Properties of carrageenan and its application

introduction

Carrageenan, also known as carrageenan and algin, is a kind of polymer hydrophilic polysaccharide extracted from red algae. It has high economic value and is one of the world's three major seaweed gum industrial products (agargel, carrageenan, algin). Carrageenan is a food additive, and food grade carrageenan is white to yellowish-brown, wrinkled surface, slightly shiny translucent flake or powder, odorless, tasteless, sticky and smooth taste. The gel formed by carrageenan is thermally reversible, that is, when heated, it melts into a solution, and when the solution is cooled, it forms a gel. Carrageenan is widely used in food industry because of its good water retention, thickening, emulsification, gelling, safety and non-toxicity.

1. Structure of carrageenan

The chemical structure of carrageenan is a linear polysaccharide compound composed of D-galactose and 3, 6-dehydrod-d-galactose residues. According to the position of the semi-ester sulfate group on galactose, carrageenan can be divided into seven types: K-carrageenan, L-carrageenan, R-carrageenan, λ-carrageenan, ξ- carrageenan, φ-carrageenan, θ-carrageenan. At present, K-type, L-type and A-type carrageenan or their mixtures are produced and used, especially K-type carrageenan.

2.the performance of carrageenan

1) Gelatinous

The gel properties of carrageenan are mainly related to its chemical composition, structure and molecular size. The formation of carrageenan gel is divided into four stages: when carrageenan is dissolved in hot water, the molecules are irregularly curled; In the process of temperature drop, its molecules turn to spiral and form a single spirochaeta. When the temperature drops again, a double helix is formed between the molecules, which is a three-dimensional network structure, and the solidification phenomenon begins at this time. When the temperature drops again, the double spirochaeta aggregates to form a gel.

2) Solubility

Carrageenan can be dissolved in warm water above 70 ° C, and the more the general sulfate content, the easier it is to dissolve. In water, carrageenan first forms colloidal particles, adding sucrose, glycerin, etc., can improve its dispersion or break the micelle with a high-speed mixer to achieve dispersion effect. In order to promote the dissolution of carrageenan, in the food industry production, hot water above 80℃ is generally used to dissolve and disperse it.

3) Stability

Carrageenan is very stable in neutral or alkaline solutions, and is most stable at a pH value of 9, even if heated, hydrolysis will not occur. In acidic solutions, especially when pH 4 is below, acid-catalyzed hydrolysis is easy to occur, thus reducing the freezing strength and viscosity. The frozen carrageenan is more stable than the solution state, and the degree of acid hydrolysis at room temperature is much less than the solution state.

4) Reactivity

The biggest difference between carrageenan and other water-soluble macromolecules is that it can react with proteins. The sulfate group on the carrageenan molecule has a very strong negative charge. Protein is an amphoteric substance. Below the isoelectric point, amino acids and carrageenan combine to produce precipitation because they hold opposite charges. Above the isoelectric point, the two hold the same charge, and polyvalent cations are used as bonding agents and carrageenan to form hydrophilic colloid.

5) Rheology

The viscosity of carrageenan solution increases exponentially with the increase of concentration and decreases exponentially with the increase of temperature. In the constant temperature state, with the increase of time, the macromolecules began to dissociate, the intermolecular entanglement decreased, and the solution viscosity decreased. The viscosity of carrageenan solution increases with the increase of pH, and the increase of acidity promotes the dissociation of carrageenan molecules and neutralizes their electrical properties, weakening the electrostatic attraction between semi-esterified sulfate groups. If the alkaline is too large, the hydroxide and the negatively charged carrageenan repulsion and reduce the entangling of molecules, so the viscosity of the solution decreases under strong acid and strong alkaline conditions.

3. Extraction method of carrageenan

The production of carrageenan in China takes euestrin and salsa as the main raw materials, and the general process is as follows:

Raw material wash and dry, alkali treatment, washing to neutral, acidification, bleaching, extraction of glue, filtration - cooling strip cutting, freezing, dewatering, thawing, drying, finished product.

Alkali treatment, acidizing bleaching and extraction of glue are the key processes of carrageenan production. These processes not only affect the performance and quality of carrageenan, but also have an important impact on the extraction rate and production cost of carrageenan.

1) Alkali treatment

The experimental results of Zhu Min et al. showed that when algae were treated with KOH at room temperature and high temperature respectively, both gel strength and yield of carrageenan products obtained were significantly superior to those obtained with NaOH under the same conditions.

