Rheological Properties of Liquid Egg Products (LEPS)

Figures & data

Table 1 Summary for the rheological studies of liquid egg products

Product	Instrument	Temperature(°C)	Fitted model	Flow behavior index (n) consistency index (K pa.s^n)	Source
Salted egg yolk (7–14 % added salt by weight)	Concentric cylinder viscometer (1–512 rpm)	5–60	Power-Law	n = 2.986 – 0.0199C – 0.048D	Ibarz^[15]
				(0.562 < n < 0.878)
				K = 1.347  ×  10^−19 exp(3929/T  +  0.303C + 0.665D)
				( 0.237 < K < 61.182)
				(T: temperature, C: salt content, D: dry extract expressed as % weight)
Egg yolk	Concentric cylinderviscometer (1–512 rpm)	5–60	Power-Law	0.80 < n < 0.89	Ibarz and Sintes^[16]
				0.14 < K < 1.91
Egg white	Cone and plate rheometer (15–130 s^−1)	45–57.5	Power-Law	0.552 < n < 0.5635	Punidadas and McKellar[17]
				0.06667 < K < 0.07292
Whole egg		45–65		0.6043 < n < 0.61009
			0.05452 < K < 0.0601
Egg yolk		50–65		0.6467 < n < 0.7478
			0.13369 < K < 0.19488
Egg yolk (salted)		50–70		0.8362 < n < 0.9023
			0.21905 < K < 0.2699
Egg yolk	Concentric cylinder viscometer (70.2–512.4 s^−1)	4–60	Power-Law	0.843 < n < 0.879	Telis-Romero et al.[18]
				0.072 < K < 1.683
Egg white	Narrow gaped rotational viscometer (8.1–147 s^−1)	2	Power-Law and Casson	NA	Tung et al.[19]

Table 2 pH of liquid egg products (LEPs) at different temperatures

Product	Temperature (°C)	pH
Egg white	4	9.43
	25	9.14
	55.6	8.61
Egg yolk	4	6.25
	25	6.13
	60	5.92
Whole egg	4	8.00
	25	7.96
	60	7.74

Table 3 Total dry solid content of liquid egg products (LEPs)

Product	Total dry solid (% weight)
Egg white	12.60 ± 0.060
Egg yolk	48.87 ± 0.307
Whole egg	25.10 ± 0.079

Figure 1 Density of different egg products as a function of temperature.

Table 4 Temperature dependency of density of different egg products

Product	Temperature range (°C)	Equation ^a	r^2	Sest
Egg white (LEW)	4–55.6	ρ=−0.0074T ^2 −0.0039T+1038.9	0.9943	1.1845
Whole egg (LWE)	4–60	ρ=−0.0036T ^2 −0.272T+1039.9	0.9968	1.6488
Egg yolk (LEY)	4–60	ρ=−0.0037T ^2 −0.52T+1042.3	0.9997	0.1756
^aT is the temperature (°C).

Figure 2 Thixotropy of liquid egg products at 4°C: (a) egg white; (b) whole egg; (c) egg yolk.

Figure 3 Thixotropy of liquid egg products at 25°C: (a) egg white; (b) whole egg; (c) egg yolk.

Figure 4 Thixotropy of liquid egg products at pasteurization temperatures: (a) egg white (at 55.6°C); (b) whole egg (at 60°C); (c) egg yolk (at 60°C).

Figure 5 (a) Time dependency of LEW and LWE at 55.6°C and 60°C (at 32.2 s⁻¹); (b) time dependency of LEY at 60°C (at 5.3 s⁻¹); (c) Time dependency of LEW and LWE at 4°C (at 32.2 s⁻¹); and (d) time dependency of LEY at 4°C (at 5.3 s^–1).

Table 5 Flow parameters for LEPs at selected temperatures

Herschel bulkley model
Product	Temperature (°C)	consistency index, K (Pa s^n)	flow behavior index, n	r^2	Sest
Whole egg	4	0.038	0.9878	0.991	0.0325
	25	0.030	0.9720	0.992	0.0138
	60	0.028	0.929	0.980	0.0252
Egg white	4	0.032	0.9607	0.995	0.1421
	25	0.024	0.9545	0.992	0.1609
	55.6	0.021	0.9436	0.986	0.0219
Newtonian model
	Temperature (°C)	viscosity (Pa.s)		r^2	Ses
Whole egg	4	0.037		0.993	0.0402
	25	0.028		0.991	0.0365
	60	0.021		0.986	0.0343
Egg white	4	0.028		0.994	0.0336
	25	0.020		0.994	0.0213
	55.6	0.017		0.989	0.0254
Power law model
	Temperature (°C)	Consistency index, K (Pa.s^n)	Flow behavior index, n	r^2	Ses
Egg yolk	4	1.013	0.9324	0.999	0.0045
	25	0.438	0.897	1	0.0016
	60	0.284	0.8777	0.999	0.0073

Table 6 Yield stress values for LEW and LWE at selected temperatures

Product	Temperature (°C)	Yield stress (Pa)
Whole egg	4	0.1654
	25	0.2049
	60	0.1947
Egg white	4	0.0704
	25	0.1157
	55.6	0.1799

Figure 6 Effect of temperature on the viscosity as a function of shear rate (s⁻¹) for (a) egg white; (b) whole egg; and (c) egg yolk.

Table 7 Flow activation energies for liquid egg products (LEPs)

Product	Ea (J/mol)	r^2
Whole egg (LWE)	10,523.86 ^a	0.9728
Egg white (LEW)	15,495.63 ^a	0.9912
Egg Yolk (LEY)	20,095.76 ^b	0.9813
^acalculated from data measured at 16.12s^−1; and
^bcalculated from data measured at 8.48s^−1.

Punidadas , P. and McKellar , R.C. 1999 . Selected physical properties of liquid egg products at pasteurization temperatures . Journal of Food Processing and Preservation , 23 : 153 – 168 .

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Telis-Romero , J. , Thomaz , C.E.P. , Bernardi , M. , Telis , V.R.N. and Gabas , A.L. 2006 . Rheological properties and fluid dynamics of egg yolk . Journal of Food Engineering , 74 : 191 – 197 .

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Tung , M.A. , Watson , E.L. and Richards , J.F. 1970 . Rheology of fresh, aged and gamma-irradiated egg white . J. Food Science. , 35 ( 6 ) : 872 – 874 .

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