Studies on foaming and physicochemical properties of egg white during cold storage

Supercritical carbon dioxide treatment improves the functional properties of pea protein: Application in eggless cakes

The use of plant proteins in food matrices is often limited due to inferior functional properties. Modification of proteins by supercritical carbon dioxide (scCO2) has gained attention in this regard as a safe, chemical-free, and sustainable technique. The present work explores the impact of process parameters of scCO2 modification of pea proteins on its structural and functional properties. This treatment induced the unfolding of protein structure as seen from an increase in intrinsic fluorescence and surface hydrophobicity, altered the secondary structure, and increased the free sulfhydryl groups. The scCO2 treatment positively affected the water and oil absorption capacities and enhanced the emulsifying and foaming capacity and stability. However, the rheological and film-forming properties of scCO2-modified protein were detrimentally affected at 350 bar. scCO2 modified pea proteins (250 bar/45 °C/60 min) revealed a uniform pore size distribution throughout the eggless cake matrix with sensory scores (7.34) comparable to that containing egg (7.59).

Technical-functional and surface properties of white common bean proteins (Phaseolus vulgaris L.): Effect of pH, protein concentration, and guar gum presence

Legumes are abundant sources of proteins, and white common bean proteins play an important role in air-water interface properties. This study aims to investigate the technical-functional properties of white common bean protein isolate (BPI) as a function of pH, protein concentration, and guar gum (GG) presence. BPI physicochemical properties were analyzed in terms of solubility, zeta potential, and mean particle diameter at pH ranging from 2 to 9, in addition to water-holding capacity (WHC), oil-holding capacity (OHC), and thermogravimetric analysis. Protein dispersions were evaluated in terms of dynamic, interfacial, and foam-forming properties. BPI showed higher solubility (>80 %) at pH 2 and above 7. Zeta potential and mean diameter ranged from 15.43 to -34.08 mV and from 129.55 to 139.90 nm, respectively. BPI exhibited WHC and OHC of 1.37 and 4.97 g/g, respectively. Thermograms indicated decomposition temperature (295.81 °C) and mass loss (64.73 %). Flow curves indicated pseudoplastic behavior, with higher η100 values observed in treatments containing guar gum. The behavior was predominantly viscous (tg δ > 1) at lower frequencies, at all pH levels, shifting to predominantly elastic at higher frequencies. Equilibrium surface tension (γeq) ranged from 43.87 to 41.95 mN.m-1 and did not decrease with increasing protein concentration under all pH conditions. All treatments exhibited ϕ < 15°, indicating predominantly elastic surface films. Foaming properties were influenced by higher protein concentration and guar gum addition, and the potential formation of protein-polysaccharide complexes favored the kinetic stability of the system.

Underlying mechanisms of egg white thinning in hot spring eggs during storage: Weak gel properties and quantitative proteome analysis

As a weakly gelling protein, hot spring egg white underwent thinning during storage. This study explored the mechanism of thinning in hot spring egg white from the perspective of "gel structure and protein composition" using quantitative proteomics, SEM, SDS-PAGE, and other techniques. Quantitative proteomics analysis showed that there were 81 (44 up-regulated and 21 down-regulated) key proteins related to thinning of hot spring egg white. The changes in the relative abundance of proteins such as ovalbumin-related Y, mucin-6, lysozyme, ovomucoid, and ovotransferrin might be important reasons for thinning in hot spring egg white. SEM results indicated that the gel network gradually became regular and uniform, with large pores appearing on the cross-section and being pierced. Along with the decrease in intermolecular electrostatic repulsion, protein molecules gradually aggregated. The particle size gradually increased from 139.1 nm to 422.5 nm. Meanwhile, the surface hydrophobicity, and disulfide bond content gradually increased. These changes might be the reasons for thinning in hot spring egg white during storage. It can provide a new perspective for studying the thinning mechanism of weakly gelling egg whites.

Quantitative proteomic analysis of chicken egg white and its components

The protein profiles and properties of chicken egg white and its three components (thick egg white, TKEW; thin egg white, TNEW; and chalaza, CLZ) were comprehensively compared. The proteomes of TNEW and TKEW are relatively similar, but the abundance of mucin-5B and mucin-6 (the two subunits of ovomucin) is significantly higher in TKEW than in TNEW (42.97% and 870.04%, respectively), while the lysozymes in TKEW are 32.57% higher (p < 0.05) than those in TNEW. Meanwhile, the properties (including the spectroscopy, viscosity, and turbidity) of TKEW and TNEW are significantly different. Comprehensively, it is speculated that the electrostatic interactions between lysozyme and ovomucin are the main reason for the high viscosity and turbidity of TKEW. Compared with egg white sample (EW), CLZ has a higher abundance of insoluble proteins (mucin-5B, 4.23-fold; mucin-6, 6.89-fold) and a lower abundance of soluble proteins (ovalbumin-related protein X, 89.35% lower than EW; ovalbumin-related protein Y, 78.51% lower; ovoinhibitor, 62.08% lower; riboflavin-binding protein, 93.67% lower). These compositional differences should explain the insolubility of CLZ. These findings are important references for deepening the research and development of egg white in the future, such as the thinning of egg white, the molecular basis of changes in egg white properties, and the differential application of TKEW and TNEW.

