Extraction and purification of alginic acid from brown algae on the east southern coast of Iran

Alginic acid is a valuable polysaccharide that is extracted from brown algae and used widely in the food, pharmaceutical, biomedical, cosmetic, textile, dyeing and printing industries as thickeners, emulsifiers, stabilizers and the ability to form gels. Extraction methods and environmental conditions are the factors of the influence on the extraction yield. Evaluation of these agents have particular importance. In this research, alginic acid was extracted using acidification and calcification methods, and were compared with each other. Temperature, concentration and time were evaluated to determine optimal extraction conditions. FTIR spectroscopy was used to identify and compare the alginic acid sample with the standard. The alginic acid sample was analyzed by using the methods provided in food chemicals codex. Based on the results, the extraction yield of alginic acid was increasing 8% by calcification method ratio to the acidification method. Effective parameters have been identified to increase the extraction yield of alginic acid, including the concentration of 3% mineral acid at 2 hours, 4% alkaline concentration at 6 hours and temperature of 40 °C. The results of analysis of alginic acid were with an average purity of 93.57%, total ash 3.13%, loss on drying 13.2%, sulfate ash 7.33%, heavy metals as lead less than 0.004%, lead and arsenic less than 10 ppm and 3 ppm respectively. These results were based on the specified range food chemicals codex, and therefore it was introduced as an alginic acid food grade. The FTIR spectrum from alginic acid sample showed in according to its standard sample.