Garden cress gum and maltodextrin as microencapsulation coats for entrapment of garden cress phenolic-rich extract: improved thermal stability, storage stability, antioxidant and antibacterial activities

Abstract

The obtained garden cress 6-day sprouts phenolic-rich extract (GCSP) contained efficient health-promoting antioxidant-phenolic compounds. To improve the stability, bioavailability, and functional properties of these valuable phenolic compounds, GCSP was encapsulated by freeze-drying technique using different ratios of garden cress gum (GG) and maltodextrin (M) in the absence and presence of sonication (S). The prepared S/GG-microcapsule retained the highest phenolic content (95%), antioxidant activity (141.6%), and encapsulation efficiency (98.2%). It displayed the highest bio-accessibility of GCSP-phenolic compounds in simulated intestine fluid (87%) and demonstrated the greatest storage-stability at 40 °C for 60 days. S/GG-microcapsule possessed better physical properties including moisture, solubility, swelling, and morphological structures using SEM. The main spectral features, crosslinking, and improved thermal stability were demonstrated for S/GG-microcapsule using FTIR and thermogravimetric analyses. S/GG-microcapsule demonstrated much greater antibacterial activity than GCSP against pathogenic bacteria. S/GG-microcapsule can be added to different food products to improve their antioxidant and antibacterial properties.

Keywords: Encapsulation efficiency; Garden cress 6-day sprouts; Lepidium sativum; Phenolic content; Storage stability.

Fig. 1a

Release rate/bio-accessibility index percentages of the GCSP-phenolic compounds from the prepared microencapsulates under simulated gastric fluid (SGF) and simulated intestine fluid (SIF). M: Maltodextrin-microencapsulate; GG: Garden cress gum-microencapsulate; S: Sonicated sample; GCSP: Garden cress 6-day sprouts phenolic extract. Values are presented as means ± SD (n = 6); Different letters are statistically different at (P < 0.01). Figure 1b. SEM micrographs of pure coating materials (maltodextrin and garden cress gum) (A and B), M-microcapsule (C and D), S/M- microcapsule (E and F), GG-encapsulate (G and H), and S/GG-encapsulate (I and J). SEM graphs were taken at low and high magnifications. M: Maltodextrin- microencapsulate; GG: Garden cress gum-microencapsulate; S: Sonicated sample

Fig. 2

(A) FTIR spectra of the prepared S/GG-microencapsulate and its coating material garden cress gum (GG-gum). TGA curves (B) and DTG curves (C) of the prepared S/GG-microencapsulate and its coating material garden cress gum (GG-gum)