Inactivation of Salmonella on In-Shell Pecans during Conditioning Treatments Preceding Cracking and Shelling

Abstract

Studies were done to determine the effectiveness of conditioning treatments for killing Salmonella in and on immersion-inoculated and surface-inoculated in-shell pecans. Treatment of immersion-inoculated, dried, stored pecans in chlorinated water (400 μg/ml) reduced Salmonella by not more than 1.6 log CFU/g. Treatment of immersion-inoculated, dried, stored pecans in chlorinated water (200 μg/ml, 1 min) followed by soaking in water for 2 h at 21°C and treating for 10 min in water at 85 to 95°C reduced Salmonella by >5.12 log CFU/g; treatment of nuts containing a low population of Salmonella (<0.60 log CFU/g) for 15 min at 90°C failed to eliminate the pathogen. Reductions of ≥6.42 log CFU/g were achieved by treating surface-inoculated nuts in water at 90 or 95°C for 80 s; treatment of nuts containing 1.78 log CFU/g at 95°C for 10 min did not eliminate the pathogen. Salmonella on surface-inoculated in-shell pecans (kernel moisture, 4.75%; water activity, 0.62) that had been dried and stored at 4°C for 3 to 5 weeks was more resistant to conditioning treatments than was Salmonella on surface-inoculated pecans (kernel moisture, 5.60%; water activity, 0.73) that were not thoroughly dried. Conditioning treatments were less effective for killing Salmonella on immersion-inoculated pecans than on surface-inoculated pecans. Response of Salmonella to conditioning treatments varied, depending on the method of inoculation and whether nuts were dried and stored between the time of inoculation and treatment, which emphasizes the importance of following practices commonly used by commercial pecan shellers when validating the lethality of conditioning treatments.