Effects of Dual-Frequency Ultrasonic Treatment on Functional and Cryoprotective Properties of Soy Protein Isolate-Curcumin Complexes

The present study investigated the effects of dual-frequency ultrasonic treatment on the functionality of soy protein isolate-curcumin complexes and their cryoprotective properties for beef myofibrillar protein (MP) gel. Control groups were created using pure soy protein isolate (SPI) or SPI-curcumin (SPI-CUR) complex without ultrasonic treatment. Subsequently, SPI underwent modification with various dual-frequency ultrasound frequencies (20/40, 25/40, 28/40 kHz, 15 min, 20 degrees C) and was then mixed with curcumin (CUR) to fabricate the USP1-CUR, USP2-CUR, and USP3-CUR complexes. Results showed that the USP1-CUR complex achieved the highest encapsulation efficiency (88.41%), loading amount (141.45 mu g mg-1 SPI) of curcumin, resulting in the enhancement of emulsifying ability index (19.54 m2 g-1) and ABTS scavenging capacity (87.59%), along with improved storage stability, thermal stability, and bioavailability. This finding was corroborated by the cohesive "cluster-like" arrangement and the robust binding between SPI and CUR observed in the USP1-CUR complex through SEM. Moreover, FTIR and XRD analyses elucidated that the interaction between CUR and SPI primarily involves hydrogen bonding and hydrophobic interactions. Furthermore, the incorporation of the USP1-CUR complex exhibited efficient cryoprotection for the MP gel, as evidenced by decreased thawing loss and carbonyl content, enhanced texture properties, and a dense network structure observed throughout freeze-thaw cycles. Molecular docking analysis further demonstrated that incorporating the USP1-CUR complex into MP facilitated the formation of strong hydrogen bonding interactions between curcumin and proteins. In conclusion, SPI subjected to rational dual-frequency ultrasound can improve the delivery efficiency of CUR and provide valuable insights for utilizing the functional complex of plant proteins and polyphenols to reduce freeze-thaw damage in meat production.