INFLUENCE OF ALKALI TREATMENT ON AGAR FROM GRACILARIA-CORNEA FROM YUCATAN, MEXICO

The effect of alkali treatments on the yield, rheological and chemical properties of agar from Gracilaria cornea growing along the Yucatan c oast were studied in order to evaluate its potential for industrial us e in an attractive economic standpoint. Alkali treatment was carried o ut with NaOH concentrations of 0.5%, 1%, 3% and 5% in a water bath at 80, 85 and 90 degrees C. Agar yield, gel strength, gelling and melting temperatures, sulphate, 3,6-anhydrogalactose and ash content were det ermined. The different combinations of NaOH concentration and treatmen t temperature strongly influenced agar characteristics. There was a va riation in the agar content for all NaOH treatments and temperature co mbinations, ranging between 14.5% to 22.1%. Although the yields obtain ed for 0.5% NaOH at all temperatures and 1% NaOH at 80 and 85 degrees C were higher than those required by the industry, the physical and ch emical characteristics of the agar were similar to those obtained for native agar from the same species. The gel strengths, sulphate content and gelation hysteresis obtained with agar from the 1% NaOH treatment at 90 degrees C are in the range required by the food industry. Treat ments with 3% and 5% NaOH at all temperatures improved significantly t he agar quality giving higher gel strengths (974-1758 g cm(-2)) than t hose reported for other Gracilaria species.