Purpose: To characterize and model Salmonella survival in dehydrated garlic granules of various sizes under different storage conditions.
Methods: A four serotype cocktail of Salmonella was inoculated into both fresh garlic and dehydrate garlic flakes to investigate 1) Salmonella survival during thermal dehydration at 75 to 85℃ for 190 min and 2) dried garlic storage at 25 and 35℃ under low and high relative humidity (RH) conditions up to 88 days. Survival kinetics of Salmonella was further modeled by inoculating the cocktail into dehydrate garlic granules of different sizes and incubating at different levels of water activity (aw) for 7 to 22 days.
Results: Over 6-log reduction was observed after dehydration of fresh garlic at 75 to 85℃ for 190 min. During storage, Salmonella population (7.63 CFU/g) dropped below the limit of detection (<1.59 CFU/g) within 9 days under both low and high relative humidity at 35℃, but persisted up to 88 days at 25℃ with 3.35 log CFU/g remaining under low RH, and 73 days before dropping below limit of detection under high RH. Weibull modeling of survival kinetics showed that storage under moderate humidity (aw=0.728) led to the longest decimal reduction time in dehydrate garlic granules of all sizes. Difference in survival kinetics was observed between different granules, which also appeared to have different levels of allicin.
Significance: This study provides quantitative data for risk assessment of Salmonella in dehydrated garlic and highlights the potential risk of Salmonella persistence during long term storage of dry garlic under certain conditions. Our results also suggest different aw/RH levels may have different effects on Salmonella survival during the storage of dried spices with natural antimicrobial activity.