Enhancement of the viability of Lactobacillus rhamnosus ATCC 7469 in passion fruit juice: Application of a central composite rotatable design

• Application of a central composite rotatable design enhanced the viability of L. rhamnosus ATCC 7469.
• Inoculum and pulp concentrations influenced viability and lactic acid production.
• The microorganisms remained with high viability in the simulation of gastro intestinal conditions.

A central composite rotatable design was employed to investigate the combined effects of inoculum concentration (0.09–2.91% V/V), and passion fruit from a Caatinga pulp concentration (2.95–17.05% V/V) on the viability of Lactobacillus rhamnosus ATCC 7469 in relation to pH. A second-order polynomial response surface equation revealed that the experimental variables significantly affected the studied response (ratio between the viability and the pH - RVpH). The determination coefficient (R2) and the cross-validated R2 (Q2) were higher than 0.99. The conditions predicted by second-order polynomial model for the higher RVpH in the levels investigated were 2.91% V/V and 14.45% V/V of inoculum and passion fruit pulp concentration, respectively. Under these conditions, viability was higher than 10 Log CFU/mL and the pH lower than 4.6. Higher RVpH indicates that the microorganism is better adapted to stress in the gastrointestinal tract. Fermented passion fruit from Caatinga juice was considered “probiotic” with a shelf life of 28 days.