Continuous process for production of scrambled eggs

Details Continuous process for production of scrambled eggs Continuous process for production of scrambled eggs

2001-09-24

2004-07-06

Weier, Anthony (Department: 1761)

Food or edible material: processes, compositions, and products

Products per se, or processes of preparing or treating...

Poultry egg is basic ingredient

C426S510000

Reexamination Certificate

active

06759076

ABSTRACT:

FIELD OF THE INVENTION
This invention is directed to a process and a system for the production of scrambled eggs. More particularly, process and the system of the invention are directed to producing homogeneous scrambled eggs with a homogenous firmness while minimizing channeling and fouling of holding tubes used to cook the egg product.
BACKGROUND OF THE INVENTION
Producing scrambled eggs having a homogeneous firmness at high volumes without channeling or fouling cooking equipment or damaging heating equipment as a result of the fouling has been a problem. During the initial heating of the eggs with a heat exchanger such as a scraped surface heat exchanger, egg has fouled the heat exchanger even to the extent of breaking the heat exchanger blades.
Holding tubes where liquid egg is held at elevated temperatures to cook the eggs develop “channeling”. This is where laminar flow develops, as egg thickens and/or coagulates at the outer boundaries of the holding tube but tends to stay liquid at the center. In this circumstance egg flows faster through the center of the holding tube than at the outer perimeter, and as a result, develops a center channel. This creates a product which is not evenly cooked. For instance, egg flowing through the center channel tends to be undercooked, resulting in a watery or mushy egg product. At the same time, egg at the outer boundaries of the holding tube tends to be overcooked, resulting in very small pieces. The typical approach for minimizing laminar flow and eliminating large distributions of residence time in a hold tube is to induce turbulent flow. Turbulence is usually induced by creating high flow velocities or by providing mechanical shear (e.g. in a screw extrusion cooker). This is not acceptable in the production of scrambled egg product, however, as the solid and partially coagulated egg is very shear sensitive, as excessive shear leads to a finely granulated product with poor mouth feel.
OBJECTS OF THE INVENTION
It is an object of this invention to provide a continuous process for making scrambled egg product which is homogeneous in firmness and which is evenly cooked.
It is another object of this invention to provide a process and system for making evenly cooked scrambled egg product having a homogeneous firmness where the process will also minimize the fouling and channeling in the equipment used to cook the egg product.
These and other objects of the invention will become apparent with reference to the following summary and description.
SUMMARY
The present invention is directed to a process for the production of scrambled egg product and a system for practicing the process of the invention. The process and system maximizes scrambled egg product consistency and/or firmness homogeneity and minimizes channeling, fouling and equipment wear previously associated with the production of scrambled eggs. Maximization of egg product homogeneity and/or consistency and minimization of channeling and fouling is provided by periodically interrupting the flow of egg through the system of the invention. Flow interruption is achieved by stopping and starting the flow of heated liquid egg product in the holding tube effective for providing a discontinuous flow of heated egg product in the holding tube. This reduces laminar flow of the heated egg product in the holding tube compared to a laminar flow of heated egg product which would develop in the holding tube without the stopping and starting.
With elimination and/or control of egg channeling in holding tubes where egg is cooked, the process of the invention eliminates or controls undercooking of the eggs and mushy texture that results from insufficient or non-uniform cooking. The process provides scrambled egg product that is sufficiently cooked to allow egg protein to coagulate and provide scrambled egg product having a homogeneous firmness of from about 20 mm to about 50 mm (as hereinafter defined) as it exits the holding tube where it is cooked. Further, it has been observed that overcooking of the egg product and/or subjecting the cooked egg product to significant shear results in an unacceptably large quantity of fines (small particles) in the final product. The process described in the invention avoids the production of these fines by minimizing the opportunity for “thermal shock” (the development of significant thermal gradients), and ensuring that the velocity, and hence residence time, of egg product in the holding tube is more uniform.
In accordance with the process of the invention, liquid egg product is first heated to a temperature less than a cooking temperature for the egg, but the temperature being sufficiently high to prevent heat shock of the liquid egg product and prevent non-uniformity in the scrambled eggs produced by the process and system of the invention. The initially heated egg then is further heated to provide a homogeneously heated egg product. This additional or further heating brings the egg to a temperature which is effective for cooking the egg product and effective for causing the heated liquid whole egg product to coagulate when the liquid egg product is held in a holding tube downstream from the area of the additional heating. This brings the egg product to a cooking temperature to provide a cooked egg product with an apparent viscosity greater than about 1500 centipoises as measured with a Brookfield viscometer with a spindle No. 5 and a constant spindle speed of 20 revolutions per minute. After the egg product is brought to a cooking temperature it is transported to a holding tube. The homogeneously heated egg product is held in the holding tube at the cooking temperature for an amount of time effective for forming a fully coagulated and cooked egg product. The flow of egg product in the holding tube is stopped and started to provide a discontinuous flow of the homogeneously heated liquid egg product in the holding tube. This stopping and starting is effective to significantly reduce the velocity gradient where egg at the center of the tube moves faster than egg at the outer periphery of the tube; and hence, reduces the range of residence times experienced by the cooked egg flowing through the holding tube as compared to the flow pattern that could be expected to develop in the holding tube with continuous feed. After cooking, the fully coagulated cooked egg product is removed from the holding tube. The process and system of the invention may be used to process and cook liquid whole egg, as well as liquid egg product as defined herein.
The initial heating of the egg product brings cool egg from temperatures such as about 39° F. (or about 4° C.) to a temperature in the range of from about 130° F. to about 154° F. in about 1 to about 25 minutes, preferably about 5 to 25 minutes. This eliminates thermal shock to the egg when brought to cooking temperature, which shock will cause a rapid and sudden coagulation of at least some part of the egg. This will ultimately cause a non-uniform coagulation and cooking of the egg product in the holding tube.
During the initial heating, the egg product may increase to a viscosity of from 100 cps to about 1500 cps (Brookfield viscometer with a spindle No. 5 and a constant speed of 20 rpm measured at 25° C.). The initial heating may be accomplished using any type of heat exchanger as known in the art for this purpose, such as a tube in tube pre-heater.
After the initial heating, the initially heated liquid egg product is further heated as uniformly as possible to bring the egg product to a cooking temperature before it is transported to a holding tube for cooking. If the egg is brought to temperature with a hot surface, a significant thermal gradient should not be allowed to develop. To this end, a scraper can be used to continuously refresh the material at the hot surface with cooler material from the bulk of the egg in the heating device. Alternatively, local turbulence may be induced in the heating device, without causing significant turbulence downstream, by using pulsed flow through the heat exchanger. The hot liquid egg is m

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