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Egg yolk is a complex supramolecular system composed of diverse proteins with high nutritional value and outstanding functional characteristics. Cryopreservation is commonly used in the food industry as an effective way to prolong egg yolk shelf life and improve transportation convenience. However, low temperature induces the aggregation of protein in egg yolk, resulting in egg yolk gelation and consequently reduced fluidity and solubility, affecting the functional properties of egg yolk, which are not conducive to the application of egg yolk in food processing. This article introduces the composition, structure and functional characteristics of egg yolk as well as the causes of egg yolk freezing and the mechanism of egg yolk gelation, and discusses the effect of egg yolk gelation induced by freezing on egg yolk quality. This review focuses on the physical, chemical and biological pretreatments for inhibiting protein aggregation during egg yolk, which is of guiding significance for inhibiting egg yolk gelation induced by freezing and for improving the quality of frozen egg yolk.

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• The mechanisms and influencing factors for the initiation of hot cracks (solidification crack, liquation crack, and ductility-dip crack) as well as cold cracks in the cladding layer of nickel-based high-temperature alloys formed by laser-based directed energy deposition are reviewed and discussed. • The propagation mechanisms of cracks after initiation during the forming process are reviewed and analyzed from the point of view of oxygen-induced crack propagation and the interactions between defects. • The main methods for inhibiting crack initiation and propagation are summarized. • Suggestions for future research are given on the mechanisms, influencing factors, and inhibition methods of crack initiation and propagation. Laser-based directed energy deposition (L-DED) has a broad application prospect in the preparation of complex structural parts, the repair of critical parts, and other aspects of Ni-based high-temperature alloys. However, the rapid solidification rate of the melt pool during the L-DED forming process, as well as the forming process characteristic of track-by-track overlapping of the cladding tracks and layer-by-layer stacking of the cladding layers, make it easy for defects, such as cracks, to appear in the multi-layer cladding layer of Ni-based alloys. Crack initiation brings hidden danger to the multi-layer cladding layer in subsequent service, and the propagation of the crack after initiation determines the final mechanical properties of the cladding layer. This paper reviews and discusses the initiation mechanisms of hot and cold cracks during the L-DED forming process, reviews and analyzes the propagation mechanisms after crack initiation in combination with the process characteristic of L-DED, and summarizes the influencing factors of crack initiation and propagation. Based on this, the main methods to inhibit crack initiation and propagation are further reviewed. The work in this paper aims to provide reference and guidance for realizing effective inhibition of crack initiation and propagation during L-DED forming of Ni-based high-temperature alloys. [ABSTRACT FROM AUTHOR]

Egg yolk is a nutrient-rich ingredient widely utilized in various food products including mayonnaise, salad dressings and cakes. Freezing could address the issue of microbial contamination and quality deterioration of liquid egg yolk during prolonged storage and transportation, which helps to preserve the nutrient content of the yolk and extend its shelf life. However, freezing could cause irreversible changes in the flowability and viscosity of egg yolk, resulting in a phenomenon known as gelation, making it difficult to mix egg yolk with other food ingredients and reducing its dispersibility and functionality. Based on the phenomenon of frozen egg yolk gelation, this paper focuses on the current research status regarding the gelation mechanism of each component in egg yolk, including the formation of ice crystals, protein denaturation and aggregation, and molecular interactions. Meanwhile, the principles underlying various methods used to inhibit gelation are discussed, encompassing physical, chemical, and enzymatic approaches. These methods inhibit frozen egg yolk gelation by different mechanisms. Comprehending the research progress of gelation and its inhibition methods can offer valuable insights for future research and the application of frozen egg yolk in food production. • The gelation phenomenon and mechanism of frozen egg yolk are reviewed. • Current inhibition methods are discussed and compared. • Future application recommendations for different inhibition methods are prospected. [ABSTRACT FROM AUTHOR]