Denaturation and the Glass Transition Temperatures of Myofibrillar Proteins from Osmotically Dehydrated Tilapia: Effect of Sodium Chloride and Sucrose

Figures & data

Figure 1 The kinetics of the sodium chloride (NaCl) and sucrose contents of tilapia fillets during osmotic dehydration using binary solutions of NaCl and sucrose or ternary solutions (NaCl-water-sucrose). w.b. = wet basis.

Figure 2 (A) DSC thermograms of tilapia muscle with different sodium chloride contents; (B) DSC thermograms of tilapia muscle with different sucrose contents; and (C) DSC thermogram of tilapia muscle with different NaCl and sucrose contents. Exothermal heat flow up.

Table 1 Denaturation temperature (T_d) and enthalpy (ΔH) of tilapia fillets after different impregnation treatments, measured by DSC

Solute content (w.b.)		Moisture content (w.b.)	Td myosin (°C)	ΔH myosin (J/g fillet)	Td actin (°C)	ΔH actin (J/g fillet)
Salt
0		0.80	54.7 ± 0.1	1.49 ± 0.22	75.2 ± 0.2	0.35 ± 0.09
2.2		0.77	53.1 ± 0.4	0.45 ± 0.01	72.5 ± 0.4	0.27 ± 0.12
2.4		0.78	52.4 ± 0.2	0.34 ± 0.04	—	—
4.0		0.75	50.8 ± 0.2	0.22 ± 0.05	70.5 ± 0.3	0.18 ± 0.07
5.3		0.74	50.7 ± 0.2	0.30 ± 0.02	70.0 ± 0.2	0.13 ± 0.05
9.4		0.69	48.7 ± 0.1	0.20 ± 0.05	—	—
11.4		0.67	43.7 ± 0.7	—	71.3 ± 0.3	0.33 ± 0.15
Sucrose
0.5		0.77	55.5 ± 0.1	1.62 ± 0.51	75.2 ± 0.2	0.35 ± 0.05
2.8		0.73	55.3 ± 0.3	1.66 ± 0.43	75.2 ± 0.3	0.32 ± 0.13
4.0		0.68	55.6 ± 0.1	1.89 ± 0.10	75.8 ± 0.1	0.57 ± 0.21
8.8		0.63	56.5 ± 0.3	1.79 ± 0.08	76.6 ± 0.2	0.42 ± 0.08
9.6		0.62	57.6 ± 0.1	1.71 ± 0.42	78.7 ± 0.3	0.38 ± 0.05
Salt	Sucrose
2.7	2.0	0.75	53.4 ± 0.2	0.42 ± 0.06	72.9 ± 0.3	0.30 ± 0.05
4.5	2.7	0.72	53.1 ± 0.1	0.46 ± 0.04	71.9 ± 0.2	0.38 ± 0.11
4.9	4.5	0.67	51.9 ± 0.3	0.38 ± 0.08	71.8 ± 0.5	0.23 ± 0.09
4.9	6.2	0.63	51.5 ± 0.3	0.36 ± 0.05	71.9 ± 0.4	0.20 ± 0.10
6.1	7.9	0.58	51.1 ± 0.1	0.26 ± 0.01	—	—
w.b.: wet basis.

Table 2 GAB parameters for Tilapia fillet

Sample	M	C	K	R^2
Untreated	0.049	7.267	0.957	0.96
O.D. in NaCl-H2O solution	0.0522	7.897	1.084	0.99
O.D. in sucrose-H2O solution	0.081	1.057	0.946	0.989
O.D. in ternary solution	0.10	0.897	1.046	0.991
C, K: constants; M: monolayer moisture.

Figure 3 Water vapour adsorption isotherms of fresh and osmotically dehydrated tilapia fillets.

Figure 4 (A) Thermograms of fresh and osmotically dehydrated tilapia fillets in different solutions at a_w= 0.11; and (B) thermograms of fresh and osmotically dehydrated tilapia fillets in different solutions at a_w= 0.85. Exothermal heat flow up.

Figure 5 (A) Thermograms of osmotically dehydrated tilapia fillets in aqueous NaCl solutions at different a_w values; (B) thermograms of osmotically dehydrated tilapia fillets in aqueous sucrose solutions at different a_w values; and (C) thermograms of osmotically dehydrated tilapia fillets in ternary solutions (NaCl-water-sucrose). Exothermal heat flow up.

Table 3 Glass transition temperature of Tilapia fillet after different impregnation treatments, measured by DSC

Treatment	aw	Xw	Tgi	Tgm	Tge
Untreated	0	0	86.64	92.02	97.40
	0.11	0.003	46.86	52.25	56.81
	0.44	0.08	53.61	59.76	62.84
	0.85	0.26	−71.01	−58.70	−48.83
O.D. in NaCl-H2O solution	0.11	0.03	51.54	82.64	87.21
	0.33	0.07	34.08	54.12	58.23
	0.53	0.11	26.52	31.82	39.74
	0.85	0.88	−100.18	−95.64	−90.49
O.D. in sucrose-H2O solution	0	0	72.2	90.06	107.92
	0.11	0.03	46.32	53.47	60.61
	0.85	0.33	−64.58	−52.97	−44.04
O.D. in ternary solution	0	0	62.22	71.94	74.72
	0.11	0.01	55.17	57.39	71.28
	0.23	0.02	22.50	36.39	39.86
	0.33	0.03	8.6	16.93	21.10
	0.44	0.07	−22.19	−12.47	−6.91
	0.61	0.18	−63.20	−59.03	−52.09
	0.76	0.44	−94.39	−91.69	−81.89
	0.85	0.63	−87.96	−81.02	−76.85
aw: water activity; Xw: moisture content; Tgi, Tgm, and Tge: initial, mid, and end transitions temperatures.

Figure 6 Thermograms of fresh fillets at different a_w values. Exothermal heat flow up.

Figure 7 Glass curves of fresh and osmotically dehydrated tilapia fillets. w.b.= wet basis.