A Comparative Study on Some Functional and Antioxidant Properties of Kilka Meat,Fishmeal, and Stickwater Protein Hydrolysates

This study determined some antioxidative activities and functional properties of hydrolyzed proteins prepared from kilka (Clupeonella sp.) meat (KMH), kilka fishmeal (KFH), and stickwater (SWH). The highest degree of hydrolysis (DH) was 25.02% (p < 0.05) in SWH; however, the difference in DH between KMH and KFH was not significant. KFH had the highest protein content (85.69%) compared with other hydrolysis samples. The Fourier transform infrared spectra of KFH had the highest amide absorption picks (p < 0.05). Solubility at neutral pH was 84.09%, 86.00%, and 93.08% for KMH, KFH, and SWH, respectively. The highest fat absorption capacity was obtained with KFH (204 mg/50 mg). KFH also showed the best foaming properties with 25.66% foaming capacity and proper stability during 60 min (p < 0.05). The highest and lowest whiteness values were obtained in KMH (72.33%) and SWH (36.54%), respectively (p < 0.05). The highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC₅₀ value of 1.99 mg/mL) and 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (IC₅₀ value of 2.00 mg/mL) radical scavenging activities were measured at the highest concentrations (40 mg/mL) in KFH (p < 0.05). KFH had the best functional and antioxidant properties, while SWH had a strong ability to inhibit lipid oxidation. Therefore, stickwater from fishmeal production factories is a potential resource for use in developing value-added products instead of being discarded.