Optimization of agar extraction from local seaweed species, Gracilaria salicornia in Tanzania

• Published in: Phycological research Vol. 67; no. 4; pp. 261 - 266
• Main Authors: Vuai, Said Ali Hamad, Mpatani, Farid
• Format: Journal Article
• Language: English
• Published: Kyoto, Japan John Wiley & Sons Australia, Ltd 01-10-2019; Wiley Subscription Services, Inc
• Subjects: Agar; Algae; alkali treatment; Dependent variables; Design of experiments; Duration; Experimental design; gel properties; Gelation; Gels; Gracilaria salicornia; Independent variables; macroalgae; Melting; Optimization; Organic chemistry; Seaweeds; Sodium hydroxide; Sulfates; Yield strength; Yields; Zanzibar; Tanzania
• ISSN: 1322-0829; 1440-1835
• DOI: 10.1111/pre.12380

SUMMARY
This study aimed to develop agar extraction protocols for Gracilaria salicornia from Tanzania and investigate its physico‐chemical characteristics. A 33 factorial experimental design was used in the extraction of agar whereby three independent variables of NaOH concentration (10, 20 and 30% w/v), alkali pre‐treatment duration (0.5, 1 and 2 h) and extraction temperatures (115, 120 and 125°C) were used to determine the optimum conditions for production of high‐quality agar. Agar yield, gel strength, sulfate content, gelling and melting temperatures were evaluated as dependent variables. The optimal condition was observed at 30% NaOH concentration, 2 h alkali pre‐treatment duration and 120°C extraction temperature. The yield, gel strength, sulfate content, gelling and melting temperatures of the agar obtained under these conditions were 26.9 ± 0.7%, 510.3 ± 16.2 g cm−2, 0.29 ± 0.04%, 39.3°C and 88.4°C, respectively. These properties are very close to that of imported commercial agar. It was concluded that the local agar is capable of replacing imported agar for most general purposes. This offers a new possibility of using quality local agar in place of commercial agar.