Thirteen edible oils: sunflower, avocado, hemp, high-linolenic flax, low-linolenic flax, safflower, walnut, roasted sesame, rice, corn, rapeseed, pumpkin seed, and hazel were studied in this work. Their fatty acid composition, iodine, acidic, peroxide, and saponification values were determined. Infrared and Raman spectra of the oils were recorded in the range 400-3200 cm −1 . The integral intensities of the bands at about 1655 and 2852 cm −1 corresponding to ν(C=C) and ν(CH 2 ) vibrations were evaluated and used to construct a relationship between the spectroscopic data and the iodine value. The following linear dependencies were obtained: I ν(C=C) /I ν(CH2) = 7.449 × 10 −4 × iodine value -0.0339 and I ν(C=C) /I ν(CH2) = 9.299 × 10 −4 × iodine value -0.023 for the infrared and Raman spectra with a correlation coefficient 0.988 and 0.976, respectively. These calibration lines can be used to determine the iodine value for oils with unknown unsaturation level, and may be applied for margarines and other fatty materials.

In the paper, a procedure was suggested for making plant oil blends of desirable physico-chemical and performance parameters. There was applied a rule of additivity of parameters of component oils in the blend to get oil products with modified nutritional characteristics. The other objective of the research study was to test the usefulness of the procedure when projecting thermal properties of the blends for deep frying. To make oil blends, plant oils were used that were produced by Oleofarm Ltd. The oil blends were analysed using chromatographic and spectroscopic methods. Their chemical parameters constituted an input dataset to make blends of expected performance properties. It was shown experimentally that it was possible to theoretically project physico-chemical and thermal parameters of the final oil blend. When knowing the chemical parameters of individual blend-forming oils, it is possible to employ them to determine the parameters of the final blend. There were suggested oil compositions for the preparation of advantageous blends to be used for deep frying and salad dressings. Thus there was confirmed the purposefulness of blending the oils in order to make a product the qualities of which could be geared to the specific utility purposes.

For this study, the thermal degradation of palm, coconut, rice bran, and rapeseed (canola) oils was studied. Products formed during deep-frying were identified using chemical methods and these results were verified with those derived from FT-IR (Fourier-transform infrared spectroscopy) studies. Mathematically processed spectral data were analyzed in terms of the breaking of double bonds, the decomposition of the carotenoids, and the reduction of the C=O carbonyl group. Clearly visible changes in the position and intensity of some bands were used for explaining the structural changes in the studied oils. These changes prove that during the heating of the oils, decomposition of the plant fat into fatty acids appears, together with the reduction of the number of certain bonds (e.g., C=C, =C-H, and C=O) and cracking of the acylglycerol chains. The iodine values of the heated oils, determined from the FT-IR spectra measurements, show a significant decrease in their degree of unsaturation level. These effects, visible in the FT-IR spectra, confirm the chemical and structural changes derived from the chemical and physicochemical studies of the plant oils. The influence of heating time on the band intensity of proteins was also studied.

There are two food production processes that involve the replacement of one ingredient with other substance or a mixture of two or more products. One of them is adulteration of food products. This applies to high-cost and high-quality oils e.g. olive oil that is frequently subject to adulteration with other edible oils of lower value. Such a food fraud affects the quality of the gentle oil and the foods the ingredient of which is olive oil. The second action often applied to the oils is blending of the variety of products originating from many different regions and countries. Sometimes the oils originating from various sources and years are blended to create a consistent taste.The subject of this paper is the application of the multi-analysis method to assess the process of the blending of several oils and thus creating a new mixture to satisfy the market demand for new hitherto unknown oils, advertised as new products. For this task we con-