Introduction of alkali soaking and microwave drying processes to improve agar quality of Gracilaria verrucosa

Abstract

Gracilaria species produce agars with low quality due to their high sulfate concentrations. For this reason, the gel properties of many Gracilaria agars must be improved by appropriate processes. In this study, we developed an improved agar extraction process for Gracilaria verrucosa by alkali soaking extraction and microwave thawing and drying. Variables such as the seaweed to alkali volume ratio, extraction time, and alkali concentration were adjusted to optimize the yield and agar quality. The yield of the agar was maximized (34.5±0.6%) using 3% alkali concentration; the lowest yield (17.0±1.7%) was obtained with 1% alkali concentration. Agar gel strengths ranged from 462.0±7 to 627.3±11 g·cm−2. We have developed a process for quickly producing an agar gel through thawing and drying using microwave radiation. This study shows the possibility of producing a high-value agar using alkali soaking extraction methods for nonedible G. verrucosa.