Physical properties of parboiled milled local rice varieties marketed in South-East Nigeria

C E Azuka; I Nkama; F U Asoiro

doi:10.1007/s13197-020-04690-1

. 2020 Aug 13;58(5):1788–1796. doi: 10.1007/s13197-020-04690-1

Physical properties of parboiled milled local rice varieties marketed in South-East Nigeria

C E Azuka ^1,^✉, I Nkama ¹, F U Asoiro ²

PMCID: PMC8021660 PMID: 33897015

Abstract

Physical properties of rice grain is important for mechanisation and proper post-harvest handling operations to prevent post-harvest loss and achieve high head-rice grains. Knowledge on the physical properties of Nigeria’s local rice is limited which has led to losses and production of low quality grains characterised by large amount of brokens and poor appearance. Physical properties of 18 local and 3 imported rice varieties (control), were evaluated using standard methods. The physical properties evaluated were grain dimensions, Arithmetic mean diameter, (AMD) geometric mean diameter (GMD), square mean diameter (SMD), sphericity, aspect ratio, surface area, general appearance, dockage and aroma. Most (77.78%) of the local rice varieties were long grain rice, 50% were slender grains and 50% were bold grains, 77.78% of the local rice varieties were heavy grains. The AMD, GMD and SMD of local rice grains ranged from 3.29–3.86 mm, 8.02–10.36 mm and 4.75–5.82 mm, respectively. The sphericity, aspect ratio and surface area were in the range of 51.25–59.23%, 0.31–0.46 and 21.87–29.44 mm², respectively. A significant percentage (50%) of the local rice were grey coloured and unappealing in appearance. All the local rice varieties had dockage (5–70%) while the imported rice varieties had no dockage and possessed translucent light-cream to yellow shades and were appealing in appearance. These data are important for correct coupling and adjustment of post-harvest processing machine to prevent losses and produce high head-rice with appealing appearance.

Keywords: Local rice, Physical properties, Dimensions, Appearance, Dockage, Head-rice

Introduction

All cultivated rice species of food crop is Oryza sativa L. (Asian rice) and Oryza glaberrima (African rice). Oryza sativa L. is the most commonly grown rice specie throughout the world today (Oko and Ugwu 2011; Michael 2008; Juliano 1993) a small amount of Oryza glaberrima, a perennial specie, is grown in Africa (Juliano 1993; Fluhr et al. 2014). A hybrid of Oryza sativa L. and Oryza glaberrima, is grown in Nigeria as it is resistant to many African abiotic and biotic stresses. Rice is a major staple food in Nigeria and Nigeria is the largest producer and consumer of rice in the West African sub-region and the world’s second largest importer of rice behind China (Maureen 2014; Diagne et al. 2011). Knowledge on the properties of Nigeria’s local rice is limited in comparison to rice species from other major rice producing countries like USA, India, China, Thailand and other Asian countries. Such properties include chemical, physical and physicochemical properties which determines the overall quality and end-use quality of a rice grain. Physical properties of rice grain is important for mechanisation and proper post-harvest handling operations to prevent post-harvest loss and achieve high head-rice. High head rice grains command premium price in International Market. Knowledge on the physical properties of Nigeria’s local rice is limited which has led to losses and production of low quality grains characterised by large amount of brokens and poor appearance. These have prevented Nigeria from selling their local rice grains in International Market. Large percentages (77.78%) of the local rice varieties from different states in South East zone Nigeria were low in their grade quality (Grade 1 and 2) when evaluated (Azuka et al. 2017). Physical properties which form part of rice quality are measured mainly by subjective and objective methods (Randall and Thompson 2009; Danbaba 2013). Among those which are objectively determined are the physical dimensions of the grain, AMD, GMD, SMD, sphericity, aspect ratio, surface area and dockage. General appearance and aroma are determined subjectively (by human senses). Colour can be measured objectively and subjectively because colour meter do not have the ability to adjust for other factors such as damaged kernels which influences colour therefore, the human eye which has the ability of making this adjustment is used to evaluate the colour quality of rice alongside with colour meter (Webb and Stermer 1972). AMD, GMD, SMD, surface area, sphericity, aspect ratio, are obtained by calculation using the grain dimensions of length, width and thickness. Care is to be taken while obtaining the grain dimensions because the machinery and operations when improperly designed using the wrong dimension would create rice kernel cracking and breakage resulting to low head-rice yield which is of low quality with poor marketing price (Ghadge and Prasad 2012).

Knowledge of the physical properties of the rice grain is used in drying, sorting, milling, processing of the grains, designing of post-harvest machine, classification and trading of rice at the international market (Danbaba 2013). The objective of this study was to determine the physical properties of the different parboiled milled local rice varieties sold in the South-East Nigeria in order to reduce the degree of low quality rice characterised by high brokens, low head-rice and poor appearance produced at the milling sites. This will facilitate value addition, quality improvement and proper postharvest processing. The physical properties evaluated were grain dimensions, AMD, GMD, SMD, sphericity, aspect ratio, surface area, general appearance, dockage and aroma.

Materials and methods

Materials

Eighteen (18) varieties of parboiled milled local rice were collected from different rice processing units and markets in Enugu, Anambra and Ebonyi State, Nigeria as shown in Tables 1, 2 and 3. Three (3) imported rice varieties were purchased from Ogige market in Nsukka LGA of Enugu state, Nigeria based on cost, commonly consumed rice variety and difference in grain length. The imported rice varieties were coded Ip1, Ip2, and Ip3 and served as controls. The samples collected were cleaned manually using plastic trays to remove husk, shrivelled kernels (defectives), stones and seeds. All samples were stored in sacks at room temperature (25 ± 2 °C) free of moisture until needed.

Table 1.

