Growth, survival, and metabolic activities of probiotics Lactobacillus rhamnosus GG and Saccharomyces cerevisiae var. boulardii CNCM-I745 in fermented coffee brews

Amidst rising demand for non-dairy probiotic foods, and growing interest in coffees with added functionalities, it would be opportune to ferment coffee brews with probiotics. However, challenges exist in maintaining probiotic viability in high-moisture food products. Here, we aimed to enhance the viability of the probiotic bacteria, Lactobacillus rhamnosus GG, in coffee brews by co-culturing with the probiotic yeast, Saccharomyces cerevisiae var. boulardii CNCM-I745. The yeast significantly enhanced the viability of L. rhamnosus GG, as bacterial populations beyond 7 Log CFU/mL were maintained throughout 14 weeks of storage at 4 and 25 °C. In contrast, the single culture of L. rhamnosus GG suffered viability losses below 6 Log CFU/mL within 10 weeks at 4 °C, and 3 weeks at 25 °C. Growth and survival of S. boulardii CNCM-I745 remained unaffected by the presence of L. rhamnosus GG. Volatile profiles of coffee brews were altered by probiotic metabolic activities, but co-culturing led to suppressed generation of diacetyl and ethanol compared to single cultures. Probiotic fermentation did not alter principal coffee bioactive compounds and antioxidant capacities; however, declines in peroxyl radical scavenging capacities were observed after ambient storage. Overall, we illustrate that yeasts are effective in enhancing probiotic bacterial viability in coffee brews, which may be useful in developing shelf stable probiotic food products.