Studies on physico-chemical characteristics of iota-carrageenan extracted by ultrasonic method

D.M.Reddy Prasad, (2006) Studies on physico-chemical characteristics of iota-carrageenan extracted by ultrasonic method. PhD thesis, Universiti Malaysia Sabah.

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Abstract

Carrageenans are water-soluble natural gums/ which occur in certain species of seaweeds. They are sulfated natural biopolymers made up of galactose units. The major varieties of seaweeds are available from South China Sea at Sabah are Caulerpa, Ulva, Sargassum, Eucheuma, Gracilaria, Gelidiella and Kappaphycus. The thermal extraction of i-carrageenan from seaweed does not give high yield and time consuming. Ultrasonic assisted extraction was proposed as an alternative method. The 20 kHz high intensity ultrasound was used in the extraction of i-Carrageenan from Eucheum denticulatum by using water as solvent. i-carrageenan yield increased from 50 to 57.2%. A simple mathematical correlation for the estimation of the solid-liquid mass transfer coefficient was derived in terms of operating conditions VIZ, amplitude, particle size and temperature for ultrasonic extraction of i-Carrageenan. The diffusion coefficient of i-Carrageenan in water was estimated from the mass transfer coefficient. Further more the conventional estimation methods of i-carrageenan in aqueous solutions need depolymerization and longer duration. The ultrasonic spectroscopy technique coupled with neural network has been developed as a alternative. In that the artificial neural network models such as Back Propagation (BPJ Radial Basis Function (RBF) and modified Functional Link Neural Network (FLNN) were used. As the RBF method showed the low estimation time of 26 sec. The modification of i-carrageenan in presence of Ag+ produced better gel characteristics. It could be more useful in pharmaceuticals industries. The physico-chemical properties like passive diffusion gel strength hysterisis and micro structure of modified i-Carrageenan gels were tested. The weight loss of the gels in passive diffusion was found to be in the range 0.7-1.2% at 240 h. The gels exhibited high firmness as the Ag+ concentration increased while decrease in the elasticity was observed. The relaxation time reached maximum at 70 mM of Ag+ and at higher concentration the gels exhibited saturation. The hysterisis of the modified gels was observed between gelation (Tg) and dissolution (Tf) temperatures and it was strongly dependent on Ag + concentration. The SEM images of the blended films showed that the roughness varies inversely with the percentage of i-Carrageenan. The results of new methods and correlations developed offer unprecedented scope of applications for developing new i-Carrageenan based products in the process industries.

Item Type:Thesis (PhD)
Uncontrolled Keywords:physico-chemical, iota carrageenan extract, ultrasonic, water soluble natural gum, seaweed, eucheum denticulatum
Subjects:T Technology > TP Chemical technology
Divisions:SCHOOL > School of Science and Technology
ID Code:6246
Deposited By:IR Admin
Deposited On:13 Jun 2013 09:55
Last Modified:13 Jun 2013 09:55

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