The effects of the four heating intensities (hot-spring egg yolk, HEY; soft-boiled egg yolk, SEY; normal-boiled egg yolk, NEY; and over-boiled egg yolk, OEY) on lipidomes of boiled egg yolks were investigated. The results indicated that four heating intensities had no significant effect on the total abundance of lipids and lipid categories except for bile acids, lysophosphatidylinositol, and lysophosphatidylcholine. However, of all the 767 lipids quantified, the differential abundance of 190 lipids was screened among the egg yolk samples at four heating intensities. Soft-boiling and over-boiling altered the assembly structure of the lipoproteins through thermal denaturation and affected the binding of lipids and apoproteins, resulting in an increase in low-to-medium-abundance triglycerides. The decreased phospholipid and increased lysophospholipid and free fatty acid in HEY and SEY suggests potential hydrolysis of phospholipids under relatively low-intensity heating. Results provide new insights into the effect of heating on the lipid profiles of egg yolk and would support the public’s choice of cooking method for egg yolks.

The process of egg yolk formation involves the transport and uptake of a large number of small molecule metabolites. A qualitative and relative quantitative analysis of metabolites in the 3 formation periods of egg yolk was performed by a liquid chromatography-tandem mass spectrometry (LC-MS/MS) analytical workflow. A total of 398 metabolites were identified, of which "amino acids and their metabolites", "lipid", and "organic acids and their derivatives" were the dominant egg yolk metabolite categories with the most metabolite species. The findings suggested that a number of amino acids, organic acids, nucleotides and their metabolites were deposited during follicular development to provide material support for later embryonic development. At the same time, some vitamins and carbohydrates were consumed during follicular development to support the normal development process. In addition, the small hierarchical follicle (SF) period may be a critical period for the regulation of the transport and deposition of some active ingredients. These results contribute to a comprehensive understanding of the nutrient deposition pattern and nutritional properties of egg yolk.

The Tibetan pig is a characteristic breed of the Qinghai-Tibet Plateau with distinct physiological and meat quality attributes. The liver lipid profile can offer an important perspective to explore the uniqueness of Tibetan pigs. A quantitative comparison of liver lipidomes revealed significant differences in the lipid profiles between Tibetan and Yorkshire pigs raised at different altitudes. The abundance of lipids in the livers of pigs raised at a high altitude was higher than that of pigs raised at a lower altitude, whereas the abundance of lipids in the livers of Yorkshire pigs was higher than that of Tibetan pigs raised at the same altitude. Of the 1101 lipids identified, 323 and 193 differentially abundant lipids (DALs) were identified in the pairwise comparisons of Tibetan and Yorkshire pigs raised at different altitudes, respectively. The DALs of Tibetan pigs consisted mainly of 161 triglycerides, along with several acylcarnitines, represented by carnitine C2:0, and significant changes in the abundance of some phospholipids. The DALs of Yorkshire pigs were more complex, with significant increases in the abundance of triglycerides, cholesteryl esters, and free fatty acids, and decreases in the abundance of some phospholipids. This research provides strong theoretical and data support for the high-quality development of the highland livestock industry.