Iswandi's+Corner

@Iswandi's Corner **THE FUNCTIONS OF HYDROCOLLOIDS** //By: Mohamad Iswandi Bin Ishak// Food hydrocolloids is a range of polysaccharides and proteins. It have their own specific functions to the food. The primary functions of hydrocolloids are thickening agents and gelling agents. Besides that, hydrocolloids also have secondary functions such as stabilisation of emulsions, suspension of particulates, to control crystallisation, encapsulation and formation of film.

The first primary function of hydrocolloids is thickening agents. The example of hydrocolloids that function as thickening agents are xanthan gum, methyl cellulose, galactomannans and carboxymethylcellulose. Xanthan gum is very high low-shear viscocity. The viscosity will be maintains in the presence of electrolyte, over a broad pH range and at high temperature. Methyl cellulose will increase their viscocity when the temperature increase but the addition of electrolyte and pH will not affect the viscosity. Galactomannans is very high low-shear viscosity and strongly shear thinning. The viscositywill be lose at high and low pH and when subjected to high temperatures. Carboxymethylcellulose is high viscosity but reduced their viscosity by addition of electrolyte and at low pH.

The second primary function of hydrocolloids is gelling agents. Gelling agents occur in two conditions which are thermoreversible gelling agents and thermally irreversible gelling agents.

The example of hydrocolloids that function as gelling agents by thermoreversible gelling agents are gelatin, agar, kappa carrageenan, iota carrageenan, methyl cellulose and others. Gelatin and agar will form a gel on cooling. The molecules undergo a coil-helix transition followed by aggregation of helices. Kappa and iota carrageenan form a gel on cooling in the presence of salts notably potassium salts. The molecules undergo a coil-helix transition followed by aggregation of helices. Potassium ions will bind specifically to the helices. In the presence of salt will reduce electrostatic repulsion between chains and promoting aggregation. Methyl cellulose will form gel on heating. The molecules associate on heating due to hydrophobic interaction of methyl groups.

The example of hydrocolloids that functions as gelling agenta by thermally irreversible gelling agents are alginate, high methoxyl pectin and others. Alginate form gels on the addition of polyvalent cations notably calcium or at low pH less than 4. The molecules will crosslinked by the polyvalent ions. Guluronic acid residues give a buckled conformation providing an effective binding site for the cations. High methoxyl pectin formed gel at high soluble solids content at low pH less than 3.5. The high sugar content and low pH will reduce electrostatic repulsions between chains.

As a conclusion, the primary functions of hydrocolloids are thickening and gelling agents on food products.