Characterization and potential application of microspheres from sodium alginate cross-linked with pectin from Citrus depressa Hayata’s peels

Background

Pectin from Taiwan Citrus depressa Hayata’s peels (CDH pectin) and sodium alginate (Na alginate) were mixed in neutral acidity to produce microhydrogel beads or microspheres. The potential use of the microspheres such as encapsulation materials for quercetin and nobiletin, DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging activity, toxic elements absorption ability, and thermal characteristics were explored.

Results

Different ratios of CDH pectin and Na alginate produced microspheres of varying sizes and shapes. The highest yield (47.59%) with the broadest diameter was obtained at a Na alginate—CDH pectin ratio of 2:1, while the smallest yield was obtained from Na alginate—CDH pectin ratio of 1:3 (24.13%). Increasing the amount of Na alginate resulted in more spherical microspheres, higher heavy metals (cobalt and nickel) removal rates, yet a lower swelling ratio. A high pectin concentration also increased the encapsulation efficiency of quercetin and nobiletin, reaching 91.5% and 86.74%, respectively. Quercetin and nobiletin release analysis (in vitro) showed a slow release of drugs from the microspheres. Less than 20% quercetin and nobiletin were released from the microspheres in SGF (simulated gastric fluid) pH 1.2 solution after 2 h and more than 40% of the encapsulated drug was released in SIF (simulated intestinal fluid) pH 6.8 after 4 h. The strong DPPH scavenging activity of quercetin (99%) was not hindered by encapsulation materials. ICP-OES (inductively coupled plasma–optical emission spectrometry) analysis demonstrated that the biopolymer can absorb cobalt and nickel from water. Thermogravimetric analysis (TGA) result showed that the combination of CDH pectin and Na alginate produced a biopolymer that exhibited a weight loss of only 1.86–4.33% at 100 °C.

Conclusions

These findings suggest that microspheres produced from CDH pectin cross-linked with sodium alginate had potential in nobiletin and quercetin encapsulation. Moreover, the polymer could absorb heavy metals and exhibit an important characteristic for hot food and beverage packaging applications.