Crude oils have to be refined before the consumption, in order to remove undesirable accompanying substances; deodorization usually is the last step in the edible oil refining. In a laboratory all-glass deodorizer experiments, degummed, refined and bleached oils from Sclerocarya birrea (SCO), Sorghum bug (SBO), Melon bug oil water extracted (MBOH 2O) and Melon bug oil solvent extracted (MBOSOL) were deodorized for different periods of times (0.5, 1, and 2 hours) at different temperatures (190, 210, and 250 °C). Quality changes (free fatty acids, peroxide values, tocopherols, sterols and phosphatides) were determined, and also stability against oxidation (Rancimat test) beside the fatty acid composition. It is clear that there was no change in the phosphatides according to deodorization temperature and time, peroxides and free fatty acids content were significantly ( P<0.05) reduced in all samples with the increase of deodorization temperature and nearly completely removed at 250°C. Tocopherols were decreased as a result of elevated temperature, and high decrease happened in high temperatures of 210 and 250 °C in all samples except MBOH 2O, where tocopherols completely removed during deodorization temperatures. The effect of deodorization on fatty acid composition indicates that, oils did not undergo any changes in the fatty acid compositions during deodorization. The oxidative stability was affected by temperature and time of deodorization, the stability increased as affected by elevated deodorization temperature in all studied samples.

Three samples, Sclerocarya birrea oil (SCO), Melon bug oil ( Aspongubus viduatus ) (MBO), and Sorghum bug oil ( Agonoscelis pubescens ) (SBO), were stored (autoxidized) in the dark at 30±2 °C for 24 months. Oil aliquots were withdrawn every 2-4 month for analyses of changes in four quality indexes, namely fatty acid composition, tocopherol content, peroxide value and oxidative stability index by Rancimat. After 24 months of storage the fatty acid composition of the three oils showed no change while tocopherol contents were decreased. SCO and MBO showed only slight changes in their oxidative stability as indicated by the peroxide value and induction period during the 24 months of storage. Sorghum bug oil showed a periodical increase in the peroxide value and had less stability as measured by the Rancimat in comparison to other oils.

The behavior of crude Sclerocarya birrea kernel oil (SCO) and Sorghum bug (Agonoscelis pubescens) oil (SBO) during deep-frying of par-fried potatoes was studied with regard to chemical, physical, and sensory parameters, such as content of FFA, tocopherols, polar compounds, oligomer TG, volatile compounds, oxidative stability, and total oxidation (TOTOX) value. Palm olein was used for comparison. Whereas potatoes fried in SCO that had been used for 24 h of deep-frying at 175°C were still suitable for human consumption, potatoes prepared in SBO that had been used for 6 to 12 h were not, considering the sensory evaluation. In looking at the chemical and physical parameters, SBO exceeded the limits, after no later than 18 h of use, for the amount of polar compounds, oligomer TG, and FFA recommended by the German Society of Fat Sciences (DGF) as criteria for the rejection of used frying oils. In contrast to SBO, SCO oil did not exceed the limits for the content of polar compounds and oligomer TG during the frying experiment. Only the amount of FFA was exceeded; this was because the amount of FFA at the beginning of the experiment was higher than for refined oils. The results showed that both oils were suitable for deep-frying of potatoes, but remarkable differences in the time during which both oils produced palatable products were found.

In a refining experiment, on a laboratory scale, crude oils from Sclerocarya birrea (SCO), sorghum bugs (SBO), water-extracted melon bugs (MBO H2O) and solvent-extracted melon bugs (MBO SOL) were processed by alkali refining. Quality changes were characterized by the determination of free fatty acids (FFA), peroxide value, tocopherols, sterols, phosphatides and stability against oxidation (Rancimat test). In addition, the fatty acid composition was determined. It is clear that the contents of phosphaticles, peroxides, tocopherols, sterols as well as oxidative stability were reduced during processing, while FFA were nearly totally removed. The content of phosphorus was reduced in SCO, SBO, MBO H2O and MBO SOL by 26, 19, 12, and 78%, respectively, while complete oil processing removed 95, 99, 96 and 99% of the FFA in crude oils, respectively. The level of total tocopherols decreased during processing by 38.7, 83.8, 100, and 33.3%, respectively. The color decreased through the processing steps up to bleaching; then, in the deodorization step, it darkened sharply in all samples. No change in the fatty acid composition was observed. The order of oxidation stability was crude > degummed > deodorized > neutralized > bleached, in SCO; and crude > degummed > neutralized > bleached = deodorized, in MBO H2O; and crude > degurnmed > deodorized > neutralized > bleached in MBO SOL; while in SBO, the order of oxidative stability was deodorized > crude > degummed > neutralized = bleached. Total sterols decreased by 42-92% in the processed oils, compared with crude oils.

