Preparation, characterization and physicochemical properties of novel low-phosphorus egg yolk protein

Effect of Four Extraction Processes with Acetone-Ethanol Protocols on the Properties of Egg Yolk Phosphatidylcholine and the Structure of Residual Protein

In this study, four acetone-ethanol protocols were employed to investigate the effect of extraction processes on the yield and purity of phosphatidylcholine (PC) from dried egg yolk powder and fresh liquid egg yolk, as well as the cholesterol distribution between the oil and PC fraction. Furthermore, the physicochemical (thermo-stability, fatty acid composition, and molecular structure) and emulsifying (zeta potential, particle size, EAI, ESI, and creaming index) properties of the final PC product were also examined. In addition, the structural characteristics of the egg yolk residual protein were highlighted to promote its application in food industries. The results showed that de-oiling with acetone prior to ethanol extraction can achieve high yield (19.92%) and purity (68.62%) of the PC product with low cholesterol content (< 0.12%). The extraction processes exhibited a significant impact on the emulsifying properties of the PC product. The creaming index of PC emulsions was higher than that of egg yolk powder emulsions with high protein concentration, suggesting that PC plays a critical role in the emulsifying stability of egg yolk protein dispersion. The structural characteristics of residual protein, including free sulfhydryl groups and primary, secondary, and ternary structures, showed considerable differentiation related to extraction processes. These findings provide a powerful tool for the dietary utilization of egg yolk PC and protein in future.

A review on recent advances of egg byproducts: Preparation, functional properties, biological activities and food applications

The rapid development of egg industries produced vast byproducts that have not been effectively used. In this paper, the comprehensive utilization of egg byproducts was reviewed. Protein extraction and enzymatic hydrolysis were the main used ways for recycle of egg byproducts. The fact that eggshell membrane could accelerate would healing and improve facial skin of healthy people for 12 weeks was found. However, salted egg white had poor functional properties owing to high salt and ultrafiltration was an effective technology to remove 92.93% of salt. Moreover, Defatted yolk protein had the great potential to be used as food additives and functional foods. Other egg byproducts such as egg inhibitor and eggshells also were discussed. The novel applications of egg byproducts in the food field included food additives, feeds, food packaging materials and nutraceuticals based on current knowledge, but the proportion needed to be improved. This paper would provide a new insight for comprehensive utilization of egg byproducts.

Molecular aggregation and property changes of egg yolk low-density lipoprotein induced by ethanol and high-density ultrasound

Solvent and physical treatment are widely used in egg yolk processing, but the detailed changes in the molecular structure of egg yolk proteins during processing are unclear. The aim of this study was to investigate the effects of ethanol and ultrasonic treatments on chicken egg yolk low-density lipoprotein (LDL). The solubility, emulsifying activity and emulsifying stability decreased by 74.75%, 46.91%, and 81.58% after ethanol treatment, respectively. The average particle size of ethanol-treated LDL increased 13.3-fold to 937.85 nm. These results suggested that ethanol treatment induced wide-ranging aggregation of LDL. In contrast to ethanol treatment, ultrasonic treatment promoted the solubility and emulsifying stability of LDL and enhanced its zeta-potential (119.56%) and surface hydrophobicity (10.81%). Based on particle size analysis and transmission electron microscopy, approximately 34.65% of LDL had undergone aggregation and the molecular interface became more flexible after ultrasonic treatment. These results revealed the detailed changes in egg yolk LDL structure and properties during solvent (ethanol) and physical (ultrasound) processing.

Egg Intake in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) are often instructed to adhere to a renal-specific diet depending on the severity and stage of their kidney disease. The prescribed diet may limit certain nutrients, such as phosphorus and potassium, or encourage the consumption of others, such as high biological value (HBV) proteins. Eggs are an inexpensive, easily available and high-quality source of protein, as well as a rich source of leucine, an essential amino acid that plays a role in muscle protein synthesis. However, egg yolk is a concentrated source of both phosphorus and the trimethylamine N-oxide precursor, choline, both of which may have potentially harmful effects in CKD. The yolk is also an abundant source of cholesterol which has been extensively studied for its effects on lipoprotein cholesterol and the risk of cardiovascular disease. Efforts to reduce dietary cholesterol to manage dyslipidemia in dialysis patients (already following a renal diet) have not been shown to offer additional benefit. There is a paucity of data regarding the impact of egg consumption on lipid profiles of CKD patients. Additionally, egg consumption has not been associated with the risk of developing CKD based on epidemiological studies. The egg yolk also contains bioactive compounds, including lutein, zeaxanthin, and vitamin D, which may confer health benefits in CKD patients. Here we review research on egg intake and CKD, discuss both potential contraindications and favorable effects of egg consumption, and describe the need for further research examining egg intake and outcomes in the CKD and end-stage renal disease population.