EFFECT OF THE ADDITION OF DIFFERENT POLYMERS ON THE ENCAPSULATION OF BIOACTIVE COMPOUNDS FROM GRAPE POMACE BY IONIC GELATION

Wine production generates approximately 17 kg of grape pomace for every 100 liters of red wine. This by-product is rich in anthocyanins with bioactive properties; however, its application in food is limited due to low stability under environmental conditions. Encapsulation by ionic gelation offers a simple and cost-effective approach to overcome this limitation, although it may allow the diffusion of water-soluble compounds. An alternative to reduce this diffusion is to add polymers to gelling solution, increasing viscosity and reducing the pore size. This study aimed to evaluate the encapsulation efficiency (EE) of phenolic compounds and monomeric anthocyanins of an extract from grape pomace, as well as the retained antioxidant capacity (RAC), in beads produced via ionic gelation using sodium alginate alone or combined with other biopolymers (whey protein isolate (WPI), gelatin, gum arabic or pectin) at concentrations of 2.5% and 5% (w/v). The goal was to identify formulations capable of enhancing retention of bioactives from Syrah grape pomace. The grape pomace extract was obtained by ultrasound-assisted extraction using a 50% (v/v) hydroethanolic solution and subsequently concentrated with a rotary evaporator to obtain a concentrated aqueous extract. Beads were formed by external ionic gelation via extrusion and evaluated for monomeric anthocyanin content, total phenolic compounds and antioxidant capacity using ABTS and DPPH assays. Among the tested formulations, WPI 2.5% showed the best performance, with anthocyanin EE of 62.24%, phenolic compounds EE of 49.51%, and RAC of 42.64% (ABTS) and 49.22% (DPPH), representing a considerable improvement over the control beads (EE of 47.25%, 22.18%, 21.48% and 23.45% for anthocyanin, phenolics, ABTS and DPPH, respectively). These results suggest that the protein nature of WPI favors the formation of stable interactions with anthocyanins, protecting them from degradation. Pectin 2.5% showed phenolic EE of 41.64% and RAC of 30.78% (ABTS) and 32.69% (DPPH), representing the second-highest RAC. Its performance was comparable to WPI 5% but at a lower concentration, providing an economic advantage. The higher retention observed for pectin may be related to its ability to form hydrogen bonds and hydrophobic interactions with bioactives. Gelatin and gum arabic formulations showed lower EE for both phenolics and anthocyanins, which could result from weaker chemical affinity with bioactive compounds and, in the case of gelatin, possible formation of insoluble complexes or thermal degradation. These findings reinforce the potential of ionic gelation as a strategy to valorize grape pomace and increase the stability of its bioactive compounds.