Energy efficient drying technologies for sweet potatoes: Operating and drying mechanism, quality-related attributes

Sweet potatoes (SPs) are a versatile tuberous crop used as subsistence and cash crop in raw and processed forms. The major issue with SPs is post-harvest losses, which result in noticeable quality decline because of inappropriate handling, storage, delayed transit, and sales, as well as microbiological and enzymatic activity. Drying is an excellent strategy for managing short postharvest storage life, preserving nutrients, and maximizing long-term benefits. However, several parameters must be considered before drying SPs, such as relative humidity, temperature, drying duration, size, and shape. The current review looks at the factors influencing SPs' moisture loss, drying kinetics, diverse drying methods, pretreatments, operating conditions, and their efficacy in improving the drying process, functional, and nutritional qualities. An optimal drying process is required to preserve SPs to obtain concentrated nutrients and improve energy efficiency to be ecofriendly. Drying sweet potatoes using traditional methods such as sun or open-air drying was found to be a slow process that could result in a lower quality. Various advanced drying techniques, like vacuum, infrared, freeze drying, and pretreatments such as ultrasound and osmotic dehydration, have been developed and are successfully used globally. The best-fit thin-layer models (Hii, Page, two-term, logarithmic) utilized for drying SPs and appropriate modeling methods for optimizing drying procedures are also discussed.

Effects of guar gum or xanthan gum addition in conjunction with pasteurization on liquid egg white

In this study, effects of varying levels of xanthan or guar gum (XG/GG, 0.05%, 0.1%, 0.2%, 0.4% and 0.8%, w/v) on the spatial structure and functional properties of egg white (EW) proteins under different pasteurization conditions of the liquid egg was evaluated. Results showed that XG could bury the aromatic ring residues and reduce the hydrophobicity of protein in EW, whereas GG could only increase the hydrophobicity. With 0.8% GG addition and pasteurization under 60℃/3.5 min, the emulsifying stability of EW was improved by nearly 100%, while with 0.8% XG addition the gel structure of EWwould become porousandloosen under each pasteurization condition. The hardness of EW gels was decreased by 90% when the concentration of XG was 0.4% or 0.8%. According to the results, the concentration of gums and the pasteurization parameters should be considered together when adding gums into the liquid egg products for pasteurization simultaneously.

The Effect of Storage Duration on Some Quality Traits and Composition of Eggs from Different Housing Systems

The effect of storage time at a temperature of 8°C on the direction and dynamics of changes in quality traits of eggs was investigated in shelled table eggs obtained from different egg production systems (cage system – CS, barn system – BS, free-range system – FRS). After 7, 14 and 28 d of storage, eggs from each housing system were tested for physical characteristics and for cholesterol content and fatty acid profile in the yolk. The weight of eggs from all studied housing systems declined with storage duration. The rate of weight loss was smallest in eggs from CS (P<0.05). Storage duration influenced eggshell traits but the rate and direction of these changes did not differ among the studied housing systems. Albumen height and Haugh unit score for eggs from rearing systems under study declined during storage (P<0.05). The greatest reduction of albumen height (18.85%) after the storage period was observed for CS eggs and the lowest (13.24%) for FRS eggs (P<0.05). No effect of storage duration on yolk colour intensity was observed for eggs from all the studied housing systems (P>0.05). Albumen pH increased with storage duration in eggs from all the egg production systems (P<0.05). The increase in the yolk pH during storage was the highest in FRS eggs and the lowest in the CS eggs. The storage duration of eggs from the different housing systems did not significantly influence albumen foaming capacity but adversely affected foam stability. There was no impact of storage duration of eggs from different housing systems on cholesterol content in the yolk. Eggs obtained from the different housing systems showed diverse fatty acid profiles in the yolk but this parameter did not significantly change during storage (P>0.05).

Determination of residual enrofloxacin in eggs due to long term administration to laying hens. Analysis of the consumer exposure assessment to egg derivatives

The use of the antibiotic enrofloxacin (ENR) in poultry is controversial. A high-performance liquid chromatography coupled to fast-scanning fluorescence detection (HPLC-FSFD) method for the determination of ENR in egg white, egg yolk, and lyophilized samples was developed. In a first analysis, the long-term administration of ENR (100 days) to laying hens was carried out to determine its presence in egg white, yolk, or both. The predominance of ENR was observed in egg white and variations in the weight of egg white and eggshell was evidenced, showing a potential problem in the industry. Eventually, the presence of ENR was confirmed in commercial lyophilized egg white samples in concentration values around 350 µg kg^-1. The consumer exposure assessment was estimated for children, adolescents, and adults. The result displayed that, in an intake of lyophilized egg white with food-producing animals, the %ADI exceeds 100%, showing toxicological levels.

Changes in microbial, physiochemical, and functional properties of pasteurized liquid whole egg during refrigerated storage

BACKGROUND

Liquid eggs have the advantages of high hygiene security, easy use, and convenient transportation, but their shelf life is only limited to 2~3 weeks. The microbial, physiochemical, and functional properties of pasteurized LWE were investigated in this study to evaluate the quality of pasteurized liquid whole egg (LWE) during refrigerated storage.

RESULTS

The tested shelf life of the pasteurized LWE was 16 days when stored at 4 °C. During refrigerated storage, Pseudomonas gradually became the dominant bacterium in LWE following lactic acid bacteria, although the initial number of Pseudomonas after pasteurization was relatively limited (< 10 CFU mL^-1 ). A total of 23 strains, including six Pseudomonas strains, were obtained. The pH of pasteurized LWE decreased with the growth of microorganisms, while the content of total volatile basic nitrogen (TVB-N) increased curvilinearly. The average particle size increased almost continuously until the sample reached its shelf life. The functional properties of pasteurized LWE were also reduced after a week of refrigerated storage at 4 °C when the microorganisms in pasteurized LWE entered an exponential growth period and the TVB-N content of pasteurized LWE reached its first peak.

CONCLUSION

During refrigerated storage, Pseudomonas was the dominant bacterium in LWE next to lactic acid bacteria. After a week of refrigerated storage at 4 °C, the particle size of LWE increased, while the functional properties of LWE reduced. This study provides a basis for extending the shelf life of liquid egg products in future research. © 2020 Society of Chemical Industry.