Influence of the Enzymatic Hydrolysis Using Flavourzyme Enzyme on Functional, Secondary Structure, and Antioxidant Characteristics of Protein Hydrolysates Produced from Bighead Carp (Hypophthalmichthys nobilis)

Abstract

In the current study, bighead carp fish were used in conjunction with the flavourzyme enzyme to obtain (FPH) fish protein hydrolysates. The optimum conditions of the hydrolysis process included an enzyme/substrate ratio of 4% and a temperature of 50 °C and pH of 6.5. The hydrolysis time was studied and investigated at 1, 3, and 6 h, and the (DH) degree of hydrolysis was recorded at 16.56%, 22.23%, and 25.48%, respectively. The greatest yield value was 17.83% at DH 25.48%. By increasing the DH up to 25.48%, the crude protein and total amino acid composition of the hydrolysate were 88.19% and 86.03%, respectively. Moreover, more peptides with low molecular weight were formed during hydrolysis, which could enhance the functional properties of FPH, particularly the solubility property ranging from 85% to 97%. FTIR analysis revealed that enzymatic hydrolysis impacted the protein's secondary structure, as indicated by a remarkable wavelength of amide bands. Additionally, antioxidant activities were investigated and showed high activity of DDPH radical scavenging, and hydroxyl radical scavenging demonstrated remarkable activity. The current findings demonstrate that the functional, structural, and antioxidant characteristics of FPH might make it an excellent source of protein and suggest potential applications in the food industry.

Keywords: CD secondary structure; FTIR; antioxidants activities; bighead carp; enzymatic hydrolysis; flavourzyme enzyme; functional characteristics.

Figure 1

Influence of enzymatic hydrolysis conditions (A) E/S ratio; (B) pH; (C) temperature; and (D) time of hydrolysis reaction on degree of hydrolysis (DH). The values represent mean ± SD (n = 3), and the various letters indicate the values are significantly different (p ≤ 0.05).

Figure 2

Molecular weight distribution of the fresh and hydrolysate products derived from fish bighead carp using flavourzyme protease under three different degrees of hydrolysis: (a) fresh sample; (b) DH 16.56% (1 h); (c) DH 22.23% (3 h); and (d) DH 25.48% (6 h).

Figure 3

Scanning electron microscopy (SEM) of protein hydrolysates at various degrees of hydrolysis; (a) DH 16.56%, (b) DH 22.23%, and (c) DH 25.48%.

Figure 4

SDS-PAGE pattern of protein hydrolysates under different degrees of hydrolysis.

Figure 5

FTIR spectrum of FPH obtained at different degrees of hydrolysis using the flavourzyme enzyme. The various values on the graphs indicate the changes in amide bands I, II, and III.

Figure 6

Protein solubility of hydrolysates obtained at different degrees of hydrolysis at pH values ranging from 2 to 10. The values represent mean ± SD (n = 3), and various letters indicate that the values are significantly different (p ≤ 0.05).

Figure 7

Antioxidant assays of FPH produced under optimal parameters at different degrees of hydrolysis, (A) DPPH radical-scavenging activity, (B) hydroxyl radical-scavenging assay, and (C) Fe⁺²-chelating activity. The results are displayed as mean ± SD with triplicates.