Content uploaded by Karzan A. Omar
Author content
All content in this area was uploaded by Karzan A. Omar on Jun 30, 2016
Content may be subject to copyright.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11084
Evaluation of Starch and Sugar Content of Different Rice Samples and
Study their Physical Properties
Karzan A.Omar*, Botan M. Salih, Nahla Y. Abdulla, Basi H. Hussin and Shiraz M. Rassul
Department of Chemistry, Koya University, Daniel Mitterrand Boulevard, Koya KOY45 AB64,
Kurdistan Region – Iraq.
Received: 28 Mar 2016 Revised: 29 April 2016 Accepted: 31 May 2016
*Address for correspondence
Karzan A. Omar
Assistant lecturer
Department of Chemistry, Koya University
Daniel Mitterrand Boulevard, Koya KOY45 AB64,
Kurdistan Region – Iraq
Email: karzan.abdulkareem@university.org
This is an Open Access Journal / a rticle distributed under the terms of the Creative Commons Attribution License (CC BY-NC-ND
3.0) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. All
rights reserved.
Rice is one of the main dietary foods widely consumed by Kurdish people in the Kurdistan Region. In
this research, five different types of rice samples have been studied. The starch content of rice samples
was found to be in the range of 81.23-92.73%. The high starch content of 92.73% was obtained by sample-5
and the low and standard of starch content of 81.23% was obtained by sample-1. The total sugar content
of rice samples was determined by using a phenol-sulfuric acid method at different hydrolysis time
under constant acid concentration (2% H2SO4) and temperature (25°C). The physical properties including
length, width, thickness, equivalent diameter, surface area, sphericity, aspect ratio, volume, bulk density,
true density, porosity, and thousand kernel weight was studied for rice samples. The physical properties
are necessary for designing appropriate equipment for process operations such as handling, transporting,
sorting, and designing storage structures in food processing industry based on their properties.
Keywords: Rice, Starch, Polarimetric method, Reduced Sugar, Phenol-Sulphuric method, Physical
Properties.
INTRODUCTION
Rice is the major food to the most people around the world. It is providing 35-60% of the caloric intake of three billion
people in Asian countries (Guyer, et al., 1998) including Kurdistan people. In the Kurdistan region, there are several
types of rice available, but Kurdi rice is an only rice cultivated in the Kurdistan region and each of them have their
RESEARCH
ARTICLE
ABSTRACT
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11085
own physical properties which are useful in sizing grain hoppers and storage facilities. Rice consists of different
components but starch is the main component of rice and it contains 80-90% of the total constituents. Starch is a
-D-(1- -D-(1-6) glycosidic bonds.
The starch granule mass comprises 70% amorphous regions, which consists of amylose and branching points of
amylopectin molecules, and 30% crystalline which is mainly composed of the outer chains of amylopectin
(Kodandaram and Bhotmange, 2014). Starch is the major dietary source of carbohydrates and it is the most abundant
storage polysaccharide in plants. Therefore, rice becomes one of many potential sources of starch. The rice starch is a
unique starch among available commercial starches due to its small granule size and its hypoallergenic residual
protein (Schoch, 1967). The shape and size of starch granules depend on the source and the ambient condition of the
growing area. Starch shapes have the forms of globular, ellipse, oval, lenticular and amorph. The sizes of starch
this research, the
polarimetric (or Ewers’) method used to determine the amount of starch content and Phenol-Sulphuric method for
total reduced sugar content. This method used due to its advantages such as low cost reagents, readily available and
most importantly, can be used to quantify monosaccharides, oligosaccharides and polysaccharides. Therefore, it has
been used to quantify the total sugar content of rice samples by constructing the calibration curve from glucose. At
the same time, their physical properties have been studied.
Experiment
MATERIALS AND METHODS
All the chemicals that used in this research were provided by Koya University in Kurdistan Region-Iraq.
Hydrochloric acid (HCl), Carrez I solution (30% ZnSO4), Carrez II solution (15% K4[Fe(CN)6] ), Phenol, (96% H2SO4).
All solutions were prepared from distilled water.
