In addition, eggs are low in saturated fat. As a result, their effect on blood cholesterol levels is likely to be clinically insignificant. What are some natural ways to reduce cholesterol? The USDA grade eggs that meet their standards. In order for them to grade eggs as free-range, for example, the eggs must come from hens with:.
One study found that organic eggs from hens with the freedom to choose their own food had higher levels of certain nutrients than eggs from caged hens. The organic eggs had significantly higher levels of protein, potassium , and copper. Another study , published in , found that hens that could roam outside in the sunlight produced eggs that contained 3—4 times as much vitamin D-3 as eggs from hens kept indoors.
The researchers suggest that allowing hens to roam may be an alternative to fortifying eggs with vitamin D. Eggs are a versatile food, and many people enjoy them fried, boiled, scrambled, or baked. They are easy to incorporate into a diet. Boiled or poached eggs , for example, are simple to make and contain no added fat.
Sprinkle pepper, chili powder, or sumac on the eggs for added flavor. Plain boiled eggs can be a good snack or a meal for a person with digestive problems or someone who is recovering from an illness. Huevos rancheros is a Latin favorite that involves an egg on a base of tomato, with herbs and other flavorings. Try this recipe. For a healthful omelet or scrambled eggs , use vegetable oil and add onion , herbs, garlic, peas, and sweetcorn for extra nutrition.
Bacteria : Raw or undercooked eggs can contain bacteria, which can enter through pores in the shells. In the U. Allergies : Some people have an egg allergy or sensitivity. A person with an allergy may experience a life threatening reaction from coming into contact with eggs or egg products.
It is important for people with allergies to remember that baked goods often contain some egg, possibly as a powder. Check ingredients lists carefully. A person with an allergy may also need to note whether a product is made in a facility that uses eggs, as trace amounts can trigger severe reactions in some people.
Pasteurization: In the U. Buying and using: Do not purchase eggs that have cracked shells or are past their expiration date. Storage: Store eggs in the refrigerator. According to the USDA , eggs can sweat at room temperature, making it easier for bacteria to enter the shells and grow. What is salmonella, and why does it matter?
Some people do not eat eggs, such as people following a vegan diet. A wide variety of vegan egg alternatives are available. During RF heating, the product to be heated forms a "dielectric" between two metal capacitor plates electrodes Figure 4 , which are alternately charged positively and negatively by a high electric current field [ 30 ].
Schematic representation of the RF heating process. Source: Marra et al. RF heating is a promising application in food processing, due to the rapid and uniform spread of heat, better penetration, and low energy consumption.
The more transparent is the product investigated and pasteurized, and the more efficient is the decontamination [ 30 , 32 ]. The immersion of the eggs in deionized water combined with the RF focused on the egg yolk and surface cooling showed a high security potential from the microbiological point of view [ 33 ]. After that, the egg was again heated for another 20 min with water at Performing this two-step process, with a total duration of The combination of the RF and hot water method was faster than the existing commercial process, using only hot water [ 34 ].
However, there is a disadvantage of RF, if it is not uniform, it can be observing the formation of coagulation rings around the egg air cell, thus damaging the decontamination process due to the impact on product quality [ 35 ]. Dehydration is a successful method of preserving eggs, it presents the advantages as follows: occupies less space in stock, provides ease of transport, good uniformity, easier use ready-to-use product , and presents stable microbiological quality [ 36 ].
One of the main procedures used to dehydrate egg and turn it into powder is the freeze-drying or cryodesiccation method. A freeze-dryer or lyophilizer is used for the process of freeze-drying; it consists of a vacuum chamber, a heat source, a condenser, and a vacuum pump Figure 5.
The main function of the vacuum chamber where the food is contained is to resist the differences in pressure so the ice melting does not occur, and the pump helps to maintain this difference by removing noncondensable gases. The heat source is responsible for producing the energy that will evaporate the ice and is the type of source that determines the type of freeze-dryer used. The condenser retains moisture from the food and prevents its increase from inside the chamber and returning to the food [ 15 ].
Main components of the freeze-dryer. Source: Cunha et al. By going through the freeze-drying process, the egg and its products retain the sensory characteristics and the nutritional quality, because the temperature is not too high.
In addition, they have an extended shelf life when packaged correctly. The main alteration that occurs in egg composition is the alteration in the quaternary and tertiary structures of the proteins. After water removal, changes occur in these structures due to exposure of the hydrophobic parts of the protein, previously protected inside the tertiary and quaternary structures, due to nonaffinity with water.
The nutritional content and aroma of the eggs do not present significant changes. In addition, with the removal of water, preservation of egg powder is maintained, due to the low humidity, which reduces microbial proliferation [ 15 , 37 ]. The main disadvantages of this method is that eggs may be susceptible to oxidation reactions lipids, carotenoids, fat-soluble vitamins, and aromatic substances if not packed into a vacuum, oxygen-impermeable, and opaque packaging [ 37 , 39 ].