Dimensions of parboiled local rice varieties sold in the South East Nigeria

Rice variety	Length (mm)	Width (mm)	Thickness (mm)	Length:width ratio	Weight (g)	Volume (ml³)	Density (g/ml³)
Imported rice variety
Ip1	7.19^ab ± 0.35	2.03^ij ± 0.15	1.69^e ± 0.12	3.57^a ± 0.34	21.00^cdefg ± 0.00	16.67^ab ± 5.77	1.33^ab ± 0.58
Ip2	7.07^abc ± 0.27	2.08^hij ± 0.12	1.77^abcde ± 0.11	3.40^ab ± 0.19	19.33^ghi ± 0.58	13.33^ab ± 5.77	1.67^ab ± 0.55
Ip3	6.11^ij ± 0.47	2.00^j ± 0.12	1.68^e ± 0.11	3.08^cde ± 0.20	18.00ⁱ ± 1.00	10.00^b ± 0.00	2.00^a ± 0.10
Enugu state
FARO 44	6.86^bcdef ± 0.31	2.24^defgh ± 0.13	1.83^abc ± 0.12	3.08^cde ± 0.20	23.00^ab ± 0.00	13.33^ab ± 5.77	1.67^ab ± 0.64
Fadama	6.12^ij ± 0.56	2.21^efgh ± 0.20	1.86^ab ± 0.16	2.79^fgh ± 0.21	20.67^defg ± 0.58	20.00^a ± 0.00	1.03^b ± 0.06
Fortin 16	6.41^ghij ± 0.27	2.26^cdefg ± 0.17	1.88^a ± 0.11	2.84^efg ± 0.27	20.67^defg ± 0.58	13.33^ab ± 5.77	1.67^ab ± 0.64
Fortin 16 (old variety)	6.45^fghij ± 0.54	2.19^efghi ± 0.21	1.85^ab ± 0.14	2.99^defg ± 0.43	21.33^bcdef ± 1.15	13.33^ab ± 5.77	1.73^ab ± 0.59
Anambra state
Omor-Mas	6.25^hij ± 0.30	2.29^cdef ± 0.09	1.73^bcde ± 0.08	2.74^gh ± 0.10	20.67^defg ± 0.58	13.33^ab ± 5.77	1.73^ab ± 0.55
R-Bus	6.60^defgh ± 0.51	2.17^efghij ± 0.22	1.70d^e ± 0.16	3.07^de ± 0.35	21.67^bcd ± 1.53	13.33^ab ± 5.77	1.67^ab ± 0.62
FARO 40	6.55^efghi ± 0.41	2.17^efghij ± 0.12	1.82^abcd ± 0.06	3.03^def ± 0.19	22.67^abc ± 0.58	20.00^a ± 0.00	1.53^ab ± 0.06
Igboukwu rice	6.07^jk ± 0.44	2.40^bcd ± 0.13	1.82^abcd ± 0.10	2.54^hi ± 0.22	22.33^bcd ± 0.58	18.33^ab ± 2.89	1.77^ab ± 0.21
Aguleri rice	6.33^ghij ± 0.56	2.57^a ± 0.13	1.86^ab ± 0.10	2.45ⁱ ± 0.22	24.33^a ± 1.53	18.33^ab ± 2.89	1.47^ab ± 0.15
Taraba rice	6.71^cdefg ± 0.36	2.14^fghij ± 0.21	1.68^e ± 0.15	3.17^bcd ± 0.36	19.67^fghi ± 0.58	13.33^ab ± 2.89	1.40^ab ± 0.40
B-G	6.50^efghij ± 0.39	2.41^bc ± 0.24	1.84^abc ± 0.11	2.73^gh ± 0.26	22.67^abc ± 1.53	16.67^ab ± 2.89	2.07^a ± 0.15
Ebonyi state
Akpujie	7.47^a ± 0.76	2.33^bcde ± 0.17	1.78^abcde ± 0.10	3.22^bcd ± 0.24	22.33^bcd ± 1.15	16.67^ab ± 5.77	1.50^ab ± 0.67
Kpurukpuru	5.69^kL ± 0.15	2.47^ab ± 0.12	1.83^abc ± 0.11	2.30^ij ± 0.14	20.00^efg ± 0.00	10.00^b ± 0.00	1.43^ab ± 0.00
Afikpo-Mas	6.72^cdefg ± 0.35	2.11^ghij ± 0.13	1.70^de ± 0.22	3.20^bcd ± 0.21	19.33^ghi ± 0.58	11.67^ab ± 2.89	1.27^ab ± 0.38
Abakiliki Mas	7.00^bcd ± 0.30	2.10^ghij ± 0.12	1.66^e ± 0.13	3.35^abc ± 0.29	20.33^efg ± 0.58	15.00^ab ± 5.00	1.30^ab ± 0.57
R-8	6.63^defgh ± 0.38	2.22^efgh ± 0.18	1.72^cde ± 0.08	3.02^def ± 0.40	19.33^ghi ± 1.53	16.67^ab ± 2.89	1.30^ab ± 0.26
306	6.93^bcde ± 0.61	2.18^efghi ± 0.12	1.77^abcde ± 0.07	3.18^bcd ± 0.28	20.67^defg ± 0.58	13.33^ab ± 5.77	1.53^ab ± 0.64
Geshua	5.55^L ± 0.31	2.57^a ± 0.27	1.74^bcde ± 0.13	2.18^j ± 0.19	19.00^hi ± 1.73	10.00^b ± 0.00	1.63^ab ± 0.17
Mean	6.53 ± 0.62	2.24 ± 0.22	1.77 ± 0.14	2.95 ± 0.44	20.90 ± 1.74	14.60 ± 4.61	1.58 ± 0.45
SE	0.14	0.05	0.04	0.09	0.54	2.42	0.28
LSD_0.05	0.38	0.15	0.11	0.24	1.55	6.91	0.81
CV (%)	6.6	7.4	6.9	9.1	4.5	28.7	31.6

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*Values are mean ± SD of replicate determination. Means in the same column carrying similar superscript are not significantly (p > 0.05) different. Extra-long—≥ 7.0; long—6.00–6.99; medium—5.0–5.99; short < 5.0

Slender—> 3.0; bold—2.0–3.0; round—< 2.0. Extra-heavy—> 25 g; heavy—20–25 g; moderately heavy < 20 g

Table 2.