Determination of starch content
Five rice samples were available in the Kurdistan Region market were selected in this research, namely: sample-1;
Kurdi, sample-2 Royal; sample-3 Knooz; sample-4 Mahmood and sample-5 Zer. A portion of 5 g of a homogenized
sample is weighed in a 100 ml Kohlrausch volumetric flask and its content is mixed with 25 ml of 1.124% HCl
solution. After addition of another 25 ml of 1.124% HCl solution, the suspension is heated on a boiling water bath for
15 min (after 3 min the content of a volumetric flask is mixed to avoid coagulation). Once the hydrolysis is finished,
20 ml of 1.124% HCl solution is added. After fast cooling (using a stream of flowing water), clarification using 5 ml of
Carrez I and Carrez II solutions. Finally, a volumetric flask is filled up with detailed water, its content is properly
mixed, and filtrated using a filtration funnel. The obtained filtrate is then transferred to a polarisation tube (2 dm)
and starch content measured by using a Polax-2L. The obtained value is firstly corrected for a temperature (20°C) by
using equation 1
= 0.0144 (20) (1)
And the amount of starch (X) in the rice samples was calculated by using equation 2
= 10
[ ] (2)
Where calculated value of optical rotation is, [ ] is the optical activity (specific rotation) (+ 185.9° rice starch)
depending on the discharge lamp and wavelength of light used and variety of starch, is the path length (2 dm), and
m is the sample weight (5 g). For a mercury discharge lamp and a wavelength ( ) of 546.1 nm.
Karzan A. Omar
et al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11086
Standard and stock solution of glucose
Stock glucose solution was made by dissolving 5 g of glucose in 100 ml of distilled water. Various dilutions of the
stock glucose solutions were made separately by pipetting a known volume of the stock solution (1, 2, 3, 4, 5, 6 and 7
ml) into a 100 ml volumetric flask and filling the volume with distilled water up to the mark. The concentrations
made for this study were: 0.05, 0.15, 0.2, 0.25, 0.3 and 0.35 g/ml. To determine the calibration curve for standard
glucose, 2 ml of each of the standard solutions was pipetted out and taken into a separate test tube. Then 0.4 ml of a 5
% aqueous solution of phenol reagent and 2 ml of 96% sulfuric acid was added. The mixture was kept for 10 min at
room temperature, and placed in a water bath at 25°C for 20 min. Then the absorbance was read at 540 nm using a
UV-visible spectrophotometer. Blank solutions were prepared in the same way as above, except that the 2 ml of the
standard solution was replaced by distilled water. Then, the amount of total reduced sugar content present in the
sample solution was calculated using the standard graph and expressed as gram glucose equivalents (GE) per 10 g of
sample (Albalasmesh, et al., 2013; Miliauskas, et al., 2004).
Determination of total sugar content
10 g of flour of each rice samples were hydrolyzed under constant concentration of sulfuric acid (2) % at
temperatures (25°C) and the different hydrolysis time (20, 40, 60, 80, and 100) minutes for optimal. The mixture was
added in glass bottles and sealed to prevent contamination and vaporization of acid due to heat. After hydrolysis, the
liquid fraction of the hydrolyzate samples was filtered and collected. A 2 ml aliquot of a sample solution was mixed
with 0.4 ml of a 5 % aqueous solution of phenol in a test tube. Subsequently, 2 ml of concentrated sulfuric acid was
added rapidly to the mixture. The test tubes were allowed to keep for 10 min at room temperature, and placed in a
water bath temperature (25°C) for 20 min for color development. The total sugar concentration was determined by
using UV-visible spectrophotometer at 540 nm wavelength of glucose absorbance and the quantification was made
from a calibration curve using glucose as standard and calculation were performed by an equation of the linear
regression obtained from the calibration curve.
Physical prosperities
The grain moisture content of each of the samples was determined by selecting 100 grains at random from the
chamber, dried down to the desired moisture content. The rice grains were randomly selected from each sample for
measuring their dimensions length (L), width (W) and thickness (T) a vernier calliper reading to 0.01mm was used.
Equivalent diameter (De)
The equivalent diameter (De) in mm considering a prolate spheroid shape for each rice samples was determined by
equation3 (Mohsenin, 1986; Jain and Bal, 1997).
=()
4
/
(3)
Sphericity (Ø)
The sphericity (Ø) is a ratio of the surface area of the sphere having the same volume as that of grain to the surface
area of the grain was determined by equation 4 (Mohsenin, 1986).
=(WT) (4)
Karzan A. Omar
et
al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11087
Grain volume (V) and surface area (S)
Grain volume (V) and surface area (S) of each sample rice were calculated by using equation 5 and 6 (Jain and Bal,
1997).
