The antioxidant activities of TRMHs as measured by β-carotene
bleaching are reported in Fig. 4c. As can be seen, the antioxidant activity
of all protein hydrolysates increased with increasing sample concentration.
TRMH-Neutrase with the lowest DH showed the highest ability to
prevent bleaching of β-carotene with 81% of inhibition at 5 mg/ml
followed by TRMH-Crude, TRMH-A26 and TRMH-Alcalase with an inhibition
of 71%, 58% and 52%, respectively. The undigested exhibited only
25% of activity at 5 mg/ml. BHA displayed a better antioxidant activity
than all hydrolysates at the same concentrations. A strong correlation
was observed in this study between the DH and the antioxidant activity
detected by β-carotene bleaching (R2 = 0.968). Wiriyaphan et al. [58]
also reported higher β-carotene bleaching activity in pepsin threadfin
bream surimi waste hydrolysate with the lowest DH (9%), and lower
activity in Alcalase hydrolysate with the highest DH (26%). In another
study, Kong and Xiong [59] reported also that the extensive hydrolysis
of zein by Alcalase, reduced the peptide's ability to act as a physical barrier
to prevent oxidants fromreaching the lipid fraction in the liposome.
In another context, Olek et al. [60] revealed that NADH can inhibit
lipid peroxidation in vitro. As depicted in Table 2, the content of
NADH in TRMH-Neutrase is the highest with 2.13 μmol/g, which may
contribute to the inhibition of β-carotene bleaching of TRMH-Neutrase