Research on the physicochemical and digestive properties of Pleurotus eryngii protein

Figures & data

Table 1. Composition of digestive juices (500 mL) used for in vitro incubation of protein sample.

Mouth		Stomach		Duodenum
Saliva		Gastric juice		Duodenal juice		Bile
KCl	0.45g	NaCl	1.375 g	NaCl	0.35 g	NaCl	2.63 g
KSCN	0.10	NaH2PO4	0.135 g	NaHCO3	1.70 g	NaHCO3	2.38 g
NaH2PO4	0.45	KCl	0.410 g	KH2PO4	0.04 g	KCl	0.18 g
NaSO4	0.275	NH4Cl	0.155 g	KCl	0.28 g	Urea	0.125 g
NaCl	0.15	CaCl2·2 H2O	0.2 g	MgCl2	0.025 g	37% HCl	0.075 mL
NaHCO3	0.845	37% HCl	0.650 mL	37% HCl	0.09 mL	BSA	0.90 g
Urea	0.20	Urea	0.045 g	Urea	0.05 g	Bile	10 g
Uric acid	5.75 mg	Glucuronic acid	0.01 g	BSA	0.50 g	CaCl2·2H2O h20H2O	0.10 g
Mucin	12.5 mg	Glucose	0.325 g	Pancreatin	2.00 g
Peroxidase	1.25 UI	Glucosamine-HCl	0.165 g	Lipase	0.50 g
NaNO2	3.45 mg	Ascorbic acid	8.8 mg	CaCl2·2 H2O	0.10 g
		BSA	0.5 mg
		Pepsin	1.25 g
		Mucin	1.5 g
		H2O2	5 μL
		FeSO4·7 H2O	5.6 mg

Figure 1. In vitro digestive model.

Figure 2. Viscosity (η) (a) and shear stress (b) of different protein concentrations (3 g/100 g (raw materials/H₂O)–9 g/100 g (raw materials/H₂O)) at 25°C.

Figure 3. Viscosity (η) (a) and shear stress (b) of 3 g/100 g (raw materials/H₂O) protein solution at different temperatures (25°C, 35°C, and 45°C).

Figure 4. Modulus of 15 g/100 g (raw materials/H₂O) protein solution at different pH at 70°C. (a) Modulus of 15 g/100 g (raw materials/H₂O) protein solution at pH 2.0. (b) Modulus of 15 g/100 g (raw materials/H₂O) protein solution at pH 5.0.

Table 2. Effect of pH on the sulfhydryl and disulfide bond contents.

pH	R-S	S-S
2.0	1.49 ± 0.34^a	1.27 ± 0.23^a
3.5	1.42 ± 0.29^a	1.63 ± 0.32^a
5.0	1.62 ± 0.41^a	1.61 ± 0.28^a
7.0	2.52 ± 0.38^b	0.92 ± 0.41^a

Note: a is control standard; b and c mean significant difference (P < 0.05).

Table 3. Connection between physicochemical and rheological properties.

	η	G’	G’’
R-S	−0.829*	0.919**	0.946**
T-S	−0.613	0.933**	0.946**
S-S	0.955**	−0.652	−0.680

Note: *means significant difference (P < 0.05); **means extremely significant difference (P < 0.01).

Table 4. The Power Law model of protein in different conditions.

		K	N	R^2
25°C	pH = 2.0	0.8566	0.3718	0.9812
	pH = 3.0	1.6412	0.3253	0.9942
	pH = 3.5	1.9249	0.3898	0.9953
	pH = 4.0	1.7519	0.3628	0.9906
	pH = 4.5	0.0611	0.4882	0.9120
35°C	pH = 2.0	0.5340	0.4327	0.9938
	pH = 3.0	0.9111	0.3935	0.9838
	pH = 3.5	1.3751	0.4151	0.9912
	pH = 4.0	1.2127	0.3958	0.9920
	pH = 4.5	0.0616	0.4774	0.9241
45°C	pH = 2.0	0.4888	0.4114	0.9903
	pH = 3.0	0.6400	0.4014	0.9650
	pH = 3.5	0.9386	0.4266	0.9929
	pH = 4.0	0.8326	0.4065	0.9837
	pH = 4.5	0.0622	0.4514	0.9175

Figure 5. Evolution of storage modulus (G’) and loss modulus (G’’) at 0.5 Hz for 15 g/100 g (raw materials/H₂O) protein solution with different temperatures by adding different concentrations of Ca²⁺.

