Food+Hydrocolloids+-+A+Summary

by Tan Lee Hoon
 * Food Hydrocolloids - A Summary**


 * Hydrocolloids** refer to a range of **polysaccharides** and **proteins** that are nowadays widely used in a variety of industrial sectors to perform a number of functions including thickening and gelling aqueous solutions, stabilising foams, emulsions and dispersions, inhibiting ice and sugar crystal formation and the controlled release of flavours, etc. The food industry, in particular, has seen a large increase in the use of these materials in recent years. Even though they are often present only at concentrations of less than 1% they can have a significant influence on the textural and organoleptic properties of food products.

Commercially important hydrocolloids can be sourced from **botanical**, **algal**, **microbial** or **animal** origins. Examples of hydrocolloids originating from botanical source include cellulose (from trees), gum arabic (a tree gum exudate), starch and pectin (from certain plants), guar gum and locust bean gum (from seeds) and konjac mannan (from tuber). Hydrocolloids from algae include agar and carrageenan (from red seaweeds), and alginate (from brown seaweeds). Microbially-sourced hydrocolloids include xanthan gum, dextran, gellan gum and cellulose whereas hydrocolloids from animals include gelatin, caseinate, whey protein, chitosan.

The main hydrocolloid **thickeners** include **xanthan gum**, carboxymethyl cellulose (**CMC**), methyl cellulose (**MC**) and hydroxypropyl methyl cellulose (**HPMC**), galactomannans (**guar** and **locust bean gums**). Each of these hydrocolloids has **varying viscosity** which can be affected by **changes in pH and temperatures**, thus playing their own unique roles in the food products they are added into.

Hydrocolloids **gelling agents** can be categorised as thermoreversible or thermally irreversible gelling agents. **Thermoreversible** gelling agents are those in which gelation occurs on **cooling or heating**. Examples include gelatin, agar, Kappa carrageenan, Iota carrageenan, low methoxy (LM) pectin, gellan gum, MC and HPMC, xanthan gum and locust bean gum or konjac mannan. **Thermally irreversible** gelling agents are those in which gelation has to be **induced by crosslinking polymer chains with divalent cations**, such as alginate, high methoxy (HM) pectin, konjac mannan and locust bean gum. [Note: Actually xanthan and locust bean gum are __not capable of forming gels__ on their own in water systems. Therefore, xanthan and locust bean gum (LBG) are __mainly used as a thickening agent__ as they creates high viscosity in water systems. However, LBG significantly improves gel strength and texture and prevents syneresis when used in __combination with carrageenan__. In addition, LBG exhibits __unique synergy with xanthan gum__ provides noticeable advantages such as the highly elastic gel formation from two thickening agents with a very limited syneresis - KARIM].

And last but not least, here are some photos I took at a hypermarket of a few examples of food products that contain hydrocolloids and their related properties in these products. Enjoy!









(Reference: Introduction to Food Hydrocolloids, P. A. Williams and G. O. Phillips, North East Wales Institute, Wrexham)