Revealing the non-enzymatic covalent interaction between neo−/crypto-chlorogenic acid and beta-lactoglobulin under nonthermal process and potential delivery capability

Several studies have shown that the protein-chlorogenic acid covalent complex has better function and stability than the non-covalent. The degree of binding between the proteins and chlorogenic acids (CQA) can be enhanced by the ultrasound process. Herein, the effects of ultrasound-assisted non-enzymatic covalent binding (the free radical induction (Vc)-ultrasound combination and the alkali treatment (Alkali)-ultrasound combination) of two chlorogenic acids (neochlorogenic acid (3-CQA), cryptochlorogenic acid (4-CQA)) and β-lactoglobulin (β-LG) on proteins structure and properties were investigated. Results showed that ULG-Alkali-4CQA exhibited a 5.1 % reduction in α-helices, a 6.8 % increase in random curl and proteins structures becoming loose and disordered. The hydrophilicity and thermal stability of β-LG were effectively enhanced by the addition of 4-CQA and the effect of alkali treatment-ultrasound combination. Curcumin (CUR) and lycopene (LYC) were successfully delivered by the covalent complexes as delivery vehicles. The encapsulation efficiencies of the ULG-Vc/Alkali-4CQA + CUR and ULG-Vc/Alkali-4CQA + LYC complexes were 82.81 %, 84.16 %, 89.56 % and 90.51 %, respectively. The stabilities of CUR and LYC in the ULG-Vc/Alkali-4CQA + CUR/LYC ternary complexes were superior to those of all the measured complexes delivery systems. The study hopes to establish a theoretical foundation and serve as a reference for the advancement of a highly stable food-grade delivery system.