The Effect of Variety and Processing Methods on the Functional and Chemical Properties of Rice Flour

Abstract

The effect of varieties, local (Abakalike) and foreign (Mama Gold) and two processing methods, semi-dry and wet grinding methods on the characteristics of rice flour were investigated. Functional and chemical properties of the rice flour were analyzed using standard methods. The functional parameters analyzed were dispersibility, relative bulk density, swelling power and water absorption capacity while chemical parameter were moisture content, protein, ash, sugar, starch, amylase and amylopectin. The parameters were influenced by variety and processing methods. Highest dispersibility, relative bulk density and swelling power values were associated with sample A which is the foreign variety, while solubility and water absorption capacity were associated with sample B, which is the local variety, all processed by the semi-dry grinding method. The semi-dry ground rice flour produced highest protein and ash as seen in sample B, while wet milled rice flour were associated with highest moisture and starch contents. The flour produced from the local rice (Abakalike) had highest protein, ash sugar and amylose over the foreign variety with all the parameters showing significant differences.

Full text

International Journal of Nutrition and Food Sciences
2016; 5(1): 80-84
Published online March 1, 2016 (http://www.sciencepublishinggroup.com/j/ijnfs)
doi: 10.11648/j.ijnfs.20160501.22
ISSN: 2327-2694 (Print); ISSN: 2327-2716 (Online)
Research/Technical Note
The Effect of Variety and Processing Methods on the
Functional and Chemical Properties of Rice Flour
Eke-Ejiofor Joy
*
, Nwiganale Ledogo
Department of Food Science and Technology, Rivers State University of Science and Technology Nkpolu, Port Harcourt, Nigeria
Email address:
joyekee@yahoo.co.uk (Eke-Ejiofor J.)
To cite this article:
Eke-Ejiofor Joy, Nwiganale Ledogo. The Effect of Variety and Processing Methods on the Functional and Chemical Properties of Rice Flour.
International Journal of Nutrition and Food Sciences. Vol. 5, No. 1, 2016, pp. 80-84. doi: 10.11648/j.ijnfs.20160501.22
Abstract:
The effect of varieties, local (Abakalike) and foreign (Mama Gold) and two processing methods, semi-dry and wet
grinding methods on the characteristics of rice flour were investigated. Functional and chemical properties of the rice flour were
analyzed using standard methods. The functional parameters analyzed were dispersibility, relative bulk density, swelling power
and water absorption capacity while chemical parameter were moisture content, protein, ash, sugar, starch, amylase and
amylopectin. The parameters were influenced by variety and processing methods. Highest dispersibility, relative bulk density
and swelling power values were associated with sample A which is the foreign variety, while solubility and water absorption
capacity were associated with sample B, which is the local variety, all processed by the semi-dry grinding method. The
semi-dry ground rice flour produced highest protein and ash as seen in sample B, while wet milled rice flour were associated
with highest moisture and starch contents. The flour produced from the local rice (Abakalike) had highest protein, ash sugar
and amylose over the foreign variety with all the parameters showing significant differences.
Keywords:
Varieties, Processing Methods, Properties, Chemical, Functional, Rice Flour
1. Introduction
Flour is the main ingredient for the confectionery industry,
making its availability and adequate supply a major economic
and political issue at various times throughout history (Palmar,
2000). Wheat is the most common base for flour while maize
flour has been used and rice can also be used in the production
of flour, though it is relatively uncommon.
Rice is the seed of the grass specie Oryza sativa (Asian Rice)
or Oryza glaberrima (African rice). As a cereal grain, it is the
most widely consumed staple food for a large part of the
world’s human population especially in Asia. Rice provides
20% of the world’s dietary energy supply, while wheat
supplies 19% and maize 50% (FAO, 2004). It is the
agricultural commodity with the third highest worldwide
production, after sugar cane and maize, (FAOSTAT, 2012).
Rice flour has about 6.5-7% protein and does not contain
gluten and is a good substitute for rye, oat or wheat flour,
which causes irritation in the digestive systems of those who
are gluten – intolerant. Rice flour is used as a thickening
agent and for making rice bread (Hosking, 1997). In most
parts of the world, the consumption of wheat based products
and other cereals containing gluten present problems for a
large number of populations who are allergic to gluten;
characterized by an inflammation of the small intestine a
disease known as celiac. This calls for an alternative to wheat
flour. Furthermore, increase in population as well as increase
in consumption rate of wheat based products has posed huge
burden on the importation, utilization and availability of
wheat. The high cost of wheat flour in non-wheat producing
countries such as Nigeria poses a problem to bakery
industries and consumers of baked products. Fortunately, in
Africa, there are numerous traditional grains with high
nutritional quality and health benefit that are underutilized,
of which rice is one. These traditional grains can contribute
substantially to daily protein need, micronutrients and
negligible amounts of fats (Stading, 2006) and increase the
potential and utilization of rice. Therefore, the main
objectives of the study were to assess the characteristics of
the rice flour using semi-dry and wet grinding methods in
relation to the functional and chemical properties of rice
flour.

