## 3 Results and Discussion
### Cluster Analysis and Raw Material Classification  
Hierarchical clustering analysis was conducted to explore the structural relationships of the raw materials and hydrolyzates of porcine organs based on the Z-scores of measured variables with regard to their antioxidant properties (DPPH, ABTS, and OH radical IC\({}_{50}\) values and reducing power). The Euclidean distance was used to calculate the dissimilarity,  
Figure 5: Hydroxyl radical scavenging activity (**a-e**) and OH radical IC\({}_{50}\) value (**f**) of Alcalase- and trypsin-medicated protein hydrolyzates from porcine organs. H, heart; K, kidney; S, spleen; V, liver; L, lung. Each error bar indicates the standard deviation (\(n=3\)). a–i means with the same letter within the result for IC\({}_{50}\) values are not significantly different (\(p\geq 0.05\)). Figure 6: Reducing power of Alcalase- and trypsin-medicated protein hydrolyzates (1 mg/mL) from porcine organs. H, heart; K, kidney; S, spleen; V, liver; L, lung. Each error bar indicates the standard deviation (\(n=3\)). a–g means with the same letter are not significantly different (\(p\geq 0.05\)). which was visualized as a dendrogram (Figure 7) using [PERSON]'s linkage method. The hierarchical clustering results clearly distinguished non-hydrolyzed controls (K, L, S, V, and H) and their hydrolyzates. There were demonstrable differences in antioxidant properties between the control group and the hydrolyzates. In non-hydrolyzed control groups, porcine heart characteristics can be easily distinguished from those of other offal. Moreover, Alcalase-mediated kidney (A-K) and trypsin-mediated lung (T-L) hydrolyzates possessed highly similar antioxidant properties, differentiating them from the other hydrolyzates. Based on the dendrogram, the data were divided into four clusters with distinct antioxidant profiles, and the treatment for each cluster was confirmed via the cluster membership number (Table 2). The key features of each cluster can be explained as follows:  
\begin{table} \begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Factor**} & **Cluster 1** & **Cluster 2** & **Cluster 3** & **Cluster 4** \\  & **(_n = 1_)** & **(_n = 4_)** & **(_n = 8_)** & **(_n = 2_)** \\ \hline Z-score (DPPH radical IC\({}_{50}\)) & 1.886 & 0.924 & \(-\)0.500 & \(-\)0.793 \\ Z-score (ABTS radical IC\({}_{50}\)) & 3.343 & 0.301 & \(-\)0.442 & \(-\)0.503 \\ Z-score (OH IC\({}_{50}\)) & 1.135 & 1.210 & \(-\)0.682 & \(-\)0.259 \\ Z-score (reducing power) & \(-\)1.396 & 0.970 & \(-\)0.583 & 1.091 \\ \multirow{2}{*}{Assigned treatment (1)} & \multirow{2}{*}{H} & \multirow{2}{*}{K, S, V, and L} & A-H, T-H, T-K, A-S, & A-K and T-L \\  & & & T-S, A-V, T-V, and A-L & A-K and T-L \\ \hline \hline \end{tabular}  \({}^{(1)}\) H, heart; K, kidney; S, spleen; V, liver; L, lung; A-, Alcalase-hydrolyzed; T-, trypsin-hydrolyzed. Cluster 1: low radical scavenging activities and reducing power (porcine heart);  
Cluster 2: moderate radical scavenging activities but high reducing power (porcine kidney, spleen, liver, and lung);  
Cluster 3: balanced radical scavenging activities but low reducing power (Alcalase- and trypsin-hydrolyzed porcine heart, trypsin-hydrolyzed kidney, Alcalase- and trypsin-hydrolyzed liver, and Alcalase-hydrolyzed lung);  
Cluster 4: strong DPPH and ABTS radical scavenging activities and high reducing power (Alcalase-hydrolyzed kidney and trypsin-hydrolyzed lung). As demonstrated, the distinct antioxidant properties of porcine organs and their hydrolyzates are important considerations when selecting initial raw materials for future  
\begin{table}