5. Opportunity and challenge of tannin extraction

Tannins commonly exist in the nature, and they are bioactive diversity such as antioxidant, antifungal, anti-virus, anti-inflammatory, and anti-parasitic. Tannins are used in numerous fields, for example, feed of ruminants, monogastric animals, etc. Each method of tannin extraction has difficult and easy points, for example, high investment, difficult operation, or popular equipment. However, all methods are based on the dynamic and static maceration. All modern techniques are supporting and improving traditional extraction methods. At the same time, the demand using tannins in the market is very huge. Therefore, opportunity of tannin extraction and commercializing tannins are great.

However, large-scale production of tannins greatly differs in comparison to small-scale production. The content, structure, and activity of tannins in plants depend on growth time of plants, habitat place of plants, species, the parts of the plants, etc. [78]. Hence, stabilizing the content, structure, and activity of tannin is difficult. Tannin content is decreased in storage time of materials. The results of the tannin activities are mainly at the laboratory level. At the same time, modern method of tannin extraction needs high investment, good manpower, and great market. There are some challenges in tannin extraction and its application into the life.

#### 6. Conclusions

The chapter presents the position and the role of tannins in plant cell structure, the harvest and treatment of plant materials, the opportunities, and the challenges of tannin extraction from plants to apply into various fields. Specially, traditional and modern methods of tannin extraction are also discussed specifically including the extraction techniques, the advantages and the disadvantages of the method, the mechanism of the extraction process, the solutions to efficiency improvement of tannin extraction, some experimental parameters of tannin extraction, some conversion process in the extraction, mathematical model of transformation, and kinetics of extraction process.

necessary [68]. The effectiveness of tannin extraction mainly depends on ionic strength [75], ions in solution [76], and characters of proteins and tannins. Some problems on technology need to consider before large production, for example, the price of enzymes, hydrolyze capacity, and operating conditions of enzymes [68].

A part of algae leave Sargassum olygocystum after being treated at 60°C with 0.3% enzyme cellulase.

A part of algae leave Sargassum olygocystum after being treated at 50°C with 0.3% enzyme cellulase.

A part of algae stem Sargassum olygocystum after being treated at 40°C with 0.3% enzyme Viscozyme L.

Tannins - Structural Properties, Biological Properties and Current Knowledge

Gamma-assisted extraction is a new method using Co-60 gamma radiation for tannin extraction. Co-60 gamma radiation increases the effectiveness of the tannins from Anacardium occidentale [77]. However, this method still needs more study to apply, and expanding ability in large scale also entails many legal issues. For tannin extraction, materials can be directly irradiated by gamma radiation, materials are then soaked in specific solvent, or the mixture of materials and solvents is directly irradiated by gamma radiation. Radiation dose of 5–25 kGy is concordant with

4.11 Gamma-assisted extraction

Figure 3.

Figure 2.

Figure 4.

68

tannin extraction from brown algae.

The presented extraction methods have the advantages and the disadvantages, but they can be used effectively in tannin extraction from plants. The methods of tannin extraction should continue to be improved to bring higher efficiency.

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