International Journal of Nutrition and Food Sciences 2016; 5(1): 80-84 81
2. Materials and Methods
2.1. Raw Materials
Rice varieties both local and foreign used for this study
were purchased from Mile One market in Diobu, Port
Harcourt. Rivers State, Nigeria.
Source: Yeh (2004)
Figure 1. Flow Chart illustrating the production of rice flour.
Preparation of Rice Flour: Rice grains from local and
foreign varieties were sorted and cleaned. Two different
methods namely semi-dry grinding and wet grinding methods
were used to produce rice flour. In the semi-dry grinding
method, one and half kilogram (1
1
/
2
kg) of the two rice
varieties were fermented in 3000ml of water for 16 hours (1: 2
ratio), then crushed and dried at 60°C for 4 hours (partial
drying) to 24% moisture content, milled and finally dried at
60°C for 12 hours then sieved with a mesh size of 125 microns.
In the wet grinding method, one and half kilogram (1
1
/
2
kg) of
the local and foreign rice were soaked in 3000ml of water for
4-5 hours at 30°C, milled in excess of water using a wet
grinder, dried in a hot air, oven at 40°C overnight, reground
and sieved with a mesh size of 125micron to obtain rice flour.
2.2. Functional Properties of Rice Flour
Dispersibility was determined by the method of Kulkarni et
al., (1991), while the relative bulk density of samples was
determined by the method described by Narayana and
Narasinya, (1984). The water absorption capacity was
determined using the method by Sosulski, (1962), with swelling
Power and Solubility determined using the method of Takashi
and Sieb, (1988). Moisture, protein and ash contents were
determined by the AOAC (1990) method. Amylose content was
determined according to the method described by Williams et
al., (1970), while amylopectin was calculated by difference
(%Amylopectin = % starch - % amylose). Starch and sugar
were determined by the method described by Eke 2006.
2.3. Statistical Analysis
The data obtained were subjected to analysis of variance
(ANOVA) using (SPSS) version 20.0 software 2007. All
analysis was done in duplicate. The measure of central
tendencies and dispersions were determined and Duncan
Multiple Range Test (DMRT) was used to separate the mean.
3. Results and Discussion
Physico-chemical properties of rice flour from semi-dry
and wet grinding methods.
The characteristics of rice flour are governed by inherent
cultivars variations, environmental variation, the grinding
methods and previous treatments (Fan and Marks 1998),
which has also affected the finding of the present study.
Table 1: Shows the functional properties of rice flour
produced by semi-dry and wet grinding methods.
Table 1. Functional Properties of Rice Flour produced from two methods (Dry and Wet grinding methods.
Sample Dispersibility Relative Solubility Relative Bulk density Swelling power Water absorption
A 67.50
a
±1.71 1.53
a
±0.07 5.60
d
±0.78 1.53
a
±0.07 7.75
a
±0.35 1.90
a
±0.07
B 58.00
b
±1.41 1.37
a
±0.08 10.08
a
±0.72 1.37
a
±0.08 7.61
a
±0.01 2.14
a
±0.11
C 60.50
c
±0.71 1.39
a
±0.05 9.07
b
±1.16 1.39
a
±0.05 7.36
a
±0.31 1.94
a
±0.05
D 61.00
d
±4.24 1.34
a
±0.07 8.44
c
±0.92 1.34
a
±0.07 7.62
a
±0.42 1.64
b
±0.54
Values are mean of duplicate determination ±Standard deviation
Means having different superscript in the same column are significantly different (p<0.05).
Key:
Sample A = Foreign Rice Flour Produced Using Semi-Dry Grinding Method (FRFSDGM)
Sample B = Local Rice Flour Produced Using Semi-Dry Grinding Method (LRFSDGM)
Sample C = Foreign Rice Flour Produced Using Wet Grinding Method (FRFWGM)
Sample D = Local Rice Flour Produced Using Wet Grinding Method (LRFWGM)
Dispersibility of rice flours ranged from 58.00% - 67.50%
with sample B as the lowest and sample A as the highest. The
results obtained from the present study showed that there were
significant differences (P < 0.05) in the dispersibility of flour
samples as a result of the different processing methods and
varietal differences. The property of dispersibility determines
the tendency of flour to move apart from the water molecules
and reveals its hydrophobic action
.
The semi-dry grinding method had higher dispersibility
than the wet grinding method. Adebowale et al., (2008)
reported that flours of higher dispersibility easily reconstitute
to give fine consistent dough during mixing. Dispersibility of

