Potato protein/sugar beet pectin glycation conjugates: ultrasound-assisted preparation and their applications as carriers of anthocyanins

Abstract

Purple sweet potato anthocyanins (PSPA) are natural phenolic substances with antioxidant functions, but their relatively low stability affects their bioavailability. The Maillard reaction can improve the functional properties of proteins, thus increasing the stability of loaded active substances. However, the Maillard reaction has several problems, such as a long reaction time and high energy consumption, ultrasound may shorten the reaction time and increase the grafting efficiency of the Maillard reaction through cavitation and mechanical effects. Therefore, this study explored the influence of ultrasound on the structure and functional properties of glycosylated potato protein (PP) through ultrasound-assisted glycosylation and investigated both the encapsulation effect of ultrasound-assisted glycosylated proteins on PSPA and the storage stability of the resulting nanocomplexes. Compared with that of the control sample, the degree of grafting of the 300 W/L ultrasonic power density sample increased from 29.75 % to 42.31 % (p < 0.05), and its solubility increased from 42.25 % to 63.57 % (p < 0.05). The cavitation produced by ultrasound transformed the ordered secondary structure (α-helix, β-sheet) of proteins into a disordered structure (β-turn, random coil), making the structure looser and more conducive to the progress of the reaction. In addition, the thermodynamic parameters of the binding process indicated that protein and anthocyanins were bound mainly by hydrogen bonds. Both PP and glycosylated PP improved the encapsulation rate of PSPA to a certain extent. Moreover, the antioxidant stability of 300-PP-PSPA increased to 34.93 % after 14 d of storage, compared to 27.95 % in the control group (p < 0.05). During the in vitro intestinal simulation digestion stage, the cumulative release rate of 300-PP-PSPA was 7 % and 48 % lower than that of PP-PSPA and unencapsulated PSPA, respectively. This finding also indicated that glycosylated PP-encapsulated PSPA can achieve slow and continuous release. In conclusion, the use of ultrasound-assisted glycosylated protein-anthocyanins nanocomplexes is a promising method for improving the stability and bioavailability of anthocyanins.