EFFECT OF HYDROTHERMAL TREATMENT ON DEHULLING AND PHYSICOCHEMICAL CHARACTERISTICS OF FINGER MILLET
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Date
2018
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Publisher
Acharya N.G. Ranga Agricultural University
Abstract
Finger millet (Eleusine coracana L.) is an important millet crop and is one
of the major sources of energy and proteins in the diet of rural population. It is
underutilized and neglected crop owing to its lower preference driven by affluence,
longer time and efforts involved in the processing and the lower cooking quality.
The seed coat is normally of brick red to dark colored and contains polyphenols and
pigments, which polymerize and turn dark and unattractive on cooking. The seed
coat is tightly attached to the soft and fragile endosperm and because of this,
polishing or milling of the finger millet to remove the seed coat has not been
successful so far. This limits the usage of the finger millet only to flour based
traditional foods and not in the grain form similar to rice. Hence the present work
was undertaken with reference to hydrothermal treatment of the finger millet,
milling of the hydrothermally processed finger millet and further processing of the
milled finger millet for preparation of different value added products meet nontraditional
consumer acceptability. Finger millet grains after cleaning, were soaked
in distilled water at 30 and 70 °C temperatures for 24 and 1.45 h respectively,
followed by steaming at 1.0, 1.5 and 2.0 kgcm-2 pressures for the duration of 20, 18
and 16 minutes respectively. Grains were then dried at 40 °C to a final moisture
content of 12.15% (w.b.) in a tray dryer. Samples were also dried to a final moisture
content of 14.09% (w.b.) to assess the milling yield of the polisher. The
physicochemical characteristics of hydrothermally treated finger millet (HTM) such
as size (longitudinal and lateral diameter), sphericity, surface area, thousand grain
weight, thousand grain volume, bulk density, particle density, porosity, color (L*,a*
and b*) and hardness were determined. The results were 1.66 mm, 1.44 mm, 0.89,
6.361 mm2, 2.61 g, 2.34 mL, 0.77 gL-1, 1.31 gL-1, 41.22%, (18.77, 5.41 and 3.78)
and 7.77 kgf respectively, for the samples soaked at 70 °C, steamed at 2 kgcm-2 and
dried to final moisture content of 12.15% (w.b.). The corresponding values for
samples dried to 14.09% m.c. were 1.58 mm, 1.44 mm, 0.90, 6.727 mm2, 2.64 g,
2.36 mL, 0.79 gL-1, 1.29 gL-1, 38.76%, (20.18, 5.88 and 3.99) and 7.6 kgf
respectively. HTM (at 70 °C, 2 kgcm-2 and 12.15%) exhibited highest milling yield,
lowest broken percentage and highest seed coat percentage and the values were
81.16%, 9.44% and 9.42% respectively. The corresponding values at 14.09% m.c.
were 87.88%, 4.44% and 7.68% respectively. Higher output capacities achieved
were 7.30 and 7.91 kgh-1 at 12.15% and 14.09% moisture contents respectively.
Nutritional values of milled finger millet for protein, fat, ash, calcium and crude
fiber were 5.84%, 0.79%, 0.99%, 193 mg/ 100 g and 1.08% respectively at 12.15%
final moisture content. Corresponding values at 14.09% m.c. were 5.66%, 0.76%,
0.97, 187 mg/100 g and 1.00% respectively. Value added products developed from
milled finger millet were; cooked milled finger millet, ready to eat (RTE) flakes and
biscuits fortified with seed coat matter of finger millet. The sensory results of these
products for overall acceptability, overall quality and eating quality were 8.2, 8.2
and 7.6 respectively which indicated higher consumer acceptability.
Keywords: Milling, sphericity, hardness, color, milling yield and RTE flakes.
Description
D5576
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