Pasteurization & Homogenization of Liquid Egg
Liquid egg products (whole eggs, egg whites, yolks) must be pasteurized to ensure food safety. Ultrasonic homogenizers deliver intense cavitation and high shear forces to kill microbes. Especially when combined with elevated temperatures (∼50°C) and pressure (mano-thermosonication), power ultrasound delivers exceptional pasteurization results. Ultrasonic food processing systems are widely used to fulfil homogenization, pasteurization and sterilization applications.
Liquid whole egg, egg white, yolk, and other blended egg products are pasteurised to ensure that no bacteria / pathogens are in the product. Microbial inactivation via pasteurization is an very important process step to prevent spoilage and food-borne illness. Conventional pasteurization is achieved by a heat treatment of the liquid egg product. However, such heat treatment affects proteins, texture and egg functionalities.
Ultrasonic pasteurization is a very effective and efficient pasteurization alternative.
Liquid egg products can be efficiently pasteurized by mano-thermosonication (MTS) where ultrasonic pasteurization is combined with heat treatment (approx. 50°C) and elevated pressure (approx. 1 barg). Under these synergetic processing conditions, a reliable bacterial reduction of 5log can be achieved. Mano-thermosonication improves the killing rate of microbes significantly: First, the sensitivity of most microorganisms to the ultrasonic treatment is significantly increased by temperatures over 50°C. Secondly, intensity and destructiveness of ultrasonic cavitation rises under elevated pressure.
The synergetic effects combined in manothermosonic pasteurization excels conventional heat pasteurization of eggs by resulting in a liquid egg product of improved quality. Liquid egg pasteurized by mano-thermosonication shows less protein denaturation, lower flavour loss, improved homogeneity and significantly higher energy-efficiency.
Hielscher’s ultrasonic flow cells ensure the passage of the liquid egg product directly through the high-intensity cavitation zone in order to ensure the uniform and complete pasteurization of the liquid egg product.
Egg white consists of approx. 90% water, egg yolk contains approx. 25% fat. Water and oil/fat are immiscible, which means that the phases tend to separate. In order to obtain a homogeneous, stable liquid whole egg product, a sophisticated emulsification method is required to prevent phase separation.
Ultrasonic cavitation and shear delivers the required energy to homogenize the liquid egg product evenly. Powerful sonication prevents phase separation by breaking the fat globules and dispersing water and fat uniformly in order to obtain a stable emulsion.
Ultrasonic cavitation treatment is a superior technique to produce nano-sized emulsions in order to obtain mechanical stability!
- mild process conditions
- pathogen removal
- extended shelf life
- uniform texture
- better nutritional and sensory attributes
- no denaturation
- no coagulation
During ultrasonic homogenization and pasteurization, additives (e.g. sugar, salt, xanthan gum etc.) can be uniformly blended into the liquid egg product.
Hielscher’s ultrasonic homogenizers are also used for production of eggnog (milk+egg-based liquor) to improve mechanical stability and shelf-life.
Ultrasonic Spray-Drying of Powdered Egg
Liquid egg can be further processed into egg powders, e.g. whole egg powder, egg white powder, yolk powder. Egg liquid exhibits shear-thinning behavior. In order to optimize the spray-dring process, ultrasonic viscosity reduction is a highly efficient technique to increase the process capacity of the spray-dryer.
Click here to learn more about the ultrasonically assisted spray-drying process!
Ultrasonic Devices for Food Processing
Ultrasonic food processing systems are well-known and proven for their reliable results in homogenization, extraction, pasteurization and sterilization of food products. Hielscher’s industrial ultrasonic processors create very high amplitudes of up to 200µm in order to deliver the required energy for pasteurization, sterilization and emulsification processes. Of course, our ultrasonic homogenizers are built for 24/7 operation under heavy-duty conditions in industry.
Besides their robustness and reliability, ultrasonic processors require only very low maintenance and are very easy to clean. All parts of the ultrasonic homogenizer, which get in contact with the food product, are made from titanium, stainless steel or glass and are autoclavable. Since every ultrasonic processor has its ultrasonic cleaner in place, they offer automatically CIP (cleaning-in-place) and SIP (sterilizing-in-place).
