Improvement and mechanism of emulsifying properties of liquid egg yolk by ozonation technology

Co-cold extrusion synergized with cysteine for enhancing physicochemical, rheological characteristics and in vitro digestibility of whey protein isolate

Impacts of co-cold extrusion (≤50 °C) of whey protein isolate (WPI) and cysteine (Cys, 0, 20, 40, 60, 80 and 100 mmol/L) on its physicochemical, in vitro digestion and rheological properties were investigated. As Cys concentration increased, the emulsifying properties and in vitro digestibility of co-extruded WPI-Cys products showed an increasing trend. Specifically, when Cys reached 100 mmol/L, surface hydrophobicity, emulsification activity index (EAI), emulsification stability index (ESI) and in vitro stomach digestibility of the co-extruded WPI-Cys products increased by 205.07%, 77.51%, 193.95% and 71.81% compared with WPI, respectively. Principal component analysis (PCA) results further indicated that co-extruded WPI-Cys at a concentration of 100 mmol/L had the best functional properties. In addition, co-extruded WPI-Cys exhibited the strongest Péclet number (Pe) value and apparent viscosity at a Cys concentration of 100 mmol/L among all samples. Therefore, co-extrusion would be an effective method for modifying WPI, providing whey protein-based ingredients with excellent functional properties for food processing.

Development and characterization of curcumin-loaded chitosan/egg yolk freshness-keeping edible films for chilled fresh pork packaging application

In this study, a novel fresh-keeping edible film was prepared using egg yolk (EY) and chitosan (CS) with varying concentrations of curcumin (Cur) for food packaging. The addition of Cur notably enhanced tensile strength, elongation at break, and water resistance from 15.70 MPa to 24.24 MPa, 43.79 % to 63.69 %, and 1.599 g·mm·(m2·h·kPa)-1 to 1.541 g·mm·(m2·h·kPa)-1, respectively. Cur also impacted moisture content, swelling degree, and film color. SEM revealed a uniform distribution of Cur, creating a smooth and dense film surface. FT-IR analysis suggested that hydrogen bonding facilitated Cur integration into the film network. The films demonstrated excellent UV-blocking and antioxidant properties attributed to Cur's chromogenic and phenolic hydroxyl groups. Consequently, they effectively inhibited lipid oxidation and weight loss in meat, thereby prolonging the shelf-life of chilled pork by at least 2 d. In conclusion, this study provided a simple and cost-effective idea to incorporate actives with EY as a natural emulsifier, presenting an effective solution for developing active packaging materials to enhance the safety and quality of meat products.

Emulsifying properties of egg proteins: Influencing factors, modification techniques, and applications

As an essential food ingredient with good nutritional and functional properties and health benefits, eggs are widely utilized in food formulations. In particular, egg proteins have good emulsification properties and can be commonly used in various food products, such as mayonnaise and baked goods. Egg protein particles can act as stabilizers for Pickering emulsions because they can effectively adsorb at the oil-water interface, reduce interfacial tension, and form a stable physical barrier. Due to their emulsifying properties, biocompatibility, controlled release capabilities, and ability to protect bioactive substances, egg proteins have become ideal carriers for encapsulating and delivering functional substances. The focus of this review is to summarize current advances in using egg proteins as emulsifiers. The effects of influencing factors (temperature, pH, and ionic strength) and various modification methods (physical, chemical, and biological modification) on the emulsifying properties of egg proteins are discussed. In addition, the application of egg proteins as emulsifiers in food products is presented. Through in-depth research on the emulsifying properties of egg proteins, the optimization of their applications in food, biomedical, and other fields can be achieved.

Tracking transformation behavior of soluble to insoluble components in liquid egg yolk under heat treatment and the intervention effect of xylitol

The heat sensitivity of egg yolk limits its application, and xylitol can improve its thermal stability. The soluble and insoluble components of egg yolk and egg yolk containing xylitol treated at different temperatures were explored from the aspects of thermal instability behavior characterization and structure property. Magnetic resonance imaging and low field nuclear magnetic resonance showed that increased temperature induced liberation and transfer of hydrogen protons. Meanwhile, the apparent viscosity of soluble components increased, while that of insoluble components decreased. Microstructure showed that heat treatment induced aggregation and lipid transfer. SDS-PAGE showed that heat treatment induced aggregation and transformation of γ-livetin and apo-LDL. The change in crystal structure, Raman spectroscopy, and 3D fluorescence spectra showed that heat treatment resulted in the unfolding of yolk proteins, especially plasma proteins. Xylitol could alleviate transformation of components by stabilizing protein structure, alleviating the damage in protein integrity and elevation in aggregation size.

Structure and surface properties of ozone-conjugated octenyl succinic anhydride modified waxy rice starch: Towards high-stable Pickering emulsion

In the present work, a dual-modified waxy rice starch (OOWRS) fabricated with OSA and ozone was successfully used to stabilize the O/W Pickering emulsion. The molecular structure, surface properties, and underlying stabilizing mechanism were systematically investigated. The results showed that oxidation occurring on the surface of OSA-modified waxy rice starch (OSAWRS) resulted in the presence of indentations and cracks. The relative crystallinity of starch was generally decreased with increasing degree of oxidation. Due to the introduction of carbonyl and the variation in surface structure, the hydrophobicity and acidity of OSAWRS were significantly enhanced after the ozone treatment. Remarkably, OOWRS stabilized Pickering emulsion exhibited a feature of typical O/W emulsion, and the 0.5 h and 1 h OOWRS emulsion exhibited a more uniform droplet size as well as a higher surface potential. We also noted that a weak-gel network was formed within the OOWRS emulsion system as the hydrophilic starch chains played a bridging role. Two reasons for the improved stability of the emulsion were the special gel structure and the enhanced electrical repulsion among the droplets. This research provides that ozone-conjugated OSA modification is a promising strategy for improving the emulsion ability of starch-based Pickering emulsions.

