Improvement of Gracilaria agar solubility by acid treatments

Abstract

In order to increase the solubility of alkali-treated agar biopolymers extracted from Gracilariopsis lemaneiformis, sixteen hydrolysis methods with four kinds of acids (sulfuric acid, acetic acid, oxalic acid, and citric acid) were evaluated to determine a suitable procedure. The agar solubility against DMSO and water were tested at 25 ℃ and 95 ℃. Among the procedures tested, partial hydrolysis with 0.001 N acetic acid for 2 ～3 h was more effective for increasing agar solubility (against DMSO at 25 ℃) while maintaining its gelling ability. The results indicated that partial hydrolysis of agar under effective conditions improves agar solubility and produces high grade agar from the Japanese agarophyte, especially Gracilaria (Gracilariopsis). The resulting high solubility agar may facilitate the spread of industrial applications of Gracilaria agars.