Thermal properties of duck fatty liver (foie gras) products

Figures & data

Table 1. Composition (w/w) of duck foie gras and sub-products.

Product	Water	Lipids	Protein
Foie gras	30.9 ± 1.7	57.1 ± 5.5	7.1 ± 0.56
Foie gras emulsion	40.5 ± 1.5	51.0 ± 5.3	5.4 ± 1.2
Duck fat	0.8 ± 0.3	99.3 ± 0.0	ND
Fat of foie gras	0.2 ± 0.0	99.9 ± 0.0	ND

ND: not determined.

n = 13.

Table 2. Fatty acid profile for fat of foie gras and duck fat.

		Fatty acid content (g/100 g fatty acids)
Nomenclature	Denomination	Fat of foie gras	Duck fat
C14:0	Myristic A.	0.9 ± 0.00	0.6 ± 0.01
C14:1	Myristoleic A.	0.1 ± 0.00	0.1 ± 0.00
C16:0	Palmitic A.	28.1 ± 0.05	26.1 ± 0.20
C16:1	Palmitoleic A.	2.9 ± 0.00	3.2 ± 0.01
C18:0	Stearic A.	10.6 ± 0.06	6.5 ± 0.00
C18:1 9t	Elaic A.	0.2 ± 0.01	0.2 ± 0.00
C18:1 9c	Oleic A.	54.9 ± 0.10	53.0 ± 0.17
C18:1 11c	Cis-Vaccenic A.	1.0 ± 0.00	1.0 ± 0.05
C18:2	Linoleic A.	0.9 ± 0.00	9.0 ± 0.04
C18:3	Linolenic A.	-	0.3 ± 0.00
C20:1	Gondoic A.	0.1 ± 0.06	0.2 ± 0.00
Unknown		0.5 ± 0.06	0.4 ± 0.00
Total saturated		39.6	33.2
Total monounsaturated		59.1	57.6
Total polyunsaturated		0.9	9.3

Figure 1. Fatty acid profile of lipids; A: Fat obtained from foie gras; B: duck fat.

Table 3. Density ρ (kg/m ³) of foie gras and their by-products at 20°C.

Product ↓	Density ρ (kg/m 3)
Foie gras (organ)	947 ± 73
Foie gras (emulsion)	928 ± 47
Foie gras (fat)	836 ± 37
Duck fat	843 ± 43

Figure 2. DSC for foie gras and by-products in the temperature range of –50 to 70°C.

Figure 3. Liquid fat fraction (LFF) at different temperatures for foie gras fat and duck fat.

Figure 4. Cp at different temperatures for foie gras and by-products; A: Foie gras; B: Foie gras emulsion; C: Foie gras fat; and D: duck fat.

Table 4. Regression terms for the heat capacity of individual components.

Component	a2	a1	ao
Water*	5.46E-06	–9.09E-05	4.1762
Protein*	–1.31E-06	1.21E-03	2.0082
Liquid fat**	–0.00004	0.0032	1.6629
Solid fat**	–0.0003	–0.0201	1.2700

*From Choi and Okos.^[9]

**Obtained in this work by polynomial regression for foie gras fat (Eq. [5]).

Figure 5. Thermal conductivity as a function of temperature, for A: duck fat and foie gras emulsion; B: foie gras fat and foie gras (organ).

Table 5. Thermal conductivity (W m⁻¹ °C⁻¹) linear and quadratic models for foie gras and its by-products.

Product	Quadratic	Linear
Foie gras	kfg = 3E-05 T^2 – 0.0017 T + 0.3428	kfg = 0.0003 T + 0.3197
Foie gras emulsion	kfge = 9E-06 T^2 – 0.002 T + 0.3866	kfge = –0.0013 T + 0.3761
Foie gras fat	kfgf = –1E-06 T^2 – 0.0005 T + 0.1915	kfgf = –0.0006 T + 0.1928
Duck fat	kdf = –1E-05 T^2 + 0.0007 T + 0.156	kdf = –0.0002 T + 0.1667

TABLE 6 Thermal diffusivity at different temperatures, α (m² s⁻¹) × 10⁻⁷

Temperature (°C)	Foie gras		Foie gras fat	Duck fat
	Organ	Emulsion
50	1.4767	1.3098	1.1262	—
55	1.4889	1.2890	1.1084	0.9567
60	1.5020	1.2691	1.0913	0.9396
65	1.5168	1.2488	1.0750	0.9258
70	1.5309	1.2314	—	0.9101

Choi, Y.; Okos, M. Effects of Temperature and Composition on the Thermal Properties of Foods. In Food Engineering and Process Applications, Volume 1, Chapter 9; Lemaguer, M.; Jelen, P.; Eds.; Elsevier Applied Science Publishers LTD, Crown House: Essex, England, 1986.

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Pham, Q.T.; Willix, J. Thermal Conductivity of Fresh Lamb Meat, Offals and Fat in the Range –40 to 30°C: Measurements and Correlations. Journal of Food Science 1989, 54, 508–515.

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