The antioxidant activity of methanolic extracts from Sclerocarya birrea kernel oil meal, extracted using two different methods was evaluated. The extraction was carried out using magnetic stirring of the material in methanol/water (80:20 v/v) overnight followed by two ultra-sonic treatments for 45 min. (Overnight extract, ONEXT) and three ultra-sonic treatments for 45 min. only (Ultra-sonic extract, USEXT), respectively. Three fractions were obtained from each extract and the contents of total phenolic compounds were determined in each fraction according to the Folin-Ciocalteau method as 34.6, 54.8, and 58.6 mg/g of dry product in ONEXT and 29.6, 84.8, 143.9 mg/g in USEXT, respectively. The antioxidant activity of the extracts was evaluated according to the β -carotene-linoleic acid assay, where the extracts and their fractions showed significant effect (p

ABSTRACT Improvement of the oxidative stability of sunflower kernel oil (SKO) by blending with highly stable unconventional edible Sudanese oils was investigated. Blends (9 : 1, 8 : 2, 7 : 3, 6 : 4, w/w) of sunflower oil with Sclerocarya (Sclerocarya birrea) oil (SCO) and melon bug (Aspongopus viduatus) oil (MBO), respectively, were studied with respect to the fatty acid composition, the oxidative stability (Rancimat 120C) and stability at 70C using peroxide value. By increasing the proportion of SCO and MBO in SKO, the linoleic acid content decreased from 46.3 to 31.2% (SCO) and 30.1% (MBO), respectively, while the oleic acid content increased from 41.3 to 51.0% (SCO) and 43.9% (MBO), respectively. As a result of blending SKO with SCO and MBO, respectively, the oxidative stability in the Rancimat test was improved from 47 to 147% in (SCO) and from 5 to 68% (MBO) compared to the SKO as control, with increasing parts of SCO and MBO, respectively. Storage of the blends at 70C showed that the increase of the peroxide value as a measure of oxidation was remarkably lower for the mixtures of MBO and SCO with SKO than for pure SKO. This study demonstrated a means for improving the stability of sunflower oil by blending with SCO and MBO.

ABSTRACT Three unusual oils, obtained from Sclerocarya birrea (Marula), Aspongopus viduatus (melon bug) and Agonoscelis pubescens (sorghum bug), collected in Sudan from Abu Gibaiha, Ghibaish and Rahad agricultural areas, respectively, were investigated. In addition to the oil content, the fatty acid as well as sterol composition was determined by capillary gas chromatography and the tocopherols were evaluated by high‐performance liquid chromatography. Oxidative stability of the oils was investigated by the Rancimat method. The oil content of seeds from S. birrea amounted to 53.5%, whereas bugs of A. viduatus and A. pubescens came to 45 and 60%, respectively. The oils contained 67.2, 46.5 and 40.9% oleic acid, 5.9, 3.4 and 34.5% linoleic acid, 14.1, 44.2 and 12.1% palmitic acid and traces of linolenic acid, respectively. The tocopherol content of these oils amounted to 13.7, 0.3 and 34.0 mg/100 g oil, respectively. Gamma‐tocopherol was the predominant tocopherol in the oil of S. birrea and A. pubescens. The total content of sterols in the three oils was 287, 17 and 450 mg/100 g oil, respectively, whereas β‐sitosterol was determined as the main compound in all oils with about 60% of the total sterols. In the oil of S. birrea higher amounts of 5‐avenasterol (4.8 mg/100 g) were found. The oxidative stability of the oils, as measured by the Rancimat test at 120C, was 43, 38 and 5.1 h, respectively.

Radiation-induced oxidation of fatty foods was detected by a chemiluminescence method. Hazelnuts, peanuts and poultry were used as foodstuff samples. Additional investigations were performed with a model system and sunflower oil. The irradiation of the samples was carried out in a x-ray-fluorescence-apparatus. Thereby it is to note that the G-value of the x-ray-radiation is much higher than the G-value of a cobalt-60-source normally used for irradiation of food. A dependence of the integral of the light curve on the irradiation doses could be proved. Investigations with model systems which contained different amounts of alpha-tocopherol showed a decreasing chemiluminescence signal at low irradiation doses in presence of alpha-tocopherol. At higher doses the chemiluminescence signal enlarges with increasing amounts of alpha-tocopherol because irradiation products of alpha-tocopherol overlay its antioxidative effect. Irradiated poultry samples differ significantly from unirradiated samples after a deep-freeze storage of 26 weeks. A quantification of the doses is not possible without knowledge of the storage time, because the integrals decrease differently after irradiation during storage. In any case the chemiluminescence method is useful as a "screening method" for the detection of irradiation of foodstuffs with the possibility of automation and high sensitivity.