Added dietary fiber reduces the antioxidant capacity of phenolic compounds extracted from tropical fruit

The effect of dietary fiber (DF) from tropical fruits on the antioxidant capacity of phenolic compounds (PC) present in the same fruits was investigated. DF obtained from tropical fruits pulp (FDF) was incubated with methanolic extracts (ME) containing PC, at pH 2.5 and room temperature for 2 h. The total soluble phenols (TSP) content and antioxidant capacity (DPPH assay) were analyzed in the resulting supernatants. Results show that the addition of FDF significantly (p<0.05) decreased the antioxidant capacity of ME from 5-20%. Among the FDF, the mango fiber affected in higher extent the antioxidant capacity. Wheat dietary fiber (WDF) was used as control. The addition of WDF decreased significantly (p<0.05) the antioxidant capacity ranging from 23-45%. The bioactive compounds bioaccesibility was also reduced with both types of fiber, being the WDF the most effective to trapping the PC. This suggests that apparently some type of physic-chemical interaction between DF and PC are occurring consequently affecting the bioaccesibility and action of antioxidants

Enzyme-Catalyzed Production of Potato Galactan-Oligosaccharides and Its Optimization by Response Surface Methodology

This work shows an optimized enzymatic hydrolysis of high molecular weight potato galactan yielding pectic galactan-oligosaccharides (PGOs), where endo-β-1,4-galactanase (galactanase) from Cellvibrio japonicus and Clostridium thermocellum was used. For this, response surface methodology (RSM) by central composite design (CCD) was applied. The parameters varied were temperature (°C), pH, incubation time (min), and enzyme/substrate ratio (U/mg). The optimized conditions for the production of low degree of polymerization (DP) PGOs were obtained for each enzyme by spectrophotometric assay and confirmed by chromatography. The optimal conditions predicted for the use of C. japonicus galactanase to obtain PGOs of DP = 2 were T = 51.8 °C, pH 5, E/S = 0.508 U/mg, and t = 77.5 min. For DP = 3, they were T = 21 °C, pH 9, E/S = 0.484 U/mg, and t = 12.5 min; and for DP = 4, they were T = 21 °C, pH 5, E/S = 0.462 U/mg, and t = 12.5 min. The efficiency results were 51.3% for substrate hydrolysis. C. thermocellum galactanase had a lower yield (35.7%) and optimized conditions predicted for PGOs of DP = 2 were T = 60 °C, pH 5, E/S = 0.525 U/mg, and time = 148 min; DP = 3 were T = 59.7 °C, pH 5, E/S = 0.506 U/mg, and time = 12.5 min; and DP = 4, were T = 34.5 °C, pH 11, E/S = 0.525 U/mg, and time = 222.5 min. Fourier transformed infrared (FT-IR) and nuclear magnetic resonance (NMR) characterizations of PGOs are presented