V = 0.25[6 L(+)] (5)
S = (2 ) (6)
Where, B = WT
Aspect ratio
The aspect ratio (Ra) was determined by using equation 7 (Varnamkhasti, et al., 2008).
= (7)
b t)
b) was determined by dividing the mass per unit volume (Fraser, et al., 1978) and the true density
t) was determined by the water displacement method (Mohsenin, 1986).
The thousand kernel weight
The thousand kernel weight was determined by randomly selecting one thousand grains from each rice samples and
weighed (Varnamkhasti et al, 2008).
Porosity
Porosity ( ) is a ratio of intergranular void space volume and the volume of the bulk grain and calculated by equation
8 (Jain and Bal, 1997; Thompson and Isaacs, 1967; Mohsenin, 1970).
= Pt Pb 100 (8)
RESULTS AND DISCUSSION
The starch content of the five different rice samples was available in the Kurdistan Region measured by polarimetric
method. The amount of starch content (%) was 81.23 in sample-1; 86.26 in sample-2; 88.96 in sample-3; 91.43 in
sample-4 and 92.73 in sample-5, and minimum and maximum amount of starch content can be observed for sample-1
and sample-5 as shown in fig. 1.The total reduced sugar content of different rice samples was determined through
the hydrolysis process at a different hydrolysis time under constant acid concentration (2% H2SO4) and temperature
(25°C). The amount of sugar produced was determined by using phenol-sulfuric acid. The glucose equivalent (GE)
was calculated from the calibration curve of glucose standards. The concentrations of unknown sugar samples were
determined from a standard curve of glucose (fig. 2), (Y=7.5864285714286x-0.45328571428571; R2= 0.9876).At 20 and
100 min hydrolysis time reduced sugar content achieved 12.15 and 12.22%, and sugar content decreased to 10.04% at
80 min, 9.83% at 60 min and 9.53% at 40 min, probably due to degradation of forming monosaccharides in the
presence of hot concentrate acid, and the maximum sugar for sample-1 was 12.22% observed at 100 min as shown in
fig. 3. The sample-2 shows almost the same amount of sugar content at 60 and 80 min hydrolysis time, which was
Karzan A. Omar
et al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11088
18.26 and 18.25%, and because of degradation which form inhibitors, the sugar content observed in lower percentage
at and 13.90% at 100 min, 14.34% at 40 min, 16.27% at 20 min as shown in fig. 4.
For sample-3, the maximum sugar content obtained 19.72% at 20 min of hydrolysis time. It seems 20 min are a
sufficient hydrolysis time to cleaved most of the glycosidic linkages compare to hydrolysis times, which was
obtained sugar content 10.24% at 80 min, 11.30% at 40 min, 12.49% at 60 min and 17.52% at 100 min, probably due to
degradations as shown in fig. 5. A 20 min of h ydrolysis time obtained 7.93% for sample-4. It was not sufficient for
cleaved of the glycosidic linkagestherefore, lower sugar content achieved, due to degradations of monosaccharides
which can be observed at 60 and 100 min sugar content was 13.83 and 12.4%. But at 40 and 80 min hydrolysis time
sugar content was 22.84 and 23.34% due to sufficient time to hydrolyze all linkages with lower degradation as shown
in fig. 6. The sample-5 at 20 to 100 min hydrolysis times obtained sugar content from 12.86, 12.26, 15.38, 13.90 and
13.98%. The maximum sugar content was 15.38% observed at 60 min from hydrolysis time as shown in fig. 7.
The summary of the physical properties of different type rice samples is represented in Table I. The moisture content
of rice samples was varied from 4.24% (sample-3) to 12.78% (sample-4) on a wet basis. The moisture content provides
valuable information to suggest the stability in storage of rice samples.The equivalent diameter and sphericity for rice
samples varied from 2.51 (sample-4) to 3.16 (sample-1), however, the lowest sphericity value were observed 34.89%
(sample-4) and the highest 55.64% (sample-1). This might be due to the typical shape of the sample-1 which has
pointed tips along the width axis, thereby increasing the characteristic width compared to other samples. The aspect
ratio distribution is important to classify the grains and determine the extent of off-size in market grade
(Varnamkhasti, et al., 2008). The aspect ratio was found to be lowest in sample-1,2,3,and 4 (0.23) and highest in
sample-5 (0.24).
