Purpose: This study determines the survival of a Salmonella cocktail on 12 types of dried fruit stored at temperatures ranging from 4°C to 45°C. The results of this study serve as the scientific basis for industry microbiological classification of those dried fruit and for potential pathogen reduction steps.
Methods: Dried fruit was inoculated using either a wet or dry technique. Aw, moisture, titratable acidity, and pH were measured throughout the inoculation process and incubation. Following inoculation, fruit and culture controls were held at 4, 10, 18, 25, 35 and 45°C. Samples (25 g) were analyzed for Salmonella initially and weekly or bi-weekly until 3 sequential negative results were obtained. Microbial analysis was conducted using plate count on trypticase soy agar and confirmed using VIDAS or FDA BAM.
Results: For both wet and dry inoculated fruit, a significant log reduction (4-7 logs) was observed by week 3 at room temperature (25°C) and higher. At 4 and 10°C, the pathogen survived for over three months, with levels dropping by 2–3 logs. All runs were conducted in triplicate.
Not all dried fruit behaved the same under similar conditions.
Significance: This study indicates that under refrigerated storage conditions following harvesting, Salmonella, if present, will survive for up to 3 months on 11 of 12 dried fruit types. In addition, for most dried fruit stored at temperatures greater than 25°C, pathogen levels decrease by 4–5 logs within 3 weeks.