Training Manual on Gracilaria Culture and Seaweed Processing in China

Table Of Contents

Prepared for the
Gracilaria Culture and Seaweed Processing Training Course
conducted by the
Zhanjiang Fisheries College
People's Republic of China
and organized by the
Regional Seafarming Development and
Demonstration Project (RAS/90/002)

August 1990

Training Manual 6


Gracilaria is a group of warm water seaweeds. There are more than one hundred species in the world, some of which have very important economic value. Gracilaria is used as food and in the preparation of food products. It is also an important raw material in agar-agar production. At present, the world's annual output of Gracilaria is about 30,000 tons, dry weight, most of which comes from natural production. For example, the natural production in Chile, Argentina, and Brazil accounts for one third of this total output. With the increasing demand for Gracilaria, greater attention has been focused on the development of its artificial culture by many countries, especially those in Southeast Asia. China is the earliest country that artificially cultured Gracilaria. Today, the culture area in South China is about 2,000 ha producing 3,000 tons dried material annually. Taiwan produces 1,000 tons dried Gracilaria yearly from 400 hectares under cultivation.

Nowadays, Gracilaria is cultured mainly using the following methods: bottom culture, raft culture, stake-rope culture and pond culture. Pond culture can be divided into two systems, monoculture and polyculture with shrimp and other species. The varieties of culture methods can be adapted for different areas.

In view of the importance of Gracilaria as a seafarming commodity, the National Coordinators of the Regional Seafarming Project recommended the dissemination of its culture and processing technology, through a regional training and demonstration activity, as a means to further increase the opportunities to develop the seafarming industry of the region.

This manual has been prepared for the training course on Gracilaria culture under the Regional Seafarming Development and Demonstration Project (RAS/90/002) to be held at Zhanjiang Fisheries College, Zhanjiang, China in August, 1990. The training course includes processing of seaweeds, thus the manual devotes a chapter on the properties, manufacture and application of agar, algin and carragenan.

The manual was edited by Professor Wu Chaoyuan who also reviewed all the manuscripts, Professor Ji Minghuo, Mrs. Li Renzhi, Associate Professor and Mr. Wang Xiaohang, Associate Professor, all of the Institute of Oceanology in Qingdao; Professor Liu Sijian of the Zhenjiang Fisheries College; and Mr. Miao Zenian, Associate Professor of the Yellow Sea Fisheries Research Institute, Qingdao. Mr. Sun Jimin of the Yellow Sea Fisheries Research Institute computer-processed the text and images. The staff of the Seafarming Development Project in Bangkok provided the final editing and prepared the manual for publication.

We would like to acknowledge the support of the Intergovernmental Network of Aquaculture Centres in Asia and the Pacific (NACA), the Institute of Oceanology of Academia Sinica, the Yellow Sea Fisheries Research Institute under the Chinese Academy of Fishery Sciences, and the Zhanjiang Fisheries College in the organization and implementation of the training course including the development and publication of this manual.

 Department of Aquatic Products
 Ministry of Agriculture
 China, May 1990

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1. Characteristics of the Genus Gracilaria and features of several important species in China

a. Characteristics of Gracilaria

2. Life History of Gracilaria

3. Effects of Environmental Factors on the Growth of Gracilaria


1. Selection of Culture Sites

a. Criteria for Selecting Inside Bay Sites

b. Criteria for Selecting Offshore Sites

c. Criteria for Selecting Ponds as Farm Sites

2. Spore Collection and Sporeling Culture

a. Collecting Spores and Culturing Sporelings in the Sea

b. Preparation of Mature Fronds of Gracilaria

c. Management of the Mature Fronds and Collection of Spores

d. Spraying of Spore-filled Water

e. The Germination of Spores

f. The Culture of Sporelings

g. Collecting Spores and Culturing Sporelings Indoor

3. Gracilaria Cultivation Methods

a. Scaterring Sporeling Culture

b. Net Culture in Tidal Zone

c. Raft Culture in Tidal Region

d. Raft Culture in Shallow Sea

e. Pond Scattering Culture

4. The Approach for Increasing the Yield of Gracilaria

a. Cutting Method

b. Increase Yield by Fertilization

c. Increasing the Yield of Gracilaria with Growth Hormone

5. Harvest and Simple Processing Methods

6. Distribution, Utilization and Conservation of the Natural Resources of Gracilaria

a. The Distribution of the Natural Resources of Gracilaria

b. Utilization of the Natural Resources of Gracilaria

c. Measures to Conserve the Natural Resources



1. Introduction

A. History

B. Definition

2. Agarophytes and Agar Production

3. Chemistry of Agar

4. Properties of Agar

A. Gelation

B. Mechanism of Alkali Modification of Agar

C. Gel Strength

D. Gelling and Melting Temperatures

E. Viscosity and Molecular Weight

F. Compatibility

5. Manufacture of Agar

A. Gelidium Agar

B. Gracilaria Ahar

C. Manufacture of Agarose

6. Application of Agar

A. In Food Industry

B. Pharmaceutical Uses

C. Biomedical Application of Agarose


1. Introduction

2. Carrageenophytes and Carrageenan Production

3. Chemistry of Carrageenans

4. Properties of Carrageenans

5. Manufacture of Carrageenans

A. K-Carrageenan

B. -Carrageenan

C. Semi-Processed Carrageenan

6. Application of Carrageenans

A. In Food

B. Pharmaceutical Uses

C. Other Industrial Uses


1. Introduction

2. Alginophytes and Algin Production

3. Chemistry of Alginates

A. Seasonal Variations in the Content and Viscosity of Alginate

B. Structure of Alginic Acid

C. M/G Ratios

4. Properties of Alginate

A. Solubility

B. Viscosity and Molecular Weight

C. Stability

D. Gelation

E. Ion-Exchange

5. Manufacture of Alginates

A. Calcification Process

B. Alginic Acid Process

C. Preparation of Propylene Glycol Alginate (PGA)

D. Preparation of G-Rich Alginate

6. Application of Alginates

A. In Food

B. In Pharmaceutical and Cosmetics

C. Industrial Applications