Quantitative assessment of the effectiveness of intervention steps to reduce the risk of contamination of ready-to-eat baby spinach with Salmonella

Abstract

The objective of this study was to develop a quantitative risk assessment model to evaluate the microbial hazards during processing of baby spinach leaves using scenario analysis and predictive microbiology. The effectiveness of intervention strategies (temperature control during harvest, washing, and irradiation) was also integrated into the risk assessment model. Monte Carlo simulation was used to take into account the variability of the model parameters.Cross-contamination seems the most probable scenario for prevalence of contamination on an entire lot of daily production. If the cross-contamination level of bacteria was low (∼1 log10 CFU/g, normal distribution) either on the field or after the washing treatments, the percentage of samples over the safety limit (1.33 log10 CFU/g of sample) increased from 16.8% to 84% for a highly cross-contaminated lot (∼3 log10 CFU/g). The risk assessment revealed that exposure of the leafy greens to irradiation (1 kGy) reduces the number of tainted samples from 84% to 0.1%, for highly cross-contaminated lots (3 log10 CFU/g).This study shows that the spinach processor can deliver a highly safe product in a cross-contamination scenario (on the field or packing shed) if the produce is harvested at 20 °C, stored for at least 5 h, washed with water and chlorine (220 ppm), and exposed to irradiation treatment with a dose of 1 kGy.