The manufacturing method of the preserved eggs

Abstract

This invention provides a method for preparing preserved eggs, comprising: step A, providing a poultry egg; and step B, soaking the poultry egg using a staged replacement soaking solution method; wherein the staged replacement soaking solution method comprises: step B-1, soaking the poultry egg in an alkaline first soaking solution; step B-2, replacing the first soaking solution with a second soaking solution containing calcium ions; and step B-3, replacing the second soaking solution with an alkaline third soaking solution. The advantage of this invention is that, by using the method for preparing preserved eggs of this invention, preserved eggs free of heavy metals, with no spots on the eggshell surface, and of stable quality can be produced. Furthermore, this method can improve the formation rate and stability of preserved egg protein and yolk, and it significantly reduces environmental harm compared to conventional methods.

Description

[Technical Field]

[0001] This invention relates to a method for preparing preserved eggs; more particularly, it is a method for preparing preserved eggs that can improve food safety and reduce environmental harm. [Previous Technology]

[0002] Century egg (also known as: preserved egg, thousand-year egg, hundred-year egg, pickled egg) is a traditional processed egg product. Its egg white is a translucent amber or brown gel and its yolk is a soft egg product, which can extend the shelf life of the egg product and also enhance the flavor of the egg product.

[0003] The method for preparing this preserved egg involves placing raw poultry eggs in a strongly alkaline environment (such as a solution), allowing the strong alkali to penetrate the pores and membrane of the eggshell and destroy the protein molecular structure, causing denaturation. Simultaneously, through the action of the strong alkali, the proteins in the preserved egg are decomposed, producing amino acids, ammonia, and hydrogen sulfide, which can stimulate appetite and aid digestion. The fat content is also reduced due to the action of the strong alkali and the effect of saponification, thus lowering cholesterol levels. Therefore, preserved eggs become easier to digest and absorb, and because the protein decomposition produces ammonia, preserved eggs have a slightly pungent ammonia odor, resulting in a diverse and multi-layered taste and aroma. Therefore, preserved egg dishes are widely praised by people of all ages. [Summary of the Invention]

[0004] However, the inventors have discovered that in conventional methods for preparing preserved eggs, an excessive amount of strong alkaline solution can liquefy the solid gel of the egg. Therefore, this strong alkaline solution typically contains heavy metal salts such as copper or lead to stabilize the colloidal structure of the protein and improve the yield of preserved eggs. These heavy metals not only form miscible precipitates that block the pores of the egg, resulting in a spotted appearance on the eggshell, but also seep into the shell during the soaking process and remain in the egg white and yolk. Although the preserved eggs produced by Taiwanese manufacturers comply with national safety regulations, with consumers becoming increasingly aware of food safety, the presence of heavy metals in food may become unacceptable in the future. Furthermore, improper handling of this heavy metal soaking solution can also cause serious environmental harm.

[0005] In order to solve the above-mentioned technical problems, the present invention provides a method for preparing preserved eggs, which includes: step A, providing a poultry egg; and step B, soaking the poultry egg using a staged replacement soaking solution method; wherein, the staged replacement soaking solution method includes: step B-1, soaking the poultry egg in an alkaline first soaking solution; step B-2, replacing the first soaking solution with a second soaking solution containing calcium ions; and step B-3, replacing the second soaking solution with an alkaline third soaking solution.

[0006] According to some embodiments of the present invention, in steps B-1 and B-3, the first impregnation liquid and the third impregnation liquid both contain sodium hydroxide solution or potassium hydroxide solution.

[0007] According to some embodiments of the present invention, in step B-1, the first impregnation solution comprises a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 3.5 to 4.5 wt.%.

[0008] According to some embodiments of the present invention, in step B-1, the poultry egg is immersed in the first immersion solution for 48 to 96 hours.

[0009] According to some embodiments of the present invention, in step B-2, the source of the calcium ions is calcium chloride.

[0010] According to some embodiments of the present invention, in step B-2, the second impregnation solution comprises a calcium chloride solution with a concentration of 1.0 to 3.0 wt.%.