Engineering properties of parboiled local rice samples

Rice variety	AMD (mm)	GMD (mm)	SMD (mm)	Sphericity (%)	Aspect ratio	Surface area (mm²)
Imported rice variety
Ip1	3.64^b ± 0.14	8.24^de ± 1.10	5.03^bcd ± 0.41	50.61^L ± 1.16	0.28^k ± 0.02	22.08^def ± 3.25
Ip2	3.64^b ± 0.11	8.68^cde ± 0.77	5.15^bcd ± 0.30	51.51^jkl ± 1.00	0.30^jk ± 0.02	23.53^de ± 2.30
Ip3	3.26^e ± 0.16	6.84^f ± 0.79	4.31^e ± 0.35	53.53^efgh ± 1.96	0.33^ghij ± 0.03	18.72^f ± 2.32
Enugu state
FARO 44	3.64^b ± 0.14	9.40^abcd ± 1.15	5.34^bc ± 0.42	53.14^ghij ± 1.17	0.33^ghij ± 0.02	26.10^abcd ± 3.53
Fadama	3.40^cde ± 0.28	8.50^cde ± 1.93	4.86^cd ± 0.76	55.56^bcd ± 1.17	0.36^ef ± 0.03	24.15^cde ± 5.81
Fortin 16	3.52^bcd ± 0.10	9.09^bcde ± 1.04	5.13^bcd ± 0.35	54.91^de ± 1.79	0.35^efg ± 0.03	25.77^abcde ± 3.55
Fortin 16 (old variety)	3.50^bcd ± 0.19	8.74^cde ± 1.44	5.02^bcd ± 0.52	54.37^defg ± 2.72	0.34^efgh ± 0.05	24.61^bcde ± 4.63
Anambra state
Omor-Mas	3.42^cde ± 0.14	8.28^de ± 0.90	4.85^cd ± 0.36	54.80^def ± 0.82	0.37^de ± 0.01	23.20^de ± 2.66
R-Bus	3.49^bcd ± 0.25	8.22^de ± 1.69	4.89^cd ± 0.70	52.93^ghij ± 1.88	0.33^ghij ± 0.03	22.64^de ± 4.89
FARO 40	3.51^bcd ± 0.16	8.64^cde ± 0.89	5.02^bcd ± 0.39	53.69^efgh ± 1.07	0.33^ghij ± 0.02	23.98^cde ± 2.46
Igboukwu rice	3.43^cde ± 0.16	8.83^cde ± 0.90	5.00^bcd ± 0.38	56.61^bc ± 1.77	0.40^cd ± 0.03	25.41^bcde ± 2.58
Aguleri rice	3.59^bc ± 0.21	10.11^ab ± 1.36	5.48^ab ± 0.54	56.82^b ± 2.27	0.41^bc ± 0.04	29.44^a ± 4.04
Taraba rice	3.51^bcd ± 0.14	8.07^de ± 1.42	4.87^cd ± 0.49	52.38^hijk ± 2.13	0.32^ghij ± 0.04	22.11^def ± 4.53
B-G	3.59^bc ± 0.21	9.68^abc ± 1.78	5.36^bc ± 0.64	55.16^cde ± 1.61	0.37^de ± 0.03	27.66^abc ± 5.70
Ebonyi state
Akpujie	3.86^a ± 0.29	10.36^a ± 1.65	5.82^a ± 0.71	51.81^ijkL ± 1.65	0.31^hij ± 0.03	28.37^ab ± 4.51
kpurukpuru	3.33^de ± 0.76	8.58^cde ± 0.70	4.83^cd ± 0.24	58.54^a ± 1.16	0.44^b ± 0.03	25.26^bcde ± 2.45
Afikpo-Mas	3.51^bcd ± 0.15	8.02^e ± 1.22	4.87^cd ± 0.42	52.27^hijk ± 1.38	0.31^hij ± 0.02	21.87^ef ± 3.62
Abakiliki Mas	3.59^bc ± 0.14	8.15^de ± 1.06	4.97^bcd ± 0.40	51.25^kL ± 0.92	0.30^ijk ± 0.02	21.98^ef ± 3.09
R-8	3.52^bc ± 0.10	8.42^cde ± 0.65	4.98^bcd ± 0.23	53.24^fghi ± 2.02	0.34^efgh ± 0.05	23.23^de ± 2.10
306	3.63^b ± 0.23	8.94^bcde ± 1.26	5.21^bcd ± 0.55	52.43^hijk ± 1.40	0.31^hij ± 0.03	24.50^bcde ± 3.40
Geshua	3.29^e ± 0.19	8.33^de ± 1.44	4.75^d ± 0.56	59.23^a ± 1.83	0.46^a ± 0.04	24.73^bcde ± 4.84
Mean	3.52 ± 0.22	8.67 ± 1.41	5.04 ± 0.55	54.04 ± 2.77	0.35 ± 0.05	24.25 ± 4.33
SE	0.06	0.39	0.15	0.52	0.01	1.20
LSD_0.05	0.16	1.10	0.43	1.46	0.03	3.35
CV (%)	5.10	14.3	9.6	3.10	8.9	15.7

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AMD arithmetic mean diameter, GMD geometric mean diameter, SMD square mean diameter

*Values are mean ± SD of replicate determination. Means in the same column carrying similar superscript are not significantly (p > 0.05) different

Means in the same column carrying similar superscript are of the same size and shape and will use the same post-harvest processing equipment while those of dissimilar superscript are significantly (p < 0.05) different and will not use the same post-harvest processing equipment

Table 3.

General appearance, dockage and aroma of parboiled rice varieties sold in South East Nigeria

Rice variety	Colour			Appearance	Dockage (%)	Aroma
Rice variety	L⁺	a*	b*	Appearance	Dockage (%)	Aroma
Imported rice variety
Ip1	50.80^ghi ± 0.36	1.13^ab ± 1.23	23.93^a ± 1.36	Clean creamy yellow	Nil	Non-aromatic
Ip2	53.63^defgh ± 2.41	1.63^ab ± 0.93	17.93^b ± 1,14	Clean light cream	Nil	Non-aromatic
Ip3	55.63^bcdefg ± 2.97	3.20^ab ± 0.53	14.37^bc ± 1.04	Clean light cream	Nil	Aromatic
Enugu state
FARO 44	55.07^cdefgh ± 1.11	1.30^ab ± 0.80	13.07^bc ± 0.32	Clean light cream	13^cd ± 0.04	Non-aromatic
Fadama	59.07^abc ± 1.21	1.17^ab ± 0.21	14.27^bc ± 1.07	Dirty light cream	5^cd ± 0.01	Non-aromatic
Fortin 16	50.20^hi ± 4.69	− 2.53^abc ± 6.91	13.37^bc ± 2.59	Dirty-grey coloured with black streaks	48^b ± 0.25	Musty odour
Fortin 16 (old variety)	55.40^bcdefg ± 2.12	2.25^ab ± 2.71	14.37^bc ± 0.89	Dirty grey coloured with black streaks	20^c ± 0.05	Non-aromatic
Anambra state
Omor-Mas	56.20^abcdef ± 2.96	− 0.23^ab ± 0.49	13.07^bc ± 2.18	Clean light cream with black streaks	10^cd ± 0.05	Non-aromatic
R-Bus	53.00^efgh ± 2.82	− 0.53^ab ± 2.95	17.07^b ± 0.93	Clean light cream with Rosy colour	18^cd ± 0.40	Non-aromatic
FARO 40	53.57^defgh ± 1.35	− 0.93^abc ± 1.04	15.07^b ± 0.81	Dirty light cream and dark gold	55^ab ± 0.08	Non-aromatic
Igboukwu rice	58.60^abcd ± 2.77	− 0.30^ab ± 0.42	15.33^b ± 2.51	Dirty light cream	08^cd ± 0.03	Non-aromatic
Aguleri rice	53.73^defgh ± 3.84	0.60^ab ± 0.17	13.87^bc ± 0.70	Dirty light cream	15^cd ± 0.06	Aromatic
Taraba rice	61.10^a ± 3.32	2.07^ab ± 2.79	14.13^bc ± 2.60	Dirty light cream	61^ab ± 0.21	Non-aromatic
B-G	51.00^ghi ± 0.26	− 0.87^abc ± 0.47	16.80^b ± 0.35	Dirty light cream	17^cd ± 0.06	Non-aromatic
Ebonyi state
Akpujie	57.63^abcde ± 2.92	1.03^ab ± 1.82	16.23^b ± 2.52	Clean light cream	17^cd ± 0.12	Aromatic
kpurukpuru	60.47^ab ± 0.93	1.40^ab ± 1.07	8.80^c ± 1.79	Clean light cream	7^cd ± 0.01	Non-aromatic
Afikpo-Mas	57.47^abcde ± 2.71	0.50^ab ± 0.36	16.53^b ± 11.34	Clean light cream	16^cd ± 0.03	Non-aromatic
Abakiliki Mas	51.47^fghi ± 1.98	− 6.80^c ± 0.98	15.57^b ± 0.60	Clean light cream and white streaks	5^cd ± 0.05	Non-aromatic
R-8	51.20^fghi ± 2.37	0.23^ab ± 12.05	14.13^bc ± 0.76	Clean light cream with black streaks	19^c ± 0.08	Non-aromatic
306	46.93ⁱ ± 4.10	− 4.10^bc ± 0.90	14.63^b ± 1.00	Clean light cream with black streaks	13^cd ± 0.04	Non-aromatic
Geshua	57.40^abcde ± 2.77	− 0.17^ab ± 0.44	14.70^b ± 1.19	Dirty red and black streak rice	70^a ± 0.11	Non-aromatic
Mean	54.74 ± 4.24	0.00 ± 3.51	15.11 ± 3.61		20 ± 0.21
SE	1.54	1.87	1.62		0.05
LSD_0.05	4.41	5.33	4.62		0.15
CV (%)	4.9	0	18.5		45.9

