Physicochemical, microbial and sensory qualities of Zobo (Hibiscus sabdariffa L.) drink blended with lemon grass (Cymbopogon citratus Stapf)

Zobo (Hibiscus sabdariffa) is a widely consumed traditional dark-red beverage in Nigeria and West Africa. This study aimed to enhance its shelf life by incorporating lemongrass (Cymbopogon citratus), a tropical herb known for its antimicrobial and medicinal properties. Five formulations were prepared: 100% Zobo (control), and blends containing 5%, 10%, 15%, and 20% lemongrass. Samples were subjected to physicochemical, microbial, and sensory analyses using standard methods. The results revealed that pH values increased progressively with higher lemongrass concentrations, ranging from 2.5 in the control to 9.5 in the highest blend. Brix values remained constant across all samples, while total soluble solids (TSS) increased, with sample E (20% lemongrass) recording the highest value (300 mg/L). Specific gravity varied slightly, with sample B showing the highest value (98.66 g/mol). By day 21 of storage, the control sample exhibited the highest microbial loads, including total plate count (11.5 × 104 cfu/mL), coliforms, Salmonella, and Staphylococcus. In contrast, samples with lemongrass (especially B to E) demonstrated improved microbial stability, with no detectable coliforms and reduced bacterial counts. However, sample E recorded the highest total fungal count (282.0 × 104 cfu/mL). A total of four microbial isolates were identified: Staphylococcus spp., Bacillus spp., Lactobacillus spp., and Micrococcus spp. The findings suggest that lemongrass incorporation improves the physicochemical quality and microbial shelf stability of Zobo drink, with moderate concentrations offering the most balanced preservation effect.