Although CA-HYP presented a slightly lower yield and higher contents of total carbohydrate and uronic acid, their composition and 13C NMR spectrum closely resembles the pectins obtained from cacao pod husks by boiling aqueous extractions (Vriesmann, Amboni, et al., 2011). It seems that, both citric acid and water, were able to remove LM pectins (DE ∼40%) probably Natural Product Library arising from the middle lamella. Fig. 4 shows the HPSEC elution profile of fraction CA-HYP. Due to the high-molar mass (1.806 × 106 g/mol), the primary peak (∼38 min) was detected
by both, the differential refractometer (RI) detector and the multiangle laser light scattering (MALLS) detector. Another peak was observed at higher elution time (>40 min), with a less intense RI signal and no MALLS detection,
indicating lower concentration and lower-molar mass (6.450 × 105 g/mol). Comparing to the pectins obtained from cacao pod husks with boiling water, CA-HYP had higher molar mass (Vriesmann, Amboni, et al., 2011). Dynamic viscoelastic properties of solutions of CA-HYP at 5 g/100 g were studied by frequency sweeps obtained at 25 °C (Fig. 5). Both elastic (G′) and viscous (G″) moduli increased with the frequency, being G′ more dependent on frequency than G″, until reach a frequency of ∼10 Hz, where the cross-over between the moduli occurs. Similar results were obtained by Vriesmann, Amboni, et al. (2011) for boiling-water extracted selleck inhibitor pectins from cacao pod husks and Min et al. (2011) for pectins from apple pomace obtained by chemical and combined physical/enzymatic treatments. However, the pectins from apple pomace at 5 g/100 g presented G″ > G′ over the range of frequency analyzed ( Min et al., 2011). These authors observed that pectins with lower DE appeared to have more elastic properties than those with higher DE ( Min et al., 2011). The results obtained for CA-HYP confirmed this trend. CA-HYP (40.3% DE) showed higher elastic properties than pectins from cacao pod husks extracted Ureohydrolase with
boiling water (42.6% DE; Vriesmann, Amboni, et al., 2011) and apple pomace pectins (58 and 69% DE; Min et al., 2011). The viscosity curve of 5 g/100 g CA-HYP aqueous solution at 25 °C (Fig. 6) showed a shear-thinning, pseudoplastic flow behavior as reported for other pectin solutions (Hwang & Kokini, 1992; Min et al., 2011; Vriesmann, Amboni, et al., 2011). Cross equation, with four parameters, can describe the general flow curve of pseudoplastic fluids (Cross, 1965). Thus, it was employed to fit the experimental data of apparent viscosity, η (Pa s), vs. shear rate, γ˙(1/s) for CA-HYP, according to the equation: η=η∞+(η0−η∞)/[1+(γ˙/γ˙b)n], where η 0 is the zero-shear rate viscosity (Pa s), η ∞ is the infinite-shear rate viscosity (Pa s), γ˙b is the shear rate at which the fluid changes from Newtonian to Power-law behavior (1/s) and n is the flow behavior index (−). The values found for the four parameters for the flow of CA-HYP were η 0: 7.993 Pa s; η ∞: 0.1189 Pa s; γ˙b. 1.607 1/s and n: 0.