Hydrophobic‐assembled curcumin–porcine plasma protein complex affected by pH

Curcumin, the active substance of turmeric: its effects on health and ways to improve its bioavailability

Turmeric (Curcuma longa L.) is a spice utilized widely in India, China, and Southeast Asia as an aromatic stimulant, a food preservative, and coloring material. The commonly used names of turmeric are castor saffron, turmeric, and saffron root. Turmeric is a yellow-orange polyphenolic natural substance derived from C. longa rhizomes. It has been used to treat common inflammatory diseases, tumors, biliary diseases, anorexia, cough, topical wounds, diabetic injuries, liver disorders, rheumatism, and sinusitis. Extensive studies on the biological properties and pharmacological consequences of turmeric extracts have been conducted in recent years. Curcumin, the primary yellow biocomponent of turmeric, has anti-inflammatory, antioxidant, anticarcinogenic, antidiabetic, antibacterial, antiprotozoal, antiviral, antifibrotic, immunomodulatory, and antifungal properties. Defense assessment tests showed that curcumin is tolerated well at high doses, without adverse effects. Thus, curcumin is a highly active biological material with the potential to treat different diseases in modern medicine. This review article focuses on curcumin's biological characteristics. The most popular methods for curcumin encapsulation are also discussed. Several effective techniques and approaches have been proposed for curcuminoid capsulation, including nanocomplexing, gelation, complex coacervation, electrospraying, and solvent-free pH-driven encapsulation. This review also highlights curcumin's chemical properties, allowing the readers to expand their perspectives on its use in the development of functional products with health-promoting properties. © 2021 Society of Chemical Industry.

pH-shifting encapsulation of curcumin in egg white protein isolate for improved dispersity, antioxidant capacity and thermal stability

Curcumin (Cur) has many functions, such as antioxidant and anti-inflammatory. However, its poor solubility and thermal stability at aqueous solutions limit its application in the food industry. In this study, egg white protein isolate (EPI) was complexed with Cur via a pH-shifting method. The effects of ultimate pH (from 5.0 to 7.0) on the physicochemical properties of the complex were studied. Cur could reach 84.4% encapsulation efficiency at pH 6.0. Meanwhile, the EPI complex could remain stable at pH 7.0 after 30 days and protect Cur from thermal degradation, thereby improving the Cur retention rate with the increasing ultimate pH. Compared with those of EPI and free Cur, the antioxidant capacity of the complex was enhanced effectively. The EPI-Cur complex was certified using UV-vis and fluorescence spectra. The fluorescence results indicated that Cur and EPI are combined through a static quenching and with a strong affinity of 1.8 × 10⁵ M^-1 at pH 6.0. In summary, this work provides a biocompatible and straightforward method for the development of nanoparticles based on egg white protein isolates, which can be used as a promising carrier for insoluble nutritional compounds.