PROTEIN ISOLATE FROM SACHA INCHI POMACE GRAFTED TO CATECHIN BY DUAL INTERMEDIATE FREQUENCY ULTRASOUND

The covalent linkage of protein with phenolic compounds through chemical and enzymatic methods constitutes a strategy to improve its functional properties such as antioxidant capacity. However, the efficacy of the aforementioned procedures necessitates enhancement. Isolated protein from by-product sacha inchi pomace (APSI) and catechin were used to produce novel antioxidant protein (APSI-CAT) by dual intermediate frequency ultrasound (dIFUs) procedure. The chemical dosimetry (H₂O₂) of the multifrequency ultrasound system (Meinhardt Ultrasonic, Germany) was determined by the modified Weissler method. APSI-CAT was obtained by the free radical H₂O₂ and ascorbic acid (Aa) procedure assisted by optimized one-pot dIFUs. The APSI solution (5 mg/mL) was sonicated at 582 KHz, amplitude = 90 % for 10 minutes. Thereafter, Aa and exogenous H₂O₂ (molar ratio = 3.4) and SAPhe (APSI/CAT ratio = 2 w/w) were added, and the mixture was sonicated at 1144 kHz, amplitude = 30 % for 20 minutes. APSI-CAT were dialyzed on a membrane with 6-8 kDa cut-off for 48 h. The APSI/CAT and APSI as control were analyzed using the following methods: i) UV-Vis spectroscopy performed in the range of 200-500 nm, FT-IR spectroscopy was carried out in the range of 4000-400 cm-1 (resolution = 4 cm-1 and 32 scans) and fluorescence sprectra at λexcitation = 285 nm and λemission = 300 to 700 nm. ii) The total phenolic compound content using a rapid Folin-Ciocalteu method and iii) The antioxidant capacity were measured by the DPPH (2,2-Diphenyl-1-picrylhydrazyl) and ABTS (2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) methods. The UV-Vis, FT-IR and fluorescence spectra exhibited characteristic peaks, which reflected the covalent binding of APSI to CAT. The total phenolic content of APSI-CAT was four times higher than that of APSI. The antioxidant capacity of APSI-CAT was superior to that of APSI, with a tenfold and eightfold increase for the DPPH and ABTS assays, respectively