The freeze-drying process is time-consuming and may last up to 48 hours, depending on the batch size and the units to be processed, increasing the cost of the process.
In addition, the freeze-dryer is a costly equipment [ 37 , 40 ]. Considering that microorganisms are naturally present in any raw food, there are concerns regarding egg contamination. In addition, eggs are an ideal growth medium for pathogenic bacteria that are dangerous to humans Salmonella, Escherichia, and Enterobacter [ 41 ]. Pasteurization techniques are used to prolong shelf life and maintain the quality of egg products.
However, thermal techniques can have negative impact on the functional properties of this food, in the amount of nutrients, taste, and texture. Although heat processes used in egg pasteurization can ensure food safety by eliminating heat-sensitive pathogens, some heat-resistant microorganisms can survive the process, spoiling the product even under refrigerated conditions [ 42 , 43 ].
In this way, new techniques are being developed and applied in the food industry. New preservation technologies are an interesting option for producing high-quality food and extend its shelf life [ 44 ]. These technologies present a moderate impact on the sensory profile and quality attributes of the processed foods such as flavor, color, aroma, and nutrients , giving food producers the opportunity to offer safe and high-quality food.
However, emerging techniques in the egg industry must be further studied, so they can be considered a successful processing and thus produce on a commercial scale. In this way, advantages and safety are provided not only to industry, but also to supermarkets and consumers [ 15 , 45 ]. New food processing technologies include the use of physical factors to process and preserve food [ 46 ].
Among the new technologies, high hydrostatic pressure HHP , pulsed electric fields PEF , treatment with ozone, ultraviolet light UV , and gamma radiation are nonthermal technologies with application in eggs and egg products. The application of HHP technology has attracted the interest of the food industry due to its microbial destruction capacity at very low or moderate temperatures, the preservation of bioactive nutrients, the improvement of the extraction of bioactive compounds, and the reduction of the allergenic potential of foods, such as eggs [ 47 ].
The HHP technology applies high pressures usually in the range of and MPa with or without heat treatments, in order to eliminate different microorganisms and to guarantee the microbiological safety of the final product. This process is operated on a batch system, usually using water as a pressure transmission medium. The food products are packaged, loaded into the pressure vessel, and then pressurized by water [ 47 , 48 ]. The HHP equipment is generally made of high-strength steel alloys, making it resistant to oxidation and rupture.
HHP mainly is applied on batch equipment; however, semicontinuous systems are available. Generally, an HHP batch equipment consists of a pressure vessel thick wall cylinder , two covers that close the pressure vessel, a yoke which controls the closing cover under the pressure condition, a pump and intensifier to create high pressure, and a process control system for loading and unloading the products [ 43 ].
An HHP batch system can be used for liquid and solid foods, while a semicontinuous HHP process can be used only for pumpable foods. During the process, the food is packed, sealed, and loaded into a sample basket.
The packaging shall consist of flexible materials, which will resist to pressurization. The sample baskets then enter the pressure vessel, which contains the pressure transmitting fluid.
Water is usually used as pressure transmitting fluid on industrial scale equipment. The pump and the intensifier provide a desired pressure by compression of the pressure transmitting fluid. Thereafter, the product is maintained under the right time and pressure to achieve the desired treatment. At the end of the treatment, the vessel is depressurized and the product is unloaded from the sample basket [ 42 , 43 ]. The application of heat combined with HHP can cause physical, chemical, or biological changes on the food product.
These changes depend on the applied pressure, treatment time, and temperature and can include protein denaturation, changes in enzyme activities [ 42 ].
Many attempts have been made to verify if the HHP technique can be used as a substitute for thermal pasteurization, and to identifying the structural changes in the components of the egg as a result of the high pressure [ 44 ].
This technique has been evaluated as an alternative to methods already used for liquid eggs, and it has been verified that the processing conditions must be well studied, as this can cause a protein coagulation [ 45 ]. It has also been reported that pressure-induced protein denaturation may occur in eggs due to the entry of water into wells of the protein molecule [ 46 ]. However, HHP at a pressure between and MPa did not cause detectable protein denaturation in liquid eggs [ 47 ].
Other research has shown that HHP treatment on liquid eggs is a successful preservation opportunity. The application of Mpa for a 2 minutes cycle in boiled eggs was able to extend the shelf life of these products during refrigeration [ 49 ]. HHP present important advantages for food processing, the fact that this technology does not produce deterioration of thermolabile nutrients such as vitamins and does not alter low molecular weight compounds, fundamentally those responsible for flavor and aroma.
