*3.4. Antioxidant Activity*

The antioxidant activity of encapsulated quercetin was investigated by ABTS and DPPH radical scavenging assays (Figure 9). The ABTS+ scavenging capacity of quercetinloaded HZ was lower than the quercetin dispersed in water and ethanol. The reason for the lower scavenging capacity of encapsulated quercetin is being embedded in the hydrophobic pockets of protein and inaccessible to ABTS+ [30]. Furthermore, the hydroxyl groups in the B ring of quercetin are the main contributor of H+ and are involved in hydrogen bonding in the composite particles, thus unavailable to scavenge the free radicals. Earlier, quercetin encapsulated in SPI and solid zein particles showed a similar reduction in the ABTS<sup>+</sup> savaging capacity. On the other hand, the interfacial chitosan-pectin coating in quercetin-loaded HZ-chi/pec particles may increase the accessibility of hydrophilic ABTS+ to quercetin, demonstrating higher scavenging of ABTS<sup>+</sup> compared with that of qHZ (Figure 9). DPPH scavenging capacity of quercetin was improved upon encapsulation in HZ and HZ-chi/pec particles by compared with that of dispersed in ethanol and water (Figure 9). Earlier, it has been reported that both zein and DPPH being soluble in ethanol–water binary medium facilitate scavenging of DPPH by hydrophobic antioxidants encapsulated in the zein particles [62,63]. The ABTS and DPPH radical scavenging assay revealed that by encapsulating quercetin in composite hollow zein particles, it could be better protected from free reactive radicals in the surrounding medium along with an improved or sustained antioxidant activity.

**Figure 9.** ABTS+ and DPPH scavenging capacity of quercetin, blank and quercetin-loaded HZ and HZ-chi/pec particles.
