Characterization of Agar Extracted from Farmed Gracilaria sp. via Different Alkaline and Temperature Treatments

Graphical Abstract  Highlight Research 7% NaOH gave the highest agar yield (13.54%) and gel strength (49.53 g/cm²). High alkali and heat reduced phytochemical content. FTIR showed structural degradation at elevated temperatures. Nutritional profile suggests similarity to Gracilaria changii.   Abstract The growing industrial demand for agar underscores the need for efficient, sustainable extraction methods that ensure both high yield and product quality. However, optimizing key processing parameters for agar extraction from farmed Gracilaria sp. remains a challenge due to variations in species composition, cultivation environment, and extraction practices. Current production often relies on empirical or non-standardized conditions, leading to inconsistencies in gel strength, color, and purity that affect industrial applicability. This study examines the properties of agar extracted from an unidentified Gracilaria species, with characteristics closely matching Gracilaria changii. Using different NaOH concentrations (3%, 5%, 7%) and temperatures (70°C, 80°C, 90°C), the effects on agar yield, gel strength, color, water retention capacity (WRC), and structure were analyzed. The highest agar yield (13.54%) was obtained at 90°C with 7% NaOH, while the best gel strength (49.53 g/cm²) was recorded at 80°C under the same alkali concentration. FTIR confirmed polysaccharide features but revealed degradation at higher temperatures. Overall, 7% NaOH was identified as the optimal alkali concentration, balancing high yield and desirable gel properties. These findings offer valuable insights for enhancing agar extraction efficiency from Gracilaria sp. and advancing standardization in industrial agar production.