Tiếng Anh Tiếng Việt



Vietnam – one of the global players in seaweed production – is increasingly focusing on in-country processing of the raw material. Short supply chains and state-of-the-art processing units guarantee high quality hydrocolloids such as agar, semi-refined carrageenan and refined carrageen

Vietnam seems to be a hidden gem when it comes to hydrocolloids. For decades most of the raw material produced in Vietnam has been exported. Only a few players were involved in adding value in Vietnam and processing dried seaweed to agar and carrageenan domestically.

In the last couple of years, the processing industry in Vietnam became very dynamic and several new players got involved in processing seaweed to hydrocolloids. In addition, the Vietnam processing industry is more and more focusing on exporting agar and carrageenan.

The shift from exporting dried seaweed as a raw material to exporting processed agar and carrageenan from Vietnam will have an impact on global supply chains for hydrocolloids. Importers of agar and carrageenan in Europe will, for example, have to rethink their supply chains and mitigate risks since other processing countries won’t be in the position to have unlimited access to the raw material anymore.

At the end, importers of hydrocolloids benefit from this shift. A simplified and shorter supply chain guarantees not only a better product traceability and a lower carbon footprint. Vietnam processors are also in a better position to work with seaweed farmers on quality standards and cultivation practices, thus ensuring a stable


The following chapter gives an overview of the different types of seaweed, the seaweed production and cultivation methods in Vietnam as well as information about production areas and the potential of seaweed farming in Vietnam.

2.1          Seaweeds as products of aquaculture

Aquaculture enterprises are firmly established as the foundation of global seaweed value chains. The Vietnam seaweed industry is based almost entirely on farmed macroalgae. This reflects a global situation where seaweed production is dominated by marine macroalgae cultivated both in marine and in brackish waters. According to FAO data, cultivation accounted for almost 96 percent of global seaweed production with algae collected from the wild accounting for a steadily diminishing percentage of production and currently accounting for 4 percent.

2.2          Classification of seaweed

Marine macroalgae, better known as seaweeds, are algae which – in contrast to microalgae or phytoplankton – are visible to the naked eye. Seaweeds can be classified according to their pigmentation, use or colloid content.


The four main groups of marine macroalgae are:

a)            Red algae or Rhodophyta

b)            Brown algae or Phaeophyta

c)            Green algae or Clorophyta

d)            Blue-green algae or Cyanophyta


Whereas some of the green and blue-green algae can be used in the human food industry as vegetables or salad ingredients, the different types of brown and red algae are used in the human and pet food industry for its colloid content. Thus, seaweed from Rhodophyta and Phaeophyta is the raw material for the production of hydrocolloids. They are widely used in the food and non-food industry as thickeners, gelling agents and stabilisers.

The hydrocolloids which can be obtained from the different types of red macroalgae are agar and carrageenan. Different types of brown seaweed can be processed to alginate. Depending on the colloid content and therefore on the type of seaweed which is used for the production of hydrocolloids, also the division of marine macroalgae into agarophytes, carrageenophytes and alginophytes exists.

Out of seaweed, Vietnam is producing especially the following three hydrocolloids: Kappa carrageenan, iota carrageenan and agar. The raw material for these three hydrocolloids are mainly three different types of seaweed: Kappaphycus alvarezii, Eucheuma denticulatum and Gracilaria, which all classified as “red algae” or Rhodophyta. Table 1 shows the hydrocolloids and the scientific names and trade names of the respective raw materials.

Carrageenan is labeled according to the way it has been produced. There is a division in refined and semi-refined carrageenan.

2.3          Seaweed cultivation

Marine marcoalgae can easily be cultivated in coastal areas. Quite often, cultivation of tropical seaweed is conducted in shallow water close to the beach. Seaweed extracts the nutrients provided from the water. It is accounted for as non-fed aquaculture. Successful seaweed cultivation can not take place close to big industrial zones or harbours. Remote areas with little pollution will provide a seaweed of better quality. Selecting an appropriate site, is a key factor to success. Influencing parameters are the following:

•             Water quality parameters: Sufficient supply of nutrients, water salinity at 28–34 part per thousand (ppt), water temperature between 26–32 C, pH level between 7–8.5, water movement (for E. cottonii slow to moderate water flow levels; E. spinosum moderate to strong water flow levels)

•             Climate: Availability of sunlight, no storms, no strong winds

•             Oceanography and environmental aspects: Substrates (for E. cottonii grows on sandy-corally to rocky substrates; E. spinosum can be cultivated on sandy-morally to rocky substrates) , no big waves, free from pollution, away from big shipping  lines


Different cultivation methods for agarophytes (gracilaria) and carrageenophytes (E. cottonii and E. spinosum) exist. The method which is used by the Vietnam seaweed farmer depends on costs for material involved, climate and tradition of use.

