Activity+1

(Activity 1)

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?=

My Answers:
1)Agar and carageenan both are extracted from seaweed.

 Agar consists of a mixture of agarose and agaropectin. Agarose is a linear polymer,made up of the repeating monomeric unit of agarobiose. Agarobiose is a disaccharide made up of D-galactose and 3,6-anhydro-L-galactopyranose.Agaropectin is a heterogeneous mixture of smaller molecules that occur in lesser amounts. Their structures are similar but slightly branched and sulfated, and they may have methyl and pyruvic acid ketal substituents. They gel poorly and may be simply removed from the excellent gelling agarose molecules by using their charge. The quality of agar is improved by toe treatment that converts of any L-galactose-6-sulfate to 3,6-anhydro-L-galactose.

Carrageenans are large, highly flexible molecules which curl forming helical structures. This gives them the ability to form a variety of different gels at room temperature. They are widely used in the food and other industries as thickening and stabilizing agents. A particular advantage is that they are pseodoplastic—they thin under shear stress and recover their viscosity once the stress is removed. All carrageenans are high molecular weight polysaccharides made up of repeating galactose units and 3,6 anhydrogalactose (3,6-AG), both sulfated and nonsulfated. The units are joined by alternating alpha 1-3 and beta 1-4 glycosidic linkages.

 Carrageenan compounds differ from agar in that they have sulfate groups in place of some hydroxyl groups.

2) The percentage of sulphate contents for kappa, iota and lambda carrageenan is different. Each repeating unit of kappa carrageenan contains 25% of sulphate content, iota contains 32% of sulphate content whereas lambda contains 35% of sulphate content.  The structure of Kappa and iota carrageenan allow segments of the 2 molecules to form double helixes which bind the chain molecules in 3 dimension network, a gel whereas the lambda carrageenan does not allow such double helixes formation. Besides, the kappa and iota carrageenan has the ability to form thermoreversible gel upon cooling of hot aqueus solutions containing various cations while the lambda carrageenan does not form gels.

= GELATINS = Download the articles on gelatin from the portal and discuss the following questions. = 1. In recent years a lot of efforts have been initiated to find new alternatives for gelatin? Why? = =2. Gelatin is always considered a special/unique ingredient that find many applications in food and non food industry. Why?? = =3. Do you think fish gelatin can be used to replaced mammalian gelatin( porcine and bovine)?? =

My Answers: 1) Yes, there is a lot of efforts have been initiated to find new alternatives for gelatin . This is due to the health-concerned issues and some social-cultural issues( caused by mammalian gelatin such as porcine and bovine).

2) Gelatin always play a vital role in food industry. It can be used to form gel, water binding, thickening, texturizing, film formation, form and stabilize emulsion. In addition, it also have protective colloids and adhesion/cohension properties. The application of gelatin is also widely used in confectionery and pharmaceutical industries.

3) Yes, fish gelatin can replace mammalian gelatin, but maybe just can in some certain extend as this two types of gelatins are composed of different combinations of amino acid. Thus, they have different physical and also chemical properties apart from have some same properties.