## 4 Conclusions  
This study confirms that major porcine organs (heart, kidney, spleen, liver, and lung) with high protein content (15.90-20.30 g/100 g) are valuable raw materials for producing antioxidant hydrolyzates. In particular, the high extractable protein content of the heart could be tentatively associated with its increased degree of hydrolysis. Trypsin achieved a lower degree of hydrolysis compared to Alcalase, likely due to the limited degradation of porcine serum albumin. The hydrolyzates exhibited significantly higher DPPH, ABTS, and hydroxyl radical scavenging activities than their non-hydrolyzed counterparts, whereas the enzymatic hydrolysis did not positively influence reducing power. The complexity of antioxidant properties, linked to raw materials, applied proteases, and antioxidant assay, observed in this study was clarified through cluster analysis. Hierarchical and k-means cluster analysis revealed distinct differences in antioxidant properties between non-hydrolyzed controls and hydrolyzates, where A-K and T-L treatments were classified as showing strong DPPH and ABTS radical scavenging activities and reducing power. Therefore, from an industrial perspective, our findings suggest that porcine organs obtained in bulk could be used to produce antioxidant hydrolyzates distinct from raw materials without necessitating additional separation of raw materials. However, in the interests of developing a high-quality, premium product with more pronounced antioxidant effects, it is recommended that kidneys be selectively processed with Alcalase (A-K) and lungs with trypsin (T-L). Further studies are warranted to elucidate the fundamental mechanisms underlying the antioxidant properties of the A-K and T-L treatments by improving the scientific understanding of the free amino acid profile and specific bioactive peptides. In addition, for the purpose of commercialization, safety evaluations and parallel in vivo studies should be conducted to confirm the suitability of hydrolyzates for use in food or feed applications.  
Conceptualization, E.J.J., [PERSON]-S.K., [PERSON]-C.S., K.-W.L. and H.-W.K.; data curation, [PERSON], W.-YS. and [PERSON]-H.S.; formal analysis, J.H., W.-YS. and [PERSON]-H.S.; funding acquisition, E.J.J., [PERSON]-S.K., E.-C.S., K.-W.L. and H.-W.K.; investigation, E.J.J., K.-S.K., E.-C.S., [PERSON]-W.L. and H.-W.K.; methodology, J.H., [PERSON]-YS. and H.-W.K.; project administration, [PERSON]-W.L. and H.-W.K.; supervision, [PERSON]-W.L. and H.-W.K.; validation, E.J.J., K.-S.K. and E.-C.S.; visualization, J.H. and H.-W.K.; writing--original draft, J.H.; writing--review and editing, E.J.J., K.-S.K., E.-C.S., D.-H.S., K.-W.L. and H.-W.K. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the Project for Development of Development of companion animal feed additives to improve palatability using byproducts, funded by the Ministry of Agriculture, Food and Rural Affairs (322089031 HD020).  
Not applicable.  
Data Availability Statement: The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.  
We thank the Ministry of Agriculture, Food and Rural Affairs (322089031 HD020) for the financial support through national funds. Furthermore, this work was supported by the Gyeongsang National University Fund for Professors on Sabbatical Leave, 2024.  
The authors declare no conflicts of interest.