Optimized agar extraction from <i>Gracilaria eucheumoides</i> Harvey

Abstract

A 33 factorial experimental design was utilized to determine the optimum alkali pretreatment conditions in the extraction of agar from <i>Gracilaria eucheumoides</i>. Three levels from each of three factors were considered: Temperature, 70, 80, 90 °C; NaOH concentration, 4, 7, 10% and; treatment duration, 0.5, 1, 2 h. The optimum conditions were found to be 90 °C, 10% and 2 h. The gel strength of the agar yielded under these conditions was 432 ± 43 g/cm2. The effects of the different alkali pretreatment conditions to the agar yield and 3, 6-anhydrogalactose and sulphate contents were also determined. Agar yield was higher at lower temperature, stronger alkali solution and shorter treatment duration. Higher 3, 6-ahydrogalactose content and lower sulphate level were obtained at higher temperature, higher alkali concentration and longer duration of treatment.