The lowest porocity value was observed in 33.34% (sample-1), which might be due to high thickness value and the
highest porocity value was 40% (sample-4), due to low thickness value.The kernel volume and surface area of
samples were observed, the mean kernel volume values were ranged from 11.80 (sample-5) to 14.33 mm3 (sample-1),
while the surface area was observed from 23.17 (sample-4) to 26.82 mm2 (sample-2). The surface area effects on
drying rates of samples which can be characterized by using the surface to volume ratio and the ratio of surface area
to volume affects drying time and energy requirements. The bulk densities of rice samples were ranged from
814.64(sample-4) to 884.52 kg/m3 (sample-2). The values for the true densities were varied from 1357.79 (sample-4) to
1419.29 kg/m3 (sample-5). The bulk density provides useful information for the design of silos and hoppers for grain
handling and storage (Nalladulai, et al., 2002).The thousand kernel weight was observed in the range from 18.74
(sample-5) to 19.91 (sample-2) for rice samples. The knowledge of thousand kernel weight is a useful index to milling
outturn.
CONCLUSION
The polarimetric method used for determination of starch in different types of rice samples. The standard amount of
starch content observed in sample-1, which is only cultivating rice available in the Kurdistan region, and c ompared
to other samples which were imported from India and Thailand. The total sugar content determined at different
hydrolysis times under the constant acid concentration and temperature, the maximum sugar achieved for sample-3
was 19.72% at 20 min, sample-5 and sample-2 were 15.38%, and 18.26% at 60 min, sample-4 was 23.34% at 80 min and
sample-1 was 12.22% at 100 min due to sufficient time to hydrolyze and cleave all glycosidic linkage in the rice
samples with occurring minimum degradations and the minimum total reduced sugar content of rice samples
observed were Sample-4 was 7.93% at 20 min, sample-1 and sample-5 were 9.56% and 12.28% at 40 min, sample-3
was 10.27% at 80 min and sample-2 was 13.90% at 100 min, probably due to insufficient of hydrolysis time or
degradations of forming monosaccharides in the presence of hot concentrated acid. The physical properties of rice
samples were revealed the variation of physical dimensions of rice sample grains varying from short to long varieties
Karzan A. Omar
et al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11089
and this information is useful for designing storage and optimizing milling processes to prevent the post-harvest and
milling losses.
ACKNOWLEDGMENTS
The authors are grateful to Dr. Tara Fuad Tahir, Head of the chemistry department and Mr. Aryan for their support
and cooperation.
REFERENCES
1. Albalasmeh AA, Berhe AA, Ghezzehei TA. A new method for rapid determination of carbohydrate and total
carbon concentrations using UV spectrophotometry. Carbohydr. Polym, 2013; 97: pp. 253– 261.
2. Fraser BM, Verma SS, Muir WE. Some physical properties of fababeans. Journal of Agricultural Engineering
Research, 1978; 23: pp. 53–57.
3. Guyer D, Tuttle A, Rouse S, Volrath S, Johnson M, Potter S, Gorlach J, Goff S, Crossland L, Ward E. Activity of
latent transgenes in Arabidopsis using a hybrid transcription factor. Genetics, 1998;149: pp. 633-639.
4. Jain RK, Bal S. Properties of pearl millet. Journal of Agricultural Engineering Research, 1997; 66: pp.85–91.
5. Kodandaram DR, Bhotmange MG. Viscosity of Starch: A Comparative Study of Indian Rice (Oryza Sativa L.)
Varieties. International Review of Applied Engineering Research, 2014; 4: pp. 397-402.
6. Li JY, Yeh AI. Relationships between thermal rheological characteristics and swelling power for various
starches. J. Food Engineer-ing, 2001;50: pp. 141-148.
7. Muhammad U, Muhammad TI, Shahid RM, Bushra I, Muhammad I. Effects of Temperature, pH and Steeping
Time on the Extraction of Starch from Pakistani Rice. International Journal of Scientific & Engineering
Research, 2014; 5: pp. 887-892.
8. Miliauskas G, Venskutonis PR, Van BT. Screening of Radical Scavenging Activity of Some Medicinal Plants and
Aromatic Plant Extract. Food Chem, 2004;85: pp. 231-237.
9. Mohsenin NN. Physical properties of plant and animal materials (2nd edn.). New York, Gordon and
Breach.;1986.
10. Mohsenin, NN. Physical properties of plant and animal material. New York, Gordon and Breach.;1970.
11. Nalladulai K, Alagusundaram K, Gayathri P. Airflow resistance of paddy and its byproducts. Biosyststems
Engineering, 2002; 831; pp. 67–75.
