Effect of temperature and extraction time on the process to obtain sodium alginate from Macrocystis pyrifera

Abstract

The alkaline extraction step of the process to obtain sodium alginate from Macrocystu pyrifera was investigated. We compared cold (28°C) and hot (80°C) treatments to determine the effect of extraction temperature on the yield and viscosity of the final product, using samples collected in Bahia Tortugas, Baja California Sur (Mexico), in the summer of 1994. At 80°C we obtained a yield of 19.10% and a viscosity of 398 cps: at 28ºC the yield was 15.53% and the viscosity was 466 cps. We conclude that hot extraction is more favourable, because the yield is statistically greater and the viscosity is the same. The effect of extraction time was also investigated in the hot process, using samples collected in Bahia Tortugas in the fall of 1990, to determine the minimum extraction time in which we can obtain high yield and quality of the final product. We tested times from 90 to 165 minutes at 80°C. In the temperature range tested, no significant difference was found between the yields or the viscosity. We conclude that the minimum extraction time is 90 minutes; however, to reach the final reaction point, the time must be extended to 120 minutes.