Rheological properties and fluid dynamics of egg yolk

Effects of konjac glucomannan on physicochemical and rheological properties of whole egg liquid and in vitro fermentation of egg curd

The mixture of proteins, polysaccharides, and other nutrients not only safeguards the nutritional value of the food but also demonstrates superior performance compared to these nutrients when used individually. This study aimed to investigate the effects of konjac glucomannan (KGM) on the properties of whole egg liquid (WEL) and the in vitro fermentation of egg curd (made by the mixture of WEL/KGM). The results revealed that the foaming ability (FA) of the mixture decreased, while the foam stability (FS), emulsifying activity (EA), and emulsion stability (ES) of the mixture increased with increasing concentrations of KGM. The concentration of KGM had a significant effect on the sol-gel transition temperature of WEL. Compared to the fermentation broth of E group (without KGM), KGM decreased the pH from 6.65 to 6.16, free ammonia content from 87.53 μg/g to 72.21 μg/g, and sulfide concentration from 580 μg/L to 470 μg/L in the WEL/KGM mixture (EK group). Moreover, KGM slowed down the gas production of intestinal protein fermentation within 10 h, without affecting the final total gas yield. These findings suggest that adding KGM can be an effective strategy to modify the properties of WEL and improve the intestinal fermentation performance of protein-rich foods.

Rheological and Flow Behaviour of Yolk, Albumen and Liquid Whole Egg from Eggs of Six Different Poultry Species

Liquid egg products are one of the basic raw materials for the food industry. Knowledge of their rheological and flow behaviour in real technical elements is absolutely necessary for the selection of suitable technological equipment for their processing. In this article, the rheological properties of liquid egg products were determined. Eggs from six different species of poultry are used: domestic hen (Gallus gallus domesticus) hybrid Hisex Brown; Japanese quail (Coturnix japonica); German carrier goose (Anser anser f. domestica); domestic ducks (Anas platyrhynchos f. domestica); domestic guinea fowl (Numida meleagris f. domestica); and domestic turkeys (Meleagris gallopavo f. domestica). Liquid egg products showed pseudoplastic behaviour in range of shear strain rates from 0.2 up to 200 s⁻¹ and at the temperature of 18 °C. Thus, the flow curves were constructed using the Ostwald-de Waele rheological model, with respect to the pseudoplastic behaviour of liquid egg products. According to the values of the coefficients of determination (R²), the sum of squared estimate of errors (SSE) and the root mean square error (RMSE), this model was appropriately chosen. Using the consistency coefficient K, the flow index n and the adjusted equations for the flow rate of technical and biological fluids in standard pipelines, the 3D velocity profiles of liquid egg products were successfully modelled. The values of the Reynolds number of the individual liquid egg products were calculated, and the type of flow was also determined. A turbulent flow has been detected for some liquid egg products.

Experimental study of physical and rheological properties of grape juice using different temperatures and concentrations. Part I: Cabernet Sauvignon

The effect of the temperature and concentration on rheological behavior of Cabernet Sauvignon juice concentrates was assessed using a rheometer over a wide range of temperature (1-66°C) and concentrations (13.6-45.0Brix) at shear rates of 0.84-212.1 1/s. The Ostwald-De Waele was the best rheological model fitted the data (R²=0.99957 and relative error=7.77%). The Cabernet Sauvignon juice concentrates presented a non-Newtonian pseudoplastic behavior (n<1). The consistency levels were significantly reduced with the increase of temperature and increased with the increase of the concentrations. The flow activation energy ranged from 28.87 (45.0Brix) to 38.05KJ/mol (37.0Brix) with a R²=0.9798 for both cases. Density and specific heat were influenced by both temperature and concentration; however, thermal conductivity was only influenced by concentration. The Cabernet Sauvignon juice concentrates will be useful as wine chaptalization agent in future studies.

The quality of eggs (organic and nutraceutical vs. conventional) and their technological properties

The aim of the study was to compare the quality of commercially available eggs: organic (attested organic farm) - OE, nutraceutical (enriched in n-3 fatty acids) - NE, vs. conventional (cage raising system) - CE and their technological (emulsifying) properties. Their basic chemical composition (i.e., moisture, protein, fat, ash) as well as mineral (Na, K, Ca, Mg, Zn, Fe, Mn, Cu) contents were assessed, and fatty acid profiles were determined. Next, the suitability of the eggs for mayonnaise production was assessed.The yolk of organic eggs contained the highest protein (17.7 g/100 g), K (134.7 mg/kg), and Cu (0.15 mg/kg) levels. Meanwhile, the yolk of conventional eggs was the most abundant in Mg (14.6 mg/kg) and Fe (9.05 mg/kg), and the nutraceutical ones - in Ca (109.0 mg/kg) as well as Mn (0.26 mg/kg). Albumen of organic eggs contained the highest level of protein (13.0 g/100 g), whereas the nutraceutical ones contained the highest levels of - ash (1.2 g/100 g), K (150.2 mg/kg), Zn (0.11 mg/kg), and Mn (0.04 mg/kg). Nutraceutical eggs contained a higher amount of n-3 and monounsaturated fatty acids but also smaller saturated fatty acids content. This beneficial fatty acids profile is particularly important from the nutritional point of view. Despite the lack of differences in emulsifying properties among the studied eggs, the mayonnaises prepared on the basis of the nutraceutical eggs showed better stability. This attribute is very important for both the producer (during product transport) and the consumer (during dish preparation).

