Effect of soaking medium on the physicochemical properties of parboiled glutinous rice of selected Laotian cultivars

Figures & data

Figure 1. Head rice yield (%) and grain hardness (N) of fresh and parboiled rice grains; (a) Thadokkham-8 (TDK8), (c) Thadokkham-11 (TDK11), and (d) Doongara (DG).* Correlation (r) between head rice yield (%) and grain hardness (N) in; (b) TDK8, (d), TDK11, and (f) DG.

*Means ± SD (n = 3). Within figure, significant differences are denoted by lowercase letters for head rice yield and uppercase letters for grain hardness at 5% probability level.

Table 1. CIEL*a*b* color space of fresh and parboiled rice grains of Thadokkham-8 (TDK8), Thadokkham-11 (TDK11), and Doongara (DG)*.

	Treatment	CIEL*a*b* color space
Rice variety	Treatment	L*	a*	b*	$\mathrm{\Delta }{E}_{ab}^{\ast }$
TDK8	Fresh	96.75 ± 0.25^a	−0.96 ± 0.02^a	0.55 ± 0.01^a	–
	Without soaking	89.00 ± 1.00^bc	−0.03 ± 0.02^b	11.23 ± 0.33^c	13.25 ± 1.01^bc
	Water (control) soaking	86.50 ± 0.50^d	0.47 ± 0.03^c	11.85 ± 0.45^c	15.32 ± 0.84^a
	3% NaCl soaking	87.50 ± 0.35^cd	0.82 ± 0.03^d	11.62 ± 0.59^c	14.33 ± 0.07^ab
	0.2% acetic acid soaking	89.50 ± 0.50^b	1.58 ± 0.13^e	9.61 ± 0.11^b	11.88 ± 0.52^c
TDK11	Fresh	96.40 ± 0.40^a	−0.97 ± 0.02^a	0.56 ± 0.02^a	–
	Without soaking	93.60 ± 0.40^b	0.15 ± 0.03^b	8.40 ± 0.60^b	8.44 ± 0.27^c
	Water (control) soaking	87.84 ± 0.41^d	1.41 ± 0.10^d	12.81 ± 0.31^d	15.14 ± 0.74^a
	3% NaCl soaking	90.52 ± 0.32^c	1.03 ± 0.04^c	11.57 ± 0.32^c	12.64 ± 0.34^b
	0.2% acetic acid soaking	90.75 ± 0.30^c	0.89 ± 0.09^c	10.65 ± 0.33^c	11.71 ± 0.36^b
DG	Fresh	93.19 ± 0.19^a	1.20 ± 0.20^a	7.25 ± 0.25^a	–
	Without soaking	89.55 ± 0.55^c	0.94 ± 0.09^ab	7.90 ± 0.30^a	3.73 ± 0.44^b
	Water (control) soaking	91.50 ± 0.50^b	0.16 ± 0.02^c	10.19 ± 0.39^b	3.56 ± 0.62^b
	3% NaCl soaking	88.50 ± 0.27^d	0.85 ± 0.14^b	11.94 ± 0.40^c	6.68 ± 0.12^a
	0.2% acetic acid soaking	92.33 ± 0.33^ab	0.20 ± 0.02^c	13.12 ± 0.32^d	6.02 ± 0.08^a

*Means ± SD (n = 3). For a particular rice variety, means with different letters in the same column denote significant difference at 5% probability level within each rice variety.

Figure 2. Pasting profiles of fresh and parboiled rice grains of Thadokkham-8 (TDK8), Thadokkham-11 (TDK11), and Doongara (DG).

Figure 3. X-ray diffraction and calculated crystallinity (%) of fresh and parboiled rice grains of Thadokkham-8 (TDK8), Thadokkham-11 (TDK11), and Doongara (DG) as shown on the right side of the figures.*.

*Means ± SD (n = 3). Within each variety, means with different letters in the same figure denote significant difference at 5% probability level.

Table 2. Experimental results of estimated GI, and gelatinization and retrogradation properties of fresh and parboiled rice grains of Thadokkham-8 (TDK8), Thadokkham-11 (TDK11), and Doongara (DG)*.

