Survival and thermal resistance of Salmonella in chocolate products with different water activities.

Contamination of Salmonella in chocolate products has caused worldwide outbreaks and recalls. There is a lack of information on the impact of water activity (a) on the stability of Salmonella in chocolate products during storage and thermal treatments. In this research, the survival and thermal resistance of a Salmonella cocktail (S. Enteritidis PT30, S. Tennessee K4643, S. Typhimurium S544) was examined in different chocolate products (dark chocolate, white chocolate, milk chocolate) at two a levels (0.25, 0.50) over 12 months at 22 °C. A reduction of 4.19 log CFU/gof Salmonella was obtained in dark chocolate after 12 months (a = 0.50, at 22 °C); less reductions were observed in white and milk chocolates. In all three products, more reductions were observed ata = 0.50 than at a = 0.25 over the 12-months storage. When treated at 80 °C, the D-values (time required to cause 1 log reduction) of the Salmonella cocktail in the chocolate samples with initial a of 0.25 were 35.7, 25.2 and 11.6 min in dark, white and milk chocolate, respectively, before the storage. The D -values of Salmonella cocktail in the samples with initial a of 0.50 were 6.45, 7.46, and 3.98 min in dark, white and milk chocolate, respectively. After 12 months of storage at 22 °C, the D-value of Salmonella cocktail decreased to 9.43 min (p < 0.05) in milk chocolate but remained 22.7 min in white chocolate with an a of 0.25 at 22 °C. The data suggests that Salmonella can survive in chocolate products for up to 12 months, and its thermal resistance remained relatively stable. Thus, Salmonella is resistant to desiccation in chocolates, particularly in milk and white chocolates, and its thermal resistance remains during one-year storage, which could pose a potential threat for future outbreaks.