A new insight into the influence of pH on the adsorption at oil-water interface and emulsion stability of egg yolk protein

This study investigated the impact of varied pH treatments on the structural, emulsification, and interfacial adsorption properties of egg yolk. The solubility of egg yolk proteins decreased and then increased in response to pH changes, with a minimum value (41.95 %) observed at pH 5.0. The alkaline condition (pH 9.0) significantly impacted the secondary/tertiary structure of egg yolk, with the yolk solution displaying the lowest surface tension value (15.98 mN/m). Emulsion stability was found to be optimal when egg yolk was used as the stabilizer at pH 9.0, which corresponded to the more flexible diastolic structure, smaller emulsion droplets, increased viscoelasticity, and enhanced resistance to creaming. At pH 9.0, proteins exhibited a maximum solubility (90.79 %) due to their unfolded conformation, yet the protein adsorption content at the oil-water interface showed relatively low (54.21 %). At this time, electrostatic repulsion between the droplets and the spatial site barrier made by proteins that were unable to efficiently adsorb at the oil-water interface kept the emulsion stable. Moreover, it was found that different pH treatments could effectively regulate the relative adsorption contents of various protein subunits at the oil-water interface, and all proteins except livetin displayed good interfacial adsorption capacity at the oil-water interface.

A Novel Approach for the Production of Mildly Salted Duck Egg Using Ozonized Brine Salting

Salted eggs are normally produced by treating fresh duck eggs with a high salt concentration in order to acquire distinctive features and excellent preservation capabilities as a result of a series of physicochemical changes. This method, however, induces a high salt content in the product. The goal of this research was to create a new way of producing mildly salted duck eggs using ozonized brine salting. The brine was made by dissolving NaCl (26% w/v) in water or ozonized water at a concentration of 50 ng ozone/mL (ozonized brine). Compared to brine, ozonized brine resulted in salted eggs with reduced ultimate salt levels in both albumen and yolk (p < 0.05). The Haugh unit of the salted eggs generated by ozonized brine was similar to that of the brine-made salted egg group (p > 0.05), but the salted egg produced by ozonized brine matured and solidified faster because the yolk index (0.62) was higher than that of the brine (0.55) (p < 0.05). The final pH of salted eggs generated with brine and ozonized brine was not different (p > 0.05). Regardless of the salting method, both salted eggs contained low TVB-N content (<10 mg/100 g). Ozonized brine increased the protein carbonyl content in salted albumen, which may be related to albumen protein aggregation and served as a salt diffusion barrier. However, after boiling the salted egg, the protein carbonyl level was comparable to that of fresh albumen. The TBARS levels of boiled salted albumen prepared with brine and ozonized brine were comparable (p > 0.05), and the value was extremely low (~0.1 mg MDA equivalent/kg). The TBARS value of the salted yolk prepared with brine was higher than that of the salted yolk prepared with ozonized brine (p < 0.05), and both salted yolks showed increased TBARS values after cooking (p < 0.05). The albumen and yolk components appeared to be altered similarly by both brine and ozonized brine, according to the FTIR spectra. Furthermore, the appearance and color of the yolk and albumen in salted eggs prepared with brine and ozonized brine were comparable. Boiled salted albumen produced with ozonized brine had a denser structure with fewer voids. This could be attributed to the final salted egg's lower salt content and lower salt diffusion rate, which were likely caused by protein oxidation and, as a result, aggregation when ozonized brine was used.

An Efficient Processing Strategy to Improve the Flavor Profile of Egg Yolk: Ozone-Mediated Oxidation

This study investigated the effect of ozone treatment on egg yolk volatiles and fatty acids. The composition and content of volatile substances and the fatty acid content of the egg yolk were changed significantly after ozonation. With proper ozone treatment (30 min), the aldehyde content in the egg yolk increased from 78.08% to 94.63%, and the relative content of dibutyl amine decreased from 1.50% to 0.00%. There were no significant differences among the types of fatty acids in the egg yolks after being treated with ozone, but there were differences in their relative contents. The results of SDS-PAGE showed no significant difference in yolk protein composition and contents among the groups. SEM results showed that moderate ozone treatment (20 min and 30 min) led to a regular and dense network structure of egg yolk. These results provided a theoretical basis for expanding the application of ozone technology in the egg yolk processing industry.

Advances, Applications, and Comparison of Thermal (Pasteurization, Sterilization, and Aseptic Packaging) against Non-Thermal (Ultrasounds, UV Radiation, Ozonation, High Hydrostatic Pressure) Technologies in Food Processing

Nowadays, food treatment technologies are constantly evolving due to an increasing demand for healthier and tastier food with longer shelf lives. In this review, our aim is to highlight the advantages and disadvantages of some of the most exploited industrial techniques for food processing and microorganism deactivation, dividing them into those that exploit high temperatures (pasteurization, sterilization, aseptic packaging) and those that operate thanks to their inherent chemical–physical principles (ultrasound, ultraviolet radiation, ozonation, high hydrostatic pressure). The traditional thermal methods can reduce the number of pathogenic microorganisms to safe levels, but non-thermal technologies can also reduce or remove the adverse effects that occur using high temperatures. In the case of ultrasound, which inactivates pathogens, recent advances in food treatment are reported. Throughout the text, novel discoveries of the last decade are presented, and non-thermal methods have been demonstrated to be more attractive for processing a huge variety of foods. Preserving the quality and nutritional values of the product itself and at the same time reducing bacteria and extending shelf life are the primary targets of conscious producers, and with non-thermal technologies, they are increasingly possible.