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*Values are means of triplicate determination ± SD. Means in the same column carrying similar superscript are not significantly (p > 0.05) different

L⁺ scale represented lightness where 100 = white and 0 = black. The a* scale indicates red spectrum when positive and green spectrum when negative, the b* scale indicates yellow spectrum when positive and blue spectrum when negative

Methods

Determinations of grain dimensions

Rice grain dimensions-grain length (L₁), width (Wd₁), and thickness (T) as shown in Table 1 were determined using a digital Vernier caliper (0.1–100 mm A&D Company Limited). According to the method of (Danbaba 2013).

Determination of grain length

Ten (10) milled whole rice grain samples of each variety were randomly selected and the length of the grains measured using a digital calliper (0.1–100 mm A&D Company Limited). The mean value of each variable was determined and noted as L₁. The value obtained was recorded as each samples’ grain length.

Determination of grain shape

Ten (10) milled whole rice grain samples of each variety were randomly selected and the width of the grains (Wd₁) determined with a digital calliper (0.1–100 mm A&D Company Limited). The mean value of each variable was obtained and the length/width ratio of the samples calculated as shown in Eq. 1:

\frac{L}{W} r a t i o = \frac{Average length of rice L_{1} (mm)}{Average width of rice {Wd}_{1} (mm)}

where L1 = length of whole rice grain, Wd1 = width of whole rice grain.

The value obtained was recorded as grain shape for each sample.

Determination of thickness

Ten (10) milled whole rice grain samples of each variety were randomly selected and the thickness of the grains measured at the tip using a digital calliper (0.1–100 mm A&D Company Limited). The mean value of each variable was determined and the value obtained recorded as each samples’ thickness (T).

One-thousand grain weight (W₁)

One hundred (100)-milled kernel representative sample (triplicates) having a moisture content of 14% for each variety were randomly selected and weight determined as described by Danbaba (2013). The weight of each sample was determined using a 500 g capacity weighing scale (Electronic Pocket Scale Model EHA251) The value obtained was multiplied by 10. The mean weight of the samples were obtained and noted as W₁.

Determination of volume of raw rice grains

Volume of raw rice grain was determined by displacement method as described by Gariboldi (1979). One hundred raw rice grains were placed in a measuring cylinder containing 20 ml of water (V₁). The new volume of water after the raw rice grains were added to the measuring cylinder was noted as (V₂). The volume of raw grains (V₃) were obtained by subtracting the Volume of water containing raw rice grains from the initial volume of water contained in the measuring cylinder (Eq. 2).

V_{3} (m l) = V_{2} - V_{1}

where V₃ = volume of raw grain; V₂ = volume of water after the raw rice grains were added to the measuring cylinder; V₁ = 20 Ml of water which was initial volume of water in the measuring cylinder before grains were added to the measuring cylinder.

Density of raw rice grain

Density of the rice grain samples were obtained) by dividing the weight of raw rice grain with its volume (Eq. 3)

Density (g/ml) = \frac{weight of raw rice grain W_{1} (g)}{Volume of raw rice grain V_{3} (ml)}

Colour characteristics

The colour characteristics of the rice samples were determined using a colour meter (CR-10 Konica Minolta Optics Inc. Japan), by visual examination as follows. One-hundred (100) grams of milled rice grain of each variety were randomly selected and placed in a petri dish. The colour reader was calibrated using a standard white paper. The lightness (L⁺), a* scale and b* scale of the rice varieties were determined by placing the colour meter close to the samples in the petri dish and capturing it. The L⁺ scale indicated lightness, where 100 = pure white and 0 = pure black. a* scale indicated red to green colour spectrum where positive value represented red colour and negative value represented green colour. b* scale indicated yellow to blue colour spectrum. Where positive value indicated yellowness and negative value represented blue colour. The samples were also analysed by visual inspection to state the level of cleanliness of the rice varieties.

Dockage determination

Dockages in the rice varieties were determined by separation of the rice grains from the foreign matter present. Ten (10) grams of rice sample was weighed and the impurities present separated from the rice grains manually by hand picking. The weight of the impurities obtained was measured using a 0.01 g sensitive scale (Mettler AE 200).

Aroma

One-thousand (1000) gram of rice samples of each variety were selected and checked subjectively (by sense of smell) for aroma and also for odour not normally associated with clean, sound, parboiled and milled rice of naturally scented and non-scented varieties.

Determination of AMD, GMD and SMD

The arithmetic mean diameter (D_a), geometric mean diameter (D_g), and square mean diameter (D_s) were determined using the expression by Asoegwu et al. (2006) given in Eqs. (4), (5) and (6), respectively.

