Juçara (Euterpe edulis) pulp as a substrate for probiotic bacteria fermentation: Optimisation process and antioxidant activity

Abstract

Juçara fruit (Euterpe edulis) has received considerable attention because of its high content of phenolic compounds. However, its suitability as a matrix for probiotic bacteria is not known yet. The objective of this study was to evaluate the pH and temperature conditions for the fermentation in juçara pulp by Lactobacillus reuteri and Lactobacillus plantarum. The optimised conditions were determined by central composite rotational design, and used for the analysis of cellular viability, sugar content, pH, lactic acid, total phenolics and antioxidant activity during 80 h of fermentation. The conditions for probiotic growth were 32 °C with a pH of 5.7 for L. reuteri and 25 °C with a pH of 5.0 for L. plantarum, and 30 h of fermentation time for both bacteria. The viabilities remained above 8.6 ± 0.2 log colony forming units (cfu)/mL, and at 536.7 mg gallic acid equivalent (GAE)/100 mL of total phenolic reached. L. reuteri consumed all of the glucose and fructose present in juçara, whereas L. plantarum used only glucose. After 28 days of refrigerated storage, the cell viability of probiotics remained at 8.7 log CFU/mL with an increase in the antioxidant activity. Juçara pulp can be effective for a probiotic growth substrate and the production of new functional beverage.