CONTROL RELEASE FROM BIOPOLYMER

Control Release from Biopolymer

Control Release From Biopolymer

Introduction

Gellan gum is a linear anionic microbial heteropolysaccharide requiring both a heating cycle and cations for gelation ([Kang and Pettitt, 1993] and [Morris, 1990]). Divalent cations have a more pronounced effect on gellan gum rheological properties than monovalent cations due to differences between the gelation mechanisms of these cation types. Divalent cations directly cross-link double helices while monovalent cations do so indirectly (Huang, Singh, Tang, & Swanson, 2004).

Gel

A gel is a sol in which the solid particles are meshed such that a rigid or semi-rigid mixture results.

Examples:

Fruit jelly is an example of a gel. Cooked and cooled gelatin is another example of a gel. The protein molecules of gelatin crosslink to form a soid mesh which contains pockets of liquid

Gellan Gum Properties

Gellan Gum is the white powder without special flavor and odor and can disintegrate without melting in 150. Gellan gum can be dissolved in the cold water, the conditions for the formation of gelling are:1.Need to heat up first 2.The existence of a certain amount of cations. In this way, the gellan gum solution can form gel after It is cooled down. The gel strength, gel forming temperature and the melting temperature is bound up with the concentration and category of the cations.

Characteristic And Efficacy Of Gellan Gum

Characteristic

Efficacy

Form high qualified gel under low concentration of 0.05~0.25%

Gellan gum is an efficient gelling agent

High stability at high temperature and low pH value

Heating and sterilization has little effect on gel strength, acid gel has comparatively long shelf life

Gel formed by Na+ and K+ can renew after heating, while gel formed by Mg2+ and Ca2+ can not

Can produce reversible and irreversible gel

Retains excellent flavor releasing ability

Improve product quality

Can be used together with other gums like starch, mixture of xanthan gum/locust bean gum

Structure of gums formed by gellan gum can be transformed from brittle to elastic

GELLAN_GUM_STRUCTURE

GELLAN GUM GELLATION

For decades microbial exopolysaccharides have been invaluable ingredients in the food industry, as well as having many attractive pharmaceutical and chemical applications. The biopolymer gellan is a more recent addition to the family of microbial polysaccharides that is gaining much importance due to its novel property of forming thermo-reversible gels when heated and cooled. It has applications in diverse fields in the food, pharmaceutical and many other industries.

Gellan gum is an anionic, high molecular weight, deacetylated exocellular polysaccharide gum produced as a fermentation product by a pure culture of Pseudomonas elodea2, with a tetrasaccharide repeating unit of one a-L-rhamnose, one ß- D-glucuronic acid and two ß-D-glucose residues3,4.  The production organism is an aerobic, gram-negative bacterium, which has been very well characterized and demonstrated to be non-pathogenic5. This organism was found during an extensive screening programme seeking naturally occurring hydrocolloids with useful properties.  

Gellan gum has the characteristic property of temperature-dependent and cation-induced gelation. This gelation involves the formation of double helical junction zones followed by a Gellan gumregation of the double helical segments to form a three-dimensional network by complexation with cations and hydrogen ...