Determination of egg yolk content in egg liqueurs

The recent Czech Food law (Decree No. 264/2003, 93/2000 and 57/2003 of the law No. 110/1997 as amended) requires the minimal concentration of egg or egg yolk content in relevant food products (mayormaises, egg pastas, egg liqueurs), however, the methods for the determination of egg and/or egg yolk content are not sufficiently specified. The presented study deals with the development and evaluation of the analytical methods for the determination of egg yolk content in egg liqueurs. Due to the high variability of the egg composition and a possible effect of processing on the composition of the product, several chemical markers were taken into the consideration: dry matter, phosphorus, fat, cholesterol, fatty acids, and lysozyme concentrations. The egg-yolk content was estimated by means of multiple regression analyses of the calibration set (model samples) and the data obtained for raw materials and described in literature. According to the egg yolk content determined, only 6 from 10 analysed samples of egg liqueurs obtained from the local market met the limit of 140 g/l (calculated with the 10% standard deviation error of estimation) required by the recent Czech legislation.