Optimization of co-fermentation of carrot and tomato juices by probiotic bacteria and yeast using a central composite design


  • O.V.S. Reddy et al.


Lactobacilli, Lysinibacillus sphaericus, Saccharomyces boulardii, Probiotication, Tomato and carrot juices, Antimicrobial activity, Sensory evaluation


In the present study, experiments were conducted on the suitability of tomato, carrot and mixed tomato+carrot juice for probiotication by Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus casei and Lysinibacillus sphaericus individually and in combination with a yeast (Saccharomyces boulardii). The combination of Lys. sphaericus and S. boulardii showed good results. Further optimization was carried out using a central composite design (CCD). The autoclaved juices were inoculated with probiotic cultures both alone or in combination with the yeast culture and incubated at 37°C for 72 h. After 24 h of fermentation, the pH levels had decreased from 6.1 to 4.0. Titratable acidity also increased from 0.12% to 0.36%, while the viable cell counts of probiotic bacteria and yeast gradually increased from 6.5 to 7.0 CFU/ml and from 5.4 to 7.9 CFU/ml, respectively. Subsequently, following further fermentation, viable cell counts decreased due to a decrease in pH and an increase in acidity as well as a lack of nutrients in the medium. The antimicrobial activity of mixed juice was found to have a maximum zone of inhibition of 11.8 mm and 9.8 mm against Pseudomonas aeruginosa MTCC 741 and Bacillus subtilis MTCC 2394, respectively. Probioticated tomato and carrot juices showed good sensory attributes.