HYDROCOLLOIDS AND GUMS

Hydrocolloids – hydrophilic, long- chain, high molecular weight molecules, with colloidal properties

In water-based systems produce gels, i.e, highly viscous suspensions or solutions with low dry -substance content

Colloid- A system in which finely divided particles are dispersed within a continuous medium in such a way that they are not filtered easily and do not settle rapidly.

INTRODUCTION

Hydrocolloid (hydrophilic colloid) – the scientific name for gums

Not real colloids – because truly water solubleSome are water soluble and form colloidal

solutions others are only able to swell in water and can be dispersed by means of shear forces

Functions - thickening or gelation, emulsifying, whipping, suspending, and encapsulating

Hydrocolloids - not real emulsifiers because - do not have the characteristic linkage of lipophilic and hydrophilic groups in the molecular structure

Hydrocolloids - linear or branched molecules Linear type (such as cellulose, amylose,

alginates, and pectin) - most abundant in nature and have sugar units that repeat over the entire length of the polymer

Have side units (influence the properties) - single or multiple sugar units, or simple as carboxyl groups, sulfate groups, or a methyl ether group

Hydrocolloids – naturally occuring and chemically modified, such as carboxymethyl cellulose (CMC), also known as cellulose gum, and propylene glycol alginate

Based on their origin and way of manufacturing,

1) hydrocolloids purely isolated from plants (without chemical modification)

2) hydrocolloids obtained by fermentation 3) plant-derived hydrocolloids that are

chemically modified4) hydrocolloids from animals

TYPES

According to their botanical origin and their function in the plant organism,

1. exudates (protective colloids being deposited on wounds)- acacia gum/gum Arabic, tragacanth, karaya gum, ghatti gum

2. seed flours (reserve polysaccharides) - guar gum, locust bean gum, tara gum, tamarind seed gum

3. extracts from land plants and marine algae (scaffolding substances) - pectins, agar, alginate, carrageenan, starches, cellulose, furcelleran, larch gum

Additionally, there are 1. microbial or bacterial polysaccharides -

xanthan, dextran, curdlan, scleroglucan, gellan, pullulan

2. modified polysaccharides - propylene glycol alginate, amidated pectin, modified starches, cellulose derivatives

3. proteins of animal origin - gelatin, caseinates

Viscosity enhancing or thickening properties Gelling propertiesSurface activity and emulsifying propertiesHydrocolloids as edible films and coatingsHydrocolloids as fat replacers

PROPERTIES

Thickener Stabilizer Emulsifier

Hydrocolloids in Food Industry

Hydrocolloid: PectinSource: FruitsMode of gelation: Interactions between the pectin molecules through hydrogen bonding

Jams and Jellies

Retards staling of bread Increases shelf life Dough conditioning Prevents lump formation Maintains the texture of final product

Hydrocolloid as a baking improver

Staling???

Emerging technology used majorly in fortification of food

Encapsulation prevents loss of essential nutrient (say DHA) during cooking process

Gelatin, Alginate with calcium or polylysine forms thin layer around the core

Microencapsulation

Application of hydrocolloids – review by Zlatica et al.

Hydrocolloids in food industry by Jafar et al. http://www.classofoods.com/page3_3.html http://www.food-info.com

References