Impact of pH and Temperature on Foodborne Pathogens’ Survival in Cold Brew Coffee

Abstract

The unique flavor and taste of cold brew coffee have made it popular in recent years. As the name suggests, it is cold-brewed, which means the absence of a thermal process in the brewing. Hence, after the roasting step, it only has to rely on the product pH and storage temperature to control the foodborne pathogens such as Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes. The purpose of this study is to investigate the effect of pH (4.9 and 5.3) and temperature (4°C and 23°C) on Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes in cold brew coffee. Cold brew coffee samples were inoculated with these organisms for 30 days, and survival data were collected. Results showed that pH affected the survival of Salmonella and E. coli. At pH 4.9, Salmonella was reduced by 5 log CFU/ml after 7 days, reaching the limit of detection in 11 days. However, at pH 5.3, 5 5-log reduction occurred after 14 days, taking 25 days to reach the limit of detection. At 23°C, both Salmonella and E. coli showed increased survival, making temperature an important factor. Listeria showed resistance to pH variations at both temperatures. Lower RMSE values for Salmonella (pH 4.9) and Listeria (pH 4.9) were observed in the log-linear model, making it a better fit. However, the Weibull model showed a better fit for Salmonella (pH -5.3), Listeria (pH -5.3), and E. coli (pH -4.9, 5.3). Overall, lower temperatures increase survival, while higher temperatures enhance the reduction in E. coli.

These findings are crucial for enhancing the safety of cold-brew coffee and providing valuable recommendations to producers, regulators, and consumers.