Objective The study aims to compare the nutritional composition and antioxidant activity of sea cucumber freeze-dried powder and peptide powder.

Methods In this study, sea cucumber freeze-dried powder and commercially available sea cucumber peptides were used as research subjects. The protein content, polypeptide content, and total sugar content were analyzed using the Kjeldahl nitrogen determination method, the GB/T 22492—2008 method, and the phenol-sulfuric acid method. Molecular weight distribution, monosaccharide composition, and amino acid composition were determined through high-performance liquid chromatography. Additionally, the in vitro antioxidant activities of both samples were assessed.

Results The protein content of sea cucumber freeze-dried powder and peptide powder was 55.06%±0.58% and 88.70%±0.63%, respectively. The peptide content was 1.78%±0.08% for the freeze-dried powder and 83.00%±0.23% for the peptide powder, while the total sugar content was 7.60%± 0.23% and 4.20%±0.17%, respectively. The protein and polypeptide contents of sea cucumber peptide powder were significantly higher than those of freeze-dried sea cucumber powder, whereas the total sugar content was lower in the peptide powder. Over 90% of the molecular weight of the sea cucumber peptide powder was less than 600 Da, indicating a smaller molecular size. The monosaccharides in the polysaccharides from the sea cucumber body wall consisted of mannose, glucosamine, galacturonic acid, glucose, galactose, and fucose, with fucose being the most abundant at 67.06%, while mannose was the least, at 1.95%. The contents of essential amino acids and total amino acids in sea cucumber peptide powder were higher than those in freeze-dried powder, suggesting that the amino acid composition of the peptide powder is superior. Furthermore, the DPPH free radical scavenging ability, hydroxyl free radical scavenging ability, ABTS free radical scavenging ability, iron reduction ability, and superoxide anion scavenging ability of sea cucumber peptide powder were greater than those of freeze-dried sea cucumber powder.

Conclusion The polypeptide content, protein content, and amino acid composition of sea cucumber peptide powder are significantly higher than those of sea cucumber freeze-dried powder. Additionally, the peptide powder has a smaller molecular weight and exhibits strong antioxidant activity in vitro.

Significance This study provides a reference for the development and utilization of sea cucumber peptide powder efficacy products.