Rheological and Textural Characteristics of Date Paste

Figures & data

Table 1 Chemical parameters of date pastes ^a

Parameters	Golden	Black
Total solids (%)	70.5 ± 0.4	83.5 ± 0.6
Soluble solids (°Brix)	60.0 ± 0.4	70.0 ± 0.6
pH	4.8 ± 0.2	4.38 ± 0.12
^aEach data is the average of three replicates. Values followed ± are the standard deviation.

Figure 1 Generalized instrumental texture profile curve obtained with the General Foods Texturometer (Szczesniak, 2002)

Figure 2 Forward extrusion (Ottawa cell) test (color figure available online).

Table 2 Instrumental texture profile analysis (TPA) of date paste

Texture parameters	Golden	Black
Hardness cycle 1 (g)	210.83 ± 7.57^a	231.16 ± 22.21^a
Adhesive force (g)	−101.83 ± 11.32^b	−126.16 ± 13.88^a
Gumminess (g)	158.51 ± 8.69^a	172.23 ± 13.33^a
Adhesiveness (g.s)	−3,135.06 ± 513.71^b	−3,860.25 ± 447.39^a
Cohesiveness	0.75 ± 0.04^a	0.74 ± 0.06^a
Chewiness (g.mm)	2,841.74 ± 341.29^b	2,877.77 ± 305.22^a
Springiness (mm)	17.89 ± 1.51^a	16.68 ± 0.68^a
Area cycle 1 (g.s)	6,372.84 ± 350.17^a	5,799.29 ± 593.26^a
Area cycle 2 (g.s)	4,792.24 ± 353.42^a	4,321.58 ± 369.15^b
Hardness cycle 2 (g)	204.33 ± 9.75^a	216.16 ± 16.62^a
Each data is the average of six replicates. Values followed ± are the standard deviation. The same upper letters are not significant at P < 0.05.

Table 3 Forward extrusion analysis (Ottawa test) of date paste

Extrusion parameters	Golden	Black
Firmness (g)	721.50 ± 45.09^a	517.52 ± 42.19^b
Adhesive force (g)	−425.25 ± 34.85^a	−437.50 ± 17.02^a
Mean load (g)	28.94 ± 10.51^a	36.05 ± 10.39^a
Total positive area (g.s)	43,950 ± 3,204.74^a	34,071.54 ± 1,377.64^b
Each data is the average of six replicates. Values followed ± are the standard deviation. The same letters are not significant at P < 0.05.

Table 4 Flow behavior parameters of date pastes obtained by some rheological models at different temperatures studied ^a

		Bingham			Casson			Herschel–Bulkley				Power–law
Date paste	Temperature (°C)	τ0B (Pa)	η B (Pa.s)	R ^2	τ0C (Pa)	η C (Pa.s)	R ^2	τ0H (Pa)	kH (Pa.s^n)	nH	R ^2	kP (Pa.s^n)	nP	R ^2
Golden	20	583.7	0.69	0.98	519.0	0.09	0.97	574.1	1.42	0.90	0.99	417.4	0.11	0.87
	40	408.1	0.19	0.77	417.5	0.01	0.63	259.5	1.34	0.81	0.72	448.1	0.06	0.58
	60	F	F	F	365.3	0.09	0.66	F	F	F	F	F	F	F
	70	F	F	F	270.6	0.19	078	F	F	F	F	F	F	F
Black	20	416.4	13.9	0.90	190.2	7.74	0.83	F	F	F	F	F	F	F
	40	363.5	5.16	0.88	267.4	1.53	0.90	F	F	F	F	215.0	0.38	0.93
	60	283.7	0.57	0.57	266.7	0.05	0.56	F	F	F	F	247.8	0.06	0.55
	70	F	F	F	307.3	0.18	0.66	F	F	F	F	192.8	0.09	0.58
^aF means failed the modeling of flow behavior data by the given rheological model.

Figure 3 Apparent viscosity–shear rate data of Golden date paste at selected temperatures.

Figure 4 Apparent viscosity–shear rate data of Black date paste at selected temperatures.

Figure 5 The effect of temperature on the viscosity of Golden date Paste (E_a calculated for the temperature range of 20–70°C).

Figure 6 The effect of temperature on the viscosity of Black date paste (E_a calculated for the temperature range of 20–70°C).

Szczesniak , A. 2002 . Texture is a sensory property . Food Quality and Preference , 13 ( 4 ) : 215 – 225 .

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