Pepsin Digestibility and Antioxidant Activity of Egg White Protein in Model Systems with Green Coffee Extract

Figures & data

Table 1 Composition of model systems and heating conditions

Model systems composition and their abbreviation		Time of heating (h)
Egg white protein 200 g	P	–
Egg white protein 200 g	P/0.5/180	0.5
Egg white protein 200 g	P/1/180	1
Egg white protein 200 g green coffee extract 3	P/1.5%/1/180	1
Egg white protein 200 g green coffee extract 6 g	P/3%	–
Egg white protein 200 g green coffee extract 6 g	P/3%/0.5/180	0.5
Egg white protein 200 g green coffee extract 6 g	P/3%/1/180	1
Egg white protein 200 g water 6 g	P/W/1/180	1
Egg white protein 200 g water 6 g green coffee extract 6 g	P/W/3%/1/180	1
Egg white protein 100 g saccharose 100 g	P/S/1/110	1
Egg white protein 100 g saccharose 100 g green coffee extract 6 g	P/S/3%/1/110	1
Egg white protein 100 g starch 100 g	P/St/1/180	1
Egg white protein 100 g starch 100 g green coffee extract 6 g	P/St/3%/1/180	1
Egg white protein 66.7 g saccharose 66.7 g starch 66,7g	P/S/St/1/110	1
Egg white protein 66.7 g saccharose 66.7 g starch 66.7g green coffee extract 6 g	P/S/St/3%/1/110	1
Egg white protein 100 g sunflower oil 100 g	P/O/1/180	1
Egg white protein 100 g sunflower oil 100 g green coffee extract 6 g	P/O/3%/1/180	1

P: protein; S: saccharose; St: starch; O: sunflower oil; W: water; Fe: ferrous ions; 1.5 or 3%: amount of added green coffee extract; 0.5 or 1: time of heating in hours; 110 or 180: temperature of heating in ^oC.

Figure 1 HPLC chromatogram of egg white protein (a) prior to enzymatic hydrolysis, (b) after 2 h of pepsin hydrolysis, 1–5 egg white protein fractions.

Figure 2 HPLC chromatogram of egg white protein amino acid profile (a) standard amino acids mixture, and (b) egg white protein.

Figure 3 Total amino acids, protein content after heating, and pepsin in vitro digestibility of egg white protein in model systems with green coffee extract. Error bars show the relative standard deviation. Total amino acids are expressed on amount of protein added to the systems. Egg protein after heating means the amount of main protein fractions remaining after treatment determined by HPLC analysis. Egg white protein digestibility is a decrease of the amount of main protein fractions caused by 2 h pepsin digestibility determined by HPLC analysis.

Figure 4 Amino acid profile of egg white protein in model systems with coffee extract (a) exogenous amino acids: leucine (LEU), lysine (LYS), isoleucine (ILE), valine (VAL), phenylalanine (PHE), threonine (THR), methionine (MET), and tryptophan (TRP), and (b) endogenous amino acids: glutamic acid + glutamine (GLU), aspartic acid + asparagine (ASP), serine (SER), arginine (ARG), alanine (ALA), proline (PRO), glycine (GLY), threonine (TYR), histidine (HIS), and cysteine + cystine (CYS). The relative standard deviation did not exceed 10%.

Figure 5 Color parameters of model systems of egg white protein with coffee extract measured in CIE L*a*b* system. Error bars show the relative standard deviation.

Figure 6 Antioxidant activity of egg white protein in model systems with coffee extract measured as redox potential (RP) and DPPH IC₅₀ scavenging activity (DPPH). Bars with the same letters (caps – DPPH) indicate no significant difference (p > 0.05).