| Egg yolk(EY)is rich in vitamins,lipids,proteins and minerals,and is an important source of dietary nutrition for humans.Egg yolk can be divided into egg yolk granules(EYG)and yolk plasma(EYP)after dilution with water and centrifugation two components.Current studies on egg yolk and its components have focused on the effects of physical and chemical treatments on the structural or functional properties of yolk particles and synergistic effects,while detailed comparisons of the types and abundance of small and medium-sized nutrients in EYG and EYP are lacking.Therefore,in this project,we will identify and quantitatively compare the lipids,metabolites and mineral elements of EY,EYG and EYP using lipidomic,metabolomic and elemental analyses,respectively,for the small molecule nutrients in egg yolk.On this basis,we studied the loading of calcium and the development of high calcium yolk granules tablets using EYG as the main ingredient.The main results of the study are as follows:Lipidomic analysis of egg yolk and its components.The results of the determination of the main nutrients of egg yolk and its components showed significant differences in the content of all nutrients of EY,EYG and EYP.Among them,EYP had the highest crude fat content;both total protein and ash content were highest in EYG(total protein content: EYG/EY=1.94,EYG/EYP=2.75;ash content: EYG/EY=2.17,EYG/EYP=2.64),and the relative content of phospholipids in EYG was higher.The results showed that EYG has a higher nutritional value compared to EY and EYP.The egg yolk and its component lipid molecules,showed a rich diversity.Lipidomic analysis based on liquid chromatography-tandem mass spectrometry showed that 702 lipid molecules were identified,mainly including 136 triglycerides,112 phosphatidylcholines,104 phosphatidylethanolamines and 50 lysophosphatidylcholines.Quantitative comparisons showed 171(EY/EYG),49(EY/EYP)and 186(EYG/EYP)differentially abundant lipids(FC>2 or <0.5,VIP≥1)in the three groups of EY,EYG and EYP samples compared two-by-two,respectively.Phospholipids are the representative lipids with different abundance in the comparison between EY and EYG,EY and EYP;while triglycerides are the most representative lipids with different abundance between EYG and EYP.Docosahexaenoic acid and eicosapentaenoic acids are mainly found in the phospholipids of EY.Analysis of small molecule metabolites in egg yolk and its fractions.Metabolomic analysis showed that 588 small molecule metabolites were identified in egg yolk and its components,of which,mainly glycerophospholipids(51.59%-66.46%),amino acids and its metabolites(27.06%-39.81%)and coenzymes and vitamins(1.21%-1.84%).The abundance of lysophosphatidylcholine(36.48%-47.49%)and lysophosphatidylethanolamine(15.02%-18.84%)was higher in glycerophospholipids.Lysophosphatidylcholine did not differ significantly in egg yolk and its components,while lysophosphatidylethanolamine differed significantly in EY and EYG.Among the amino acids and their derivatives,significant differences were found in EY,EYG and EYP(19.21%-28.99%),with the highest abundance of DL-leucine(5.42%-9.03%).Among the coenzymes and vitamins,pantothenic acid(0.56%-1.56%)had the highest abundance and was significantly different among the three samples.Many vitamins,choline and other small-molecule active components were identified in egg yolk and its components.Among them,riboflavin and sn-glycero-3-phosphorylcholine were both in high abundance in EYP.Study on calcium loading of yolk granules and development of high calcium yolk granule tablets.The mineral elements of egg yolk and its components were determined by inductively coupled plasma emission spectrometry(ICP-OES),and the results showed that phosphorus,calcium,iodine,potassium,magnesium,sodium,iron and zinc,which are the eight mineral elements,were more abundant in egg yolk and its components(all >1 mg/kg),and all of them were significantly different.The calcium content of EYG was significantly higher than that of EY and EYP,and the free calcium content was found to be significantly lower after alkali treatment of EYG solutions with certain concentrations,i.e.,the alkali-treated EYG solutions have the potential for further calcium adsorption.By adjusting the p H,calcium chloride concentration and EYG solution concentration,it was found that the yolk granules were able to stably adsorb approximately 30% of their own total calcium again,based on the mass of EYG and the mass of adsorbed calcium.FTIR and circular dichroism spectroscopy revealed that calcium loading did not change the absorption peak position of the yolk granules,but changed their protein structure from β-turning to β-folding.The thermal stability of yolk granules was improved after calcium loading.The microscopic morphology of yolk granule powder changed from aggregated state to slab-like after alkali treatment and calcium loading treatment.The tablets were prepared by adding excipients to the powder of yolk granules loaded with calcium according to the set prescription and using the direct compression method,and were examined according to the Chinese Pharmacopoeia(2020 edition),and the performance of the tablets were all in accordance with the standard.In this study,the types and contents of nutrients in egg yolk and its components were identified and quantitatively compared using lipidomic,metabolomic and mineral elemental analyses,and the material spectrum of egg yolk and its components(yolk granules and yolk plasma)was systematically investigated from various dimensions such as types,contents and structures.The results of the study provide an important reference for the comprehensive understanding of egg yolk and its components,egg yolk processing and nutritional characteristics research. |
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