Fermentation of apple juice using selected autochthonous lactic acid bacteria

Introduction. Dairy products are the most common probiotic food. However, due to lack of enzyme lactase, their ingestion for lactose intolerant people is a challenge. Fruit juices are rich in nutrients and have proved to be effective carriers or growth media for probiotics, specifically for lactic acid bacteria; they are also lactose-free and can be taken by lactose intolerant individuals. Materials and methods. Self-made apple juice and selected lactic acid bacteria were used in the study. The number of viable bacterial cells was determined by a serial dilution method; titratable acidity was determined by automatic titrator; sugars and organic acids concentrations were measured using High-Performance Liquid Chromatography; total phenolic compound content was determined by the Folin-Chiocaltus method; and the antioxidant activity was determined by FRAP (ferric-reducing antioxidant power) assay. Results and discussion. Selected Lactiplantibacillus plantarum strains were used to ferment apple juice. The optimal conditions for the fermentation were an initial pH 4.5 and 24 h duration, with maximum bacterial cells viability 8.23 +/- 0.17 log CFU/mL and 8.55 +/- 0.19 log CFU/mL for L. plantarum 74 and L. plantarum 76, respectively. Characteristics of apple juice were changed during fermentation, particularly, after 48 hours of fermentation, an increase in the titratable acidity caused the pH decrease and gradual decrease of the sugar contents was also observed. The highest production of lactic and malic acids were observed during 48 h of fermentation with the strain L. plantarum 74. The fermented juice with L. plantarum 52, L. plantarum 74, and L. plantarum 76 had concentration of total phenolic compounds 532.9 +/- 26.7 mg GAE/ L, 587.3 +/- 29.4 mg GAE/L, 488.4 +/- 24.4 mg GAE/L and antioxidant activity 281.6 +/- 14.1 mg AAE/L, 300.6 +/- 15.0 mg AAE/L, 172.8 +/- 8.6 mg AAE/L, respectively after 72 h of fermentation. Conclusion. Apple juice fermented with selected strains of Lactiplantibacillus plantarum was enriched with lactic acid bacteria and can be used as a probiotic product that people with lactose intolerance can consume.