Browsing by Author "Shanthini, R."

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    Enhancing Sesame Oil Quality by Heat Treatment
    (Uva Wellassa University of Sri Lanka, 2018) Kuruppuarachchi, S.M.; Shanthini, R.
    Heating, in general, destroys quality of edible oils. Since heated sesame oil is rich in antioxidants (AO) such as sesamol, in this research, we tested the hypothesis that quality of sesame oil was preserved during heating. Oil was extracted using a screw expeller from 70:30 black:white sesame seeds. A 2-factor-2-level design of experiment with centre point was used. Factors and levels were temperatures (T) at 70 °C and 180 °C and durations (t) at I and 4 hr. Choice of the said levels were governed by no appreciable changes in oil characteristics being detected with oil heated for 1 h at 70 °C (denoted by lowest level, LL) and considerable changes being detected with oil heated for 4 hr at 180 °C (denoted by highest level, HL). Crude oil samples, in duplicate, were oven-heated and centrifuged at 2200 g for 10 min. AO activity was quantified by assessing the 2,2-dipheny1-1-picrylhydrazyl radicals scavenging activity (RSA, in %) of oil samples. Free fatty acid content (FFA, as % oleic acid) was also assessed. Analysis of variance results of estimated interaction models of RSA and FFA revealed that all coefficients were statistically significant (p <0.05) and adjusted R2 were 94 and 88%, respectively. AndersonDarling tests revealed that residuals of both models were normally distributed. Said models showed that fitted mean of RSA of sesame oil at HL was 5.8 times the mean at LL and fitted mean of FFA reduced from 1.8 at LL to 0.9 at HL. Increase in RSA of sesame oil with heating may be attributed to the conversion of sesamolin to sesamol, a potent AO. Further experimentation showed that more than 30 hr of heating at 180 °C was required for RSA of sesame oil to start declining, which may be explained by potential destruction of sesamol. Decrease in FFA may be attributed to evaporation of fraction of free fatty acids during heating. It was, therefore, concluded that heating in the parameter space studied enhanced sesame oil quality by raising its AOA and lowering its FFA.
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    Impact of Seed Moisture Content on Yield, Antioxidant Activity and Free Fatty Acid Content of Sesame Oil
    (Uva Wellassa University of Sri Lanka, 2018) Abeysekara, D.C.; Shanthini, R.
    This research was undertaken to assist Sri Lankan sesame oil producers to further enhance yield and quality of their products. Oil samples were extracted using a screw expeller, in triplicate, from blackish (86±1%) sesame seeds having moisture content (M) of 0.3, 3.3, 3.6, 4.6, 5.1, 6.3, 7.0 and 7.9% on dry basis (db). Oil samples were half filled in clear glass bottles and stored on table top for 4 months. Antioxidant activity (AOA) was determined by quantifying the amount of 2, 2- diphenyl- 1 -picrylhydrazyl (DPPH) radicals scavenged by phenolic fractions of oil. Free fatty acid in oil (FFA, % as oleic acid) was also determined. Oil yield (Y g oil per 100 g dry weight of seeds) was estimated as Y = 0.6M3-11.8M2+71.9M-95.9 and mean temperature (°C) of oil being extracted as T = -1.5M2+14.9M+21.8 with 99.7% and 90.3% variability in Y and T explained by M, respectively. Maximum Y of 45.0+0.2 and T of 60+3 °C were close to M of 4.6 and 5.1% db, and these values were significantly different from other M values studied. FFA contents of all oil samples studied were well below 3.0 and therefore satisfied the quality standard for FFA of sesame oil. Minimum and maximum FFA contents of 0.810.1 and 2.2±0.1 were obtained at M of 4.6 and 7.9% db, respectively, both of which were significantly different from FFA of all other M values studied. No significant differences were observed among ADA of oil samples studied which spanned the range of 0.67 to 0.75 µmot DPPH loss per g oil. It could therefore be concluded that 4.6 to 5.1% db seed moisture contents gave the seeds adequate amount of water to maintain the temperature required to assist in cell wall rapture and in pushing oil out of the seeds and through the voids with ease while preventing plasticization within the seeds. Lowest and the significantly different FFA content obtained suggested that an M of 4.6% db was the best choice for delaying potential oil oxidation leading to rancidity during oil storage.