Gracilaria can be cultivated on lines, ropes or nets, in ponds or tanks, in open waters on the bottom of bays, reef flats or estuaries. The cultivation of Gracilaria in ponds, together with shrimp or other fish is quite successful in Vietnam. It is known as the mixed farming method. The impurities released from the fish, are used as nutrients by the seaweed.

For E. cottonii and E. spinosum, three different methods can be employed: Off-Bottom method, floating raft method and long-line method.

Description of Wooden stakes are driven method into the sea bottom in a straight row. Between the stakes, ropes and seedlings are attached. A raft made out of bamboo contains several ropes on which seedlings can be at- tached to. The raft is se- cured with a sack of sand etc.Suitable method for cul- tivation areas with waves in deeper areas   A long rope is suspended by floaters such as empty plastic bottles. On that rope the seedlings can be attached.

In Vietnam, the long-line method is widely used due to its lower material costs and the ease of implementati- on. Seedlings can be attached to the ropes in different ways. Most commonly plastic strings – also known as tie-ties– are used. Small parts of them stay in the raw material and may not be detected before seaweed processing. Blue or black specks (depending on the original color of the plastic string) can be easily seen in a white powder. Taken into account, that the obtained processed seaweed product is intended for human consumption, it goes without saying that the food product should be plastic-free. Instead of tie-ties, other farming technologies such as the Made Loop method exists. For this easy to apply method the seedlings are attached to lines instead of plastic strings. To mitigate supply chain risks, purchasers should request from their suppliers that the raw material comes from tie-tie free farms.


Basically, there are two different methods how to reproduce seaweed. In the vegetative reproduction process, one seaweed seedling is simply grown to an appropriate size for harvesting and then cut into small pieces. These pieces will be used as new seedlings for the next cultivation period. This type of reproduction method is the most common among Vietnam seaweed farmers.

The other method is known as generative process. The life cycle of red algae is divided in an alternation of generations, also known as metagenesis. In one generation, sporophytes can reproduce themselves by releasing spores which grow in the generative process described above. In the next generation, it is the gametophyte who becomes fertile, releases sperm and eggs that together form new sporotypes.

It takes approximately 45 days from seedling to harvest to obtain a high-quality raw material which gives a good gel strength. With new reproduction methods such as tissue-culture, this time can be reduced to 30 days.


All seaweed production from Vietnam is based on genera that are indigenous to the archipelago but cultivars move freely among regions of northeast Asia so it is impossible to definitively trace their origins. Most cultivars have been selected by farmers from natural populations but some are have passed through tissue culture laborato- ries of research institutions on their way to commercial development.

The predominant Vietnam seaweed crops are Kappaphycus alvarezii (cottonii of the trade) and Kappaphycus striatus (sacol of the trade). Virtually all production is sun-dried; then sold as raw material for the production

of kappa carrageenan. At least 50 % of Kappaphycus crops are exported to China; about 20 % are processed by domestic processors and the balance is sold to carrageenan manufacturers in the Philippines and other countries. Carrageenan is similar in characteristics between the species but some processors differentiate between them.

During early years of seaweed farming in Vietnam K. alvarezii cultivars of various origins dominated production volume but the K. striatus cultivar known as “sacol” is increasingly spreading throughout the archipelago. This spread is attributed to apparent resistance of the sacol cultivar to seasonal temperature impacts. The production of Eucheuma denticulatum (spinosum of the trade) accounts for at least 200,000 tons of fresh production per annum. It serves mainly as a source of iota carrageenan but an appreciable quantity is subjected to solar “bleaching” and sold for direct consumption as sea vegetables; mainly to China. Most spinosum is exported as raw, dried seaweeds (RDS) but production of semi-refined iota carrageenan by domestic processors is a growing trend.


