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Products that affect the gel strength, gelling property, modify the gel texture and elasticity of agar are called synergies. However, antagonists are the products that decrease the gelling ability of agar or obstruct the gelling process completely.

Traditionally, Nikan values are used to determine the agar gel strength. The name Nikan comes from the traditional Japanese Nikan Sui method. According to this method force applied by a plunger for 20 s, to shatter a gel with the use of a cylindrical piston of 1 cm³ surface value is equal to one Nikan value. This method is still being used over the globe by most industry, even though there are more precise and accurate methods have been developed.

Acid and Alkali Hydrolysis

Like the other polysaccharides, agar also loses its molecular weight and gelling strength due to hydrolysis. If agar stays in lower pH (below 5.5) and higher temperature for longer time, it loses its gelling strength due to acid hydrolysis. It occurs more readily in agars. On the other hand alkaline hydrolysis of agar, doesn’t occur below 8 pH. However enzymatic hydrolysis isn’t relevant due to the very few agarases. Mainly bacillus marine bacteria like Esquizosaccharomycetes, synthesise agarases and these bacteria do not reside in food products.

Chaotropic Agents

Proton capturing chemicals compounds are called chaotropic agents, and they can disturb the agar gelation by stopping the hydrogen bridge formation between two subsequent agarose molecules. Since food products don’t carry any chaotropic agents like lithium perchlorate, lithium acetate, magnesium chloride, phenol, guanidinium chloride or 2-propanol etc, agar can be used in food stuffs.

Tannic Acid

Tannic acid is another potential inhibitor or agar gelation. Tannic acid is found in some fruits such as cranberries, apricots, peaches, grapes, etc. Glycerol can inhibit the reaction of tannic acid in agar, therefore adding some amount of glycerol during preparing food stuffs can avoid the gel breakage.

Sugar

The reaction between sugar molecule and agar can be observed in Graclaria agars. When these agars are dissolved into aqueous solution with the sugar concentration around 60%, the reaction between the hydrogen bonds of agarobiose and the molecules of sugar, takes place. The thread pitch of gelling helices causes the synergies in the agars of higher gel strength and lower sulfate content. Sugar reactivity usually occurs due to the presence of 3-6, anhydro bridges in agarose of higher molecular weight, around 140 kD. It should be considered here that L-galactose have tendency to aid the construction of hydrogen bridges in agars.

Agar–Locust Bean Gum (LBG) Synergies

It has been observed that agar–locust bean gum or LBG-synergies are only feasible in the agars of Gelidium and Pterocladia agarophytes. LBG-synergies increases the gel strength, transforms the gel texture in such a way that gel stiffness drops off and gel flexibility is elevated, making the gel less fragile. On the other hand, agars extracted from Gracilaria algae do not illustrate such synergies. In their case, gel rigidity drops with the decrease in gel concentration. The synergies between agar and locust bean gum occur due to agaropectin of Gelidium and Pterocladia, but agaropectin of Gracilaria doesn’t show such connections.