactants, SDS or Tween 80 did not significantly affect E. coli O157:H7 populations. SO and TDS at concentrations of 1.0% were effective in reducing E. coli O157:H7 populations in bacterial suspension. E. coli O157:H7 with an initial population of 7.1 log CFU/ml was not detectable (detection limit: 1 log CFU/mL) after 1 min in 1.0% TDS or after 2 hr in 1.0% SO. On spinach leaves, SO at 1% did not significantly affect E. coli when compared to a water wash during 7 days post-treatment storage at 4C. However, TDS (1.0%) wash was as effective as 200 ppm chlorine in reducing population of spot inoculated E. coli O157:H7, achieving 3.1 and 2.7 log CFU/per leaf at day 0, and 1.4 and 1.9 log CFU/leaf at day 7 when compared with a water wash. In addition, the inoculation method had a notable effect on the efficacy of surfactants and other sanitizers in reducing E. coli O157:H7 populations. E. coli O157:H7 inoculated on spinach leaves by spotting was easier to inactivate than those by dipping. Overall, our results showed that SO and TDS may be potential sanitizers in inactivating human pathogens such as E. coli O157:H7.