Effect of Food Structure, Water Activity, and Long-Term Storage on X-Ray Irradiation for Inactivating Enteritidis PT30 in Low-Moisture Foods.

Recent outbreaks and recalls of low-moisture foods contaminated with have been recognized as a major public health risk that demands the development of new mitigation strategies and technologies. This study aimed to assess the efficacy of X-ray irradiation for inactivating on or in almonds (kernels, meal, butter), dates (whole fruit, paste), and wheat (kernels, flour) at various water activities (a) and storage periods. The raw materials were inoculated with Enteritidis PT30, conditioned to 0.25, 0.45, and 0.65 a in a humidity-controlled chamber, processed to various fabricated products, and reconditioned to the desired a before treatment. In a storage study, inoculated almond kernels were stored in sealed tin cans for 7, 15, 27, and 103 weeks, irradiated with X ray (0.5 to 11 kGy, targeting up to a ∼2.5-log reduction) at the end of each storage period, and plated for survivors to determine the efficacy of irradiation in terms of -value (dose required to reduce 90% of the population). was least resistant (-value = 0.378 kGy) on the surface of almond kernels at 0.25 a and most resistant (-value = 2.34 kGy) on the surface of dates at 0.45 a. The -value was 61% lower in date paste than on whole date fruit. Storage of almonds generally had no effect on the irradiation resistance of over 103 weeks. Overall, these results indicate that product structure (whole, meals, powder, or paste), water activity (0.25 to 0.65 a), and storage period (0 to 103 weeks) should be considered when determining the efficacy of X-ray irradiation for inactivating in various low-water-activity foods.