D_{a} = \frac{(L + W + T)}{3}

D_{g} = {(L W T)}^{\frac{1}{3}}

D_{s} = {[\frac{(L W + W T + T L)}{3}]}^{\frac{1}{2}}

Determination of sphericity, aspect ratio and surface area

The sphericity, aspect ratio and surface area were determined using Mohsenin (1986) and Jain and Bal (1997) as shown in Eqs. (7), (8) and (9), respectively.

\emptyset = \frac{{(L W T)}^{\frac{1}{3}}}{L}

R_{a} = \frac{W}{L}

S_{a} = \frac{π {(W T)}^{\frac{1}{2}} L^{2}}{2 L - {(W T)}^{\frac{1}{2}}} .

Statistical analysis

The study adopted a completely randomised design. The data generated were subjected to one way analysis of variance (ANOVA) using SPSS version 20.0. Means were separated using Duncan’s Multiple Range Test (DMRT) and significance was accepted at 0.05 level of probability (Akande et al. 2017).

Results and discussion

Table 1 shows the grain dimensions of local and imported rice varieties marketed in South-East Nigeria. A high percentage (77.78%) of the local rice varieties were long grain rice (6.07–6.93 mm) along with Ip3 (6.11); 50% were slender grains (3.02–3.35) and 50% were bold grains (2.18–2.99) as described by FAO (see foot note). Length: width ratio (shape) is said to be probably the most meaningful of the determinations since it is used in sizing rice with slotted sieves or precision graders (Webb and Stermer 1972). Large percentage (77.78%) of the domestic rice varieties were heavy grains (20.00–24.33 g) along with Ip1 (21.00 g) Significant percentage (44.44%) of the local rice varieties which were heavy grains had thousand grain weight higher than Ip1 (21.00) which was the heaviest imported rice variety. These domestic rice varieties with higher grain weights will sell at a higher price in international market than the imported rice varieties when rice is sold by weight. Akpujie an extra-long local rice grain had the longest length (7.47 mm) compared to Ip1 (7.19 mm) and Ip2 (7.07 mm) which are also extra-long grains. Almost all (92.86%) of the long-grain local rice varieties had a longer length than Ip3 which is a long-grain. Nigerians seek for long-grain imported rice which are sold at higher prices in Nigerian markets because rice consumers perceive imported rice to be of higher quality than local rice. These local rice varieties when properly processed and being of better quality in length, weight and price than the imported rice would command a high market share than the imported rice and preserve Nigeria’s foreign revenue due to exports.

There were no significant (p > 0.05) differences in the volume of rice grains (10.00–20.00 ml³) of a large percentage (76.19%) of the local and imported rice varieties evaluated. The values obtained were within the range of values (16.25–22.02 ml³) reported by Nádvorníková et al. (2018) for eight staple rice cultivars consumed in Kyrgyzstan. Similar values (13.94–26.75 ml³) were also reported for Iranian rice by Varnamkhasti et al. (2008). The differences in volume dimension could be as a result of variation in grain dimensions as noted by Nádvorníková et al. (2018). Grains highest in volume will occupy more storage space during transportation and sales. In international market trading when rice is traded in volume, grains highest in volume will be beneficial to the seller because it will occupy more storage space while those of low volume will be beneficial to the buyer. In transportation of rice grains, grains of less volume will attract less transportation cost because it will occupy less storage space than those of high volume. Geshua and Kpurukpuru (10.00 ml³) will attract less transportation cost than Fadama and FARO 40 (20.00 ml³).

There were no significant (p > 0.05) differences in the density (1.00–2.07 g/ml³) of a large percentage (85.71%) of the rice varieties. The rice varieties were almost the same among themselves in their density. Values reported were within the range of value (1.17–1.41 g/ml³) reported by Nádvorníková et al. (2018) for eight staple rice cultivars consumed in Kyrgyzstan Grains of higher density is desirable as it will command higher price in international market trade where rice is sold according to weight.

Table 2 shows the AMD, GMD, SMD, sphericity, aspect ratio and surface area of local rice varieties. The AMD values of the local rice varieties were (3.29–3.86 mm) while that of the imported rice varieties were (3.26–3.64 mm) which were all within the same range. There were no significant (p > 0.05) differences among Ip3 (3.26), Geshua (3.29) and kpurukpuru (3.33) in their AMD despite Ip3 being a long grain rice while Geshua and Kpurukpuru were medium grain rice varieties. Significant (p < 0.05) differences existed in the AMD of Akpujie (3.86), Ip1 (3.64), Ip2 (3.64) and Abakiliki-Mas (3.59) despite all of them being extra-long grain rice. AMD is independent of grain size and is specific for each rice grain. Similar values (3.14–3.47 mm) were reported by Nádvorníková et al. (2018) for eight staple rice cultivars consumed in Kyrgyzstan. Mir et al. (2013) also reported 3.60–3.79 mm for Indian varieties and (Varnamkhasti et al. 2008) measured 3.30 mm and 3.40 mm on cultivars from Iran.

The GMD of the local rice varieties ranged from 8.02 to 10.36 mm, while that of imported rice varieties ranged from 6.84 to 8.68 mm. Significant (p < 0.05) differences existed in the GMD of Akpujie (10.36 mm), Ip1(8.24 mm) and Ip2 (8.68 mm) despite all of them being extra-long grain rice. Akpujie which is an extra-long grain rice did not differ significantly (p > 0.05) from B-G (9.68 mm) and FARO 44 (9.40 mm) which are long grain rice. Significant (p < 0.05) differences existed in the GMD of Akpujie and Abakiliki-Mas (8.15 mm) despite both being extra-long grain rice. GMD is independent of grain size.

Akpujie which is an extra-long grain rice differed significantly (p < 0.05) in SMD (5.82 mm) from Ip1 (5.03 mm), Ip2 (5.15 mm) and Abakiliki-Mas (4.97 mm), which are also extra-long grain rice. There was no significant (p > 0.05) difference in SMD between Abakiliki-Mas, R-8 (4.98 mm) and 306 (5.21 mm), despite that Abakiliki-Mas is an extra-long grain size while 306 and R-8 are long grain rice. SMD is independent of grain size. AMD, GMD and SMD are useful in estimating the size of machine components for separation, cleaning, sorting and grading processes. They are important in design of storage structures and transportation of rice grains. In designing machine for these purposes these diameters should be used to reduce losses and avoid poor post-harvest handling operations.

