The effect of different extraction methods and pre-treatments on agar yield and physico-chemical properties of Gelidium latifolium (Gelidiaceae, Rhodophyta) from Sinop Peninsula Coast of Black Sea, Turkey

Abstract

The present study aimed to investigate the effect of different pre-treatments and extractions methods on the yield and quality of agar extracted from Gelidium latifolium Bornet ex Hauck from the coast of Sinop Peninsula, Turkey, and to evaluate its potential as an economic source of agar for industrial applications. The different extraction methods including autoclave, water bath, and water bath plus magnetic stirrer were tested with various pre-treatments (no treatment, waiting for 15 h in pure water, washing with 80% ethanol). The agar yield and physico-chemical properties (gelling and melting temperature, pH, viscosity, and ash, and sulfate contents) were evaluated at the optimal extraction conditions. The highest agar yield (%) was recorded with the water bath plus magnetic stirrer extraction method (45.79 ± 0.85% of dry wt), while the lowest yield was recorded with the autoclave extraction method (37.29 ± 0.76%). The gelling and melting temperatures ranged between 39.06 ± 0.26 and 37.16 ± 0.16 °C, and 94.8 ± 0.29 and 79.5 ± 0.50 °C, respectively. The highest crude ash content was recorded with water bath plus magnetic stirrer extraction method (3.36 ± 0.11%). The pH values ranged between 6.69 ± 0.11 and 5.17 ± 0.47. The agar viscosity ranged from 281.33 ± 1.33 to 133.33 ± 1.33 mPa s and total sulfate content was between 3.02 ± 0.25 and 0.54 ± 0.11%. The agar extracted from G. latifollium from Turkey seems to have potential industries applications considering its higher yield, desirable gelling and melting properties, optimum pH, ash, and sulfate content.