The production of farmed Gracilaria species is mainly from ponds where it is often grown along with prawns and/ or milkfish. Most of the crop is processed into agar by domestic processors. Crop production is estimated to be at least 500,000 wet tons per annum.. Increased utilization of available pond areas would permit a major production increase. There are also opportunities to farm Gracilaria species in the sea.

Projects are underway in Vietnam to extend cultivation to genera of carrageenan, agar and other seaweeds in addition to the ones already developed. Sargassum, a “brown” seaweed that is harvested from wild populations, is being considered for farming. Also there is expanding cultivation of seaweeds as sea vegetables including Caulerpa and there are projects developing the production of several genera of microalgae. Vietnam is on track to satisfy much of the world’s growing need for algal biomass.

2.5          Quality, traceability and standards of seaweed in Vietnam

Seaweed quality varies widely among sources and it can range from the excellent to the unacceptable. Quality received by buyers is a reflection of their purchasing strategy. Full traceability to seaweed sources is feasible in Vietnam for any buyer who seeks it. All quality problems have solutions that can be readily implemented.

Traceability and information flow in Vietnam are facilitated by assistance through government agencies and trade organizations as well as through internet information sites (e. g. jasuda.net) and wireless communication systems. A high proportion of value chain players, including farmers, have mobile phones that they use to trade information nationally and with neighboring seaweed producing countries.

In addition to quality standards established between buyers and sellers, Vietnam producers are applying both international and national standards. The Standar Nasional Vietnam” (SNV) was developed to cover all products and processes related to production of seaweed and seaweed products. The SNI are harmonized with inter- national standards that are applied to export products including CCRF, CITES, ISO, HACCP and SPS agreements.

2.6          Social and economic dimensions of seaweed farming in Vietnam

Almost all Vietnamn seaweed production takes place in coastal villages that effectively control adjacent nearsho- re waters. Seaweeds have proven to be lucrative cash crops for regions where cash can be hard to come by. Most seaweed enterprises are community-based family businesses that are clustered into producer groups. On average, individual household income from part-time seaweed farming is about 500 US$ per month based on production of about 5 wet tons of seaweed per month. This income is above the national average and it can be increased by those who wish to expand production on a full-time basis. This cash income directly benefits an estimated 70,000 families across Vietnam and indirectly benefits entire communities through multiplier effects.


The most important processed seaweed products in Vietnam are the hydrocolloids agar and carrageenan. The following chapter gives an overview about the raw material which is used for the production, the processing technologies of agar and carrageenanand their applications.


3.1          Agar


Agar is a natural hydrocolloid extracted from seaweeds all belonging to the Rhodophyceae class (red algae). Two genera, Gelidium and Gracilaria, account for most of the raw material used for the extraction of agar.

Extraction of Gelidium species gives the higher quality agar measured as gel strength. However, nearly all Gelidium used for commercial agar extraction still comes from natural resources in the wild, resulting in a certain limitation of supply. Gelidium is a small, slow growing plant and while efforts to cultivate it in tanks and ponds have been biologically successful, it has so far not been proved to be economical feasible.

In the past, Gracilaria species were once considered unsuitable for agar production because the quality of the agar was considered inferior due to lower gel strength. But in the 1950s, it was found that pre-treatment of the seaweed with alkali before extraction although lowering the yield gave a good quality agar with higher gel strength.

This allowed expansion of the agar industry, previously limited by the supply of Gelidium available, and led to the harvesting of a variety of wild species of Gracilaria in countries such as Vietnam.

Cultivation methods were then developed, both in ponds and in the open waters of protected bays. Today the supply of Gracilaria in Vietnam is mainly cultivated. The country has become one of the largest and best positioned supplier of agar to the food industry worldwide.


The basic principle in all processes for the production of agar is simply an extraction of the agar from the seaweed after it has been cleaned and washed. This step is necessary to remove any foreign material such as sand, salts, sticks and any debris which may appear naturally with the seaweed.

