Agar Agar

Properties

Agar agar is a thermos-reversible gel and is considered to be the strongest natural gelling agent. It is odor and colorless. It gels even at low concentrations. It is completely soluble in boiling water but also can be dissolved even at low temperatures. It gels at a temperature from 35 to 45C and melts at temperatures from 80 to 95C making it the only hydrocolloid that can gel at sterilization temperatures. Agar Agar has good synergies with sugar and with different hydrocolloids.

 Features

E-No. E 406
Origin Seaweed extract
Chemical composition Galactose and anhydro-galactose;
low sulfate content (<4.5%, mostly 1.5–2.5%)
Nutritional value (in 100 g) – metabolism 1425 kJ (340 kcal);
slow resorption
Fiber content 2.2% (42% protein, 36% carbohydrates)
Toxicology No health concerns, consumption generally
1–2 g per day (mild laxative effect at 6 g per day);
no ADI value defined;
considered as food in Asia, not as an additive
Solubility at low temperature (H2O) Insoluble
Appearance of an aqueous solution Opaque, yellowish
Viscosity of solution in water Low, insoluble in cold water
Impact of heat on viscosity in water (pH 7) Soluble at T>80 °C (176 °F)
Viscosity development in water at pH 7
(T=0–100 °C) 		Forms a thermoreversible gel after the dissolution
and cooling to 35 °C (95 °F) (gel melts at
T>85 °C (185 °F))
Shear stability High
Thickening effect High (gel formation)
pH stability Medium, hydrolysis by cooking in an acidic system
Decomposition Combination of heat+low pH (below pH 4)
Film formation High
Emulsion stabilization No
Gelation Thermoreversible gelation after heating to
T>80 °C (176 °F) and cooling to 35 °C (95 °F); also gels in saturated sugar solutions; gelation temperature is independent of sugar concentration
Gel strength and gel stability High gel strength, gels are highly heat-stable
Gel transparency Low
Tendency for gel synaeresis High
Impact of electrolytes (cations +, 2+, 3+) No
Reaction with Ca2+ ions No
Protein activity Low/no
Crystallization control No
Synergistic effects with other hydrocolloids + LBG or guar: less syneresis, more elasticity;
+ 10% LBG: maximum gel strength (+8%);
+ 10% konjac: maximum gel strength
Other synergistic effects Enhanced gel strength with high sugar concentrations (>60%) for some agar types
Negative interactions Tannic acid can inhibit the gelling process;
gum karaya reduces the gel strength of agar gels;
Proton scavengers like potassium iodide, urea,
Guanidine, sodium thiocyanate, and so on block the gelling process and prevent agarose gel formation
Dosage level in foods Low, typical 0.5-2%, gelation already at 0.2%

Applications

Foods

  • Bakery
    Cake icings, Pie fillings, Bread dough, Chiffon pies
  • Beverages
    Clarifying and refining juices, beers, wines, and vinegars
  • Dairy Products
    Ice Creams, Puddings, Flans, Yogurts, Fermented Milk, Sorbets, Gelled Milk 
  • Meat Products
    Pureed Meats, Canned fish, Poultry 
  • Sweets and Confectionary
    Gumdrops, Candy bars, Jelly candies, Jams, Marmalades, Comfitures, Dessert Gel, Meringues

Other

  • Medical and Pharmaceutical Industry
    Microbiology, Laxative, Therapeutic agent, Suspension agent of emulsion, Stabilizing agent of solution.
  • Other applications
    Dental prosthetics, Electrophoresis, Chromatography, Impression materials, Biotechnology