Fig. 3: Citric acid-based hydrolysis and fermentation affect flavanone profiles in citrus extracts.

a Schematic diagram of extract preparation. For citric acid hydrolyzed extract (CAE), bioflavonoid complex was treated with citric acid solution at 90 °C for 4 h. Then, sodium citrate solution was added to reach a final concentration of 10% (w/w). Aqueous extract (AQE) was prepared with water instead of citric acid. For fermentation, AQE and CAE were incubated with L. plantarum at 37 °C for 24 h (referred to as FermAQE and FermCAE). Control extracts were diluted in modified MRS and incubated without bacteria (referred to as AQE and CAE). b Influence of hydrolysis with increasing citric acid (CA) concentrations (0.25 M CA, 0.50 M CA, or 1.00 M CA) on flavanone concentrations in citrus extracts before incubation with bacteria. Data are mean ± SD of n = 4 samples/treatment. Differences to 0 M CA are analyzed by ordinary one-way ANOVAs with Dunnett’s multiple comparison test, with exception of data set for hesperidin which is analyzed with Kruskal’s test with Dunn’s multiple comparisons test. c Increase in aglycones after 24 h-incubation with L. plantarum. For calculation of the aglycone increase, the initial aglycone concentration (at 0 h) was subtracted from the total concentration at 24 h. Data are mean ± SD of n = 5 samples/treatment. Differences to 0 M CA are analyzed by Kruskal’s test with Dunn’s multiple comparisons test. d Flavonoid concentrations in the final extracts prepared with water (AQE and FermAQE) or 0.25 M CA (CAE and FermCAE). Data are mean ± SD of n = 9 samples/extract. Differences between treatments are analyzed by ordinary one-way ANOVAs with Tukey’s multiple comparison test (narirutin, neohesperidin and hesperetin) or Kruskal’s test with Dunn’s multiple comparisons test (naringin, naringenin-7-O-glucoside, naringenin, hesperidin and hesperetin-7-O-glucoside).