Comparison of oil quality extracted from selected conventional and non conventional sources of vegetable oil from Malawi

Abstract

In this study, oil quality with respect to physicochemical and phytochemical characteristics extracted from nonconventional seed oil namely Moringa oleifera, Adansonia digitata, Parinari curatellifolia and Cajanus cajan and conventional seed oil namely soybean (Glycine max) and groundnut (Arachis hypogaea) was assessed and compared. Results showed that there were significant differences in various quality parameters such as saponification number, peroxide value, free fatty acids in oils extracted from non-conventional and conventional sources. Oil yield ranged from 4.71 to 46.05% with pigeon peas registering the lowest yield and P. curatelifolia registering the highest yield. The following range of values in quality parameters were obtained: values in saponification number ranged from 55.91 mg KOH/g (C. cajan) to 220.54 mg KOH/g (groundnut): Peroxide value ranged from 2.79 meq O 2 /kg (M. oleifera) to 10.47 meq O 2 /kg (C. cajan): Free fatty acids ranged from 1.11 mg/100 g (P. curatelifolia) to 4.80 mg/100 g (pigeon peas): Specific gravity ranged from 0.87 (P. curatelifolia) to 0.91 (groundnuts): Oxalate ranged from 75.41 mg/100 g (groundnuts) to 632.56 mg / 100 g (pigeon peas): Acid value ranged from 2.21 mg KOH/g (P. curatelifolia) to 9.53 mg KOH/g (Pigeon pea): Iodine value ranged from 35.53 g/100 g (P. curatelifolia) and alkaloids ranged from 58.28 mg/g (M. oleifera) to 123.60 mg/g (groundnuts). Irrespective of the source of the oils, it was observed that the values in most of the oil quality parameters were within the acceptable levels. The findings in this study have demonstrated that nonconventional sources of oil have the potential to adequately supplement oils used for domestic consumption as well as industrial use in Malawi and therefore reduces the volumes of imported oils hence safeguarding foreign reserves.

Modelling and Optimization of Processing Factors of Pumpkin Seeds Oil Extraction under Uniaxial Loading

“…The lower PV, AV, and FFA values agreed with the results published by [80] which indicates that the extracted oil is of high quality under the pretreatment temperatures between 22 • C and 80 • C. [81] reported lower FFA content of 0.30% for cold-pressed oil from uncooked pennycress seeds compared to cooked seeds which increased FFA from 0.37 to 0.51%. High FFAs in crude oil results in high losses during the refining process [51]. The values obtained were within the allowable limit for edible oils [79,82].…”

“…The FFA values were between 0.559 ± 0.008 and 0.587 ± 0.008 (mg KOH/g oil). Peroxide value measures the degree of peroxidation or adulteration which could be used to evaluate the quality and stability of oils during storage [50,51,78]. Acidity is a parameter related to oil processing, preservation, and quality of the raw material.…”

“…The peroxide value (PV), acid value (AV), and free fatty acid (FFA) of pumpkin seed oil extracted at laboratory temperature of 22 • C and pretreatment temperatures from 40 • C to 80 • C were determined using the procedures described by [50][51][52]. For PV, 5 g of the oil sample was weighed into a volumetric flask.…”

Assessment of Quality and Efficiency of Cold-Pressed Oil from Selected Oilseeds

“…Every 7 days, a pipette filler bulb was used to syphon off or recover the cleaned oil into a separate container without any sediments, as shown in Figure 2II. The cleaned oils obtained during the 7 days of storage were used for quality assessment in terms of peroxide value, PV (meq O 2 /kg oil), acid value, AV (mg KOH/g oil), free fatty acid, FFA (mg KOH/g oil) and iodine value, IV (g l/100 g), via a titration technique following AOAC procedures [7,82]. The cumin seed oil was exempted from the quality evaluation due to low oil output and the difficulty of separating the seedcake sediments from the oil (Figure 2If).…”