82 Eke-Ejiofor Joy and Nwiganale Ledogo: The Effect of Variety and Processing Methods on the
Functional and Chemical Properties of Rice Flour
sample A (67.50%) was significantly higher than sample B
(58.00%), C (60.50%) and D (61.00%). However, the results
obtained were lower than the findings of Adebowale et al.,
(2012) with a value of 73.00% -76.50%.
Relative bulk density ranged from 1.34g/ml in sample D as
the lowest to 1.53g/ml in sample A as the highest. The present
results are higher than the findings of Okoye & Mazi, (2011)
with a maximum value of 0.98g/ml. Bulk density is dependent
upon the particle size of the samples and can also be described
as a measure of heaviness of a flour sample. In agreement with
this statement, Akubor and Obieguna (1999) reported that
bulk density of a sample could be used in determining its
packaging requirements, material handling and application in
wet processing in the food industry, as this relates to the load
the sample can carry if allowed to rest directly on one another.
Processing methods and variety did not have any significant
affect on the relative bulk density of the rice flour samples.
Solubility ranged from 5.60% - 10.08% with sample A
having the lowest value and sample B having the highest. The
result of this finding falls within that reported by Eke and
Owuno, (2012) who reported a value of 5.36 – 15.10% for
wheat/three leaf yam composite flour blend. Increase in
solubility would result from the shortening of the chain length
of the starch molecules with a corresponding weakening of the
hydrogen bonds holding the granules together (Sapade and
Grys, 1991). Solubility showed significant differences (P <
0.05) in both processing method and variety, with the Wet
grinding method having a higher solubility value than the
semi-dry grinding method.
Swelling power ranged from 7.36% - 7.75% with sample C
as the lowest and sample A as the highest. The result of the
present study is lower than the findings of Adebowale, et al
(2012) who reported a value of 9.87% - 10.34% for
sorghum/wheat composite flour. Swelling power is a measure
of hydration capacity, because its determination is a weight
measure of swollen starch granules and their occluded water.
Food eating quality is often connected with retention of water in
the swollen starch granules (Rickard et al 1992). Furthermore,
swelling power determines the extent to which a flour sample
increases in volume when soaked in water in relation to its
initial volume. Moorthy and Ramanujam (1980) also reported
that the swelling power of flour granules is an indication of the
extent of associative forces within the granule, while Loos et al.,
(1981) also related swelling power to the water absorption
index of the starch based flour during heating.
Similarly, water absorption capacity ranged from 1.64ml/g -
2.14ml/g with sample D (1.64ml/g) having the lowest value
and sample B (2.14ml/g) having the highest. This report
agreed with the findings of Onabanjo et al (2014) with a value
ranging from 1.88ml/g – 2.14ml/g. The disparities observed in
the water absorption capacity values could be attributed to the
method used as well as the varietal differences. The result
obtained shows that the flour has a good ability to bind water.
This result suggests that rice flour could be used in
confectioneries. Water absorption capacity represents the
ability of a product to associate with water under conditions
where water is limiting (Singh 2001). Niba et al., (2001)
described water absorption capacity as an important
processing parameter that has implications for viscosity.
Furthermore, water absorption capacity is important in
bulking and consistency of products as well as baking
applications. High water absorption capacity is attributed to
lose structure of starch polymers while low value indicates the
compactness of the structure (Adebowale et al., 2005).
However swelling power and water absorption capacity were
not affected by processing method or variety of rice.
Table 2: shows the chemical properties of the flour
samples. Moisture content of the different rice flour samples
ranged from 6.58% - 6.60% with sample A having the lowest
and sample D having the highest value. This finding was
slightly higher than that reported by Ocloo et al., (2010) of
6.09%, but lower than that reported by Prasad et al (2012)
who reported a moisture content of (12.11% to 13.14%) for
Pusa 1121 rice flour. Amornrat and Karmontip (2004) also
reported a value of 6.34% - 8.57% respectively for wet and
dry milled jackfruit seed flour. Moisture provides a measure
of the water content of the flour samples and its total solid
content. It is also an index of storability of the flour. Reduced
moisture content implies better shelf life and stability.
Table 2. Chemical Composite of rice flour produced from two methods (Dry and wet grinding methods).
Sample Moisture Protein Ash Starch Sugar Amylose Amylopectin
A 6.58
c
±0.02 7.35
d
±0.12
0.92
b
±0.04
54.80
b
±0.05
1.71
b
±0.02
32.74
b
±0.13
22.06
c
±0.13
B 6.60
c
±0.02
8.98
a
±0.12
1.14
a
±0.02
56.29
a
±0.55 1.93
C
±0.02
32.85
a
±0.13
23.44
b
±0.13
C 7.25
b
±0.02
7.75
c
±0.14 0.89
b
±0.05
56.40
a
±0.36 1.78
a
±0.02
32.63
b
±0.13
23.77
a
±0.12
D 7.68
a
±0.02
8.55
b
±0.08
1.05
a
±0.02
52.64
c
±0.27 1.97
f
±0.02 32.88
a
±0.06
19.76
d
±0.06
Values are mean of duplicate determination ±Standard deviation
Means having different superscript in the same column are significantly different (p<0.05).
Key:
Sample A = Foreign Rice Flour Produced Using Semi-Dry Grinding Method (FRFSDGM)
Sample B = Local Rice Flour Produced Using Semi-Dry Grinding Method (LRFSDGM)
Sample C = Foreign Rice Flour Produced Using Wet Grinding Method (FRFWGM)
Sample D = Local Rice Flour Produced Using Wet Grinding Method (LRFWGM)
Protein content of the rice flour ranged from 7.35% in
sample A to 8.98% in sample B. The present study showed
that variety and processing method had significant difference
with the local variety having higher protein content. The
protein content in the present study falls within the range
(6.3-9.5%) recorded by Derycke, et al (2005). The observed
difference may be due to variety and processing methods. To
support this finding, Chen (1995), Juliano and Hicks (1996)

