Microencapsulation of antioxidant phenolics from tamarind seed peels using chia gum and maltodextrin

Abstract

Tamarindus indica seeds/seed peels (TSP) are the main waste products from the tamarind industry and contain valuable bioactive antioxidant-phenolic compounds that promote human health; however, their application is limited due to their instability and poor solubility. Encapsulation is becoming more important in several industries due to its potential for preserving and delivering valuable and delicate bioactive compounds. This study targets the microencapsulation of TSP-phenolic compounds for incorporation into functional food formulations. By employing the freeze-drying method, three microcapsule formulations were developed using chia gum (CG), maltodextrin (M), and a mixture of the two (M/CG) as coating materials. The formed M-, M/CG-, and CG-microcapsules showed remarkable encapsulation efficiency of 88.0, 90.0, and 95.0%, respectively. They preserved most of the TSP-phenolic content (87.5-96.3%) and antioxidant activity (86.0-98.8%). They demonstrated higher digestibility percentages in the intestinal media (53.0-70.0%) than in the gastric media (29.0-36.0%), especially the microcapsules coated with CG. They kept the TSP-antioxidant-phenolic content safe at 40 °C for 2 months. The microcapsules demonstrated improved microstructures, swelling, solubility, and moisture content. Crosslinking and enhanced thermal stability were also proven for microcapsules via FTIR and thermogravimetric studies. In addition, the prepared microcapsules displayed better antimicrobial activity against the examined bacterial strains, with minimum bactericidal concentrations ranging from 0.61 to 1.4 mg/mL. In conclusion, the encapsulation improved the stability, bioavailability, and antibacterial properties of TSP-phenolic compounds, making them suitable for food and pharmaceutical applications.

Keywords: Tamarindus indica; Bioavailability; Encapsulation; Peels; Phenolic compounds; Stability.

Fig. 1

(A) In vitro release profile of phenolic content from the prepared microcapsules in simulated gastric fluid (SGF) and simulated intestine fluid (SIF), (B, C) Storage stability of the total phenolic content and total antioxidant activity of the TSPE and the prepared microcapsules stored at 40 °C for 8 weeks. TSPE: Tamarind seed peel extract M: Maltodextrin-microcapsule; M/CG: Maltodextrin-Chia gum microcapsule and CG: Chia gum microcapsule. Values are provided as means ± SD (n = 4). Different letters in the same column are statistically different at (P < 0.01).

Fig. 2

SEM images of the purified chia gum (a) and maltodextrin (b) as coating materials, M-microcapsule (c), CG-microcapsule (d), and M/CG-microcapsule (e). M: Maltodextrin-microcapsule; M/CG: Maltodextrin-Chia gum microcapsule and CG: Chia gum microcapsule.

Fig. 3

FTIR spectrum of the maltodextrin and M-microcapsule (A), the purified chia gum, CG-microcapsule, and M/CG-microcapsule (B). M: Maltodextrin-microcapsule; M/CG: Maltodextrin-Chia gum microcapsule and CG: Chia gum microcapsule.

Fig. 4

TGA curves (A) and DTG curves (B) of the purified chia gum and maltodextrin as coating materials and the obtained microcapsules. M: Maltodextrin-microcapsule; M/CG: Maltodextrin-Chia gum microcapsule and CG: Chia gum microcapsule.