Singh, Mar 2009 – Factors Affecting the Content of Trans Fats in Eggs

The studies have been carried out to emphasize a proper methodology for determining trans fats, to determine natural levels of trans fats in egg without added trans fat in the hen’s ration, and to ascertain the effect of feeding various types of fats on trans fats levels in eggs. Hens were fed with diets containing five different types of fats, varying in trans-fat levels. The diet and egg samples were analyzed for trans-fatty acids by two different methods, i.e, Gas Chromatograph (GC) system and Fourier Transform Infrared (FTIR) spectroscopy. The trans-fat contents of standard ration with 0% added fat/oil, and /or the ration containing added soybean oil, and the egg samples obtained from the hens fed with these diets were below the detection limit of the GC system. Thus, hens fed with trans-fat free diets produced eggs that did not contain detectable levels of trans-fats. The trans-fat levels in the other diets (standard laying ration + tallow, standard ration + shortening, and standard ration + tallow-shortening blend) were found to be 2.78%, 3.25% and 2.85% trans-fat/total fat, respectively, whereas the egg yolk from hens fed with these diets showed only 0.60%, 0.78% and 0.73% trans-fat/total fat, respectively. Therefore, about a quarter of trans-fats available in each ration were deposited in egg yolks of hens consuming these rations. The concentrations of trans fats determined by GC were below the limit of detection for FTIR method. A correlation coefficient of 0.988 was found between GC and FTIR results of diets containing tallow, shortening, and tallow-shortening blend and pure fat samples. No correlation could be made with the egg yolk data as the low levels of trans-fat in egg yolk could not be quantified by FTIR method.