## 3 Results and Discussion
### The Digestive Effect on Amino Acids  
The release of FAAs from the digestive process of initially frozen samples ranged between 1 and 111 mg/100 g dry weight (Figure 6). Glutamic acid and glycine/arginine were the dominating FAAs throughout the digestive process. Amino acids such as alanine, histidine, isoleucine, tyrosine, and valine showed an insignificant increase in concentration at the end of digestion (165 min) compared to the beginning of digestion (0 min). However, asparagine, glutamine, leucine, lysine, methionine, phenylalanine, serine, and threonine showed a significant increase (\(p<0.05\)) in FAAs concentration at the end of storage (165 min) compared to the beginning of the digestive process (0 min). Asparatic acid, glutamic acid, and glycine/arginine showed a significant decrease (\(p<0.05\)) in concentration at the end of digestion (165 min) compared to the beginning of the digestive process (0 min). The release of FAAs from the digestive process in freeze-dried samples ranged between 0 and 21 mg/100 g dry weight (Figure 7). Through the digestive process, glutamic acids were the dominating FAAs followed by glycine/arginine, except at the end of digestion (165 min). Amino acids such as asparagine, glycine/arginine, histidine, lysine, methionine, phenylalanine, serine, and threonine showed a significantly higher (\(p<0.05\)) FAAs concentration at the end of digestion (165 min) compared to the beginning of digestion (0 min). However, aspartic acid showed a significantly lower (\(p<0.05\)) FAAs concentration at the end of digestion (165 min) compared to the beginning of digestion (0 min) due to no detection during analysis. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Samples**} & **FRAP (mmol TE/** & **ABTS (mmol PGE/** & **ORAC (mmol TE/** \\
**100 g Dry Weight** & **100 g Dry Weight** & **100 g Dry Weight)** \\ \hline Frozen & 3.2 \(\pm\) 1.7 * & 0.1 \(\pm\) 0.0 & 229.6 \(\pm\) 107.9 * \\ Freeze-dried & 1.2 \(\pm\) 0.2 & 0.3 \(\pm\) 0.1 * & 130.7 \(\pm\) 37.1 \\ \hline \hline \end{tabular}  
* Denotes statistically significant differences (\(p<0.05\)), between values in the same column calculated by ANOVA.  
\end{table} 
Table 3: The antioxidant activity measured by ferric reducing antioxidant power (FRAP), 2\({}^{\prime}\)-azin-bis-(3-ethylbenzothazoline-6-sulfonic acid) (ABTS), and oxygen radical absorbance capacity (ORAC) in frozen (dry weight) and freeze-dried (dry weight) red sea cucumber (_Parastichopus tremulus_). The frozen samples have theoretically been calculated from wet weight to dry weight. The results are presented as Trolox equivalents (TE)/100 g or Propyl gallate equivalents (PGE)/100 g dry weight as mean \(\pm\) standard deviation (\(n=10\)). The FAAs concentration increased during digestion, with the largest increase seen in the large intestinal phase (165 min). Frozen samples showed an increase in all FAAs concentrations throughout the digestive process, except aspartic acid. Freeze-dried samples showed an increase in all FAAs concentrations throughout the digestive process, except aspartic acid, glutamic acid, and glycine/arginine. As already mentioned, asparagine and glutamine are determined during acid hydrolysis and are thus included as aspartic and glutamic acid. The digestion process and the availability of amino acids are determined by the effectivity of the digestive process, the food matrix, and the chemical composition of the raw material [66]. The decrease in glutamic acid and glycine/arginine could be due to  
Figure 6: The free amino acids (FAAs) concentration before (0 min), during (75 min), and at the end (165 min) of the simulated gastrointestinal digestion for frozen red sea cucumber (_Parastichopus tremulus_) (\(n=10\)). The frozen samples have theoretically been calculated from wet weight to dry weight. The results are presented as mean \(\pm\) standard error as mg/100 g dry weight. Means with different letters (a, b) indicate significant differences (\(p<0.05\)) throughout the digestive process.