Survival of Salmonella spp. and Listeria monocytogenes in Hot Cocoa Drink Mix When Prepared Using Common Reconstitution Methods

Introduction: Salmonella spp. and Listeria monocytogenes are known biological hazards in milk powders and cocoa products. Proper preventive controls need to be in place. Both of these ingredients are commonly used in the formulation of hot cocoa drink mixes. Common reconstitution methods for these drink mixes use hot water or milk. However, consumer studies indicate variability in temperatures for the consumption of hot beverages. Due to such a high degree of inconsistency of beverage temperature preference, little is known about the lethality to Salmonella spp. and L. monocytogenes when cocoa is prepared using these methods.

Purpose: The purpose of this project was to examine the lethality of Salmonella spp. and L. monocytogenes in hot cocoa drink mix using common reconstitution instructions.

Methods : Salmonella spp. and L. monocytogenes inoculated nonfat dry milk was added to hot cocoa drink mix and reconstituted using 177.4 ml preheated water or milk at 120, 160, 180, 200, and 210°F in a static state or under mechanical shaking for 30, 60, and 90 seconds. Recovery data was log-transformed and analyzed using ANOVA at P<0.05.

Results : Salmonella and L. monocytogenes were significantly decreased with the shake method compared to the hold method and both pathogens decreased with an increase in time and temperature. Inactivation kinetics in both pathogens remained the same across all replications. While a significant decrease of both Salmonella spp. and L. monocytogenes began at 180°F at 30 s, a temperature of at least 180°F with shaking for at least 90 s was required to achieve a minimum four-log CFU/g reduction.

Significance : A microbiological contamination risk may exist in milk or cocoa powders used in drink mixes. As shown by this study, the risk is not easily eliminated by simply following common reconstitution instructions.