The sphericity of the local rice grains evaluated ranged from (51.25 to 59.23%) while that of imported rice varieties ranged from (50.61 to 53.53%). Significant (p < 0.05) differences exist in the sphericity of long grain rice. There was no significant (p > 0.05) difference in the sphericity of extra-long and long grain rice. Sphericity is independent of grain size. The span of results in sphericity measurement ranged from 48.00 to 59.00% for eight staple rice cultivars consumed in Kyrgyzstan as reported by Nádvorníková et al. (2018). According to Mir et al. (2013) Indian brown rice had their sphericity in range of 37.40–63.44%. Diaz et al. (2015) observed Japanese rough rice (Japonica, Indica and NERICA) sphericity to vary from 38 to 55%. Varnamkhasti et al. (2008) showed the sphericity of Iranian rice in range of 37–46%. Sphericity helps to know the opening of the sieve, how rice grains will assume an orientation and roll in hoppers when left in its natural rest position, development of an aperture size of components and modelling of such system. The sphericity of rice grains were lower compared to that of peas (77.37–86.15%) (Salah et al. 2014). Lower sphericity values suggest that the kernels tend towards a cylindrical shape and not spheroid like peas. The lower values of the sphericity generally indicate a likely difficulty in getting the kernels to roll than that of peas which are spheroid grains. They can, however, slide on their flat surfaces. This tendency to either roll or slide should be necessary in the design of hoppers for milling process (Ghadge and Prasad 2012) by utilising the specific sphericity of each rice variety.

The aspect ratio of the local rice varieties evaluated ranged from 0.31 to 0.46 while the imported rice varieties were within the range of 0.28–0.33. Significant (p < 0.05) differences existed in the aspect ratio between Ip1 (0.28) and Akpujie (0.31) despite both being extra-long grain rice varieties. There was no significant difference between Abakiliki-Mas (0.30), Afikpo-Mas (0.31) and 306 (0.31) despite Abakiliki-Mas being an extra-long grain rice while 306 and Afikpo-Mas are long-grain rice. Aspect ratio is independent of grain size. Values reported by Nádvorníková et al. (2018) were within the same range (0.39–0.55). Varnamkhasti et al. (2008) recorded values of 0.28–0.29 while (Mir et al. 2013) reported (0.19–0.43) for different cultivars of rice aspect ratio. Aspect ratio helps in the designing of sorting equipment and storage structures.

The surface area of the local rice varieties were in the range of 21.87–29.44 mm² while the imported rice varieties were in the range of 18.72–23.53 mm². Significant (p < 0.05) differences existed in surface area of Akpujie (28.37 mm²) and Abakiliki-Mas (21.98 mm²) despite both, being extra-long grain rice varieties. There were no significant (p > 0.05) differences between Geshua (24.73 mm²), kpurukpuru (25.26 mm²), R-8 (23.23 mm²) and 306 (24.50 mm²) despite R-8 and 306 being long grain rice while Geshua and kpurukpuru are medium grain rice varieties. Values reported by Nádvorníková et al. (2018) varied from 25.35 to 31.90 mm². (Mir et al. 2013) reported values of 34.32 mm–43.78 mm² for paddy rice from India. The surface area of rice kernel is independent of grain size and it’s a relevant tool in determining the shape of the seeds. Surface area is important during heat and mass transfer for drying and aeration processes.

Ip1 and Ip2 which are extra-long grains were not significantly (p > 0.05) different from each other in AMD, GMD, SMD, aspect ratio, sphericity and surface area and will therefore use the same post-harvest processing equipment. Ip3 a long grain variety is significantly (p < 0.05) different from Ip1 and Ip2 in all the aforementioned parameters and will not use the same post-harvest processing machine. Fadama, Fortin 16 and Fortin 16 (old variety) were not significantly (p > 0.05) different from each other in all their engineering properties and therefore will continue to use the same post-harvest processing equipment as it is the practice. The result of this research should be used for design and adjustment of milling machine and other post-harvest handling equipment in order to avoid loss of grains and produce high quality rice characterised by high head-rice and appealing appearance. Another application of this data can be in recognition of these rice varieties.

Table 3 shows the general appearance, dockage and aroma of domestic rice varieties sold in South-East Nigeria. General appearance is used to describe colour and translucence of milled rice grain (Webb and Stermer, 1972). In evaluation of the colour of parboiled milled rice using a colour meter, all the rice varieties had an off-white appearance (46.93–61.10) in lightness. This shows that parboiled milled rice do not have white colour. There were no significant (p > 0.05) differences in the a* scale of all the rice varieties but 50% of the domestic rice varieties had negative values. The negative value may be as a result of the grey coloured or streaked appearance of the rice varieties affected. For b* parameter, all of the local rice varieties had significant positive value (8.80–23.93) indicating yellowness and not blueness. Parboiled milled rice have shades of yellow colour. The colour of milled rice range from white to light cream, yellow, grey or rosy depending on whether it is parboiled or raw milled rice. Grey colour of milled rice is unappealing. Rice with grey colour falls in the category of grade 3 quality while rice with white, yellow or light cream colour are of premium quality (Semple et al. 1992).

In visual examination by sense of sight all the imported rice varieties were clean and appealing in appearance. Ip1 had clean yellow appearance. The yellow colour of Ip1 may be as a result of high steam treatment during parboiling. A significant percentage (50%) of the local rice varieties, majorly rice varieties from Ebonyi State had clean light-cream coloured appearance which is desirable and appealing, though some had black and red streaks. About 50% of the domestic rice grains (especially rice varieties from Anambra and Enugu State) had unappealing grey colour appearance relating to grains covered with ashes. Grey coloured rice showed that the rice grains were not properly processed and cleaned which makes it unappealing and unattractive. According to Akaeze (2010), imported rice cleanliness is the overwhelming technical feature explaining the expansion of imported rice consumption in Nigeria at the cost of local rice market development. It is therefore essential that proper cleaning of the milled local rice varieties is incorporated in all the rice mills in Nigeria since the local rice varieties have better grain dimensions than imported rice. This is essential to create acceptance, increase consumption and improve the market share of the milled local rice varieties. Appearance of food is usually the first sign of edibility (Ihekoronye and Ngoddy 1985).

In dockage determination, the imported rice varieties had no impurities while all of the domestic rice varieties had impurities (5–70%). Dockage in rice reduces quantity of useable rice and detracts the quality of rice. It increases the time of preparation of the rice for consumption because the impurities have to be removed first before the rice grain can be cooked. Significant percentage (50%) of the domestic rice varieties were clean in appearance (Table 3) but still had dockage. The domestic rice varieties need to be cleaned of all foreign matter to enhance convenience using aspirators and other cleaning devices to obtain a dockage free local rice like imported rice.

