Investigation on total phenolic content, antioxidant activity, and emulsifying capacity of sodium alginate from Nizimuddinia zanardini during microwave-assisted extraction; optimization and statistical modeling

In recent years, the use of microwave technology (MAE) for the extraction of bioactive compounds from algae has shown great research interest due to its high and fast extraction performance. Alginate is a marine polysaccharide that has found numerous applications in the food industry due to its favorable properties. Although the MAE of alginate has been reported in the previous scientific papers, none of them investigated the effects of MAE variables on the functional properties of the extracted polymer. Therefore, the present study aimed to optimize microwave-assisted extraction (MAE) conditions of sodium alginate for its antioxidant activity (AA), emulsifying capacity (EC), and total phenolic contents (TPC). The Box–Behnken design was used to study the effects of four variables including extraction temperature (45–75 °C), microwave power (300–500 W), extraction time (1–30 min), and solvent-solid ratio (10–30 mL/g). The statistical optimization revealed that extraction with the temperature of 22 °C and the solvent-solid ratio of 20 mL/g for 22 min with a microwave power of 412 W was the best combination of these variables. The corresponding experimental values for AA, EC, and TPC were 65.24%, 65.15%, and 1.560 g GAE/100 g DM of sodium alginate, respectively. Predicted values were in close agreement with experimental ones. Developed models were significant (p < 0.05) with high regression coefficients (R 2 > 0.9) and insignificant lack of fits that confirm the validity of RSM models to optimize extraction conditions of sodium alginate from N. zanardini .