PROCESS OPTIMIZATION FOR MILLING OF MOONG BEANS (Vigna radiata)
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Date
2013
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Publisher
PAU
Abstract
During the processing operation such as dehulling and splitting of moong beans,
engineering properties are bound to change due to various pretreatments. So engineering
properties like arithmetic diameter, geometric mean diameter, sphericity, surface area,
volume, thousand grain weight, bulk density, true density, porosity, angle of repose, static
coefficient of friction and compression loading behaviour of three varieties of moong beans
i.e. SML 668, SML 832 and PAU 911 were evaluated at different moisture contents ranging
from 3-25% (w.b.). Investigations were carried out to optimize the processing parameters for
milling of moong beans. Processing parameters selected for optimization were blower speed
and feed rate for cleaning, sieve size for grading and oil and water levels for secondary
processing. Two mills i.e. horizontal type mini dal mill and CFTRI mini dal mill were used
for the experiment. SML 832 variety was selected for the process of optimization. The moong
beans were firstly cleaned taking different blower speeds i.e. 4.9, 6.5 and 8.8 m/s and
different feed rates i.e. 4, 12 and 20 kg/min and cleaning efficiency and cleaning loss were
taken as responses. Cleaning efficiency of moong beans was found maximum i.e. 99.90% and
cleaning loss was minimum i.e. 0.1% at 6.5 m/s blower speed and 4 kg/min feed rate. Sieve
sizes; 5/32” and 3/16” were found to be optimum for efficient separation of moong beans in
two grades. For secondary processing, three oil and water levels selected were; 0.1, 0.2 and
0.3% and 15.16, 18.67 and 22.10% (w.b.), respectively and dehulling efficiency and degree of
dehulling were taken as responses. The pretreatment levels were optimized using Historical
Data Design (Response Surface Methodology). 0.21% oil level and 17.79% (w.b.) water level
were the optimized pre-treatment levels at which maximum dehulling efficiency (78.5412%)
and degree of dehulling (96.2142%) were obtained. These optimized conditions were adopted
to compare different methods of milling and degree of dehulling, dehulling efficiency,
dehulling index, percent broken and husk content were taken as responses. Method two i.e.
alternate wetting and drying was found to yield better results in terms of degree of dehulling,
dehulling index and percent broken.
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