PRODUCTION, PROPERTIES, AND USES OF ALGINATE

알긴, 알긴산소다로 알려진 해조 추출물의 용도및 적용방법에 관한 기초적인 지식을 정리한다. 관련된 업무에 종사하거나 자료가 필요하신 분들에게 도움이 되기를 바라면서 정리한다.

원료

알긴산소다를 생산하는 원료들은 매우 다양하고, 나라마다 차이가 있다. 다음의 그림을 참조하면 알긴산소다를 생산하기위한 원료들을 지역별로 파악할 수 있다. 중국은 라미나리아가 주종이지만, 양 문제 등으로 칠레 혹은 페루에서 일부의 원료를 수입하여 자생하는 조체와 혼합하여 생산하고 있다. 섬유 가공용 알긴산소다의 경우 이들 원료 조체의 종류에 따라 분자량, M/G비, 유동성, 점도 등 품질이 달라진다. 

특히 M/G비는 조체에 따라 다르고, 대부분의 제조업체에서는 이를 분석할 수 없고, 제조자들도 이를 품질 특성의 조절을 위한 평가 기준으로 수립하지 않고(명월, 쥬다양은 관리를 하고 있는 것으로 파악된다.) 있다. G Block이 많은 조체를 사용하면 칼슘이온의 제거가 쉽지 않고, 유동성도 매우 저하한다.  

---- 작성중

중국산 알긴산소다의 품질 - 날염용 호료

중국산의 경우 이와같은 물성을 이해하고 있는 생산자는 소수이다. 또한 중국산 알긴산소다의 경우, 이와 같은 기본적 노하우가 부재한 업체가 대부분이고, 생산 시 이런 기술적 요소를 관리, 적용하는 업체도 물론 소수이다. 뿐만 아니라 순수 알긴산소다를 생산한 다음 추가적으로 증량제를 넣어 표면 단가를 낮추어 전세계 시장에 뿌리고 있다. 매달 컨테이너 베이스의 상품을 구매하고 있지만 관리하기가 쉽지 않다.

이들 원료별 생산 현황은 다음의 chart와 같다.

Seaweeds can be classified into three broad groups based on pigmentation: brown, red and green. Botanists refer to these broad groups as Phaeophyceae, Rhodophyceae and Chlorophyceae, respectively. Brown seaweeds are usually large, and range from the giant kelp that is often 20 m long, to thick, leather-like seaweeds from 2-4 m long, to smaller species 30-60 cm long.

Alginates are refined from brown seaweeds throughout the world. None of the usual seaweeds for alginate production are cultivated. They cannot be grown by vegetative means, but must go through a reproductive cycle involving an alternation of generations this makes cultivated brown seaweeds too expensive when compared to the costs of harvesting and transporting wild seaweeds. The only exception is for Laminaria japonica, which is cultivated in China for food but the surplus material is diverted to the alginate industry in China.

Alginates from different species of brown seaweed often have variations in their chemical structure, resulting in different physical properties. For example, some may yield an alginate that gives a strong gel, another a weaker gel; one may readily give a cream/white alginate, another may give that only with difficulty and is best used for technical applications where color does not matter.

제조공정

갈조류에서 알긴산소다를 생산하는 공정은 칼슘법과 염산법의 2가지로 대별된다. 그리고 생산자의 노하우에 따라 제품의 품질은 매우 달라질 수 있다. 뿐만 아니라 규모나 기술에 따라 원가도 상이하게 나올정도로 복잡한 단위공정을 거쳐 (약 18~20 단위의 공정이 필요함) 생산되기 대문이다. 일반적인 제조방법은 다음 그림과 같다. 

   

ALGINATES ?

Alginates* were first isolated by Stanford by alkalineextraction of brown algae a process used for iodine extraction.

The use of the brown seaweeds is well-known since ancient times: Chinese people and Romans used themin medicines and cosmetic preparations. Production on an industrial basis started in the United-States around 1930. At the beginning,Alginates were used for the production of canned foods intended for seamen.

• Algin is also the genenc term for salts of alginic acid

STRUCTURE

Alginic acid is a polyuronide made up of a sequence of two hexuronic acid residues: 3-D-mannuronic acid unit and α-L-guluronic acid.

When examining the Haworth formula, it can be observed that the two acid residues involve epimerization at C-5. The only difference is the occurence of the linkage C-5 - C-6, above or below the medium plane of the ring. The bulkiness and the interactions, due to the acid function at C-6, dictate the conformation of the ring and involve the equatorial position of the acid function. The 3-D-mannuronic acid unit adopts always the C conformation and α-L-guluronic acid residue the C conformation.

