Antimicrobial effect of natural fruit extracts against Salmonella on whole and fresh-cut Cucumbers

Authors: BYUN, SUYEUN - Gachon University; CHEN, CHI-HUNG - US Department Of Agriculture (USDA); YIN, HSINBAI - US Department Of Agriculture (USDA); Patel, Jitu

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2022
Publication Date: 1/29/2022
Citation: Byun, S., Chen, C., Yin, H., Patel, J.R. 2022. Antimicrobial effect of natural fruit extracts against Salmonella on whole and fresh-cut Cucumbers. Journal of Food Safety. https://doi.org/10.1111/jfpp.16437.
DOI: https://doi.org/10.1111/jfpp.16437

Interpretive Summary: The per capita consumption of fresh cucumbers has increased in the U.S. in the past decade. Fresh cucumbers contaminated with bacterial pathogens have been implicated in several foodborne outbreaks of illnesses. Chemical antimicrobials such as chlorine are commonly employed to remove bacterial contamination on vegetables; consumers' preference for chemical-free food have led research on natural antimicrobials to control bacteria on vegetables. The effect of fruit extracts for killing Salmonella on whole and fresh-cut cucumbers was investigated. Cucumbers inoculated with cocktail of Salmonella enterica were sprayed with 1 ml fruit extracts: lemon (10%), yuzu (10%), naringin (1%), or resveratrol (1%), stored at 10°C or 22°C for 7 days, and surviving Salmonella populations on cucumbers were determined. Among the four fruit extracts, 10% lemon was the most effective antimicrobial treatment throughout the storage study. The lemon extract significantly reduced Salmonella on whole cucumbers by 1.8 log and 2.5 log CFU/g after 7 days of storage at 10' and 22', respectively. Similarly, Salmonella were declined by ~ 2 log CFU/cm2 on first- and second-cut slices of the cucumbers treated with 10% lemon extract. The findings of this study are useful to organic cucumber packers and retailers for controlling bacterial contamination on whole and fresh-cut cucumbers and to minimize foodborne illnesses.

Technical Abstract: The efficacy of fruit extracts for reducing Salmonella on whole and fresh-cut cucumbers was investigated. Fresh Persian cucumbers (5 cm2 area) were spot inoculated with cocktail of three Salmonella enterica serovars (3.5 log CFU/cm2). Each inoculated area was sprayed with 1 ml fruit extracts: lemon (10%), yuzu (10%), naringin (1%), or resveratrol (1%). Treated cucumbers were stored at 10°C or 22°C for 7 days and surviving Salmonella populations on cucumbers were determined by spiral plating on XLT4 agar. For fresh-cut study, cucumbers were inoculated as one 10 µl spot of Salmonella inoculum, followed by spraying with the aforementioned treatments. Cucumbers were sliced for 5 times (0.5 cm thickness) and slices were individually stored at 4' for 2 days. Salmonella populations on cucumber slices were determined. Salmonella on 1% naringin- and resveratrol-treated whole cucumbers were significantly reduced to < 0.5 log CFU/cm2 compared to 3.6 log CFU/cm2 recovered from the control cucumbers on day 7 at 22'. Among the four fruit extracts, 10% lemon was the most effective antimicrobial treatment throughout the storage study. Treatment with 10% lemon significantly reduced Salmonella on whole cucumbers by 1.8 log and 2.5 log CFU/g after 7 days of storage at 10' and 22', respectively. Similarly, Salmonella populations were declined by ~ 2 log CFU/cm2 on first- and second-cut slices of the cucumbers treated with 10% lemon (P<0.05). The results of this study support that fruit extracts especially lemon could potentially be used to reduce Salmonella on cucumbers at the post-harvest level.