Elucidation of soaking and steaming duration in parboiling: effects on the physical quality and appearance of local rice cultivars

Figures & data

Figure 1. Flow chart of paddy grains soaking and parboiling processes.

Figure 2. Detailed information on the steaming pan. (A) False bottom on the water, (B) wet paddy in mesh sacks on the false bottom, (C) steam outlet, (D) steam regulator on the steam outlet, (E) wet paddy in mesh sacks covered with cloth, and (F) the size of the steaming pan.

Figure 3. The moisture content of paddy grains and water temperature of Surkha Zurati (A) and Barah (B) rice cultivars during soaking by days.

Table 1. Effects of different soaking and steaming durations and methods on physical parameters of local rice cultivars.

Variety	Treatment	Steaming time (min)	Moisture content (%) before milling	Paddy weight (kg)	Milled rice weight (kg)	Milling recovery (%)
Surkha Zurati	Cloth + lid	15	11.8 ± 0.34	48.9 ± 0.57	35.2 ± 0.80	71.3 ± 0.007
		20	12.4 ± 0.20	49.5 ± 0.17	34.7 ± 0.49	70.3 ± 0.012
		25	12.0 ± 0.08	49.6 ± 0.11	35.7 ± 1.06	72.1 ± 0.019
	Cloth	15	12.0 ± 0.14	48.5 ± 0.60	35.2 ± 0.49	73.6 ± 0.019
		20	12.1 ± 0.18	48.2 ± 0.77	34.0 ± 0.40	70.5 ± 0.006
		25	12.2 ± 0.20	49.1 ± 0.23	34.7 ± 0.49	70.8 ± 0.016
P – value			ns	ns	ns	ns
Barah	Cloth + lid	15	12.0 ± 0.12	49.3 ± 0.28	35.1 ± 0.63	71.3 ± 0.016
		20	11.7 ± 0.12	49.6 ± 0.38	35.5 ± 0.54	71.5 ± 0.007
		25	14.9 ± 2.51	49.7 ± 0.18	35.1 ± 0.18	70.6 ± 0.014
	Cloth	15	11.9 ± 0.18	48.9 ± 0.54	33.8 ± 0.54	69.1 ± 0.004
		20	12.3 ± 0.26	49.2 ± 0.17	34.8 ± 0.49	70.7 ± 0.007
		25	12.1 ± 0.18	50.0 ± 0.15	34.9 ± 0.20	69.8 ± 0.012
P – value			ns	ns	ns	ns

Data presented as means ± standard errors. Differences among means were considered using Tukey’s test at a 0.05% level and ns indicates not significant.

Table 2. Physical characteristics of rice grains at different soaking and steaming duration and methods.

Cultivar	Treatment	Steaming duration (min)	Head rice (g)	Broken grain (g)	Chalky grain (g)	Head rice ratio (%)	Chalky grain (%)	Broken grain (%)
Surkha Zurati	Cloth + lid	15	149.6 ± 0.92 c	50.4 ± 0.92 c	7.4 ± 0.05 c	74.8 ± 0.004 b	3.7 ± 0.000 c	25.2 ± 0.004 c
		20	164.3 ± 0.01 b	35.7 ± 0.01 d	4.8 ± 0.01 d	82.1 ± 0.005 a	2.4 ± 2.453 d	17.9 ± 0.005 d
		25	175.5 ± 1.21 a	24.5 ± 1.21 e	2.3 ± 0.14 e	87.8 ± 0.006 a	1.1 ± 0.000 e	12.3 ± 0.006 e
	Cloth	15	119.0 ± 0.57 e	81.0 ± 0.57 a	10.5 ± 0.57 b	59.5 ± 0.002 c	5.3 ± 0.002 b	40.5 ± 0.002 a
		20	128.7 ± 0.66 d	71.3 ± 0.66 b	12.7 ± 0.43 a	64.3 ± 0.003 c	6.3 ± 0.002 a	35.7 ± 0.003 b
		25	147.7 ± 0.37 c	52.3 ± 0.37 c	7.9 ± 0.40 c	70.8 ± 0.029 b	4.0 ± 0.002 c	26.1 ± 0.001 c
Treatment (T)			***	***	***	***	***	***
Steaming (S)			***	***	***	***	***	***
T × S			**	**	***	ns	***	*
Barah	Cloth + lid	15	148.4 ± 0.63 c	51.6 ± 0.77 d	5.0 ± 0.28 b	74.2 ± 0.003 c	2.5 ± 0.001 a	25.8 ± 0.003 d
		20	159.5 ± 0.60 b	41.1 ± 0.83 e	3.2 ± 0.11 c	79.8 ± 0.003 b	1.6 ± 0.000 b	20.5 ± 0.004 e
		25	163.7 ± 0.43 a	36.3 ± 0.51 f	2.3 ± 0.05 d	81.8 ± 0.002 a	1.2 ± 0.000 c	18.2 ± 0.002 f
	Cloth	15	112.7 ± 0.49 e	87.3 ± 0.43 a	6.1 ± 0.11 a	56.3 ± 0.002 f	3.1 ± 0.000 a	43.6 ± 0.002 a
		20	128.7 ± 0.46 d	71.3 ± 0.86 b	3.8 ± 0.17 c	64.4 ± 0.002 e	1.9 ± 0.000 b	35.7 ± 0.004 b
		25	140.4 ± 0.27 c	59.4 ± 0.51 c	2.2 ± 0.05 d	70.2 ± 0.001 d	1.1 ± 0.000 c	29.7 ± 0.002 c
Treatment (T)			***	***	**	***	ns	***
Steaming (S)			***	***	***	***	***	***
T × S			***	***	**	***	ns	**

Data presented as means ± standard errors. Differences among means were considered using Tukey’s test at a 0.05% level. *, **, *** and ns indicate significant differences at 0.05%, 0.01%, 0.001% and not significant differences, respectively.

Figure 4. The appearance of parboiled rice grain of Surkha Zurati under different steaming durations and covering methods.

Figure 5. The appearance of parboiled rice grain of Barah cultivar under different steaming durations and covering methods.

Data availability statement

All data are available within this publication.