Simulated Digestion of Red Sea Cucumber (Parastichopus tremulus): A Study of Protein Quality and Antioxidant Activity

Sea cucumbers from unharvested areas, are underutilized resources which may have the potential to become a future food resource. The aim of this study was to evaluate protein quality and investigate the changes in antioxidant activity from frozen and freeze-dried red sea cucumber (Parastichopus tremulus) subjected to digestion, using an in vitro digestion model. P. tremulus constituted high moisture content (90%), comparable protein (4%) and ash (4%) content, and low lipid (1%) content. The biochemical components in freeze-dried samples were largely retained during the freeze-drying process. Frozen samples showed significantly higher (p < 0.05) antioxidant activity compared to freeze-dried samples (calculated on a dry weight basis). The quantity of essential amino acids was high (31%) and corresponds to the Food and Agriculture Organization of the United Nations reference protein. Frozen samples showed an increase in antioxidant activity during digestion measured by three different antioxidant assays. Freeze-dried samples only showed an increase in one of the antioxidant assays. Correlations (p < 0.05) were found between specific free amino acids and antioxidant activity. The amount of free amino acids exceeded the threshold to taste bitter, umami, sour, and sweet flavors. This study showed that P. tremulus constitutes good protein quality, performed antioxidant activity, and has the potential to be used as a flavor-enhancing ingredient.