Extraction of sodium alginate by dielectric barrier discharge (DBD) plasma and the comparative study on rheological features

In this study, sodium alginate (SA) was extracted from Macrocystis pyrifera using dielectric barrier discharge (DBD) plasma (DBD-SA). Its structure and rheological properties were compared with those of conventionally sodium-carbonate-extracted SA (SC-SA). DBD plasma technology offers significant advantages, most notably its SA extraction yield of 48.53%, which is 8.8% higher than that of the traditional sodium carbonate method (39.73%). It also significantly shortens extraction time and lowers energy consumption. Additionally, the absence of alkali makes it compliant with the principles of green chemistry. Fourier-transform infrared spectroscopy (FTIR) confirmed that DBD-SA retained its fundamental polysaccharide backbone and key functional groups. By analyzing nuclear magnetic resonance (NMR) spectra, DBD-SA showed a high quantity of both homo polymeric mannuronic and guluronic blocks (FMM = 0.33) and (FGG = 0.33), respectively, and the mannuronic/guluronic ratio of 0.54. However, DBD caused mild polysaccharide degradation, resulting in a lower molecular weight and solution viscosity. The molecular weight of DBD-SA is 34.98 kDa. These findings demonstrate that DBD plasma extraction is a sustainable and efficient method for producing SA, offering reduced chemical use, shorter processing times, and lower energy consumption.