[0011] According to some embodiments of the present invention, in step B-2, the poultry egg is immersed in the second immersion solution for 12 to 36 hours.

[0012] According to some embodiments of the present invention, in step B-3, the third impregnation solution comprises a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 3.5 to 4.5 wt.%.

[0013] According to some embodiments of the present invention, in step B-3, the poultry egg is immersed in the third immersion solution for 30 to 38 days.

[0014] According to some embodiments of the present invention, a disinfection step is further included before step A: disinfecting the surface of the eggshell of the poultry egg.

[0015] The advantage of this invention is that by using the method for preparing preserved eggs of this invention, preserved eggs that are free of heavy metals, have no spots on the eggshell surface, and have stable quality can be produced. Moreover, the method for preparing preserved eggs can improve the formation speed and stability of preserved egg protein and preserved egg yolk, and it can significantly reduce the harm to the environment compared with conventional methods.

Implementation Method

[0020] The following embodiments should not be considered as unduly limiting the present invention. Those skilled in the art to which this invention pertains may modify and vary the embodiments discussed herein without departing from the spirit or scope of the present invention, and such modifications and variations shall still fall within the scope of the present invention.

[0021] To make the description of the present invention more detailed and complete, illustrative descriptions of embodiments and specific examples of the present invention are provided below, but these are not the only forms of implementing or applying the specific examples of the present invention. In this specification and the appended claims, unless the context otherwise requires, "a" and "the" are also to be interpreted as plural.

[0022] Although the numerical ranges and parameters used to define the present invention are approximate values, the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any value inevitably contains standard deviations due to individual test methods. Here, the word "approximately" means that the actual value falls within the acceptable standard error of the mean, which is a consideration for those skilled in the art to which this invention pertains.

[0023] The term “poultry eggs” as used in this article refers to chicken eggs, duck eggs, goose eggs, quail eggs, pigeon eggs, sparrow eggs, or ostrich eggs, etc.; duck eggs are preferred.

[0024] Example

[0025] [Preparation method of preserved eggs]

[0026] Please refer to Figure 1. This invention provides a method for preparing preserved eggs, comprising: step S100, providing a poultry egg; and step S200, soaking the poultry egg using a staged replacement soaking solution method. Preferably, after step S100, a disinfection step S10 may be included to disinfect the eggshell surface, such as, but not limited to, dry disinfection by irradiating the eggshell surface with ultraviolet light or bactericidal light, or wet disinfection by washing the eggshell surface with clean water. Specifically, the staged replacement soaking solution method comprises three stages: step S210, soaking the poultry egg in an alkaline first soaking solution; step S220, replacing the first soaking solution with a second soaking solution containing calcium ions; and step S230, replacing the second soaking solution with an alkaline third soaking solution. According to a preferred embodiment of the invention, the poultry egg used in the method for preparing preserved eggs is a duck egg.

[0027] According to one embodiment of the present invention, the first impregnation solution used in step S210 is a strong alkaline solution to cause a chemical change in the protein. Under the action of this strong alkali, the protein of the egg is thinned and the protein structure can be fully unfolded. At this time, the exposed thiol groups will form disulfide bonds to form a gel, and it can also facilitate the entry of calcium ions in the subsequent step S220. According to a preferred embodiment of the present invention, the first impregnation solution contains a sodium hydroxide solution or a potassium hydroxide solution; preferably, the first impregnation solution contains a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 3.5 to 4.5 wt.%, the concentration being specifically, for example, but not limited to, the following values ​​or any two of them: 3.5 wt.%, 3.7 wt.%, 3.9 wt.%, 4.0 wt.%, 4.1 wt.%, 4.3 wt.%, and 4.5 wt.%; more preferably, the first impregnation solution contains a sodium hydroxide solution with a concentration of 4.0 wt.%. Not limited by any specific theory, if the concentration of the first soaking solution is too low, the protein structure of the egg will not be able to unfold properly, which is not conducive to the formation of the subsequent gel. If the concentration of the first soaking solution is too high, the strong alkali will enter the egg white or yolk too quickly, increasing the speed of protein structure unfolding. Even if a gel is formed, the gel is prone to liquefaction due to excessive alkalinity and is also prone to alkaline hydrolysis, resulting in an unpleasant flavor in the subsequently produced preserved egg. According to another preferred embodiment of the present invention, the soaking time of the egg in the first soaking solution is 48 to 96 hours, specifically, but not limited to, the following values ​​or any two of them: 48 hours, 52 hours, 56 hours, 60 hours, 64 hours, 68 hours, 72 hours, 76 hours, 80 hours, 84 hours, 88 hours, 92 hours, and 96 hours; more preferably, the soaking time of the egg in the first soaking solution is 72 hours. If the soaking time is too long or too short, it will negatively affect the subsequent solidification process of the egg, thereby reducing the stability of the preserved egg.