Rice can be aromatic or non-aromatic. Most of the domestic rice varieties were non-aromatic. Fortin 16, a local rice variety had a musty repulsive odour. The musty repulsive odour could have been as a result of poor storage in unclean environment or along with materials having objectionable odour as rice can easily pick up odour. Grains should be stored in well ventilated and clean environments to prevent objectionable odours. Ip3 along with, Aguleri rice and Akpujie had sweet fragrance while all other varieties do not have any aroma or odour associated with them. Grains which are aromatic had higher concentration of 2-acetyl-1-pyroline (Anon 2014).

Conclusion

A high percentage (77.78%) of the domestic rice varieties found in South-East Nigeria are long grain rice and heavy grains; 50% were slender, 50% were bold and all had a fairly uniform density and volume. The local rice varieties being of better quality in dimensions (length and weight) and price than the imported rice would command a high market share than the imported rice when properly processed. The AMD, GMD and SMD of local rice grains ranged from 3.29–3.86 mm, 8.02–10.36 mm and 4.75–5.82 mm, respectively and were all independent of the grains. The sphericity, aspect ratio and surface area were 51.25–59.23%, 0.31–0.46 and 21.87–29.44 mm², respectively and were all independent of the grains but specific for each grain. Care should be taken while designing post-harvest processing machine using these values to avoid losses and obtain high head-rice. All rice varieties from South East Nigeria had an off-white appearance. Most of the domestic rice varieties were non aromatic and all had some dockage (5–70%) as compared to the imported rice varieties with no dockage. Removal of dockage in local rice will create a high market share for local rice. Physical properties of different rice varieties is essential in order to reduce post-harvest losses, facilitate value addition, quality improvement and design of machines for postharvest processing, leading to high head rice yield which is desirable and of premium price in international trade.

Footnotes

Publisher's Note

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References

Akaeze OH (2010) Consumer preference for imported rice in Nigeria-perceived quality differences or habit persistence? M.Sc. Dissertation, Michigan State University
Akande SA, Onyegbula AF, Salawu RA, Oladipo AK, Adetunji CO. Effects of post-harvest handling on hydrogen cyanide content of cassava products obtained from Ilorin-West urban markets, Nigeria. Afr J Food Sci. 2017;11(11):362–368. doi: 10.5897/AJFS2017.1537. [DOI] [Google Scholar]
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Asoegwu SN, Ohanyere SO, Kanu OP, Iwueke CN. Physical properties of African Oil Bean Seed (Pentaclethra macrophylla) Agric Eng Int CIGR J. 2006;VII 05(006):1–16. [Google Scholar]
Azuka CE, Nkama I, Danbaba N. Grade quality of parboiled milled domestic and imported rice varieties sold in southeast Nigeria. Innovare J Food Sci. 2017;5(3):1–7. [Google Scholar]
Danbaba N. Rice grain quality a compendium of evaluation techniques. Badeggi: Food Technology and Value Addition Program, National Cereals Research Institute; 2013. [Google Scholar]
Diagne A, Bamba I, Manful J (2011) Historic opportunities for rice growers in Nigeria. Inter-réseaux développement rural. http://www.inter-reseaux.org/revue-grain-de-sel/51-special-issue-nigeria/article/historic-oppotunities-for-rice?lang=fr. Accessed 28 Mar 2014
Diaz EO, Kawamura S, Koseki S (2015) Physical properties of rough and brown rice of Japonica, Indica and NERICA types. Agric Eng Int CIGR J Special Issue: 18th World Congress of CIGR: 274–285
Fluhr K, Yang W, Mills K, Connett-Porceddu M, Jefferson R, Nottenburg C, Bacon N (2014) Rice background. In: Rice genome landscape. http://www.patentlens.net/daisy/RiceGenome/2697.html. Accessed 20 April 2014
Gariboldi F (1979) Rice testing methods and equipment. FAO Agricultural Services_Bulletin No. 18. Published by Food and Agriculture Organisation of the United Nations, Rome
Ghadge PN, Prasad K. Some physical properties of rice kernels: variety PR 106. J Food Process Technol. 2012;3(8):175. doi: 10.4172/2157-7110.1000175. [DOI] [Google Scholar]
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Jain RK, Bal S. Physical properties of pearl millet. J Agric Eng Res. 1997;66:85–91. doi: 10.1006/jaer.1996.0119. [DOI] [Google Scholar]
Juliano BO. Rice in human nutrition. Rome: Food and Agriculture Organisations of the United Nations; 1993. [Google Scholar]
Maureen A (2014) Rice: Nigeria in race to meet 2015 target. http://www.punchng.com/business/industry/rice-nigeria-in-race-to-meet-2015-target/. Accessed 28 Mar 2014
Michael T (2008) Edible water plants: aquatic vegetables. http://natures-water.com/education_information/edible_plants/. Accessed 28 Mar 2014
Mir SA, Bosco SJD, Sunooj KV. Evaluation of physical properties of rice cultivars grown in the temperate region of India. Int Food Res J. 2013;20(4):1521–1527. [Google Scholar]
Mohsenin NN. Physical properties of plant and animal materials. 2. New York: Gordon and Breach Science Pub; 1986. [Google Scholar]
Nádvorníková M, Banout J, Herák D, Verner V. Evaluation of physical properties of rice used in traditional Kyrgyz Cuisine. Food Sci Nutr. 2018;6:1778–1787. doi: 10.1002/fsn3.746. [DOI] [PMC free article] [PubMed] [Google Scholar]
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Salah G, Khosro M, Abdolvahed K, Hadi G. Evaluation the some physical properties of chickpea seeds in Kurdistan Region of Iran. Int J Agric For. 2014;4(3A):4–7. doi: 10.5923/s.ijaf.201401.02. [DOI] [Google Scholar]
Semple RL, Hicks PA, Lozare JV, Castermans A (1992) Towards integrated commodity and pest management in grain storage. http://www.fao.org/docrep/x5048e/x5048e03.htm
Varnamkhasti MG, Mobli H, Jafari A, Keyhani AR, Soltanabadi MH, Rafiee S, Kheiralipour K. Some physical properties of rough rice (Oryza sativa L) grain. J Cereal Sci. 2008;47(3):496–501. doi: 10.1016/j.jcs.2007.05.014. [DOI] [Google Scholar]
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[CR1] Akaeze OH (2010) Consumer preference for imported rice in Nigeria-perceived quality differences or habit persistence? M.Sc. Dissertation, Michigan State University

[CR2] Akande SA, Onyegbula AF, Salawu RA, Oladipo AK, Adetunji CO. Effects of post-harvest handling on hydrogen cyanide content of cassava products obtained from Ilorin-West urban markets, Nigeria. Afr J Food Sci. 2017;11(11):362–368. doi: 10.5897/AJFS2017.1537. [DOI] [Google Scholar]

