Influence of modified blanching treatments on inactivation of Salmonella during drying and storage of carrot slices

Documented outbreaks of human illness associated with consumption of minimally processed produce have increased in recent years. This study evaluated the influence of modified treatments on inactivation of Salmonella during preparation, home-type dehydration (60 °C, 6 h) and storage of carrot slices. Inoculated (five strains, 7.8 log cfu/g) slices were subjected to the following treatments: (i) untreated control, (ii) steam blanching (88 °C, 10 min), (iii) water blanching (88 °C, 4 min), (iv) blanching in a 0.105% citric acid solution (88 °C, 4 min), or (v) blanching in a 0.21% citric acid solution (88 °C, 4 min), dried for 6 h at 60 °C (140 °F), and stored for up to 30 d. Bacterial populations were reduced by 3.8–4.1, 4.6–5.1 and 4.2–4.6 log cfu/g immediately following steam, water or citric acid blanching, respectively. After 6 h of dehydration, total reductions were 1.6–1.7 (control), 4.0–5.0 (steam blanched), 4.1–4.6 (water blanched) and 4.9–5.4 (blanched in citric acid solution) log cfu/g. Populations continued to decrease throughout storage, but were still detectable by direct plating at 30 d on all samples except for those blanched in 0.21% citric acid. Results suggest that blanching carrot slices, particularly blanching in 0.21% citric acid, before drying should enhance inactivation of Salmonella during home-type dehydration and storage.