12. Singh N, Singh J, Kaur L, Singh SN, Singh GB. Morpho-logical, thermal and rheological properties of starches
from different botani-cal sources. Food Chem, 2003; 81: pp. 219-231.
13. Schoch TJ. Properties and uses of rice starc. Starch Chemistry and Technology, 1967; pp. 79–86.
14. Thompson RA, Isaacs GW. Porosity determination of grains and seeds with air comparison pycnometer.
Transactions of ASAE, 1967;10: pp. 693–696.
15. Varnamkhasti MG, Mobli H, Jafari A, Keyhani AR, Soltanabadi MH, Rafiee S, Kheiralipour K. Some physical
properties of rough rice (Oryza sativa L.) grain. Journal of Cereal Science,2008; 47: pp. 496–501.
Karzan A. Omar
et al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11090
Fig. 1: Amount of starch content (%) in flour of different rice samples
Fig. 2: Calibration curve of standard glucose for determination of total sugar content.
Rice samples
0
20
40
60
80
100
Concentration of glucose (g/ml)
0.0 0.1 0.2 0.3 0.4
0.0
0.5
1.0
1.5
2.0
2.5
Karzan A. Omar
et al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11091
Fig. 3: Amount of sugar content (% w/w) of the rice sample-1 at different hydrolysis time of 10%
biomass under constant concentration of (2% H2SO4) and temperature (25°C).
Fig.4: Amount of sugar content (% w/w) of the rice sample-2 at different hydrolysis time of 10%
biomass under constant concentration of (2% H2SO4) and temperature (25°C).
Time (min)
0
5
10
15
Time (min)
0
5
10
15
20
Karzan A. Omar
et al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11092
Fig. 5: Amount of sugar content (% w/w) of the rice sample-3 at different hydrolysis time of 10%
biomass under constant concentration of (2% H2SO4) and temperature (25°C).
Fig. 6: Amount of sugar content (% w/w) of the rice sample-4 at different hydrolysis time of 10%
biomass under constant concentration of (2% H2SO4) and temperature (25°C).
Time (min)
0
5
10
15
20
25
Time (min)
0
5
10
15
20
25
Karzan A. Omar
et al.
Indian Journal Of Natural Sciences www.tnsroindia.org.
© IJONS
Vol.6 / Issue 36 / June 2016 International Bimonthly ISSN: 0976 – 0997
11093
Fig. 7: Amount of sugar content (% w/w) of the rice sample-5 at different hydrolysis time of 10%
biomass under constant concentration of (2% H2SO4) and temperature (25°C).
Table I physical property of different type rice samples.
Time (min)
0
5
10
15
20
Property Sample-1 Sample-2 Sample-3 Sample-4 Sample-5
Length (mm)
5.34±0.25
8.34±0.35
8.55±0.39
8.41±0.49
7.80±0.54
Width (mm)
2.75±0.16
1.95±0.07
1.94±0.07
1.94±0.05
1.88±0.17
Thickness (mm)
1.77±0.25
1.70±0.17
1.52±0.04
1.41±0.14
1.51±0.06
Moisture (wet basis)
12.78±1.42
7.47±0.66
4.24±0.48
8.03±0.97
7.07±0.63
Equivalent diameter
(mm)
3.16±0.36 2.85±0.24 2.66±0.12 2.51±0.14 2.51±0.20
Sphericity (%)
55.64±3.38
36.00±0.71
34.38±1.16
33.89±1.73
36.14±2.45
Aspect ratio
0.23±0.02
0.23±0.01
0.23±0.02
0.23±0.02
0.24±0.03
Volume (mm3)
14.33±2.26
14.15±1.93
13.50±1.14
12.41±1.08
11.80±1.43
Surface area (mm2) 23.27±2.70 26.82±2.22 25.75±1.51 24.26±1.63 23.17±1.78
Bulk density (kg/m3) 881.00±3.37 884.52±9.17 856.39±21.03 814.64±12.64 875.23±21.70
True density (kg/m3) 1362.46±14.96 1386.21±41.52 1404.00±24.93 1357.79±13.51 1419.29±10.76
Porosity (%) 35.33±0.57 36.17±1.25 39.00±1.32 40.00±1.00 38.33±2.44
Thousand kernel
weight
19.72±0.02 19.91±0.01 19.53±0.01 19.83±0.02 18.74±0.03
Karzan A. Omar
et al.