[0028] According to one embodiment of the present invention, the calcium ions used in step S220 are used to improve the stability of the gel colloid generated in the aforementioned steps and to increase the formation rate of the gel colloid. Specifically, the method for replacing the impregnation solution from step S210 to step S220 can be, for example, as follows: firstly, the first impregnation solution is temporarily extracted and stored, and then the second impregnation solution containing calcium ions is added to soak the aforementioned poultry eggs; at this time, the calcium ions will enter the albumen through the pores of the eggshell, and the aforementioned unfolded protein structure will form ion bridges with the calcium ions to increase the strength of the gel colloid, thereby improving its stability and thermal stability, and thus avoiding the occurrence of liquefaction; furthermore, the presence of calcium ions can reduce the electrostatic repulsion between negatively charged protein molecules, so that protein molecules can contribute more connection points to increase the formation rate of the gel colloid. In addition, since the alkaline first impregnation solution is removed first and then the second impregnation solution containing calcium ions is added, the problem that calcium ion precipitation cannot be effective due to the conventional method of directly adding calcium ions to an alkaline solution can be avoided. According to a preferred embodiment of the present invention, the source of the calcium ions is calcium chloride; preferably, the second impregnation solution comprises a calcium chloride solution with a concentration of 1.0 to 3.0 wt.%, specifically, but not limited to, the following values ​​or any two of them: 1.0 wt.%, 1.5 wt.%, 2.0 wt.%, 2.5 wt.%, and 3.0 wt.%; more preferably, the second impregnation solution comprises a calcium chloride solution with a concentration of 2.0 wt.%. Not limited by a specific theory, if the concentration of the second soaking solution is too low, it cannot improve the stability of the gel colloid, resulting in gel liquefaction defects during subsequent soaking in the third soaking solution. If the concentration of the second soaking solution is too high, in addition to waste, when replacing the third soaking solution in subsequent steps, it may excessively increase the precipitation formed at the pores of the egg, resulting in excessively low alkalinity of the third soaking solution. Furthermore, due to excessive pore blockage, the concentration of the third soaking solution entering the egg is too low, affecting the ripeness, color, and flavor of the produced preserved egg. According to another preferred embodiment of the present invention, the soaking time of the egg in the second soaking solution is 12 to 36 hours, specifically, but not limited to, the following values ​​or any two of them: 12 hours, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, and 36 hours; more preferably, the soaking time of the egg in the second soaking solution is 24 hours. Not limited by any specific theory, if the poultry egg is soaked in the second soaking solution for too long, it may increase the risk of microbial contamination during soaking and increase time costs; if the poultry egg is soaked in the second soaking solution for too short a time, the concentration of calcium ions entering the poultry egg will be insufficient, resulting in a decrease in the speed of protein gelation and the stability of the formed gel colloid.

