Author: Dhrub Ghimire
Ghimire, Dhrub, 2019 Encapsulation of fish oil using H2O2-oxidative modified sodium alginate and carrageenan mixture to reduce oil leakage, Flinders University, College of Medicine and Public Health
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Alginate and carrageenan are commonly identified polysaccharides that are contained in the seaweed (brown algae) and red algae respectively. These are the polysaccharides with high commercial value due to their gelling and stabilizing properties. These polysaccharides have shown various commercial application individually and in incorporation with one another. Alginates have molecular weight in ranges from low to high (commercially available alginates ranging between 32 kDa and 400 kDa). Their gelling property with ions like calcium is dependent on the molecular weight and viscosity. The first phase this experiment, made modifications on the molecular weight and viscosity of the sodium alginate (Sigma Aldrich) using hydrogen peroxide as an oxidizing/depolymerizing agent at different time conditions (30 min to 3h) and concentration of hydrogen peroxide (0.3% v/v, 0.5% v/v and 1.0% v/v). Then, determined the molecular weight and viscosity of the oxidized alginate at different oxidation time and concentration of hydrogen peroxide used using HPLC and viscometer. The viscosity and MW of oxidized were significantly reduced, the lowest being at 3h of oxidation. Also, the oxidation process was rapid during the first hour when 1.0% (v/v) of the hydrogen peroxide was used for oxidation. And the second phase of the experiment, studied the gelling behavior of the oxidized alginate whether it has same gelling property as before. Also, G/M (Guluronic acid and Manuronic acid) ratio of the oxidized alginate were determined to study if there is any change in the G/M ratio. Guluronate (G) part of the alginate is responsible for the gelling property and there was no significant difference between the control (unoxidized from Sigma Aldrich) and oxidized alginate. This gave the idea that the modified alginate still has good gelling property. Next, we incorporated this modified alginate with carrageenan to make a strong and stable biofilm that can be used for commercial applications. Alginate and carrageenan were mixed in different ratios making final concentration of 1% (w/v) and the mixture solution was allowed to form gel in 0.5% (w/v) calcium chloride containing 20% (v/v) ethanol and physical properties were studied. The film made up of combination of 0.3% (w/v) alginate and 0.7% of carrageenan (w/v) was selected for the study of the stress, strain and swelling ratios. The mixed film showed slow and steady swelling behavior compared to only alginate and only carrageenan gels. Finally, we used 0.3% (w/v) oxidized alginate and 0.7% (w/v) carrageenan mixture to encapsulate the fish oil (10% v/v) and the encapsulation efficiency and stability of the encapsulated beads were compared with final 1% w/v (0.3% w/v medium viscosity alginate and 0.7% w/v carrageenan mixture w/v). The modified alginate-carrageenan mixture showed excellent efficiency and very good stability after 1 week of incubation than the 1% (w/v) unmodified alginate-carrageenan mixture. We used amount of beads surface oil and oil in gelling solution to determine the efficiency of encapsulation and stability. Most stable were the beads lower the surface oil of the encapsulated beads. This experiment found that higher molecular weight sodium alginate can be oxidized to make low molecular weight and less viscous without losing its gelling properties and the modified alginate can be incorporated with another polysaccharide carrageenan to form a more stable material that can have high commercial application (encapsulation of fish oil done in this experiment). High molecular weight and high viscosity alginate are found to be immunogenic and hard to biodegrade, so this study can significantly address that problem. However, there are some limitation of this study as we used only two different types of alginate (unoxidized and oxidized) and carrageenan. In further research polysaccharides with varying molecular weight and viscosity can be studied. Also, the properties of mixed polysaccharide films can be optimized for commercial application that can be used as packaging material and that somehow could be the alternative to non-degradable commercial polyethene.
Key words: Alginate, carrageenan, encapsulation, stability, efficiency, G/M ratio
Keywords: Alginate, Carrageenen, Oxidation of sodium alginate, Hydrogen peroxide oxidation of seaweed polysaccharides, H2O2, Encapsulation, fish oil
Subject: Biotechnology thesis
Thesis type: Masters
Completed: 2019
School: College of Medicine and Public Health
Supervisor: Prof. Wei Zhang