Prevalence and survival of Escherichia coli during onion production and postharvest storage: influence of soil amendment, field curing, and storage temperature

Authors: APPOLON, CHARLES - University Of Florida; Bardsley, Cameron; KHAREL, KARUNA - Louisiana State University; DUNN, LAUREL - University Of Georgia; DANYLUK, MICHELLE - University Of Florida; SCHNEIDER, KEITH - University Of Florida

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2026
Publication Date: 2/10/2026
Citation: Appolon, C.B., Bardsley, C.A., Kharel, K., Dunn, L.L., Danyluk, M.D., Schneider, K.R. 2026. Prevalence and survival of Escherichia coli during onion production and postharvest storage: influence of soil amendment, field curing, and storage temperature. Food Control. 184. https://doi.org/10.1016/j.foodcont.2026.112038.
DOI: https://doi.org/10.1016/j.foodcont.2026.112038

Interpretive Summary: This study evaluated how heat-treated poultry pellets used a soil amendment may influence the transfer of E. coli to onions, determined the impact of field curing on E. coli once on the onions, and identified the effect storage temperature has on E. coli survival on onions. Field plots that were sprayed with a determined dose of E. coli and were either amended with heat-treated poultry pellets or had no amended added. Two weeks after the application of the amendments and the E. coli, onions were planted in the field and were grown using conventional growing techniques. Once harvested the amount of E. coli was measured on the onion. Onions were left to cure in the field and the amount of E. coli was measured again. The results of this study found that using the heat-treated poultry pellet increased the level of the E. coli on the onions during harvest compared to the onions in the plots that didn't have any amendments. Field curing decreased the level of E. coli on the onions. Onions contaminated with E. coli were stored at 20 and 30 °C and the E. coli levels were monitored. E. coli levels declined faster on onions when stored at a higher temperature. This study shows that the use of heat-treated poultry pellets, curing, and storage temperature influence the contamination and survival of E. coli on onions providing growers and processors with strategies that can be used to control E. coli contamination and survival.

Technical Abstract: Biological soil amendments of animal origin can introduce foodborne pathogens into vegetable production soils and are frequently applied during onion production, a commodity associated with multiple foodborne outbreaks in recent years. This study assessed the prevalence of Escherichia coli (E. coli) on onions grown in heat-treated poultry pellets amended plots, its survival during field curing, and the influence of storage temperature on its survival during subsequent storage. Vidalia onions were transplanted into E. coli inoculated field plots that were either unamended or amended with heat-treated poultry pellets . E. coli populations in the field plots were monitored through harvest and after a 14-day field curing period. Inoculated onions were stored at 20 and 30°C and sampled at predetermined time points (0-96 h) to assess survival. Samples were enumerated for E. coli using standard plating and most probable number methods followed by enrichment for confirmation. Onions from heat-treated poultry pellet -amended plots had a significantly higher prevalence of E. coli (80.00%) at harvest compared to onions in unamended plots (13.33%). Curing significantly reduced E. coli prevalence on the onions in heat-treated poultry pellet plots from 80.00% to 6.67% (p<0.01). Storage temperature, time and their interaction significantly influenced E. coli reduction (p<0.05), with a faster die-off at 30°C than at 20°C. These results suggest that higher temperatures can favor a faster E. coli decline on onions over time.