A small foot print and versability allow for an hassel-free integration of Hielscher’s ultrasonicators into production lines. Retro-fitting into existing lines can be accomplished easily.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:
|Batch Volume||Flow Rate||Recommended Devices|
|10 to 2000mL||20 to 400mL/min||UP200Ht, UP400St|
|0.1 to 20L||0.2 to 4L/min||UIP2000hdT|
|10 to 100L||2 to 10L/min||UIP4000|
|n.a.||10 to 100L/min||UIP16000|
|n.a.||larger||cluster of UIP16000|
- Lee, D.U.; Hein, V.; Knorr, D. (2003): Effects of combination treatments of nisin and high-intensity ultrasound with high pressure on the microbial inactivation in liquid whole egg. Innovative Food Science & Emerging Technologies 2003.
- Nakamura, R.; Mizutani, R.; Yano, M.; Hayakawa, S. (1988): Enhancement of Emulsifying Properties of Protein by Sonicating with Egg Yolk Lecithin. Journal of Agricultural and Food Chemistry 36, 1988. 729-732.
- Raso, J.; Pagán, R.; Condón, S.; Sala, F.J. (1998): Influence of Temperature and Pressure on the Lethality of Ultrasound. Applied and Environmental Microbiology, 64/2, 1998. 465–471.
- Sargolzaei, J.; Mosavian, M.T.H.; Hassani, A. (2011): Modeling and Simulation of High Power Ultrasonic Process in Preparation of Stable Oil-in-Water Emulsion. Journal of Software Engineering and Applications 4, 2011. 259-267.
- Sun, Y.; Yang, H.; Zhong, X.; Wang, W. (2011): Ultrasonic-Assisted Enzymatic Degradation of Cholesterol in Egg Yolk. Innovative Food Science & Emerging Technologies 12/4, 2011. 505-508.
- Suslick, K.S.; Flannigan, D.J. (2008): Inside a Collapsing Bubble: Sonoluminescence and the Conditions During Cavitation. Annu. Rev. Phys. Chem. 59, 2008. 659–83.
Related Research Results
Javad Sargolzaei et al. (2011) modified the application of high power ultrasound in preparation of stable oil-in-water emulsion. All emulsion samples were prepared by using a Hielscher ultrasonic processor UP200H. The effect of pH, ionic strength, pectin, Guar gum, lecithin, egg yolk, and xanthan gum as well as the time of sonication, temperature and viscosity of oil-water mixture on the specific surface area and size of droplets, and creaming index of the emulsion samples was investigated. The experimental data were analyzed with Taguchi method and optimum conditions were determined. In addition, an adaptive neuro-fuzzy inference system (ANFIS) was employed to modeling and categorizes the properties of the resulted emulsion. The results showed that increasing sonication time narrowed the range of droplets size distribution. Pectin and xanthan enhanced the stability of emulsion, although they had different impacts on the emulsion stability when used individually or together. Guar gum improved the viscosity of the continuous phase. Emulsions stabilized by egg yolk were found to be stable to droplet flocculation at pH 3 and at relatively low salt concentrations.
Ultrasonic Degradation of Cholesterol in Yolk
Sun et al. (2011) developed an ultrasonic-assisted enzymatic process of cholesterol degradation in natural egg yolk. They aimed for the catalytic activity of cholesterol oxidase against egg yolk cholesterol with the goal to obtain a cholesterol reduced egg yolk without affecting the major nutrients composition of egg yolk. Cholesterol oxidase was used to catalyze the degradation of cholesterol in egg yolk. Firstly, a 30g portion of the egg yolk was pretreated by ultrasonic for 15min at 200W and then incubated for 10h with cholesterol oxidase concentration of 0.6U/g egg yolk at 37°C. Finally, the cholesterol level in egg yolk was reduced to 8.32% of its original concentration without affecting the quality attributes of the yolk.
Facts Worth Knowing
What is Ultrasonic Cavitation?
Sonication creates emulsions through high power ultrasound-driven oscillations, which cause acoustic cavitation. The term cavitation describes the formation, growth, and implosive collapse of cavities (vacuum bubbles) in a liquid. Ultrasonic / acoustic cavitation produces local conditions inside the bubbles of ~5000 K, ~1000 atm, heating and cooling rates that exceed 1010 K/s and liquid jets with up to 300m/s. (Suslick et al. 2008) The intense forces, high shear, streaming and turbulences resulting from the bubble implosion deliver the energy to break particles and droplets for dispersion & emulsion size reduction, lyse cell walls, initiate chemical reactions.
