Effects of drying on the physicochemical properties and the fatty acids composition of some edible leafy vegetable oils

Author(s): O.Aletor, A.R.Abiodun

Greenamaranth (Amaranthus hybridus), Scent leaf (Ocimumgratissimum),Basil leaf (Ocimum basilicum),Bitterleaf(Vernoniaamygdalina)andFluted pumpkin leaf (Telferia occidentalis)were subjected to sun-drying and freeze-drying. TheOils extracted fromthe pulverized samples were divided into two portions, first portion analysed for fatty acids compositionwhile physicochemical propertieswere determined on the second portion. On the average, freeze-dried leaves, oil contained 76.76% (range 64.99-88.26%) total unsaturated acidwhichwas significantlyhigher (P<0.05level) thansun-dried leaves, oil of total unsaturated acid 70.42%(range 58.19- 83.57%).Sun-dried leaves, oil containedsignificantly higher (P<0.05 level)mean free fattyacid (FFA) and mean peroxide value (PV) 2.03%(range 1.3±0.0- 2.6±0.1%); 5.13mg/g (range 3.6±0.1-6.8±0.1mg/g) than freeze-dried leaves,oil ofmean FFAandmean PV 1.60% (range 1.0±0.0-2.5±0.1%); 4.05mg/g (range 2.8±0.1-5.4±0.2mg/g) while freeze-dried leaves, oilhadsignificantlyhigher (P<0.05level)mean iodine value (IV) 122.2mg/g (range 105.0±0.0- 139.0±1.0mg/g) than sun-dried leaves,oil ofmean IV 113.5mg/g (range 97.0±1.0-131.0±0.0). Of the dryingmethods, freeze-drying had significantly higher (P<0.05 level) percentage of unsaturation, higher IV, lower FFAand lower PV than sun-drying. Hence, freeze-dryingwould appear to bemore promising.

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