Antioxidant and sensory properties of protein hydrolysate derived from Nile tilapia (Oreochromis niloticus) by one- and two-step hydrolysis

Abstract

Antioxidant and sensory properties of Nile tilapia protein hydrolysates prepared by one- and two-step hydrolysis using commercial proteases were investigated. Hydrolysates prepared using single protease including Alcalase (HA), Flavourzyme (HF), Protamex (HPr) and papain (HPa) had increases in antioxidant activities as the degree of hydrolysis (DH) increased up to 40 % (P < 0.05). Amongst all hydrolysates, HA having 40 % DH showed the highest antioxidant activities. When HA was further hydrolysed by papain, the resulting hydrolysate (HAPa) exhibited the highest antioxidant activities for all assays tested (P < 0.05). ABTS radical scavenging activity and metal chelating of HAPa generally remained constant in a wide pH range (1-11) and during heating at 30-100 °C. Both activities increased in the simulated gastrointestinal tract model system, especially in intestine condition. HAPa (100-1,000 ppm) could retard lipid oxidation in β-carotene-linoleate and lecithin-liposome model systems in a dose dependent manner. Peptides in both HA and HAPa with molecular weight of 513 Da and 1,484 Da possessed the strongest ABTS radical scavenging activity and metal chelating activity, respectively. The amino acid profile of both HA and HAPa contained a high amount of hydrophobic amino acids (38.26-38.85 %) and had glutamic acid/glutamine, lysine and aspartic acid/asparagine as the dominant amino acids. However, HAPa showed a higher acceptability than did HA, owing to the lower bitterness. Therefore, the use of Alcalase in combination with papain for hydrolysis of protein isolate rendered the hydrolysate with antioxidant properties and reduced bitterness, which could serve as the functional supplement.

Keywords: Antioxidant activity; Commercial proteases; Nile tilapia; Protein hydrolysate; Two-step hydrolysis.

Fig. 1

Antioxidant activities of Nile tilapia protein hydrolysate prepared using various single proteaseses with different DHs determined by DPPH radical scavenging activity (a), ABTS radical scavenging activity (b), FRAP (c) and metal chelating activity (d). HA, HF, HPr and HPa: hydrolysate prepared using Alcalase, Flavourzyme, Protamex and papain, respectively. Bar represent stand deviations (n = 3). Different lowercase letters within the same type of enzyme and different uppercase letters within the same DH indicate the significant differences (P < 0.05)

Fig. 2

Antioxidant activities of Nile tilapia protein hydrolysate prepared by a two-step hydrolysis using various proteases as determined by DPPH radical scavenging activity (a), ABTS radical scavenging activity (b), FRAP (c) and metal chelating activity (d). HA: hydrolysate prepared using Alcalase. HAF, HAPr and HAPa: HA further hydrolyzed with Flavourzyme, Protamex and papain, respectively. Bar represent stand deviations (n = 3). Different lowercase letters in the same parameter indicate the significant differences (P < 0.05)

Fig. 3

Antioxidant stability of the selected Nile tilapia protein hydrolysate prepared using two-step hydrolysis process (HAPa) as affected by pH (a), heating (b) and GIMs (c) as monitored by ABTS radical scavenging activity and metal chelating activity. Bars represent standard deviation (n = 3)

Fig. 4

Changes in A₄₇₀ of β-carotene linoleic acid system (a) and the formation of CD (b) and TBARS (c) in lecithin liposome system containing the selected Nile tilapia protein hydrolysate (HAPa) at different levels. Bars represent standard deviation (n = 3)

Fig. 5

Elution profiles of antioxidant peptides from the selected Nile tilapia protein hydrolysates, HA and HAPa, by a Sephadex G-25 column as monitored by A₂₂₀ and A₂₈₀ (a and c). Elution was performed using distilled water with a flow rate of 0.5 ml/min. Fractions (3 ml) were determined for ABTS radical scavenging activity and metal chelating activity (b and d). Solid arrows in (a) and (c) indicate the standard peaks. Dash arrows in (b) and (d) indicate the peaks with antioxidant activities