Pre-harvest treatment for reduction of foodborne pathogens and microbial load on tomatoes

Abstract

A new bactericide comprised of two chemicals, levulinic acid and sodium dodecyl sulfate (SDS), was evaluated for its efficacy on tomatoes to reduce contamination by foodborne pathogens at pre-harvest stage. Two approaches, one as prevention and the other as the treatment, were compared on Salmonella, Shiga toxin-producing Escherichia coli (STEC), and Listeria monocytogenes contaminated tomato plants. Results obtained from inoculation studies on tomato plants confirmed that this bactericide reduced the count of Salmonella, STEC, and L. monocytogenes populations substantially (P < 0.05) when compared with water and chlorine treatment. Results obtained from spray treatment on tomato plants with commercial product of “FIT-L” (1:88 diluted in water, v/v; final concentration at 0.5% levulinic acid plus 0.05% SDS) indicated that total average aerobic bacteria counts were 5.8 and 4.1 log CFU/fruit before and after treatment, respectively. Average reduction was 1.7 log CFU/fruit (P < 0.05). The total coliform counts before and after treatment was 4.2 and 3.0 log CFU/fruit, respectively. Average reduction was 1.2 log CFU/fruit (P < 0.05). Salmonella and E. coli O157:H7 from all tomato fruit (200) collected before and after treatments were negative. For isolation of Listeria demonstrated that eight of 100 tomato fruit before treatments were positive, including 4 as L. ivanovii, 2 as L. monocytogenes, and 2 as L. grayi. However, all tomato fruit samples (100) after treatment were negative for Listeria. Results revealed that the application of this organic bactericide was effective for reduction of foodborne pathogens and microbial loads in pre-harvest tomatoes.