The purpose of this attemt was to evaluate the influence of deep-frying fat on the quality of frying pastry and observe chemical changes of frying fat during frying.The samples of frying pastry were provided by factory Penam s. r. o., Rosice. Four sorts of soft-centered friedcakes and not soft-centered friedcakes were evaluated. The samples of hydrogenated fat were taken twice always at the beginning and at the end of the frying. This lasted 7 days. Chemical analyse and qunatification fatty acid by using gass chromatography were took by these samples. The sensor eva­lua­tion was made by ten expert evaluators. Evaluators focused on following deskriptors: form, appearance, crumb, aroma, flavour of soft centred and flavour of product. We have found significant statistical differences between the products fried in the fat which was changed before and after the frying. The most differences were registered by porosity, plumpness, flavour of crumb and placement fill.Acidity number of fat increased linearly. Peroxid number decreased at the beginning and than increased again.