Abstract
This study aimed to assess the suitability of roselle drink as a non-dairy carrier for probiotic Lacticaseibacillus rhamnosus GG (LGG), and compare the effects of thermosonication versus pasteurisation as well as probiotic inoculation mode (free or encapsulated) on the probiotic viability, microbiological safety, chemical, physical, and sensory properties of Roselle drink with free and encapsulated LGG. Roselle drink produced was either pasteurised (72 °C, 15 s) or thermosonicated (25kHz frequency, 40 °C for 30 minutes) before inoculation for fermentation (37 °C, 12 h) with free or encapsulated L. rhamnosus GG, respectively, while the untreated roselle drink served as the control. All roselle drink samples were evaluated for chemical [pH, Total Titratable acidity (TTA) and anthocyanin content], microbiological [Total Viable Count (TVC) of L. rhamnosus GG, enumeration of fungi, coliforms, and Salmonella and Shigella spp. using the pour plating method] properties. The microorganisms enumerated were expressed in Colony Forming Units per mL (CFU/mL). Sensory evaluation was conducted on a 9-point hedonic scale. Data were analysed using ANOVA at p < 0.05. The pH of all the fermented roselle drinks significantly (p < 0.05) decreased from the initial 3.4 (0 h) to 2.7 - 2.9 (12 h). The TTA of thermosonicated roselle drink with free (UF) or encapsulated L. rhamnosus GG (UE) was significantly higher (p < 0.05) than the pasteurised counterpart by the end of the 12-h fermentation. Anthocyanin and redness attribute (a*) were highest in UF (16.84 ± 0.06 mg/100 mL and 19.90 ± 0.35, respectively). Total Viable Count (TVC) of free or encapsulated L. rhamnosus GG in pasteurised or thermosonicated roselle maintained above 10 Log CFU. Fungi, coliforms, and Salmonella and Shigella spp. were not observed in all the treated samples, whereas the control had significantly higher coliforms (1.1 x 103 CFU/mL). The taste and overall acceptability of sensory qualities in all LGG-fermented samples ranked above 7 on a 9-point hedonic scale, higher in the thermosonicated sample with encapsulated L. rhamnosus GG. Thermosonicated roselle drink exhibited improved physicochemical properties, anthocyanin content, and sensory attributes compared with pasteurised samples, while supporting probiotic viability and ensuring microbiological safety. Roselle drink is a suitable carrier for probiotic Lacticaseibacillus rhamnosus GG and is a promising health-promoting beverage.