The agar is extracted by heating in water for several hours. During this process the agar dissolves in the water. The mixture is then filtered to remove the residual seaweed. The hot filtrate is cooled and forms a gel which contains about one percent agar. The gel is broken into pieces and washed to remove all soluble salts, and, if necessary, it can be bleached to reduce the color. After this step, water is removed from the gel, either by a freeze-thaw process or nowadays more likely by squeezing it under pressure. Remaining water can then be removed by drying. The final step is to mill the agar to a suitable and uniform particle size.

There are some differences in the treatment of the seaweed prior to extraction, depending on the type of seaweed. With Gelidium the process is simply washing with plain water or sometimes with a little acid to facilitate extraction. Whereas Gracilaria must be treated with alkali before extraction to obtain the optimal gel strength. For the alkali treatment, the seaweed is heated in 2–5 percent sodium hydroxide at 85–90 °C typically for one hour. After the removal of the alkali, the seaweed is washed with water, and sometimes with weak acid to neutralize any residual alkali.

For the hot-water extraction, Gelidium is more resistant. The extraction of this type of seaweed takes often place under pressure (105–110 °C for 2–4 hours) as this is faster and gives higher yields. Gracilaria is usually just extracted with water at 95–100 °C for 2–4 hours. The hot extract is given a coarse filtration to remove the seaweed residue, filter aid is added and the extract is passed through a filter press equipped with a fine filter cloth to ensure removal of any insoluble products.


The name “agar” or “agar-agar” originates in Vietnam. The widespread use of agar is caused by its ability to form gels, and the unique properties of these gels. Agar dissolves in boiling water and when cooled it forms a gel between 32 and 43 °C, depending on the seaweed source of the agar. In contrast to gelatin gels, that melt around 37 °C, agar gels do not melt until heated to 85 °C or higher. In food applications, this means there is no requirement to keep them refrigerated in hot climates. This large difference between the temperature at which a gel is formed and the temperature at which it melts is unusual, and unique to agar. Many of its applications take advantage of this difference.


About 90 % of the agar produced is intended for food applications, with the remaining 10 % being used for bacteriological and other biotechnology applications. Agar has a preferential status all over the world: It is derived from a vegetable source, easy to use without any knowledge in chemistry needed and most importantly, agar has never received any negative comments. In addition, agar is tasteless and does not interfere with the flavors of foodstuffs, in contrast to some other gelling agents. 

In the baked goods industry, the ability of agar gels to withstand high temperatures means agar can be used as a stabilizer and thickener in pie fillings, icings and meringues. Cakes, buns, etc., are often pre-packed in various kinds of modern wrapping materials which often stick to the product, especially in hot weather. By reducing the quantity of water and adding some agar, a more stable, smoother, non-stick icing for the product is obtained.For the same reasons, one of the larger application for agar in North America is on donuts. Nowadays, agar from Gracilaria are often preferred in confectionery with a very high sugar content, such as fruit candies.

In Asian countries, agar is a traditional and popular component of jellies. Probably, this has its origin in the early practice of simply boiling seaweed, straining it, adding flavors to the liquid before it cooled and formed a jelly. It is believed that this was the way agar was invented as a gelling agent already several hundred years ago. A popular Japanese sweet dish is mitsumame It consists simply of cubes of agar gel containing fruit and added colors. It can be canned and sterilized without the cubes melting.

Agar is also used in gelled meat and fish products, and is preferred to gelatin because of its higher melting temperature and gel strength. It also improves the texture of dairy products like cream cheese and is often used in yoghurt, especially in North America.

Unlike starch, agar is not readily digested and therefore adds little calorific value to food. In addition, it is described as a high fiber additive. Agar is often used in vegetarian foods such as meat substitutes.

In the pharmaceutical industry, agar is used as a growth substrate to obtain clones or copies of particular plants in nurseries. Bacteriological agar is used in testing for the presence of bacteria. It is specially purified to ensure that it does not contain anything that might modify bacterial growth. The highest quality agar and its derivative agarose is used for biotechnological applications of DNA research and gel electrophoresis and diagnostic purposes.

