Fat loss during cooking of duck "foie gras": the biochemistry of lipids

The technological yield, which is evaluated by the fat loss during pasteurization or sterilization, is the principal quality trait related to the French Foie Gras production: it participates in the uniformity of the end product and the profitability of a sales unit.
Aim of this work is to identify biological characteristics, more than liver weight and lipid rate, which contribute to the variability in fat loss during cooking because, despite the progressive industrialization of the market and homogenization of the product, a great individual variability still exists.
Particularly, the attention has been focused on lipid’s classes in order to determine if they are involved in this kind of problem, and the principle was to compare the amount of each class between the high and low fat loss during cooking.
In order to (i) improve the repeatability of the overall results, (ii) confirm and validate the former results and (iii) include the fasting before slaughtering during the second step as a variation factor, two field trials of 97 and 238 animals have been planned.
Analyzing the global results it has been observed that there are certain lipid’s pool components involved in technological yield of recurrent importance: cholesterol is an interesting parameter which has shown statistical relevance when it has been compared for different levels of technological yield. It shows a good correlation value with technological yield, with the dry matter content and finally with the fatty liver weight. Correlations, as a possible linkage to fat loss, have been found also between free fatty acids, some triglycerides, diglycerides and light fatty livers characterized by a low technological yield.
Overall, even though it has not been possible to link the lipid profile with fat loss during cooking, confirming the complexity of the problem, the correlations among certain parameters which have been above mentioned could be an interesting starting point for future research projects to highlight the mechanisms involved in this phenomenon.