Proximate Composition and Heavy Metal Content of Edible Seaweed from Kappaphycus alvarezii and Caulerpa cf. macrodisca ecad corynephora

Abstract

Edible seaweeds, such as Kappaphycus and Caulerpa genera, have been popularly consumed for centuries by the local people in the Tawi-Tawi, Philippines. This study examined the proximate composition and heavy metal contents of two edible seaweeds, namely Kappaphycus alvarezii (KA) (Rhodophyta) and Caulerpa cf. macrodisca ecad corynephora (CMC) (Chlorophyta), which are readily available in the public market of Bongao, Tawi-Tawi, Philippines. The results revealed significant differences in their proximate compositions. The moisture content was remarkably higher in KA (16.96±0.02 g.100-1g) than that of CMC (10.49±0.08 g.100-1g). CMC contained significantly more crude protein (7.14±0.80 g.100-1g) than KA (2.73±0.40 g.100-1g). The carbohydrate content of KA (44.82±0.34 g.100-1g) was significantly higher than that of CMC (38.09±0.71 g.100-1g). The ash content was notably greater in CMC (44.00±0.66 g.100-1g) than in KA (34.91±0.39 g.100-1g). The total fat content was substantially higher (p≤0.05) in KA (0.60±0.30 g.100-1g) than in CMC (0.28±0.01 g.100-1g). The heavy metal contents (mg.kg-1) followed the order of K > Zn > Fe > Pb > Cu > Mn > Cd for KA and Zn > Mn > Pb > K > Fe > Cu > Cd for CMC. Fe, K, Cu, and Cd were significantly higher in KA than in CMC, while Zn, Mn, and Pb were remarkably higher in CMC than in KA. However, all these heavy metals were found to be within safe limits of WHO, the US (EPA and FDA), and EMA. These findings underscore the importance of considering these factors in seaweed consumption, affirming their enduring significance in human diets.