STUDY OF RADIO FREQUENCY DRYING OF PADDY GRAIN
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Date
2015
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Acharya N.G. Ranga Agricultural University, Guntur
Abstract
The drying characteristics of a paddy grain (NLR 33 892) were studied using
Radio Frequency Dryer (RFD). The drying chamber of the RFD consisted pair of electrodes of size 75 cm X 55 cm and a grain holding cell of 36 L X 25.5 W X 5.5 H, cm3. The cell was filled with grain for three levels of bed thickness (2, 3 and 4 cm) to
study the drying and drying rate curves. The weight of the drying grain was recorded at
every 1 min interval to calculate the moisture loss. The obtained data was plotted and
analyzed for moisture loss and drying rate. It was observed that the drying curve
followed the falling rate period for all the bed thickness experiments conducted in Radio
Frequency drying. The longest time of drying 9 min was observed in the experiment
where the grain bed thickness was 3 cm whereas the shortest time of drying 6 min was
observed in the experiment where the grain bed thickness was 4 cm. It was also found
that the drying rates were decreased along with the drying bed thickness.
The milling and cooking quality characteristics of Radio Frequency dried paddy
were studied as affected by the drying bed thickness at four levels (2.00, 3.00 and 4.00
cm). The milling of rice was evaluated using the combined huller cum sheller based on
the percentage of milled rice, head rice and broken rice. Similarly, the quality of
cooking of rice of RF dried paddy were evaluated in terms of minimum cooking time,
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water uptake ratio, grain elongation ratio and volume expansion ratio in percentage. The
milling percentages of RF dried paddy found were 78.89%, 77.06% and 76.32% at 2, 3
and 4 cm thick grain bed in RF drying. The average milled rice quantity of sun dried
paddy found was 79.19 g and its milling efficiency was 79.19%. In comparison, the
highest milling efficiency found was 79.19% in sun dried and the lowest milling
efficiency found was 76.32% at 4 cm thick bed in RF dried. The head rice yield was
found to be 35.90, 48.06, 61.17 and 27.79% for the grain dried at 2, 3, 4 cm bed
thickness in RF and sun dried paddy, respectively. The broken rice recorded 42.99,
29.00, 15.16 and 51.40% for the grain dried at 2, 3, 4 cm bed thickness in RF and sun
dried. The water uptake ratio varied from 3.54, 3.54, 3.54 and 3.38 for the grain dried at
2, 3 and 4 cm bed thickness in RF and sun dried paddy, respectively. The grain
elongation ratio was found to be 1.68, 1.67, 1.66 and 1.76 for the grain dried at 2, 3, 4
cm bed thickness in RF and sun dried paddy. The volume expansion results found in
Radio Frequency dried were 4.63, 4.76 and 4.89 whereas in sun dried was 4.32. Among
all the grain bed thickness investigated, the 2 cm thick bed yielded better results in
terms of less brokens and more head rice when compared to 3 and 4 cm thick beds dried
under RFD.
Key Words: Radio Frequency dying; Drying curve; Drying rate; Paddy; Milling; Cooking.
Description
D5215
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