abstract
- This study evaluated Instant Controlled Pressure Drop (DIC) as a thermomechanical pretreatment to optimize the aqueous extraction of phenolic compounds and antioxidant capacity from Ilex guayusa leaves. Thirteen DIC treatments were applied under varying steam pressures (0.10¿0.30 MPa) and treatment times (10¿35 s), and the effects of processing conditions were analyzed using response surface methodology. DIC pretreatment significantly improved the functional properties of guayusa extracts compared with untreated controls. The highest experimental total phenolic content (6536.96 mg GAE/100 g d.b.) was obtained at 0.13 MPa and 31 s, corresponding to a 19.7% increase over the control, while the greatest radical scavenging activity was observed at 0.27 MPa and 31 s, reaching 71.89% RSA. The highest TEAC value was also achieved at 0.13 MPa and 31 s, reaching 253.05 mg Eq Trolox/100 g d.b. Response surface modeling identified prolonged treatment times as the principal factor favoring phenolic release and antioxidant enhancement, with predicted optimal conditions occurring between 28 and 35 s depending on the response. For total phenolic content and radical scavenging activity, the global predicted optimum was located at 0.30 MPa, whereas TEAC enhancement was predicted to be maximized at 0.10 MPa. Response surface methodology further identified operational zones where DIC treatment maximized extract functionality, providing practical guidance for process optimization and supporting the future industrial implementation of DIC-assisted guayusa processing.