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. SCHEME 1 FIG. 1. Development of the content of polar compounds in Sclerocarya birrea oil (I), Sorghum bug oil (N), and palm olein (L) during frying of prefried potatoes at 175°C.a Determinations were carried out in triplicate, and the mean value ± SD is reported. Means within a column followed by different superscripts are significantly different (P < 0.05).

The methanolic extracts from Sclerocarya birrea leaves (SCL), roots (SCR), barks (SCB), and kernel oil cake (SCK) were examined for radical scavenging capacities and antioxidant activities. The total phenolics of the extracts was determined spectrophotometrically according to the Folin-Ciocalteau method using gallic acid as standard solution. The total phenolic compounds were found as 304.5, 367.5, 593, 148.0 and 258.0 mg g -1 of dry product, respectively. The extracts of SCL, SCR, SCB and SCK were markedly effective in inhibiting the oxidation of linoleic acid and subsequent bleaching of b-carotene in comparison with the control. Based on oxidation of b-carotene ⁄ linoleic acid, the SCK extract is the most effective followed by SCR, SCL and SCB extract. The antioxidant activity determined by the DPPH (1,1-diphenyl-b-picrylhydrazyl) method revealed that the SCK extract had the highest antioxidant activity on DPPH free radicals followed by SCB, SCR and SCL extracts. The effect of different extracts on the oxidative stability of sunflower oil at 70°C was tested in the dark and compared with BHA. The oil peroxide values (PVs) were generally lower with the addition of extract in comparison to a control.

The 2S albumin storage protein of Ricinus communis consists of the two heterodimeric proteins Ric c 1 and Ric c 3 each of which is composed of a small and a large subunit linked together by disulphide bridges. The complete primary structures of both heterodimeric proteins were determined by enzymatic degradation and automated Edman degradation. The sequences of all four chains correspond to the known cDNA sequence of the gene of a presumed precursor molecule and to the previously determined partial sequences for Ric c 1 and Ric c 3. In addition, few differences in amino acid positions were found which seem to be related to different varieties of R. communis. Sequence comparisons with 2S albumin from other plant genera revealed high degrees of homology and support the view of a common genetic origin of this protein family. Ric c 1 and Ric c 3 which have 11,212 and 12,032 daltons, respectively, share a similar molecular size, biological function and allergenicity with the 2S albumins from Brassica juncea (Bra j 1E) and Sinapis alba L (Sin a 1). Ric c 1 and Ric c 3 may be classified as isoallergens if, additionally, the high degree of similarity in the position of polar residues is taken into account.

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, OXIDATIVE STABILITY OF SUNFLOWER OIL 151 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.