Analysis of hydrocolloid excipients for controlled delivery of high-value microencapsulated prickly pear extracts

Abstract

Prickly pears (Opuntia ficus-indica) are potential sources of functional ingredients because they are rich in betalains and phenolic compounds. However, mentioned bioactives may degrade during storage when exposed to air, light, and heat which could limit their application. To increase the stability and bioaccessibility of prickly pear extracts, we compared the ultrasound-assisted freeze-dried microencapsulation of seven excipient mixtures. The physical and physico-chemical properties (humidity, hygroscopicity, thermal analysis and morphology) and the qualitative and quantitative analysis of betalains and phenolic compounds (measured by high performance liquid chromatography) were analysed in each microparticle formulation. Stability-improving factors such as low humidity and hygroscopicity were observed in all microparticles. However, microparticle morphology was influenced by the excipient formulation. Encapsulation efficiency was higher than 60% for betalains and phenolic acids, however, flavonoids encapsulation efficiency was 14–35%. Based on the previous, the three best microparticles were selected: 100% maltodextrin (E2); 50% maltodextrin, 25% microcrystalline cellulose, 15% hydroxyl‑propyl-methyl cellulose, and 10% xanthan gum (E5); and 100% β-cyclodextrin (E7). A static in vitro gastrointestinal digestion (INFOGEST method) was performed with these microparticles where the quantitative analysis of the bioactive compounds (HPLC) and their bioaccessibility was assessed. The bioaccessibility of bioactive compounds in encapsulated prickly pear extracts was improved when compared to the control. Microparticles containing maltodextrin and microcrystalline cellulose (E2) had the highest bioaccessibility and showed potential for the future formulation of functional foods.