Figure 6. The surface hydrophobicity (H₀) of Pleurotus eryngii protein.

Note: a is control standard; b and c mean significant difference (P < 0.05).

Table 5. The contents of sulfhydryl and disulfide bond of protein treated by heat and ultrasound.

	R-SH (μmol/L)	T-SH (μmol/L)	S-S (μmol/L)
Non-treatment group	0.110 ± 0.006^a	0.207 ± 0.017^a	0.048 ± 0.012^a
Heat treatment group	0.175 ± 0.002^b	0.255 ± 0.002^a	0.039 ± 0.002^a
Ultrasound treatment group	0.292 ± 0.014^c	0.337 ± 0.008^b	0.025 ± 0.004^b

Note: a is control standard; b and c mean significant difference (P < 0.05).

Table 6. Secondary structure of the Pleurotus eryngii protein.

Secondary structure	Wavelength (cm^−1)	Non-treatment	Heat treatment	Ultrasound treatment
α -helix	1,649–1,658	12.88% ± 0.32	33.93% ± 0.21	25.22% ± 0.11
β-sheet	1,610–1,640, 1 692	43.30% ± 0.09	26.66% ± 0.17	29.25% ± 0.21
β-turn	1,661–1,689	21.74% ± 0.12	17.61% ± 0.08	28.76% ± 0.13
Random coil	1,643–1,644	22.08% ± 0.13	21.80% ± 0.12	16.77% ± 0.19

Figure 7. The FT-IR spectra of Pleurous eryngii protein in the region of 400~4000 cm^–1.

Figure 8. The fitted peaks of Pleurous eryngii protein in the region of 1600~1700 cm^–1.

Table 7. The denaturation temperature (Tm) and enthalpy change (△H) of Pleurotus eryngii protein.

	Non-treatment group	Heat treatment group	Ultrasound treatment group
Tm(°C)	84.85 ± 0.02	91.43 ± 0.04	94.51 ± 0.03
△H(J)	0.543 ± 0.07	0.195 ± 0.02	0.183 ± 0.03

Figure 9. The DSC and TG results of Pleurous eryngii protein.

Figure 10. DH and VDP of Pleurous eryngii protein

Note: a is control standard, b and c means significant difference (P < 0.05).

Table 8. Amino acid composition of protein digestive juice.

Amino acids	Non-treatment group	Heat treatment group	Ultrasound treatment group
Threonine	5.08% ± 0.12	1.22% ± 0.11	2.60% ± 0.12
Serine	-	-	2.41% ± 0.08
Alanine	-	-	9.35% ± 0.02
Viline	30.51% ± 0.07	13.41% ± 0.10	22.26% ± 0.14
Isoleucine	5.08% ± 0.03	1.22% ± 0.05	5.89% ± 0.12
Leucine	-	60.98% ± 0.13	22.92% ± 0.10
Tyrosine	28.81% ± 0.11	-	8.34% ± 0.08
Phenylalanine	-	-	4.94% ± 0.12
Hlstidine	-	-	2.00% ± 0.03
Lysine	30.51% ± 0.05	23.17% ± 0.12	19.28% ± 0.08

Note:“-” means not detected.

Figure 11. The peptide content of protein digestive juice Note: a is control standard, b and c means significant difference (P < 0.05)

Figure 12. The absorption intrinsic of Pleurous eryngii protein and protein digestive products.

Figure 13. The antioxidant of protein digestive products.