EFFECT OF MILLING VARIABLES ON THE DEGREE OF MILLING OF UNPARBOILED AND PARBOILED RICE

Figures & data

Figure 1. Effect of weight of sample (unparboiled Pusa No.1) milled in the mill chamber on degree of milling.

Effect of Weight of Sample Milled on Different Parameters After 120 s of Milling

Parameter	Weight (g)	Jaya Unparboiled	Jaya Parboiled	PR-106 Unparboiled	PR-106 Parboiled	Pusa No. 1 Unparboiled	Pusa No. 1 Parboiled
Degree of milling (%)	130	10.54	5.00	12.24	6.13	8.49	6.45
150	8.91	4.17	10.01	4.69	7.70	5.18
170	7.75	4.04	8.22	4.50	5.24	4.97
l/b ratio	130	2.55	2.58	3.21	3.36	4.03	4.18
150	2.59	2.63	3.25	3.40	4.08	4.24
170	2.64	2.67	3.28	3.43	4.14	4.27
Head rice yield (%)	130	56.45	69.85	57.66	70.80	75.55	89.46
150	56.71	72.23	58.27	73.32	75.67	91.20
170	56.83	77.65	59.46	77.67	80.39	91.60
1000 kernel weight (g)	130	21.53	22.08	15.56	16.17	16.39	16.84
150	21.73	22.39	15.77	16.26	16.50	17.33
170	22.31	22.71	15.80	16.39	16.88	17.65
Bulk density (g/l)	130	838.30	743.70	751.80	679.70	714.00	661.66
150	813.60	727.60	744.8	692.06	693.55	658.60
170	810.80	707.30	736.4	687.00	680.40	653.80

Values of l/b ratio are mean of ten observations whereas those for 1000 kernel weight, bulk density and head rice yield are mean of three observations.

Figure 2. Effect of parboiling on the degree of milling of different cultivars.

Regression Coefficients Showing the Effect of Weight of Sample Placed in the Mill Chamber on Degree of Milling

Term	Jaya	PR-106	Pusa No. 1
Constant (a)	0	0	0
X 1(b 1)	−0.188**	−0.114*	−0.015
X 2 (b 2)	23.34***	15.485*	3.308
X 3 (b 3)	0.214***	0.273***	0.194***
X 1 ^2 (c 1)	0.0004**	0.00012	−9.8×10^−5
X 2 ^2 (c 2)	−8.97***	−6.964**	−1.854
X 3 ^2 (c 3)	−0.0004***	−0.00049***	−0.0004***
X 1 X 2 (d 2)	0.025***	0.0386***	0.0196**
X 1 X 3 (d 3)	−0.00031***	−0.00054***	−0.0004***
X 2 X 3 (e)	−0.4207***	−0.0489***	−0.0179***
R ^2	98.6	98.2	97.7

where X ₁ (weight of sample milled), X ₂ (1 for unparboiled and 2 for parboiled), X ₃ (duration of milling).* p<0.5, ** p<0.05, *** p<0.005.

Figure 3. Effect of weight applied on the mill chamber on the degree of milling (unparboiled Pusa No.1).

Effect of Weight Applied on Sample Milled on Different Parameters After 120 s of Milling

Parameter	Weight (g)	Jaya Unparboiled	Jaya Parboiled	PR-106 Unparboiled	PR-106 Parboiled	Pusa No. 1 Unparboiled	Pusa No. 1 Parboiled
Degree of milling (%)	130	8.91	4.17	10.02	4.69	7.70	5.18
150	9.77	4.66	12.44	5.38	8.54	5.63
170	11.4	5.09	15.42	6	10.14	6.14
l/b ratio	660	2.59	2.63	3.25	3.40	4.08	4.24
760	2.56	2.57	3.22	3.30	4.00	4.03
860	2.52	2.53	3.19	3.20	3.87	3.89
Head rice yield (%)	660	56.71	72.23	58.27	73.32	75.6	91.2
760	55.33	70.48	56.58	68.79	73.50	90.6
860	54.04	68.03	53.02	65.76	71.02	89.74
1000 kernel weight (g)	660	21.73	22.39	15.77	16.26	16.5	17.33
760	21.65	22.23	15.72	16.19	16.46	17.19
860	21.58	22.09	15.66	16.1	16.40	17.07
Bulk density (g/l)	660	813.64	727.68	744.86	692.06	693.55	658.69
760	820.6	736.66	766.46	710.31	701.92	668.16
860	829.24	751.18	784	727.42	711.52	677.72

Values of l/b ratio are mean of ten observations whereas those for 1000 kernel weight, bulk density and head rice yield are mean of three observations.

Regression Coefficients Showing the Effect of Weight Placed in the Mill Chamber on Degree of Milling

Term	Jaya	PR-106	Pusa No. 1
Constant (a)	1.011	−3.65	9.37
X 1(b 1)	0.0117	0.035*	0.0015
X 2 (b 2)	−9.87***	−17.58***	−18.03***
X 3 (b 3)	0.145***	0.1604***	0.132***
X 1 ^2 (c 1)	1.35×10^−7	−6.2×10^−6	8.5×10^−6*
X 2 ^2 (c 2)	4.721***	9.157***	7.839***
X 3 ^2 (c 3)	−0.0005***	−0.0007***	−0.0005***
X 1 X 2 (d 2)	−0.0056***	−0.0135***	−0.006***
X 1 X 3 (d 3)	5.57×10^−5	0.0001***	5.07×10^−5**
X 2 X 3 (e)	−0.047***	−0.064***	−0.0305***
R ^2	97.9	97.3	97.8

Where X ₁ (weight of sample mill chamber), X ₂ (1 for unparboiled and 2 for parboiled), X ₃ (duration of milling).* p<0.5, ** p<0.05, *** p<0.005.

Figure 4. Effect of presence of husk on degree of milling (Pusa No. 1).

Relationship Between Degree of Milling and Milling Duration in the Presence of Husk

Presence of Husk (%)	Cultivar	Unparboiled/Parboiled	Regression Equation	R ^2
0	Jaya	Unparboiled	y=−0.0004x ^2+0.1194x+0.2117	0.996
5	Jaya	Unparboiled	y=−0.000x ^2+0.1154x+0.3676	0.991
0	Jaya	Parboiled	y=−0.0004x ^2+0.0786x+0.5087	0.953
5	Jaya	Parboiled	y=−0.0002x ^2+0.0614x+0.3511	0.97
0	PR-106	Unparboiled	y=−0.0006x ^2+0.1595x−0.1534	0.996
5	PR-106	Unparboiled	y=−0.0005x ^2+0.1585x+0.7512	0.983
0	PR-106	Parboiled	y=−0.0004x ^2+0.081x+0.6709	0.942
5	PR-106	Parboiled	y=−0.0002x ^2+0.0626x+0.5194	0.951
0	Pusa No. 1	Unparboiled	y=−0.0003x ^2+0.1063x−0.099	0.999
5	Pusa No. 1	Unparboiled	y=−0.0003x ^2+0.1031x+0.0157	0.998
0	Pusa No. 1	Parboiled	y=−0.0005x ^2+0.1001x+0.4157	0.975
5	Pusa No. 1	Parboiled	y=−0.0003x ^2+0.0862x+0.3748	0.999

y=degree of milling (%).x=milling duration (s).