3.2          Carrageenan


The original source of carrageenan was the red seaweed Chondrus crispus collected from natural resources along the west coasts in Europe and the east coast provinces of Canada. As the carrageenan industry expanded, the demand for raw material began to strain the supply from natural resources, although Chondrus had been supple- mented by species of Gigartina from Spain and especially Chile.


The introduction of cultivation of species of Eucheuma in the Philippines during the 1970s provided the carra- geenan industry with a much enhanced supply of raw material. A further advantage of this cultivated material was that one species contained almost exclusively a particular type of carrageenan (kappa-carrageenan) while a second species contained predominantly a second type (iota-carrageenan), each type having its own particular applications. Chondrus and Gigartina contains a mixture of two types (kappa and lambda) that could not be separated during commercial extraction. Today most of the raw material comes from the two Eucheuma species originally cultivated in the Philippines, but their cultivation has now spread to some other warm-water countries especially Vietnam where the natural conditions are most favorable.


According to the production process, there is a differentiation between refined and semi-refined carrageenan. Refined carrageenan is the original carrageenan. For many years it was the only carrageenan permitted in food products.

The main difference between refined carrageenan (RC) and semi-refined carrageenan (SRC) is that SRC contains the cellulose that was in the original seaweed while in refined carrageenan this has been removed by filtration during the processing. Refined carrageenan will therefore give a clear solution, while PNG gives a cloudy solution limiting the applications of SRC. For both products the seaweed is washed to remove sand, salts and other foreign matter.

Production of refined carrageenan

After the seaweed has been cleaned, for refined carrageenan it is then heated with water containing an alkali for several hours. This step is necessary to extract the carrageenan and at the same time increasing gel strength in the final product. The seaweed that does not dissolve is removed by centrifugation or a coarse filtration, or a combina- tion. The solution is then filtered again in a pressure filter using a filter aid in order to ensure complete removal of any insoluble particles.

Then the dissolved carrageenan has to be recovered. There are two methods for isolating it. Traditionally, an alcohol-precipitation method is generally used as carrageenan is insoluble in high-alcohol concentrations. This method has the advantage that it can be used for all types of carrageenan.

Another method similar to the method used for making agar was later applied also to the refined carrageenan production. Therefore, some agar processors in Vietnam are now using their equipment and similar techniques to produce refined kappa carrageenan as well. This gelling method is most suitable for kappa carrageenan. The gel is mainly dehydrated by squeezing as for agar. But it could also be recovered with a freeze-thaw process.

The gel method relies on the ability of kappa carrageenan to form a gel with potassium salts. The gel may be formed in various ways. The most common method is to force water out of the gel by applying pressure to it, using similar equipment to that used for agar. After squeezing for several hours the sheets of gel are chopped, dried in a hot air dryer and milled to an appropriate particle size. Inevitably, with the gel method the product contains some potassium chloride.

Production of  semi-refined carrageenan

Also for the production of semi-refined carrageenan, the seaweed needs to be washed before further processing. For the production of SRC the carrageenan is never actually extracted from the seaweed. The principle is rather to wash everything out of the seaweed that will dissolve in alkali and water and leave the carrageenan and other insoluble matter behind. This insoluble residue, consisting largely of carrageenan and cellulose, is then dried and sold as SRC. Because the carrageenan does not need to be recovered from the solution, the process is much shorter and cheaper.

In the production of SRC the washed and cleaned seaweed is heated in an alkaline solution of potassium hydroxi- de for about two hours in order to increase the gel strength of the carrageenan in the seaweed and at the same time dissolve any soluble protein, carbohydrate and salts without dissolving the carrageenan. After the alkali treatment and water washing, the product is chopped and dried in a closed dryer which will keep the bacterial count low enough to make a human-food grade product.

Alkaline treated Eucheuma cottonii seaweed not produced according to the requirements for food applications is normally referred to as ATC. Often it is simply sold as chips (ATCC) which are typically used for the extraction of refined carrageenan, for canned pet food or non-food applications.


Carrageenan is one of the most diversified food additives due to the broad range of gelling and emulsifying properties – ranging from a soft elastic to a very brittle gel – and the ability to substitute to a large degree both gelatin and agar.

