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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL ECOLOGY AND SAFETY OF FRESH ON-FARM ORGANICALLY GROWN PRODUCE Title: Antimicrobial activity of apple, hibiscus, olive, and hydrogen peroxide formulations against Salmonella enterica on organic leafy greens

Authors
item Moore, Katherine -
item Patel, Jitu
item Jaroni, Divya -
item Friedman, Mendel
item Ravishankar, Sadhana -

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 12, 2011
Publication Date: October 1, 2011
Citation: Moore, K., Patel, J.R., Jaroni, D., Friedman, M., Ravishankar, S. 2011. Antimicrobial activity of apple, hibiscus, olive, and hydrogen peroxide formulations against Salmonella enterica on organic leafy greens. Journal of Food Protection. 74(10):1676-1683.

Interpretive Summary: The effect of natural antimicrobials (plant extracts) in killing Salmonella on organic fresh produce was evaluated. The leafy greens tested included organic romaine and iceberg lettuces and organic adult and baby spinach. Produce leaves were inoculated with Salmonella Newport (6 log CFU/ml) and immerged in apple and olive extract formulations (1%, 3%, and 5%) or hibiscus formulations (10%, 20%, and 30%) for 2 min, and then stored at 4 °C. Surviving populations of S. Newport in fresh produce were determined during storage at day 0, 1, and 3. Olive extract exhibited the greatest antimicrobial activity, resulting in 2-3 log CFU/g reductions for each concentration and type of leafy green by day 3, followed by Apple extract and Hibiscus concentrate. The maximum reduction by hydrogen peroxide (3%) was about 1 log CFU/g. These natural antimicrobials also reduced background microflora of organic leafy greens up to 2.8 logs. This study demonstrates the potential of natural plant extract formulations to inactivate S. Newport on organic leafy greens.

Technical Abstract: Salmonella enterica is one of the most common bacterial pathogens involved in foodborne outbreaks with fresh produce in the last decade. In an effort to discover safe antimicrobials for use on fresh produce, the objective of the present study was to evaluate the effectiveness of different antimicrobial plant extract/concentrate formulations on four types of organic leafy greens inoculated with S. enterica serovar Newport. The leafy greens tested included organic romaine and iceberg lettuces and organic adult and baby spinach. Each leaf sample was washed, dip inoculated with S. Newport (106 CFU/ml) and dried. Apple and olive extract formulations were prepared at 1%, 3%, and 5% concentrations and hibiscus was prepared at 10%, 20%, and 30%. Inoculated leaves were immersed in the treatment solution for 2 min, and individually incubated at 4 °C. Following incubation, samples were taken at day 0, 1, and 3 for enumeration of survivors. Our results showed that the antimicrobial activity was both concentration- and time-dependent. Olive extract exhibited the greatest antimicrobial activity, resulting in 2-3 log CFU/g reductions for each concentration and type of leafy green by day 3. Apple extract showed 1-2 log reductions by day 3 on various leafy greens. Hibiscus concentrate showed an overall reduction of 1 log CFU/g for all leafy greens. The maximum reduction by hydrogen peroxide (3%) was about 1 log CFU/g. The antimicrobial activity was also tested on the background microflora of organic leafy greens and reductions ranged from 0-2.8 logs. This study demonstrates the potential of natural plant extract formulations to inactivate S. Newport on organic leafy greens.

Last Modified: 7/28/2014
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