Hydrocolloid gelling agents and their applications

The most important hydrocolloid food gelling agents are gelatine, starch, pectin, carrageenan and alginate, but also agar, celluloses, gellan gum, konjac, milk proteins and soy proteins can be used as gelling agents. Xanthan gum is widely used in weakly gelled type foods such as salad dressings. Dairy dessert gels, jams and table jellies are typical examples of gelled foods, but also meat products or noodles can be gels. Hydrocolloids can form molecular gels through association of parts of the molecules forming 'junction zones'. The type of binding in the junction zone and the amount of molecules forming the junction zones are the most important factors determining the rheological and thermal properties of the gel. The most important hydrocolloid interactions are charge effects, steric hindrance, excluded volume effects and incompatibility. If particles are present, adsorption and depletion flocculation can take place. Gel properties are important for flavour release from gelled foods, whereas the clarity and surface smoothness of gels mainly depend on the presence and structure of insoluble components.