Metabolomic study of fatty livers in ducks: Identification by 1H-NMR of metabolic markers associated with technological quality

The control of fatty liver fat loss during cooking is a major issue. Previous studies showed that fat loss was influenced by bird production factors and liver technological treatments. However, part of the variability in fat loss remained uncontrolled. To provide enhanced insights into the determinism of fatty liver quality, liver hydrophilic metabolite profiles were measured by nuclear magnetic resonance of the proton (H-1-NMR). The study aimed at i) comparing fatty livers with extreme fat loss values and ii) at characterizing the effect of postmortem evolution of livers during chilling. A group of 240 male mule ducks (Cairina moschata x Anas platyrhynchos) was reared and overfed. Their livers were sampled at 20 min and 6 h postmortem. Of these birds, 2 groups of ducks were built with extreme values on the technological yield (TY; TY = 100 - % fat loss; the low-fat-loss group, TY = 89.9%, n = 13; and the high-fat-loss group, TY = 68.3%, n = 12, P < 0.001). The H-1-NMR analyses showed that the high-fat-loss livers were more advanced in postmortem biochemical and structural changes than low-fat-loss livers early postmortem. The high-fat-loss livers were characterized by hydrolysis of glycogen into glucose, worse integrity of cell membrane with diminution of compounds of phospholipids, and higher catabolic processes. The accelerated postmortem processes may be the origin of the differences in fat loss during cooking. During the early postmortem period, the adenosine triphosphate amount in liver cells was strongly reduced and lipolysis of triglycerides seemed to be enhanced. The glycogen stored in liver was first converted into glucose, but contrary to what happens in postmortem muscles, glucose was not converted into lactate.