[0029] According to one embodiment of the present invention, the method for replacing the impregnation liquid from step S220 to step S230 can be, for example, as follows: first, the second impregnation liquid is extracted, and then the alkaline third impregnation liquid is added to soak the aforementioned enhanced gelation egg; at this time, the calcium ions remaining in the pores of the egg will form a precipitate with the third impregnation liquid, which will partially block the pores of the egg, thereby reducing the rate at which the third impregnation liquid penetrates into the egg, thus preventing the third impregnation liquid from penetrating excessively and becoming too alkaline, thereby avoiding the aforementioned gel colloid from liquefying; in addition, the inventors have also found that the egg soaked in the second impregnation liquid can further increase the formation rate of the gel colloid under the action of the calcium ions contained in it and the alkaline third impregnation liquid. According to a preferred embodiment of the present invention, the third impregnation solution comprises a sodium hydroxide solution or a potassium hydroxide solution; preferably, the third impregnation solution comprises a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 3.5 to 4.5 wt.%, specifically, but not limited to, the following values ​​or any two thereof: 3.5 wt.%, 3.7 wt.%, 3.9 wt.%, 4.0 wt.%, 4.1 wt.%, 4.3 wt.%, and 4.5 wt.%; more preferably, it comprises a sodium hydroxide solution with a concentration of 4.0 wt.%; in another preferred embodiment, the third impregnation solution is actually the first impregnation solution, that is, the first impregnation solution temporarily extracted and stored in step S210 is used as the third impregnation solution in step S230. Not limited by any specific theory, if the concentration of the third soaking solution is too high, the eggs may experience an increased risk of gel liquefaction due to excessive alkalinity, or be prone to alkaline hydrolysis, resulting in unpleasant flavors in the preserved eggs, while also increasing time costs. If the concentration of the third soaking solution is too low, the preserved eggs will lack sufficient maturity, color, and flavor. According to another preferred embodiment of the present invention, the soaking time of the eggs in the third soaking solution is 30 to 38 days, specifically, but not limited to, the following values ​​or any two of them: 30 days, 31 days, 32 days, 33 days, 34 days, 35 days, 36 days, 37 days, and 38 days; more preferably, the soaking time of the eggs in the third soaking solution is 38 days. Not limited by any specific theory, if the poultry eggs are soaked in the third soaking solution for too long, the resulting preserved eggs will have too high an alkalinity, which will increase the risk of liquefaction of the protein gel and also increase the time cost; if the poultry eggs are soaked in the third soaking solution for too short a time, the resulting preserved eggs will be insufficient in terms of maturity, color and flavor.

[0030] In summary, by using the method for preparing preserved eggs according to the present invention, preserved eggs that are free of heavy metals, have no spots on the eggshell surface, and have stable quality can be produced. This method for preparing preserved eggs can improve the formation speed and stability of preserved egg protein and yolk, and it can significantly reduce environmental harm compared to conventional methods.

[0031] The present invention has been described in detail above. However, the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications that can be made by those skilled in the art without departing from the spirit and scope of the present invention shall still fall within the protection scope of the present invention. [Simplified Explanation of the Diagram]

[0016] To make the above and other objects, features, advantages and embodiments of this application more readily understood, the accompanying drawings are described below:

[0017] Figure 1 is a flowchart of the steps of a method for preparing preserved eggs according to one embodiment of the present invention.

[0018] Figure 2 is a flowchart of the steps of the staged replacement impregnation liquid method according to one embodiment of the present invention.

[0019] Figure 3 is a photograph of a preserved egg prepared according to the method of the present invention. [Biomaterial Storage]

[0033] None

Claims

1. A method for preparing preserved eggs, comprising: Step A: Provide one egg; Step B involves soaking the eggs using a staged replacement soaking solution method. This staged replacement soaking solution method includes: Step B-1, soaking the eggs in an alkaline first soaking solution; wherein the first soaking solution contains a sodium hydroxide solution or potassium hydroxide solution with a concentration of 3.5 to 4.5 wt.%, and the eggs are soaked in the first soaking solution for 48 to 96 hours; Step B-2, replacing the first soaking solution with a second soaking solution containing calcium ions; wherein the second soaking solution contains a calcium chloride solution with a concentration of 1.0 to 3.0 wt.%, and the eggs are soaked in the second soaking solution for 12 to 36 hours; and Step B-3, replacing the second soaking solution with an alkaline third soaking solution, wherein the third soaking solution contains a sodium hydroxide solution or potassium hydroxide solution with a concentration of 3.5 to 4.5 wt.%. The poultry eggs are soaked in the third soaking solution for 30 to 38 days.

2. The preparation method as described in claim 1, further comprising a sterilization step after step A: sterilizing the eggshell surface of the poultry egg.

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