Rice variety	Treatment	GI	Thermal properties
			Gelatinization				Retrogradation
			To	Tp	Tc	ΔH	To(r)	Tp(r)	Tc(r)	ΔH(r)	R%
TDK8	Fresh	116.2 ± 0.2^b	66.4 ± 0.0^a	73.7 ± 0.4^a	89.9 ± 1.6^a	10.4 ± 0.5^a	51.7 ± 0.0^a	58.5 ± 0.5^a	65.2 ± 1.3^a	0.2 ± 0.0^a	2.1 ± 0.1^a
	Without soaking	111.8 ± 0.3^c	50.6 ± 0.4^b	58.1 ± 0.2^b	62.6 ± 0.2^b	5.1 ± 0.1^b	40.6 ± 0.4^b	52.4 ± 0.4^b	60.3 ± 0.2^b	0.1 ± 0.0^b	2.0 ± 0.1^a
	Water (control) soaking	108.0 ± 1.0^d	48.2 ± 0.1^c	56.1 ± 0.4^c	61.1 ± 0.2^b	3.5 ± 0.2^c	NDˆ	NDˆ	NDˆ	NDˆ	NDˆ
	3% NaCl soaking	119.2 ± 1.0^a	47.3 ± 0.2^d	54.4 ± 0.4^d	58.0 ± 0.0^c	3.5 ± 0.0^c	NDˆ	NDˆ	NDˆ	NDˆ	NDˆ
	0.2% acetic acid soaking	100.4 ± 0.2^e	45.8 ± 0.2^e	54.0 ± 0.0^d	57.4 ± 0.3^c	3.0 ± 0.1^c	NDˆ	NDˆ	NDˆ	NDˆ	NDˆ
TDK11	Fresh	105.9 ± 0.2^b	64.8 ± 0.1^a	71.0 ± 0.2^a	81.1 ± 0.2^a	9.1 ± 0.2^a	50.6 ± 0.4^a	57.5 ± 0.4^a	63.82 ± 0.17^a	0.20 ± 0.01^a	2.14 ± 0.02^a
	Without soaking	101.5 ± 0.3^c	49.5 ± 0.5^b	57.1 ± 0.1^b	61.1 ± 0.2^b	4.4 ± 0.2^b	40.1 ± 0.1^b	50.6 ± 0.4^b	59.06 ± 0.17^b	0.10 ± 0.00^b	2.15 ± 0.00^b
	Water (control) soaking	97.7 ± 1.0^d	47.3 ± 0.2^c	54.4 ± 0.4^c	58.2 ± 0.2^c	3.6 ± 0.0^c	NDˆ	NDˆ	NDˆ	NDˆ	NDˆ
	3% NaCl soaking	108.9 ± 1.0^a	45.8 ± 0.2^d	53.7 ± 0.3^c	57.3 ± 0.3^d	3.1 ± 0.1^d	NDˆ	NDˆ	NDˆ	NDˆ	NDˆ
	0.2% acetic acid soaking	90.1 ± 0.2^e	43.4 ± 0.4^e	52.6 ± 0.4^d	56.4 ± 0.3^e	2.0 ± 0.1^e	NDˆ	NDˆ	NDˆ	NDˆ	NDˆ
DG	Fresh	94.8 ± 1.4^a	72.3 ± 0.7^a	77.1 ± 0.5^ab	83.0 ± 1.5^a	3.4 ± 0.0^a	43.7 ± 0.2^a	56.4 ± 0.0^a	62.9 ± 0.2^a	2.0 ± 0.0^a	59.2 ± 0.0^a
	Without soaking	84.3 ± 0.5^b	70.9 ± 0.2^b	77.6 ± 0.3^a	82.6 ± 0.2^a	3.1 ± 0.1^b	43.1 ± 0.1^b	55.9 ± 0.1^b	61.8 ± 0.1^b	1.6 ± 0.1^b	51.8 ± 1.3^b
	Water (control) soaking	78.4 ± 0.8^c	70.1 ± 0.1^bc	76.8 ± 0.1^bc	81.5 ± 0.1^a	3.0 ± 0.0^c	42.9 ± 0.1^b	55.5 ± 0.1^c	60.8 ± 0.0^c	1.4 ± 0.0^c	48.9 ± 1.5^c
	3% NaCl soaking	85.6 ± 1.4^b	70.1 ± 0.1^c	76.1 ± 0.1^cd	78.7 ± 0.2^b	2.4 ± 0.1^d	41.0 ± 0.1^c	54.9 ± 0.1^d	59.9 ± 0.0^d	1.1 ± 0.0^d	45.7 ± 0.3^d
	0.2% acetic acid soaking	72.2 ± 0.8^d	69.9 ± 0.1^c	75.5 ± 0.1^d	77.6 ± 0.2^b	1.9 ± 0.1^e	39.9 ± 0.1^d	54.0 ± 0.1^e	59.4 ± 0.2^e	0.9 ± 0.0^e	44.9 ± 1.2^d

ˆNot detected.

*Means ± SD (n = 3). For a particular rice variety, means with different letters in the same column denote significant difference at 5% probability level within each rice variety.

Figure 4. Textural profile analysis of fresh and parboiled rice grains of Thadokkham-8 (TDK8) and Doongara (DG).**Means ± SD (n = 3). Within each variety, significant differences are denoted by lowercase letters for hardness and uppercase letters for adhesiveness at 5% probability level.