Inulin is a non-digestible polysaccharide that can have different amorphous/crystalline physical states. This research evaluated the encapsulation of quercetin (Q) and ellagic acid (EA) by spray-drying with amorphous and semicrystalline inulin on the release in colonic simulated conditions with inulinase.

EA encapsulation was performed by applying a Box-Behnken design. The independent variables were inlet air temperature (Ta, 120-200°C), infeed temperature (Ti, 5-85°C), and EA:inulin ratio (1:100-1:200). The response variables were the encapsulation efficiency (EE) and crystallinity index (CI). Infeed dispersion was fed in a spray-dried. The Ta and EA:inulin ratio were established by desirability function to maximize both EE and CI, whereas the Ti was defined from a differential scanning calorimetry analysis of the infeed dispersion. On the optimal conditions, EA and Q microparticles were formulated with amorphous (A) and semicrystalline (SC) inulin, and EE was evaluated. In addition, colonic simulation release was studied by incubating microparticles for 48 h to 37 °C with inulinase (5 U/mg substrate).

The optimal spray-drying operation conditions were 120°C and 1:160 ratio for Ta and EA:inulin ratio respectively. A-EA and A-Q microparticles were obtained by feeding the infeed dispersion to 85 °C, while SC-AE and SC-Q were fed to 37 °C. The EE for EA microparticles (A-AE: 96.1%, SC-AE: 85.3%) was significantly higher than Q microparticles (A-Q: 24.8%, SC-Q: 24.7%). EA colonic bioaccessibility decreased from 9.7% to 3.6% in the first 10 h, keeping constant until 48 h. Nonetheless, the encapsulation improved AE bioaccessibility by 5.7 times at the beginning of the colonic phase. Whereas Q bioaccessibility did not improve by encapsulation, keeping at 7.5% in A-Q and decreasing from 7.0 to 4.6% from 4 h in SC-Q.

In conclusion, polyphenol (hydrophobicity) and the physical properties of the microparticles (amorphous-crystalline state) influence colonic bioaccesibility.