2011 International Conference on Alternative Energy in Developing Countries and Emerging Economies
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Considering the SEC for three drying condition showed
that drying with IR at power input of 1,000W and
1,500W and drying temperatures ranging of 60-100
o
C
were lower than HA+IR and HA drying. This is because
infrared waves can penetrate into the interior of parboiled
rice, where it is converted to thermal energy, providing a
rapid heating mechanism. Moreover, the high IR power
input consumed higher SEC.
H. Texture
TABLE V
HARDNESS, STICKINESS AND ADHESIVENESS OF PARBOILED
RICE DRIED WITH DIFFERENT DRYING STRATEGIES
Condition
Hardness (kg) Stickiness (kg) Adhesiveness (kg.s)
Control rice
27.15
b
-0.193
a
-0.008
a
Reference
rice
25.65
a
-0.881
b
-0.082
b
HA+IR1500 W
60.0
26.76
b
-0.201
a
-0.008
a
78.1
28.15
c
-0.177
a
-0.012
a
98.8
28.56
c
-0.175
a
-0.007
a
HA+IR1000 W
61.3
27.72
b
-0.194
a
-0.012
a
84.3
29.75
c
-0.166
a
-0.012
a
99.7
29.58
c
-0.167
a
-0.015
a
IR1500 W
62.9
29.55
b
-0.245
b
-0.011
a
78.4
29.25
b
-0.195
ab
-0.009
a
96.8
29.29
b
-0.141
a
0.005
a
IR1000 W
61.3
28.21
cd
-0.215
a
-0.007
a
80.9
27.47
bc
-0.203
a
-0.003
a
95.8
28.72
d
-0.179
a
-0.007
a
HA
61.1
26.51
ab
-0.236
b
-0.012
a
78.6
27.09
b
-0.165
ab
-0.008
a
100.0
27.21
b
-0.138
a
-0.006
a
The results of hardness and stickiness of parboiled
rice were compared to the raw rice are illustrated in Table
5. The result was revealed that the hardness of control
rice and parboiled rice dried with different drying
strategies was significantly higher than that of raw rice
because of the partial gelatinization in the parboiled rice
leading to increase in strength of rice. The hardness of
parboiled rice slightly increased with an increase in
drying temperature. It should be suggested that the higher
degree of gelatinization occurred at higher drying
temperature. Then the hardness of parboiled rice dried
with different drying strategies was considered, the result
showed that not clearly different. For the stickiness and
adhesiveness of parboiled rice were significantly lower
than the raw rice because of the partial gelatinization
occurred. Nevertheless, the drying temperature and
drying strategies did not significantly affect to the
stickiness of parboiled rice.
V. CONCLUSIONS
Parboiling process of this experiment consisted of
70
q
C hot water soaking for 3 hr, ambient air tempering
for 24 hr, steaming for 30 min and drying with IR and
HA+IR drying can maintain quality of parboiled rice and
had low energy consumption, especially on IR drying.
GAB’s model was the best fitting to the ex
perimental
results. However, the drying kinetics of parboiled rice
was well explained by diffusion model. An effective
diffusion coefficient for parboiled rice was in ranges 0.67
x 10
-9
to 3.2 x 10
-9
m
2
/s. To study the effect of drying
strategies and drying temperature of dried parboiled rice,
the conclusion was that the head rice yield using
combined HA+IR drying yielded a higher value than IR
drying while yellowness and whiteness of rice are
significantly affected by drying temperature and drying
strategies. The results suggested that the combined
HA+IR drying was an efficient method for improve
HRY, yellowness and whiteness of rice and maintain
qualities of dried rice. In the other hand, the combined
HA+IR drying takes a high operation time and has
relative high energy consumption compared to the IR
drying.
A
CKNOWLEDGEMENT
The authors would like to thank the Office of the
Higher Education Commission, Thailand, in providing
financial grant under the program
Strategic Scholarships
for Frontier Research Network for the Thai Doctoral
degree Ph.D. Program
. We would like to thank also
Department of Chemical engineering, Faculty of
Engineering and Department of Physics, Faculty of
Science and graduate school of Prince of Songkla
University for financial support. In addition, we thank
Pattalung Rice Research Center and Agricultural and
Seafood Product and Technology for SME-OTOP
Research unit (ASPT) for quality testing of rice.
R
EFERENCES
[1]
AOAC.,
Official Methods of Analysis, The Association of Official
Analytical Chemists
, Washington D.C., USA. 1996.
[2]
Bhattacharya, KR.,
Parboiling of Rice
. In: Rice Chemistry and
Technology. ed. by Champagne ET, St. Paul,Minn.: AACC Int.
2004, pp. 329
–
404.
Fig. 4. Energy consumption of parboiled rice.
0
40
80
120
160
200
Specific energy
consumption. (MJ/kg
water evaporated)
61.1 78.6 100
Drying temperature (°C)
HA
HA+IR 1500W
HA+IR 1000W
IR 1500W
IR 1000 W