The high pressure does not favor the Maillard reaction or enzymatic browning; thus, it does not alter the natural flavor or color of the food [ 50 , 51 ]. The application of HHP causes a number of changes in the morphology, cell membrane and biochemical reactions of microorganisms, and all these processes are related to microbial inactivation.
In particular, the cell membrane is considered the main target for inactivation of microorganisms induced by pressure, and it is generally accepted that leakage of intracellular constituents across the permeabilized cell membrane is the most direct reason for cell death by high-pressure treatment [ 50 , 52 ]. Research shows, in addition to the applied pressure level and treatment time, the critical parameters for microbial inactivation are pH, water activity aw , and treatment temperature: a microorganisms become more susceptible to pressure at lower pH [ 53 ]; b water activity reduction exerts a protective effect on microorganisms against high-pressure treatments [ 54 , 55 ]; and c thermal processing with temperatures above or below room temperature tends to increase the rate of inactivation of microorganisms [ 56 ].
The effect of microbiological inactivation on egg products by HHP was reported in a study that showed the low-pressure ranges are used to reduce the microbial load of liquid eggs by 3 log. The study concludes that increased pressure may increase the effectiveness of the treatment and thus lead to the processing of microbiologically safe products [ 57 ]. This technology has great potential for use in food processing, since it is efficient in the elimination of microorganisms, thus providing microbiological safety and increased shelf life, maintaining the nutritional and sensorial characteristics of foods [ 50 ].
Pulsed electric field PEF , or high-intensity electric field HELP , is one of the nonthermal processing technologies of interest to scientists and the food industry; it is new and alternative method for preserving liquid foods. In addition, it is a promising alternative to traditional heat treatments, which presents good results, not only by enabling the destruction of microorganisms and the inactivation of enzymes, but also by maintaining the flavor, color, texture, vitamins and not only by enabling the destruction of microorganisms and the inactivation of enzymes, but also by maintaining the flavor, color, texture, vitamins, and functional thermolabile components [ 58 ].
Food processing by applying PEF involves subjecting the product to repeated electric fields constituting the number of pulses for short time intervals microseconds in order to inactivate enzymes and destroy microorganisms [ 59 ]. This method uses high voltage pulses on a treatment chamber containing food between two electrodes.
The high electric intensity is acquired by accumulating a large amount of energy in a condenser, which supplies and discharges the energy in the form of pulses, for short periods of time, uniformly and with a minimum increase of temperature [ 60 , 61 ]. Figure 6 shows two types of treatment chambers used in the PEF process.
Types of treatment chambers used in the PEF process. Source: Fani [ 62 ]. The PEF technology can be one of the most suitable methods for liquid food processing. In the last years, the technology received considerable attention from scientists, governments and interested industries as a potential technique to be fully expanded in the future year [ 45 ].
Research shows that PEF technology has been used successfully to pasteurize foods such as dairy products, a variety of fruit juices, liquid eggs, and creamy soups [ 63 ]. The application of PEF in the control of spoilage or pathogenic microorganisms in different egg products has been highlighted. It has been reported that this method effectively reduces the activity of numerous microorganisms in egg products [ 64 ].
Liquid egg is widely used by the food industry and other commercial food manufacturers due to the convenience, ease of handling, and longer shelf life compared to shell eggs. Egg is a polyfunctional ingredient because of its thickening, gelling, emulsifying, foaming, coloring, and flavoring attributes, which can be used to modify the organoleptic and technological properties of many food products.
In addition, liquid egg products are also valuable because of their high-quality protein content and low cost [ 65 , 66 ]. Although thermal treatments represent the most available pasteurization methods for liquid eggs, they can affect their functional properties and degrade the quality of the products. Thus, the application of PEF, as a nonthermal food processing technology, might be an alternative to conventional thermal preservation methods. Combined methods with PEF, such as homogenization, show a great potential to preserve the liquid egg with small modifications of its native color, viscosity, and foaming capacity [ 45 ].
Microbial inactivation by electrical pulses depends on several factors that are critical to treatment efficacy. These factors can be classified by process parameters pulse intensity, treatment time, and temperature , product attributes pH, ionic compounds, and conductivity , and characteristics of microorganisms type, concentration, and growth stage [ 67 ]. Gram-positive bacteria are more resistant to electrical pulsed treatment than Gram-negative bacteria; this factor may be due to the rigidity of the peptidoglycan layers present in its cell wall.
Due to their larger size, fungi are more sensitive to this treatment than bacteria [ 68 ]. The exposure of a biological cell to a high-intensity pulsed electric field leads to a phenomenon of membrane permeabilization.
This leads to pore formation, which is reversible if the electric field is below a certain critical value and for a short period of time. This phenomenon is called electroporation and is used in genetic engineering. McKee S. Close Menu. Can you freeze eggs? Shell Eggs U. Egg Products U.
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