No abstract

Pilot-scale supercritical fluid extraction of okra seeds was carried out, using carbon dioxide as solvent, at temperatures of 40, 50 and 60 • C and pressures of 150, 300 and 450 bar. Laboratory-scale Soxhlet extraction of the ground seeds was carried out with ethanol and n-hexane. The yields of supercritical fluid extraction and n-hexane Soxhlet extractions were similar. The ethanol Soxhlet extraction gave the highest yield, but the concentrations of β-sitosterol and tocopherols in this extract were lower than in the supercritical fluid extraction product. The fatty acid profiles of the extracts were determined, and a high unsaturated/saturated ratio was observed. The fatty acid compositions were only slightly different for oils obtained by the different extraction methods.

Solid-phase microextraction (SPME) was developed to determine volatile substances from liquid, gas or even solid materials. This technique has been successfully applied for soil, waste water, blood and urine samples, but in spite of its advantages there are still few applications for vegetable oils. SPME is applicable to determine the aroma and other volatile compounds of the oil, which are characteristic to its origin and oxidative status.In this study the sensitivity and selectivity of some commercially available SPME adsorption materials (polydimethylsiloxane, divinylbenzene, carboxen) were compared. The diverse types of stationary phases were investigated by applying standard oils containing volatile substances from 9-90 mg/kg concentrations. SPME fibre was placed into the headspace of an oil sample in a 30-ml headspace vial thermostated at 80 °C for 45 min. The extracted volatile materials were desorbed from the fiber in the injection port of the gas chromatograph at 250 °C. Identification of the extracted compounds is based on pure standards and mass spectra. The reliability of the SPME sampling method was studied by parallel measurements.The 2-cm long fibre coated with divinylbenzene (50 µm) and carboxen (30 µm) proved to be the most appropriate to determine the volatile oxo-materials from vegetable oils. The method was successfully applied to follow up the formation of volatile substances (e.g. hexanal, t-2-hexenal, t-2-heptenal, t-2-octenal, nonanal, t,t-2,4-nonadienal, t-2-nonenal, t-2-decenal, t,c-and t,t-2,4-decadienal, 2-pentylfuran, 1-octen-3-ol) during deep frying in sunflower oil.

BACKGROUND: The goal of this work was to utilize the sea buckthorn pomace, which is the by-product of a sea buckthorn juice process. Pilot plant supercritical fluid extraction (SFE) experiments were performed in a 5 × 10 −3 m 3 volume high-pressure vessel. The effects of pressure and temperature on extraction yield and recoveries of biologically active components were studied using a 3 2 full factorial design. The pressure and temperature were varied over the ranges of 30-46 MPa and 313-353 K, respectively. The extract samples were analysed by TLC-densitometry, UV/VIS spectrofotometry and HPLC methods.

Whereas solid phase microextraction (SPME) combined with gas chromatography is a wide‐spread technique in certain fields of food analysis this technique is quite new for the analysis of vegetable oils. The method is sensitive enough to follow changes in the oxidative state of vegetable oils by measuring the amount of volatile materials produced during storage and the refining process. In the present study degummed rapeseed oil was bleached using different activated bleaching earths applied in four dosages. Their effect on lipid degradation was determined both by traditional methods (e.g. UV absorbance, p‐anisidine value) and by the SPME‐HS method. Although the p‐anisidine value (p‐AV) gives only the concentration of β‐unsaturated aldehydes it correlates well to the amount of total volatile substances as determined by SPME at the headspace of the sample. The extracted volatile materials were separated and identified by gas chromatography combined with mass spectrometry. SPME gives more information about the stage of oxidation and the applied bleaching earth by quantifying the volatile compounds. Additionally SPME does not require any toxic reagent such as p‐methoxy aniline which is used to determine the p‐AV. Although bleaching is very important it was disregarded in recent years. Therefore one of the aims of the present study is to draw back more attention towards bleaching.