Controlled coacervation of antioxidants as a way to produce functional food ingredients with increased bioavailability

Relevance. The polyphenolic substance curcumin is a rather well-studied and gaining popularity plant antioxidant. To date, quite a few pharmacological properties that curcumin is capable of demonstrating in living organisms are known. However, the barrier factors for the bioactive action of curcumin are its extremely pronounced hydrophobicity, chemical instability, and the ability to be significantly degraded by gastrointestinal enzymes. All of this requires the search for approaches to minimize the negative effects on curcumin when it is used as a food functional ingredient. Encapsulation of curcumin in natural biopolymers, including by complex coacervation, could be one such approach. The study was based on an assessment of the possibility of using complex coacervation to obtain a curcumin-based functional ingredient with pronounced antioxidant properties. 

Methods. Curcumin was chosen as the object of study, beef gelatin and citrus pectin were used for the encapsulating system. Initially, the yield of protein-polysaccharide capsules at different pH values was evaluated. The efficiency of encapsulation of curcumin in protein-polysaccharide capsules with a different ratio of "curcumin — gelatin" was evaluated. The antioxidant properties of curcumin in its original form and encapsulated were studied, and the preservation of these properties after the process of digestion was evaluated. 

Results. The results showed that the process of protein-polysaccharide capsule formation was quite effectively controlled by changes in the pH of the system. Thus, a pH jump from 7 to 3 achieved the highest value of the protein-polysaccharide capsule yield (more than 70 %). The efficiency of loading curcumin into gelatin-pectin capsules was maximal when using a "curcumin — gelatin" ratio of 1:1. However, even the maximum encapsulation efficiency did not exceed 50%. At the same time, the use of encapsulation technology made it possible to preserve the antioxidant properties of curcumin. The loss of antioxidant activity of unencapsulated curcumin after the process of in vitro digestion was practically 50 % compared to the initial non-encapsulated form. The antioxidant activity of curcumin encapsulated in protein-polysaccharide capsules remained at the level close to the initial form.  The results obtained confirmed the possibility and feasibility of using the proposed approaches to obtain food ingredients with antioxidant properties based on curcumin encapsulation. The research was supported by a grant from the Russian Science Foundation 22-76-00059. 

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