Efficacy of phenolics from agri-byproducts in vegetable oil
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Date
2018
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CCSHAU
Abstract
The present study was undertaken to determine the efficacy of phenolics from pod coat of pulses in
stabilising soybean oil. Pod coat of five pulse crops (cowpea, clusterbean, mungbean, Mothbean and
pigeonpea) were extracted with three solvents (acetone, ethylacetate and chloroform). Phytochemical
constituents (phenols, flavonoids, tocopherols and tannins) and DPPH free radical scavenging activity
were estimated by using spectroscopic methods. Folin-Ciocalteu procedure and aluminium chloride
colorimetric methods were used for evaluation of total phenolic content and flavonoid content
respectively. Among the various extracts, highest yield was observed in acetone extract of clusterbean
(5.44%) while lowest was observed in chloroform extract of cowpea (2.99%). Total phenolic content
(mg GAE/g) varied from 7.24-24.18 in all of the extracts. Similarly, flavonoids (mg CAE/g) ranged
from 3.30 to 10.77 in all of the extracts. Tocopherol content (mg/g) was highest in ethylacetate extract
of pigeonpea (9.56) while lowest in chloroform extract of cowpea (3.41). Tannin content (mg TAE/g)
was highest in acetone extract of clusterbean (2.48) while lowest in chloroform extract of mungbean
(0.71). Results obtained by DPPH method showed that free radical scavenging capacities of various
pod coat extracts from different species of legumes ranged from 54.95 to 78.21%. Their IC50 values
(mg/mL) varied from 0.23- 0.83. Analogous to results obtained for total phenolics and flavonoids, free
radical scavenging activities were highest in acetone extract of clusterbean. The high content of total
phenolics and total flavonoids indicated that these bioactive metabolites contribute to synergistic effect
for the antioxidant activity. Moreover, a highly significant correlation (p<0.05) between free radical
scavenging efficiencies and phenolic contents as well as flavonoids was observed in most of the
extracts under study. All extracts were added to crude soybean oil at two concentrations (1000 and
2000ppm). Soybean oil sample stabilized with various extracts were incubated at 50ÂșC for a period of
28 days. Effect of incorporation of these extracts on oxidative stability of crude soybean oil was
measured in terms of various oxidative quality indices. Among the three extracts, acetone extract was
found most effective in retarding oxidative degradation of soybean oil during incubation. Extracts were
more effective at 2000ppm concentration in comparison to 1000ppm. Among the five crops, cluster
bean extracts displayed highest inhibition towards oxidation of soybean oil. The results concluded that
the pod coat extracts of these pulses may be valuable natural antioxidant sources and are potentially
applicable in both medicine and food industry.
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