2) Acidification bleaching

When Huang Jiakang et al. studied the bleaching process of carrageenan, they concluded that the color, glue yield and gel strength of carrageenan products can be comprehensively taken into account by acidizing and bleaching again with oxalic acid in the acidizing bleaching process.

3) Different extraction methods

Tang Yishan et al. proposed two new extraction processes of carrageenan from Euestrum, namely, high pressure air extraction and high pressure steam extraction. The experimental results showed that the yield of steam high pressure extraction was lower than that of normal pressure extraction and the gel strength decreased greatly, while air high pressure could achieve a higher yield in a shorter time. In addition, pretreatment with 100U/g cellulase before extraction could increase the yield by 3.69%.

4. the main application of carrageenan

The application of carrageenan in food industry mainly focuses on its gelling, thickening and protein reaction.

1) Application in beverages

① The application of milk drinks, fruit juice pulp drinks and solid drinks

Carrageenan has a unique ability to react with proteins in milk, so it can form a thixotropic shake solution structure in milk drinks, preventing the formation of precipitation due to aggregation between particles. Carrageenan is used to make cocoa milk with cocoa powder. Adding carrageenan as a stabilizer can make the cocoa powder evenly dispersed in the milk and prevent the cocoa powder from forming a precipitate. When the juice drink is placed for a little longer, the small pulp particles contained in it will sink and affect the appearance. As a suspension agent and stabilizer, carrageenan can make fine pulp particles uniformly suspended in the juice, greatly slowing down the sinking speed. At the same time, due to the low viscosity of carrageenan, it is not easy to make a living, and can improve the taste of drinking. Using carrageenan as stabilizer in solid beverage can improve its impact, and the drink is stable and not easy to stratify.

② The application of alcoholic beverages

Carrageenan can be used as a clarifying agent and a foam stabilizer in alcoholic beverages. Because carrageenan can interact with protein, it is an effective wort clarifying agent, making the product clear and transparent, conducive to yeast growth, and conducive to filtration, reduce filtration loss, improve the wort yield, improve the biological stability of beer, extend the shelf life of beer.

2) The application of cold drinks

Carrageenan has a good milk protein reaction ability, which can prevent whey separation after adding CMC. In the production of ice cream, adding a small amount of ice cream emulsifying stabilizer will make ice cream have a higher expansion rate and a smooth and stable structure.

3) Application in meat products

Carrageenan used in ham and ham sausage has the functions of gel, emulsification, water retention, elasticity enhancement, etc. The most important is to provide appropriate water retention. Even when it is used to make products with high production rate, it also has good water retention, and because it can be complexed with protein, it provides a fairly good organizational structure, so that the product has the functions of fine, good slice, good taste, etc., and is a necessary additive for the production of ham sausage.

4) Applications in candy manufacturing

Using carrageenan to make transparent fruit jelly has long been produced in our country. Carrageenan jelly has good transparency, bright color, uniform, smooth, small viscosity, crisp and delicious.

5) Application in jelly production

Because of its unique gel properties, carrageenan has become the preferred gel agent for jelly. Jelly made from carrageenan is elastic and non-hydrophobic. It can replace commonly used AGAR, gelatin and pectin. Jellies made of AGAR are less elastic and more expensive; The disadvantage of using gelatin to make jelly is that the solidification and melting point is low, and the preparation and storage must be refrigerated at low temperature; The disadvantage of using pectin is that it can solidify when a high concentration of sugar and the right pH are required.

6) The application of bread and cream snacks

Fresh bread is soft and elastic but easy to age when placed, the hardness and brittleness of the bread are gradually increased, and the special flavor of the bread is gradually disappeared, adding carrageenan (0.012% to 0.02%) can increase its water retention ability, thereby delaying aging and keeping the bread fresh.

5. Development prospect of Carrageenan

Carrageenan has good gelatinability, solubility and stability, which makes carrageenan widely used in the field of food processing and production. The reactivity with protein is not possessed by all water-soluble polymers, which makes it of high application value in dairy products. With the further study of the structure and properties of carrageenan, the application of carrageenan is more and more extensive, especially its broad-spectrum antiviral activity, which has attracted great attention from pharmacologists at home and abroad. Carrageenan oligosaccharides and oligosaccharides produced by biodegradation have unique new physiological activities, such as anti-virus and anti-tumor. It is believed that in the future, the application field of carrageenan will be more and more extensive.