Non-linear viscoelastic behavior of cooked white, brown, and germinated brown Thai jasmine rice by large deformation relaxation test

Figures & data

Figure 1. KMITL texture test rig.

Table 1. Instrumental texture characteristics of cooked Thai jasmine rice.

Thai jasmine rice samples	Strain at maximum force	Initial firmness (N/mm)	Average firmness (N/mm)	Toughness (N mm)	Relaxation ratio
White rice	0.605 ± 0.025^a	0.44 ± 0.07^b	2.41 ± 0.19^b	29.84 ± 1.62^a	0.20 ± 0.01^b
Brown rice	0.573 ± 0.023^b	0.53 ± 0.09^a	2.75 ± 0.28^a	28.94 ± 1.78^a	0.23 ± 0.01^a
Germinated brown rice	0.536 ± 0.029^c	0.61 ± 0.11^a	3.00 ± 0.35^a	28.18 ± 2.03^a	0.23 ± 0.01^a

Mean ± standard deviation are given in the table.

The same letters in the same column mean that the mean values are not significantly different at a confidence level of 95% (p < 0.05).

Figure 2. Average force-time curves obtained from the simple compression test and relaxation test on cooked Thai jasmine rice.

Figure 3. Average force-time curves obtained from the simple compression test of cooked Thai jasmine rice.

Table 2. Relaxation parameters of four different non-linear viscoelastic models for cooked Thai jasmine rice samples.

Thai jasmine rice sample	Model type	k1	k2	n	RSE	R^Citation2	A	α	Fe	RSE	R^Citation2		a	b	RSE	R^Citation2
White rice	Eq. (1)	2.05 ± 0.12^a	1.25 ± 0.02^b		0.233 ± 0.007	0.951 ± 0.004
	Eq. (2)	1.81 ± 0.13^a	1.24 ± 0.02^b	0.91 ± 0.04^a	0.229 ± 0.008	0.953 ± 0.004
	Eq. (3)						6.30 ± 0.32^a	0.10 ± 0.01^b	4.41 ± 0.23^b	0.381 ± 0.010	0.870 ± 0.006
	Eq. (4)												0.49 ± 0.03^b	0.61 ± 0.04^c	0.233 ± 0.007	0.951 ± 0.004
Brown rice	Eq. (1)	1.64 ± 0.18^c	1.30 ± 0.02^a		0.208 ± 0.005	0.946 ± 0.003
	Eq. (2)	1.47 ± 0.15^b	1.29 ± 0.02^a	0.91 ± 0.04^a	0.203 ± 0.004	0.948 ± 0.004
	Eq. (3)						5.63 ± 0.14^b	0.12 ± 0.01^a	4.87 ± 0.22^a	0.339 ± 0.006	0.855 ± 0.006
	Eq. (4)												0.62 ± 0.07^a	0.80 ± 0.08^a	0.208 ± 0.005	0.946 ± 0.003
Germinated brown rice	Eq. (1)	1.88 ± 0.18^b	1.30 ± 0.02^a		0.228 ± 0.011	0.947 ± 0.003
	Eq. (2)	1.52 ± 0.16^b	1.28 ± 0.01^a	0.83 ± 0.07^b	0.210 ± 0.011	0.955 ± 0.006
	Eq. (3)						5.63 ± 0.30^b	0.10 ± 0.01^b	4.95 ± 0.21^a	0.362 ± 0.012	0.866 ± 0.007
	Eq. (4)												0.54 ± 0.06^b	0.70 ± 0.07^b	0.228 ± 0.011	0.947 ± 0.003

Equation (1) .

Equation (2)

Equation (3)

Equation (4) when .

R²: coefficient of determination; RSE: residual standard error.

Mean values in a column of the same equation followed by different letters (a–c) differ significantly (p < 0.05).

Figure 4. A typical relaxation curve fitted for cooked white rice by four different models of Eq. (1) ; Eq. (2) ; Eq. (3) , and Eq. (4) when .

Figure 5. A typical relaxation curve fitted for cooked brown rice by four different models of Eq. (1) , Eq. (2) , Eq. (3) , and Eq. (4) when .

Figure 6. A typical relaxation curve fitted for cooked germinated brown rice by four different models of Eq. (1) , Eq. (2) , Eq. (3) , and Eq. (4) when .

Department of Industrial Promotion. Knowledge of innovation. http://library.dip.go.th/Industrial%20Innovation/www/pro_det1-015.html (accessed June 23 2016).

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