International Journal of Nutrition and Food Sciences 2016; 5(1): 80-84 83
reported that the semi-dry and wet grinding process which
involved soaking of rice kernels resulted in leaching out of
protein and other soluble substances.
Ash content of the flour samples ranged from 0.89% -1.14%
with sample C having the lowest and sample B having the
highest. The result also showed that ash was less in the wet
ground flour than the semi dry ground flour. This finding is
in agreement with that of Prasad et al (2012). There was no
significant varietal difference (P≤0.05) in ash. Ash is the
organic residue remaining after the organic matter has been
burnt away (Ocloo et al., 2010).
Sugar content ranged from 1.71% - 1.97% with sample A as
the lowest and sample D as the highest. The result of the
finding is lower than the findings of Adebowale, et al., (2012)
who reported a value of 3.97%– 5.31% for sorghum /wheat
composite flour. Furthermore the local rice variety had more
sugar than the foreign rice variety as shown in samples B and
D. Chen (1995) reported that some soluble sugars were
washed away during soaking of rice kernels which were
subjected to semi-dry and wet grinding methods.
Starch content ranged from 52.54% - 56.40% with sample
D as the lowest and sample C as the highest. The starch
content ranging from 52.54% - 56.40% showed that there was
a significant difference (P < 0.05) in samples A and D.
Amylose content ranged from 32.63% - 32.88% with
sample C (32.63%) as the lowest and sample D (32.88%) as
the highest. The result of this finding was higher than the
findings of Prasad et al (2012) who reported a value of
16.21% and 17.81% for wet and semi dry ground flour
respectively. Eke and Owuno, (2012) also reported a lower
value of 29.27% - 32.21% for wheat/three – leaf yam
composite flour blend. Fan and Marks (1998) also reported
that rice flour mainly differ in the amylase content which
determine the gelatinization temperature and in general the
pasting behavior and viscoelastic properties. The amylose
content of raw materials is an important factor with regard to
the end use properties of various products such as noddles
(Sievert and Lausanne 1993). Juliano and Perdon (1975),
reported that rice varieties are classified according to their
amylose content which can either be non-waxy (8-37%) or
waxy glutinous (0.8-1.3%). This has also shown that the rice
varieties under review are non- waxy. Raja and Ramakrishma
(1990) reported that heat treatment caused a reduction in
amylose content of starch based products. However, the
processing methods did not affect the amylose contents of the
two rice varieties.
The amylopectin content ranging from 19.76% – 23.76%
was lower than the findings of Eke and Owuno, (2012) who
reported a value of 66.27-76.79% for wheat /three-leaf ram
composite flour blend. The observed difference may be as a
result of their different origin.
The results from the physical damage of the native
amylopectin lead to the degradation of the flour into low
molecular weight fragments which may disrupt the glycosidic
linkages and the disulphide bonds of the native grain (Prasad
et al., 2012). The result of the present study has shown that
amylopectin is a function of the starch and amylose content
of flour meaning that one is a function of the other and both
properties are important in food preparation and development.
Amylopectin contributes to high viscosity and waxiness in
starch (Eke-Ejiofor and Kin-Kabari, 2010). There were
significant differences (P≤0.05) in the processing methods
for all the chemical parameters determined.
4. Conclusion
The present study showed that different processing methods
and variety resulted in variation in the functional and chemical
characteristics of rice flour for different uses. The semi-dry
grinding method was more suitable for the production of rice
flour in terms of its functional properties as it had better
solubility and water absorption capacity, while local rice was
more preferred to foreign variety as it had better protein, ash
sugar and amylase contents.
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