Microbiological Quality of Roasted Coffee and Survival Dynamics of Dry-Inoculated Bacteria During Storage

This study evaluated the microbiological quality of 78 roasted coffee samples commercialized in Brazil, including whole-bean and ground products, and investigated the survival of bacterial species of food safety importance in roasted ground coffee during storage. Although all samples complied with Brazilian legislation, roasted coffee exhibited a diverse microbiological profile, including spoilage microorganisms, coliforms, mesophilic bacteria, and aerobic mesophilic sporeformers. In contrast, Salmonella, Escherichia coli, Staphylococcus aureus, Bacillus cereus spores, and thermophilic sporeformers were not detected. MALDI-TOF analysis identified a predominance of Bacillus and Staphylococcus species, including opportunistic microorganisms such as Klebsiella pneumoniae and Staphylococcus epidermidis. A dry inoculation challenge test demonstrated that both species remained viable in vacuum-packaged roasted ground coffee stored at 25°C for up to 42 days, exceeding the recommended post-opening shelf life. Weibull modeling indicated good fit for the survival curves and revealed distinct survival behaviors between microorganisms. Despite the persistence observed under low water activity conditions, coffee brewing with hot water resulted in non-detectable levels of both microorganisms throughout storage. PRACTICAL APPLICATIONS: This study showed that roasted coffee, whether whole bean or ground, can carry different types of microorganisms, including some capable of forming spores. Certain bacteria (S. epidermidis and K. pneumoniae) were able to remain alive in roasted coffee for more than 42 days at 25°C, demonstrating their ability to survive in this low-moisture environment. However, neither microorganism was detected in the final beverage after coffee brewing. These findings reinforce the importance of good hygiene and handling practices during coffee production and commercialization to maintain hygienic quality and minimize potential concerns for vulnerable populations.