The investigations by partial hydrolysis carried out by Haug and Larsen and more recently the studies by C NMR Spectra (Nuclear Magnetic Resonance Spectroscopy) show that these two monumer residues do not display a random distribution but occur in blocks containing about 20 units.

homogeneous blocks of mannuronic acid residues M.M.M.M 

homogeneous blocks of guluronic residues G.G.G.G 

alternating blocks of these two acid residues M.G.M.G

Macromolecules are associations of these blocks at various degrees depending on the species used and to a lesser degree the maturity of the seaweed and the area of harvesting. Infrared spectroscopy provides a rough but rapid information regarding the percentage of mannuronic acid residues and guluronic acid units.

The distribution of the monomer residues controls the alginate capacity to form gel. The guluronic blocks have the conformation best suited to the calcium-induced gelation.

Brown seaweeds are found along rocky coasts. They grow along the North atlantic coastline; mainly in the United-States, Great-Britain, France (Brittany) and Norway.

In France, brown seaweeds are harvested along the Brittany coasts. Alginates are essentially extracted from:

Laminaria digitata hyperborea 

Ascophyllum nodosum

 Fucus serratus

These seaweeds display large variations in mannuronic/guluronic proportions.

BOTANICAL SOURCE

ALGINATES EXTRACTION PROCEDURE

All processing stages are based upon the two following properties: alkaline metal alginates are soluble in water, alginic acid and its calcium derivative have very limited solubility in water.

DEMINERALIZATION

The process consists of macerating seaweeds with diluted mineral acid, which allows ion exchange between the calcium of alginate and the hydrogen of the acid used. Thus the alginate contained in the algae is converted to alginic acid by systematic lixiviation, while non-desirable constituants (fucoidine mannitol, mineral salts…) are removed.

ALGINATE EXTRACTION

The demineralized seaweeds are then ground in the presence of an alkali or an alkaline salt which neutralizes alginic acid and converts it to the soluble alginate corresponding to the salt used. The insoluble matters (cellulosic and proteinic components) are removed by filtration, floatation and settling.

COLLOIDS COAGULATION

This is carried out by a mineral acid to the alginate solution. The alginic acid precipitate is then washed and dried.

NEUTRALIZATION e.g. PREPARATION OF THE DIFFERENT ALGINATES

Alginic acid is neutralized with different alkaline bases or basic components according to the type of alginates required. It occurs:

by mixing the components or. by exchange in alcohol. The final product is then dried, milled and sieved to the desired particle size.

Production of sodium alginate

INSOLUBLE CALCIUM AND MAGNESIUM SALTS OF ALGINIC ACID IN SEAWEED ↓Na2CO3 (alkaline extraction)

SOLUBLE SODIUM ALGINATE PLUS INSOLUBLE SEAWEED RESIDUE ↓Filtration

SODIUM ALGINATE SOLUTION + CaCl2↓

INSOLUBLE CALCIUM ALGINATE ↓

HCl↓

INSOLUBLE ALGINIC ACID

Na2CO3 or NaOH↓

SODIUM ALGINATE

CALCIUM ALGINATE PROCESS ALGINIC ACID PROCESS

Uses of Alginate

Thickener

• ices and ice creams
• products for pastries
• toothpastes
• cosmetics
• textile printing
• paper printing
• water flocculation
• Gelling agent

In the presence of calcium and acid

reformed or structured products entrapment and immobilization of enzymes and microorganisms absorbent products

날염용 호료로서의 Sodium alginate

알긴산소다를 날염용 호료로 사용함에 가장 문제가 되는 것은 유동성이다. 다른 호료에 비해 유동성이 기본적으로 양호하다. 그러나 저가 제품의 경우, 분자량이 가장 큰 고점도 알긴산소다를 생산한 후 중국에서 이미 증량제 들(SHMP, STPP, 망초, 기타)을 혼합하여 표면 단가를 조정한 후 전 세계에 공급을 하고 있는 상황이라 구매자가 이를 컨트롤 할 수 없는 상황이다.

대부분의 수입업자들은 퓨어(순수) 알긴산소다라는 말을 엄청 남용한다. 물론 판매를 위해서 그런 용어를 사용하는데, 최종 사용자들도 이를 그대로 답습하여 순수 알긴을 좋아한다. 그러나 현재 한국에서 수입한여 판매되는 날염용 알긴산소다의 경우, 순수 알긴산소다는 거의 없어 보인다.