Fritura de patatas en aceite de girasol. Estudio comparativo del grado de alteración del aceite de la freidora y del extraído de las patatas

Fatty Acid Changes in High Oleic Acid Sunflower Oil during Successive Deep-Fat Fryings of Frozen Foods

High oleic acid sunflower oil (HOSO) is a monounsaturated oil that is being extensively used in frying. The level of total altered fatty acids and the fatty acid pattern of a fryer oil was used to evaluate the alteration of a HOSO used 20 times to fry various frozen foods with frequent replenishment (FR) or without replenishment (NR) with fresh oil during the frying. In addition, the levels of total altered fatty acids and the fatty acid composition of the fat extracted from the fried potatoes after numerous fryings were determined and compared to those of the corresponding fryer oils. Altered fatty acids increased linearly through 20 fryings within FR and NR in the frying oil and also in the fat extracted. Although differences were not quantitatively relevant, changes tended to be higher in the extracted fat, and in the NR modality as a consequence of oil renovation and fat exchange between the frying oil and the potatoes. The decrease in the oleic acid content in the oil was more pronounced ( p< 0.001) in NR than in FR method, and more (at least p< 0.01) in the oils than in the corresponding extracted fats. Nevertheless, other fatty acids remained quite stable and similar or increased during frying, by both methods. These results suggest that total fatty acid alteration measure is a useful tool for frying assessments, and that they must be related not only to the degradation of unsaturated fatty acids but also to migrations of some fatty acids from the frozen prefried foods to the fryer oil as revealed by composition of the fat extracted from the fried potatoes.

Cyclic fatty acid monomer formation in domestic frying of frozen foods in sunflower oil and high oleic acid sunflower oil without oil replenishment

During the frying process, oxidation, hydrolysis, polymerization, isomerization, and cyclization occur. Polymers and Cyclic fatty acid monomers (CFAM) are potentially toxic, and the latter are detected at relatively low levels (0.01-0.7%) in used frying oils. Twenty fryings of different frozen foods were carried out over 10 consecutive days in sunflower oil (SO) and in high oleic acid sunflower oil (HOSO). Fatty acid methyl ester derivates were hydrogenated with platinum oxide catalyst under hydrogen. Ethyl palmitate was added as an internal standard before hydrogenation. The CFAM obtained were isolated, concentrated and quantified by HPLC using a reverse-phase column followed by gas chromatography. Linear adjustments between total and individual CFAM content and the number of frying operations performed with both oils were established by analysis of variance. The comparison between linear equation adjustments of both oils was performed by a two-way analysis of covariance. After 20 fryings 15.4 +/- 0.06 g polar content/100 g oil, 7.15 +/- 0.08 g polymers/ oil, 11.52 +/- 0.08 g polymers/100g oil and 855 +/- 8.9 mg CFAM/kg oil were detected in SO. A 10 mg/100 mg oil of altered fatty acid content correspond to 700 mg/kg CFAM, while 25% polar material and 10% polymer content would correspond to about 850-1,000 mg CFAM/kg oil. Data suggest that frying with SO produces in each new frying 9 mg CFAM/kg more than frying with HOSO (p < 0.001). After frying cyclopentyl structures were more than twice as abundant as cyclohexyl fatty acids in both oils. Bicyclic compound formation was significantly higher in SO (p < 0.001). Because digestion and absorption of polar material, polymers and CFAM occur, data clearly show the advantageousness and advisability of frying with HOSO rather than SO.