Effect of Sodium Alginate Concentration on the Physicochemical, Structural, Functional Attributes, and Consumer Acceptability of Gel Beads Encapsulating Tangerine Peel (Citrus reticulata Blanco ‘Cho Khun’) Extract

The effect of varying sodium alginate (SA) concentrations (1%, 2%, and 3%; SA1-SA3) on the encapsulation of tangerine (<i>Citrus reticulata</i> Blanco 'Cho Khun') peel extract (TPE, 0.5% <i>w</i>/<i>v</i>) into hydrogel beads was evaluated. Overall, the results showed that increasing SA concentration significantly altered bead characteristics: lightness (L*) decreased from 56.35 to 45.57, red-green axis (a*) shifted negatively from -1.32 to -6.87, and yellow-blue axis (b*) increased from -17.81 to 6.41. Moisture content (97.85% to 93.16%) and water activity (0.96 to 0.93) declined with higher SA, while hardness increased (4.12 to 5.17 g). ζ-potential values shifted from -29.10 mV (SA1) to -39.10 mV (SA3), confirming enhanced electrostatic stabilization. FTIR spectra revealed characteristic alginate functional groups, and morphological analysis showed smoother, denser beads at higher SA concentrations. Phenolic (47.86-48.51 mg GAE g^-1 DW) and flavonoid (34.02-36.68 mg QE g^-1 DW) contents were well-retained, supporting antioxidant activities (DPPH 70.34-72.54%; ABTS 65.66-66.91%). Antimicrobial tests demonstrated > 4-log reductions against <i>E. coli</i> and <i>P. aeruginosa</i>. Sensory evaluation revealed that higher SA concentrations improved texture and taste. Overall, SA encapsulation, particularly at 3%, effectively stabilized TPE, preserving its functional properties for potential food and nutraceutical applications.