FTIR-based functional group changes and bioactivity evaluation of milkfish (Chanos chanos) protein hydrolysates produced by bromelain

The hydrolysis of milkfish ( Chanos chanos ) protein using bromelain enhance its bioactivity by cleaving peptide bonds and generating bioactive peptides with potential health benefits. This study aimed to characterize functional groups and evaluate the antibacterial, antidiabetic, and toxicity activities. Hydrolysis was performed using different enzyme concentrations (5–7%) and hydrolysis times (5–7 h). The resulting hydrolysates were analyzed using FTIR, and their bioactivities were assessed through antibacterial assays against Escherichia coli and Staphylococcus aureus , α-amylase inhibition, and a brine shrimp lethality test (BSLT). FTIR results revealed structural modifications, indicated by the disappearance of the amide B band and the absence of the amide II band at 5% enzyme concentration, suggesting changes in protein secondary structure and hydrogen bonding. The highest antibacterial activity was observed at 7% for 7 h, with inhibition zones of 13.36±0.28 mm against E. coli and 11.93±0.20 mm against S. aureus . The lowest LC 50 value 22.98±17.52 ppm was recorded at 5% for 7 h, indicating notable toxicity. The strongest α-amylase inhibition was obtained at 5% for 5 h, with an IC 50 value of 118.09±80.76 ppm. Overall, the hydrolysates showed strong antibacterial activity, preliminary toxicity potential based on BSLT, and relatively weak antidiabetic activity.