As shown by our results, static pressure is a very efficient means of increasing lethality of ultrasound waves (UW) / manosonication (MS). This increase becomes greater when the amplitude of UW is higher. Between 50 and 58°C, the lethality of heat can be increased by combining heat treatments with UW under pressure (MS). The lethality of this treatment (MTS) is equivalent to the additive lethal effect of heat and UW. MS and MTS treatments could become an alternative for the inactivation, in heat-sensitive media (i.e., liquid egg), of Y. enterocolitica and possibly other microorganisms. It might also find applications in foods in which the high intensity of heat treatments required (e.g. low-water-activity foods) would impair food quality. (cf. Raso et al. 1998)
Researcher has revealed that nonthermal food preservation technologies, such as sonication, does not affect, as much as thermal processes, nutritional and sensory attributes of processed foods.
Eggs: Composition & Characteristics
Whilst chicken eggs are the most commonly consumed bird egg, also other varieties of bird eggs, e.g. ostrich, duck, quail, goose eggs etc., are used as food and food ingredients.
Eggs offer multi-functionality and are therefore widely used as ingredient in manifold food products.
Functional attributes of eggs include the properties of coagulation and binding, flavor, color, foaming, emulsifying as well as inhibited crystal growth in confectionary. To maintain these functionalities of egg, a mild pasteurization is required avoiding protein denaturation.
Liquid egg products range from liquid whole egg, egg white, and yolk to scrambled egg mixes and other specialized egg products. Liquid egg products are available as ready-to-use products or in frozen form. Liquid egg can be further refined into egg powders, e.g. whole egg powder, egg white powder, yolk powder. Egg powder is made from fully dehydrated eggs by spray-drying the eggs in the same way that milk powder is produced. Advantages of powdered eggs over fresh eggs include low price, reduced weight per volume of whole egg equivalent, shelf life, less storage space, and needlessness of refrigeration.
Heat-Sensitivity of Egg Proteins
Eggs contain several heat-sensitive proteins that are an important factor to consider when liquid egg (also known as breaker eggs) is processed and pasteurized. Especially liquid egg white products are sensitive to processing conditions, especially heat. The temperature for egg white proteins denaturation varies between 61°C (for Ovotransferrin) and 92.5°C (for G2 Globulin). Livetins, lysozyme,
ovomacroglobulin and ovoglobulin G3 are the least heat stable proteins, while ovotransferrin, ovoinhibitor and ovoglobulin G2 were found to be the most heat stable proteins in egg. Protein sensitivity to heat can be influenced by the addition of salt and sugar, which increases the heat stability of heat-sensitive proteins.
Not only sugar and salt, also carbohydrates, such as sucrose, glucose, fructose, arabinose, mannitol and xylose, protect proteins from denaturation during heat treatments (pasteurization).
Coagulation temperature of whole egg: at 73°C
In order to obtain a homogeneous liquid egg product, the liquid egg must be mechanically stabilized in order to prevent separation into two phases.
An emulsion is a mixture of two or more immiscible / non-blendable liquids. Technically, emulsions are a subdivision of colloidal systems of two or more phases. In emulsions, both the dispersed/internal and the continuous/external phase are liquid. In emulsions, two immiscible liquids are blended by dispersing one liquid (the dispersed phase) in the other (the continuous phase). Emulsifying agents are utilized to obtain long-term mechanical stability of the system.
Lecithin, which is e.g. a component in egg yolk, is a commonly used food emulsifier for food and industrial applications. Besides lecithin, egg yolk contains several amino acids that functions as emulsifiers, too. Egg yolk contains approx. 5-8grams of lecithin, which is why egg yolk is an important ingredient in many emulsion-based recipes such as mayonnaise, hollandaise, dressings, and sauces.
Egg-white proteins contain amino acids. When the protein is curled up, the hydrophobic amino acids are packed in the center away from the water and the hydrophilic ones are on the outside closer to the water.
When an egg protein is up against an air bubble, part of that protein is exposed to air and part is still in water. The protein uncurls so that its water-loving parts can be immersed in the water—and its water-fearing parts can stick into the air. Once the proteins uncurl, they bond with each other—just as they did when heated—creating a network that can hold the air bubbles in place.
Eggnog is a milk-based drink which consists in milk, eggs, sugar and flavourings and sometimes alcohol. It is a sweet, rich, creamy dairy-based beverage traditionally made with milk, cream, whipped egg whites, egg yolks, and sugar. Optionally, when produced as liquor, distilled spirits such as brandy, rum or bourbon are incorporated.