Encapsulation of tannins and tannin-rich plant extracts by complex coacervation to improve their physicochemical properties and biological activities: A review

Abstract

As a major class of dietary polyphenols, tannins are demonstrated to have various health-promoting properties. Although tannins have been widely utilized in food, pharmaceutical and many other industries, the applications of tannins are quite limited due to their poor stability, sensory attributes and bioavailability. Encapsulation helps improve all of these properties. Complex coacervation, one of the most effective encapsulation techniques, is known for its simplicity, low cost, scalability and reproducibility in encapsulation of functional components. In recent years, complex coacervation has been successfully used for encapsulation of tannins and tannin-rich plant extracts. In this article, the research progress in encapsulating tannins and tannin-rich plant extracts by complex coacervation to improve their physicochemical properties and biological activities is critically reviewed for the first time. Encapsulation of tannins and tannin-rich plant extracts can effectively improve their sensory characteristics, stabilities, bioavailability, anti-hypercholesterolemia, anti-diabetic, antioxidant, anticancer and antimicrobial activities. In particular, the enhancement of biological activities of tannins and tannin-rich plant extracts is usually correlated to their improved physicochemical properties imparted by the encapsulation technique. Moreover, we introduce the issues that need to be further resolved in future studies on encapsulation of tannins and tannin-rich plant extracts by complex coacervation.

Keywords:

• Biological activities
• complex coacervation
• nanoencapsulation
• physicochemical properties
• tannins

Author contribution

Xiangquan Zeng: Methodology, Writing-original draft (lead), Funding acquisition. Weibo Jiang, Zhenjiao Du: Writing-review & editing (Supporting). Jozef L. Kokini: Conceptualization, Supervision, Writing-review & editing (Lead), Project administration, Funding acquisition.

Declaration of competing interest

The authors declared no conflict of interest in this study.

Additional information

Funding

Xiangquan Zeng is grateful for the scholarship provided by the China Scholarship Council [CSC Student ID: 201906350061] and the Scientific Research Foundation of Beijing Technology and Business University [Project No: QNJJ2022-10]. Dr. Jozef Kokini’s research at Purdue University, United States, is partly supported by The William R. Scholle Endowment [Grant No: F.00093509.06.001] and USDA [Grant No: 2017-67017-26472].