carrageenan+and+agar

By : Ayuni Shazwani @carrageenan and agar Yes, carrageenan and agar have common.

What do carrageenan and agar have in common?
 * 1) Think about the chemical structure of carrageenan and agar - what do they have in common?
 * 2) What are the differences between kappa, iota and lambda carrageenan? Why?


 * __Answer__**


 * 1) Carrageenan and agar have some common functional properties . The both of them is are **main hydrocolloid gelling agents**. Beside tha t, In addition, carrageenan and agar also have common in both gums form gel on cooling are thermoreversible gelling agent such as gel formed on cooling . [ What about differences in chemical structure? ]

Structural unit
Carrageenan consists of alternating 3-linked-β-D-galactopyranose and 4-linked-α-D-galactopyranose units.

Molecular structure Carrageenan
Carrageenans are linear polymers of about 25,000 galactose derivatives with regular but imprecise structures, dependent on the source and extraction conditions. Idealized structures are given below and κ-carrageenan, for example, has been found to contain a small proportion of the dimer associated with ι-carrageenan.

2. Differences between kappa, iota and lambda carrageenan :

This units are different for each type of carrageenan. · 25% of sulphate content approximately. || · 32% of sulphate content approximately. || · 35% of sulphate content approximately. || How does difference in sulphate content relate to the functional properties of kappa, iota, and lambda carrageenans? Basically carrageenan structure is composed of linear polysaccharides that have a sulfate content 0f 15-40%. This chain not homogeneous, therefore is usual to speak us ( check grammar ) the repeating unit and it refers to the principal disaccharide unit. Commercial carrageenans are not pure kappa, iota, and lambda, but contain a varying amount of the others type, the extract amount depending on the weed source and the extraction process.
 * **Number** ||  **Types Carrageenan**  ||  **Differences**  ||
 * 1 || Kappa Carrageenan ||  · The repeating units is D- Galactose-4-Sulphate linked with 3, 6-anhydrous-D-Galactose.
 * 2 || Iota Carrageenan ||  · The repeating units is D- Galactose-4-Sulphate linked with 3, 6-anhydrous-D-Galactose-2-Sulphate.
 * 3 || Lambda Carrageenan ||  · The repeating units is D- Galactose-2-Sulphate and D-Galactose-2.

The chemical reactivity of carrageenans is primarily due to their half-ester sulphate group,which are strongly anionic. the free acid is unstable, and commercial carrageenans are in its sodium, calcium or potassium salts or usually as amix of all these. These cations associated with the polysaccharide chain determine the final properties of the carrageenan, associated with the polysaccharide chain determine the final properties of the carrageenan.
 * dispersability and solubility
 * gelation
 * stability
 * interaction with other gums
 * protein reactivity