EFFECT OF DIFFERENT PRETREATMENTS ON THE STORAGE STABILITY OF PEARL MILLET FLOUR
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Date
2023-05-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ACHARYA NG RANGA AGRICULTURAL UNIVERSITY
Abstract
Pearl millet (Pennisetum glaucum L) is a good source of energy, protein,
vitamins, minerals and is rich in unsaturated fatty acids. Pearl millets contain a higher
amount of fat (7.0 to 7.9 %) and this fat content of pearl millet plays a vital role in its
shelf-life because hydrolysis and oxidation of triglycerides release non esterified fatty
acids. Hence, a study was undertaken to know the effect of different pretreatments on
the storage stability of pearl millet flour. The pretreatments like dry heating (40, 50, 70
,100 and 110 °C) for different times (10, 35, 60 and 70 min); blanching at 98 °C for
different times (10, 20, 30 s) followed by drying; micro wave heating at different powers
(140, 420, and 700 W) and times (30, 40, 60, 100 and 110s); infrared heating at different
powers (300, 500, 700 W), bed thickness (0.5, 1, 1.5 cm) and times (1,3,5 min) were
given to the pearl millet grains and flour. Physico-chemical properties such as bulk
density, angle of repose, coefficient of static friction, free fatty acid, peroxide value
were determined. Response Surface Methodology (RSM) was used to optimize the
pretreatments. Statistical analysis of all experimental data was carried out by following
standard procedures.
After different pretreatments, pearl millet flour was packed in polythene ziplock bags (HDPE) and labelled. For all the samples after treatment, free fatty acids
(FFA), peroxide values (PV) and microbial count were determined. Of all the
treatments, samples which recorded least FFA and PV were chosen for storage studies
along with the control sample. During the storage, FFA and PV were determined at 5days
interval for a period of two months. Among all the treatments, least percentage increase
(0.28 % to 3.18 %) in FFA content and peroxide value (1.5 to 22.5 meq O2/kg sample)
were observed in microwave treated flour (T3) at 700 W for 100 sincreased from during
storage. Least microbial contamination was observed in microwave treated flour (T3)
at 700 W for 100 s (T3). The colonies started on 30th day and limit reached on 55th day
(51colonies). During storage of 60 days no larvae, adults, insects were identified in the
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pearl millet flour. Food product (Roti) was prepared from microwave treated flour
scored highest in terms of quality attributes. Pretreatment to the flour alone was better
compared to pretreatment to grain and the resultant flour in terms of quality attributes.
Keywords: Dry heat treatment, Infrared treatment, Blanching, Microwave treatment,
RSM, Free fatty acid, Peroxide value, Microbial count and Insect count.
Description
EFFECT OF DIFFERENT
PRETREATMENTS ON THE
STORAGE STABILITY OF PEARL
MILLET FLOUR