[CR3] Anon (2014) Rice varieties, types and forms of rice. http://www.foodreference.com/html/art-rice-varieties.html

[CR4] Asoegwu SN, Ohanyere SO, Kanu OP, Iwueke CN. Physical properties of African Oil Bean Seed (Pentaclethra macrophylla) Agric Eng Int CIGR J. 2006;VII 05(006):1–16. [Google Scholar]

[CR5] Azuka CE, Nkama I, Danbaba N. Grade quality of parboiled milled domestic and imported rice varieties sold in southeast Nigeria. Innovare J Food Sci. 2017;5(3):1–7. [Google Scholar]

[CR6] Danbaba N. Rice grain quality a compendium of evaluation techniques. Badeggi: Food Technology and Value Addition Program, National Cereals Research Institute; 2013. [Google Scholar]

[CR7] Diagne A, Bamba I, Manful J (2011) Historic opportunities for rice growers in Nigeria. Inter-réseaux développement rural. http://www.inter-reseaux.org/revue-grain-de-sel/51-special-issue-nigeria/article/historic-oppotunities-for-rice?lang=fr. Accessed 28 Mar 2014

[CR8] Diaz EO, Kawamura S, Koseki S (2015) Physical properties of rough and brown rice of Japonica, Indica and NERICA types. Agric Eng Int CIGR J Special Issue: 18th World Congress of CIGR: 274–285

[CR9] Fluhr K, Yang W, Mills K, Connett-Porceddu M, Jefferson R, Nottenburg C, Bacon N (2014) Rice background. In: Rice genome landscape. http://www.patentlens.net/daisy/RiceGenome/2697.html. Accessed 20 April 2014

[CR10] Gariboldi F (1979) Rice testing methods and equipment. FAO Agricultural Services_Bulletin No. 18. Published by Food and Agriculture Organisation of the United Nations, Rome

[CR11] Ghadge PN, Prasad K. Some physical properties of rice kernels: variety PR 106. J Food Process Technol. 2012;3(8):175. doi: 10.4172/2157-7110.1000175. [DOI] [Google Scholar]

[CR12] Ihekoronye AI, Ngoddy PO. Integrated food science and technology for the tropics. London: Macmillan Publishing Press Ltd; 1985. [Google Scholar]

[CR13] Jain RK, Bal S. Physical properties of pearl millet. J Agric Eng Res. 1997;66:85–91. doi: 10.1006/jaer.1996.0119. [DOI] [Google Scholar]

[CR14] Juliano BO. Rice in human nutrition. Rome: Food and Agriculture Organisations of the United Nations; 1993. [Google Scholar]

[CR15] Maureen A (2014) Rice: Nigeria in race to meet 2015 target. http://www.punchng.com/business/industry/rice-nigeria-in-race-to-meet-2015-target/. Accessed 28 Mar 2014

[CR16] Michael T (2008) Edible water plants: aquatic vegetables. http://natures-water.com/education_information/edible_plants/. Accessed 28 Mar 2014

[CR17] Mir SA, Bosco SJD, Sunooj KV. Evaluation of physical properties of rice cultivars grown in the temperate region of India. Int Food Res J. 2013;20(4):1521–1527. [Google Scholar]

[CR18] Mohsenin NN. Physical properties of plant and animal materials. 2. New York: Gordon and Breach Science Pub; 1986. [Google Scholar]

[CR19] Nádvorníková M, Banout J, Herák D, Verner V. Evaluation of physical properties of rice used in traditional Kyrgyz Cuisine. Food Sci Nutr. 2018;6:1778–1787. doi: 10.1002/fsn3.746. [DOI] [PMC free article] [PubMed] [Google Scholar]

[CR20] Oko AO, Ugwu SI. The proximate and mineral composition of five major rice varieties in Abakiliki South-Eastern Nigeria. Int J Plant Physiol Biochem. 2011;3(2):25–27. [Google Scholar]

[CR21] Randall GM, Thompson JF (2009) Rice quality handbook. Google books. http://books.google.com.ng/books/about/rice_quality_handbook.html?id=ni4c73mfavuc&redir_esc=y. Accessed 28 Mar 2014

[CR22] Salah G, Khosro M, Abdolvahed K, Hadi G. Evaluation the some physical properties of chickpea seeds in Kurdistan Region of Iran. Int J Agric For. 2014;4(3A):4–7. doi: 10.5923/s.ijaf.201401.02. [DOI] [Google Scholar]

[CR23] Semple RL, Hicks PA, Lozare JV, Castermans A (1992) Towards integrated commodity and pest management in grain storage. http://www.fao.org/docrep/x5048e/x5048e03.htm

[CR24] Varnamkhasti MG, Mobli H, Jafari A, Keyhani AR, Soltanabadi MH, Rafiee S, Kheiralipour K. Some physical properties of rough rice (Oryza sativa L) grain. J Cereal Sci. 2008;47(3):496–501. doi: 10.1016/j.jcs.2007.05.014. [DOI] [Google Scholar]

[CR25] Webb DB, Stermer RA. Criteria of rice quality. In: Houston DF, editor. Rice chemistry and technology american association of cereal chemists. St. Paul: Incorporated; 1972. pp. 102–139. [Google Scholar]

PERMALINK

Physical properties of parboiled milled local rice varieties marketed in South-East Nigeria

C E Azuka

I Nkama

F U Asoiro

Abstract

Introduction

Materials and methods

Materials

Table 1.

Table 2.

Table 3.

Methods

Determinations of grain dimensions

Determination of grain length

Determination of grain shape

Determination of thickness

One-thousand grain weight (W₁)

Determination of volume of raw rice grains

Density of raw rice grain

Colour characteristics

Dockage determination

Aroma

Determination of AMD, GMD and SMD

Determination of sphericity, aspect ratio and surface area

Statistical analysis

Results and discussion

Conclusion

Footnotes

References

ACTIONS

PERMALINK

RESOURCES

Cite

Add to Collections

PERMALINK

Physical properties of parboiled milled local rice varieties marketed in South-East Nigeria

C E Azuka

I Nkama

F U Asoiro

Abstract

Introduction

Materials and methods

Materials

Table 1.

Table 2.

Table 3.

Methods

Determinations of grain dimensions

Determination of grain length

Determination of grain shape

Determination of thickness

One-thousand grain weight (W1)

Determination of volume of raw rice grains

Density of raw rice grain

Colour characteristics

Dockage determination

Aroma

Determination of AMD, GMD and SMD

Determination of sphericity, aspect ratio and surface area

Statistical analysis

Results and discussion

Conclusion

Footnotes

References

ACTIONS

PERMALINK

RESOURCES

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One-thousand grain weight (W₁)