Submitted in partial fulfillment of the requirements for the degree of Master of Science in Food Engineering and Bioprocess Technology, School of Environment, Resources and Development

Thesis (M. Sc.) - Asian Institute of Technology, 2013

The aim of this study was to modify the kappa carrageenan(seaweed sulphated polysaccharides)to carboxymethylatedkappa carrageenan in order to achieve the kappa carrageenan derivative with modified physicochemicaland biological properties. The carboxymethylatedkappa carrageenanswere synthesized at differentconditions of temperature, concentration of alcohol,sodium hydroxide and proportion of chloroacetic acid. The temperaturesand concentrationsof each componentproduce different degree of biological activityforcarboxymethylated kappa carrageenan. The introduction of carboxymethyl group improved the antimicrobial,antioxidant and gelling ability of kappa carrageenan. The formation of carboxymethylated kappa carrageenan was confirmed by using theFouriertransform infrared spectroscopy (FTIR)analysis of samples. The antimicrobial effectsof carboxymethylated kappa carrageenan indicated that they were effective and had potential to inhibit the growth of both gram positive(Lactobacillus plantarum and Staphylococcus aureus)and gram negative(E. coli and Salmonella)bacteria.The carboxymethylated kappa carrageenan with improved antimicrobial, antioxidant, and rheological profile can be used in food and pharmaceutical industries and can reduce the use of various synthetic chemical preservativewhich are associated with various health hazards.