Reducing Risk of Salmonellosis through Egg Decontamination Processes

Eggs have a high nutritional value and are an important ingredient in many food products. Worldwide foodborne illnesses, such as salmonellosis linked to the consumption of eggs and raw egg products, are a major public health concern. This review focuses on previous studies that have investigated the procedures for the production of microbiologically safe eggs. Studies exploring pasteurization and decontamination methods were investigated. Gamma irradiation, freeze drying, hot air, hot water, infra-red, atmospheric steam, microwave heating and radiofrequency heating are all different decontamination methods currently considered for the production of microbiologically safe eggs. However, each decontamination procedure has different effects on the properties and constituents of the egg. The pasteurization processes are the most widely used and best understood; however, they influence the coagulation, foaming and emulsifying properties of the egg. Future studies are needed to explore combinations of different decontamination methods to produce safe eggs without impacting the protein structure and usability. Currently, eggs which have undergone decontamination processes are primarily used in food prepared for vulnerable populations. However, the development of a decontamination method that does not affect egg properties and functionality could be used in food prepared for the general population to provide greater public health protection.

Effect of storage duration on the rheological properties of goose liquid egg products and eggshell membranes

In practice, goose eggs are increasingly used and, therefore, the rheological properties have to be known for processing. The eggs of geese (Landes Goose, Anser anser f. domestica) were stored for one, 2, 3, 4, 6, and 8 wk at a constant temperature 4°C. First of all, the egg quality parameters were described in terms of egg weight, egg weight loss, egg shape index, yolk height, albumen height, yolk index, albumen index, and Haugh units. In the next step the rheological behavior of liquid egg products (egg yolk, albumen, and whole liquid egg) was studied using a concentric cylinder viscometer. Flow curves of all liquid egg products exhibited non-Newtonian shear thinning behavior. This behavior can be described using the Herschel-Bulkley model and for technical application using the Ostwald-de Waele model. The effect of the storage duration on the rheological behavior is different for the different liquid egg products. With the exception of very low shear rates, the viscosity of the egg yolk as well as of the whole liquid egg decreases with storage time. At lower shear rates there is a tendency toward increased albumen viscosity with storage duration. The storage duration also affects the mechanical properties of the eggshell membrane. This effect has been evaluated in terms of the ultimate tensile strength, fracture strain, and fracture toughness. All these parameters increased with the loading rate, but decreased during the egg storage. These mechanical phenomena should be respected, namely in the design of the egg model for the numerical simulation of the egg behavior under different kinds of the mechanical loading.

Effect of ethanol, dry extract and reducing sugars on density and viscosity of Brazilian red wines

BACKGROUND

Density and viscosity are properties that exert great influence on the body of wines. The present work aimed to evaluate the influence of the alcoholic content, dry extract, and reducing sugar content on density and viscosity of commercial dry red wines at different temperatures. The rheological assays were carried out on a controlled stress rheometer, using concentric cylinder geometry at seven temperatures (2, 8, 14, 16, 18, 20 and 26 °C).

RESULTS

Wine viscosity decreased with increasing temperature and density was directly related to the wine alcohol content, whereas viscosity was closely linked to the dry extract. Reducing sugars did not influence viscosity or density. Wines produced from Italian grapes were presented as full-bodied with higher values for density and viscosity, which was linked to the higher alcohol content and dry extract, respectively.

CONCLUSION

The results highlighted the major effects of certain physicochemical properties on the physical properties of wines, which in turn is important for guiding sensory assessments.

Fluid dynamics of liquid egg products

The rheological behavior of liquid egg products (egg yolk, egg white, and whole liquid egg) was studied using a concentric cylinder viscometer. Eggs of three poultry specimens were used: hen (Isa Brown), Japanese quail (Coturnix japonica), and goose (Anser anser f. domestica). Rheological behavior was pseudoplastic and flow curves fitted by the power law model (Herschel-Bulkley and Ostwald-De Waele). The meaning of rheological parameters on friction factors and velocity profiles during flow of liquid egg products in tube has been shown.