In Europe, both refined and SRC are permitted in human food:

•             Refined carrageenan (RC) is labeled “carrageenan”

•             Semi-refined carrageenan (SRC) is labeled “processed Eucheuma seaweed” or “PES”,

Some years ago, the FDA declared SRC suitable for the use in human food in the USA and to be labelled as “carrageenan” with the same status as that of the refined carrageenan product.

Carrageenan is used in processed foods for stabilization, thickening and gelation driven by the consumers’ need for convenience, appealing food textures, advances in food processing, and new food products. It is used worldwide to enhance ice creams eliminating formation of ice crystals, chocolate milk, custards, cheeses, jellies, confectionary products, meat and for clarification of beer and wine.


Carrageenan has a high reactivity with a range of materials including and most importantly milk proteins so it can be efficient at low concentrations in dairy products to prevent fractionation of milk constituents. A major applicati- on is in chocolate milk where carrageenan is able to keep the cocoa particles in suspension.

Today, processed meat and poultry products offer the largest application for carrageenan worldwide with its many properties such as water binding and retention, fat substitution, control of syneresis and dehydration and enhancement of juiciness. Improved slice ability is especially important in high-speed slicers.

Kappa carrageenan obtained from the seaweed E. cottonii needs potassium salt to gel. It then results in brittle gels. Kappa carrageenan is soluble in hot water and shows synergistic effect with other food additives like locust bean gum, guar gum and xanthan.

Iota carrageenan gels most strongly with calcium salts, resulting in elastic gels with no syneresis. The gels furthermore freeze-thaw stable. Iota carrageenan is obtained from the seaweed E. spinosum.

Carrageenan is also widely used in the canned pet food industry and in some non-food applications such as toothpaste and air fresher gels.

3.3          History of seaweed processing and future outlook

Seaweed farming and processing technologies developed elsewhere during the 1970s and 1980s. They were commercially applied in Vietnam about a decade later during the 1980s and 1990s. This occurred as wireless communication technology and developing transport links enabled value chain development across the thous- ands of islands that span three time zones in the Vietnamn archipelago. Vietnam emerged as the major producer of tropical seaweeds by the mid-2000s.

Both international and domestic companies are involved in producing and processing Vietnamn seaweed crops. There are opportunities for global value chain players to participate in Vietnamn seaweed production develop- ment at several value chain levels.

As of 2014 most Gracilaria was made into agar by national processors and was sold into domestic markets but most Kappaphycus and Eucheuma was exported as raw-dried seaweeds. Processors based in Vietnamn are capable of making refined and semi-refined kappa carrageenan and semi-refined iota carrageenan and can do so with competitive production costs. At least one major end user discovered decades ago that SRC from Vietnamn producers is cost effective but most solution providers retain legacy links to processors outside Vietnam even though they are processing Vietnamn-sourced seaweed. Vietnamn processors are therefore striving to penetra- te such global markets for their carrageenan and agar building block products.


Currently, the list of the Vietnamn Seaweed Industry Association (ASTRULI) comprises of 16 seaweed processors. However, the country has listed a total of 37 national seaweed processing industries. They are distributed among 11 provinces.

The transition is being catalyzed by public and trade organizations including government ministries, international assistance organizations and research consortia in Vietnam; and innovative enterprises building strategic business alliances among domestic and international value chain stakeholders.

Initiatives include development of more productive agronomy practices; implementation of diversified, ecosystem approaches to aquaculture within coastal communities; and innovative new processes and products.

At the farm level step-change innovation is possible as more efficient farming methods are combined with advanced post-harvest treatment. Lower-labor farming methods not only reduce production cost but also open up large areas for farm development by enabling planting in deeper waters.

Processing that commences with live seaweeds at the farm level greatly enhances seaweed value by enabling effective recovery of seaweed solids and seaweed juice that feed into multi-stream, zero-effluent (MUZE) proces- sing systems. Systems such as these make it feasible to develop remote, unpopulated areas using a ‘plantation’ approach to seaweed aquaculture systems. In populated regions developing technologies enable the implementa- tion of ‘nucleus-plasma’ systems, such as those successfully operated at large scale in Vietnam poultry and prawn production.

International involvement in such developments is already beginning in Vietnam. There is ample opportunity for European companies to get involved as a development partner as Vietnam evolves from technology follower to technology leader.