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The effects of sodium tripolyphosphate and sugar on cold-set gel properties of egg yolk/κ-carrageenan/xanthan gum mixed dispersions were investigated by zeta potential, rheological measurements, gel textural analysis and low-field nuclear magnetic resonance (LF-NMR). As the yolk content increased to the 5 g/100 mL in aqueous systems, phase separation of mixed gel could be observed, due to the relatively rough gel appearance. Furthermore, the addition of phosphate could significantly improve the phase separation of mixed gels by elevating the pH and reducing zeta potential. The increase in the content of yolk and sugar brought an enhancement in gel storage modulus, while the addition of phosphate induced a dramatic decrease in the gelation rate of mixed gels. Textural analysis confirmed that hydrogen bonding interaction was the important force, which determined gel strength of the ternary composite cold-set gelation system. The result of LF-NMR revealed that there was a negative correlation between the decrease of proton mobility of immobilization water and the increase of gel strength in different sample series. • The phase separation of composite gels could be improved by polyphosphate. • Changes in G′ and hardness of composite gels depend on the hydrogen bonds. • Gel strength has a strong relation with the proton mobility of composite gels. [ABSTRACT FROM AUTHOR]

Egg yolk powder is a widely used functional food ingredient due to its beneficial physicochemical and nutritional properties. However, its utilization in food can be limited due to its relatively high lipid content and low water-solubility. To address this issue, a two-step processing method utilizing enzymatic treatment combined with subcritical fluid extraction was investigated in this study. This method effectively reduced lipid content and improved water-solubility of egg yolk powder. An alcalase enzyme concentration of 500 U/g, extraction temperature of 313.15 K, extraction time of 120 min and a solid-liquid ratio of 1:9 (g:mL) produced powder with 20% lipid content and 71% water-solubility. Enzymatic hydrolysis clearly enhanced subcritical fluid extraction efficiency. This was attributed to hydrolysis disrupting the structure of egg yolk particles and facilitating the release of enclosed lipid molecules and was confirmed by scanning electron microscopy and laser confocal microscopy. [Display omitted] • Low-fat (20%) egg yolk powder with high water solubility (71%) was developed. • Enzymatic hydrolysis combined with subcritical fluid extraction was used. • Enzymatic hydrolysis improved the water solubility. • The highest oil extraction efficiency was achieved using 500 U/g alcalase. • Disruption in egg yolk structure promoted oil release. [ABSTRACT FROM AUTHOR]