Seaweed (Macrocystis pyrifera) as a sustainable low-sodium natural salt substitute: conventional solid-liquid extraction v/s ultrasonic extraction

Excess dietary sodium is a key contributor to hypertension and cardiovascular disease. Seaweeds, naturally rich in potassium and other minerals, offer a sustainable source of salt substitutes. In this study, mineral salts were extracted from the brown macroalga Macrocystis pyrifera using (i) solid–liquid extraction in an agitating water bath and (ii) ultrasound-assisted extraction in an ultrasonic bath. The effects of extraction time (5–60 min) and temperature (20–60°C) on salt yield, specific energy consumption (SEC), and mineral composition were evaluated using a full factorial design. Both methods produced salts with high potassium (183 g/kg) and a low sodium-to-potassium (Na/K) ratio (0.46). Conventional solid-liquid extraction delivered higher yields (p<0.001), whereas ultrasonication enhanced magnesium and calcium release (p<0.05). Statistical significance was determined using two-way ANOVA (α=0.05). Considering yield and SEC, the most efficient conditions were 20°C for 30 min (agitating bath) and 20°C for 15 min (ultrasonic bath). These results demonstrate the feasibility of producing functional seaweed salt with a favorable Na/K ratio from M. pyrifera , supporting its application as a clean-label salt substitute in food processing and health-focused formulations. • Seaweed salts from M. pyrifera exhibited high potassium and relatively low sodium. • The Na/K ratio was as low as ~0.46, favorable for sodium-reduction strategies. • Agitating-bath extraction produced higher yields than ultrasonication (p < 0.001). • Ultrasonication increased Mg and Ca levels in the recovered salts (p < 0.05). • Energy-efficient operating windows identified at 20 °C (15–30 min).