The reducing powers of TRMHs, aswell as ascorbic acid, as a function
of their concentrations are shown in Fig. 4b. The ability of TRMHs to
reduce Fe3+ to Fe2+ was concentration dependent and the values increased
with increasing concentration of samples. Nevertheless, all hydrolysates
showed lower reducing power activities than did ascorbic
acid at the same concentrations. TRMH-Neutrase showed the highest
activity (absorbance=1.39 at 5mg/ml), while TRMH-Alcalase showed
the lowest activity (absorbance = 1.07 at 5 mg/ml). The undigested
muscle showed only an absorbance of 0.77 at 5 mg/ml. Similar results
were found byNasri et al. [4]who reported that hydrolysis of gobymuscle
improved twice the reducing power activity. The reducing power of
TRMHswas also in accordance with DPPH. Therefore, a medium degree
of hydrolysis was appropriate to obtain hydrolysate with good antioxidant
activity. Intarasirisawat et al. reported that the defatted skipjack
roe Alcalase hydrolysate with excessive hydrolysis degree had a lower
reducing power [53]. By contrast, the reducing power activity of porcine plasma hydrolysates increased with the increase of DH [54]. The difference
in the antioxidant activity is influenced by the sequence and the
exposure of terminal amino acids of peptides obtained as well as the
DH which influenced greatly the peptide chain length