Egg coating fresh-keeping material

Abstract

The invention belongs to the technical field of fresh-keeping materials, and relates to an egg coating fresh-keeping material. The preparation method comprises the following steps: stirring a chitosan (CS) solution and a konjac glucomannan (KGM) solution to prepare a KGM-CS compound membrane solution; and then adding the tangerine extract into the KGM-CS compound film solution, and uniformly mixing to prepare the egg coating fresh-keeping material. The plant extract is taken as a natural preservative, so that the preservative has the advantages of safety, no toxicity and high efficiency, and the indexes such as egg yolk index, half unit and egg yolk pH of the stored eggs can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of fresh-keeping materials, in particular to an egg coating fresh-keeping material. Background Art

[0002] Eggs are easily affected by various factors and deteriorate during storage and transportation. The principle of egg coating preservation technology is mainly to achieve the preservation effect by coating a layer of protective film on the surface of the egg. This layer of film can close the pores on the eggshell, thereby preventing bacteria, mold and other microorganisms from invading the inside of the egg, while also reducing the evaporation of water in the egg, maintaining the freshness of the egg and extending its shelf life, reducing losses caused by corruption and deterioration. The extension of the shelf life and the stability of the product reduce the loss of eggs during transportation and storage, and reduce the cost investment in logistics, warehousing and other links.

[0003] Food preservation has now become an important issue for people to explore, including how to maintain the nutritional value of food, extend the shelf life of food while ensuring food safety, reduce food waste and a series of other issues. At present, traditional chemical preservation technology is applied to all aspects of food preservation, but people do not have enough trust in traditional chemical preservatives. Certain chemical preservatives, such as sodium nitrite and sulfur dioxide, may cause harm to human health if consumed for a long time. For example, sodium nitrite will combine with hemoglobin to form nitrosohemoglobin, causing hemoglobin to lose its oxygen-carrying capacity and affecting the functions of various organs in the body. Sulfur dioxide will combine with hemoglobin to form methemoglobin sulfite, which will also affect the oxygen-carrying capacity of hemoglobin and may irritate the respiratory mucosa, causing symptoms such as coughing and asthma.

[0004] How to provide a fresh-keeping material that can enhance consumers' sense of safety regarding spreadable fresh-keeping is an urgent problem that those skilled in the art need to solve. Summary of the invention

[0005] The purpose of the present invention is to provide an egg coating preservation material to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing an egg coating preservation material, the steps comprising:

[0008] Chitosan (CS) solution and konjac glucomannan (KGM) solution were stirred to prepare KGM-CS composite membrane solution;

[0009] The tangerine peel extract is added to the KGM-CS composite film solution and mixed evenly to obtain the egg coating preservation material.

[0010] Furthermore, the CS solution is prepared by adding CS into an acetic acid solution with a concentration of 1% and stirring the mixture uniformly.

[0011] Furthermore, the concentration of the CS solution is 0.5-2.5 wt %.

[0012] Furthermore, the KGM solution is prepared by adding KGM into water and stirring the mixture evenly.

[0013] Furthermore, the concentration of the KGM solution is 0.2-1.0 wt %.

[0014] Furthermore, the volume ratio of the CS solution to the KGM solution is 1:1.

[0015] Furthermore, the stirring time is 2 hours and the temperature is 50°C.

[0016] Furthermore, the mass fraction of the tangerine peel extract in the egg coating preservative material is 0 to 2.5%, and is not 0.

[0017] The second technical solution of the present invention is to provide an egg coating fresh-keeping material prepared by the above method.

[0018] The third technical solution of the present invention is to provide an application of the above-mentioned egg coating fresh-keeping material in egg preservation.

[0019] The present invention discloses the following technical effects:

[0020] The present invention uses plant extracts as natural preservatives, which have the advantages of safety, non-toxicity and high efficiency. It has significant antibacterial activity and can inhibit or kill pathogenic microorganisms, thereby extending the shelf life of eggs. Compared with traditional chemical preservatives, plant extracts are more environmentally friendly and can reduce the impact on the environment. At the same time, with the enhancement of health and environmental awareness, consumers are more inclined to choose products using natural ingredients, and plant extracts meet this demand. Plant extracts can be used as effective ingredients for egg coating preservation, and the optimal ratio combination of composite coating materials is obtained through single factor experiments and orthogonal experiments. The present invention studies and explores the optimal values ​​of CS concentration, KGM concentration, and tangerine peel extract concentration on egg coating preservation through single factor experiments, and then determines the optimal plant extract coating ratio, i.e. 2% CS+0.8% KGM+1% tangerine peel extract, through orthogonal experiments. The storage properties of egg coating were studied on the composite film with a determined concentration ratio, and the egg yolk index, Haugh unit, yolk pH and other indicators were measured. The results showed that the preservation effect of egg coating at this concentration ratio was significantly better than that of other experimental groups, providing a reference for the research on egg coating preservation.

[0021] The present invention explores the preservation effects of different CS concentrations, KGM concentrations, and tangerine peel extract concentrations on eggs, studies the preservation effects of coating preparation ratios at different concentrations on eggs, considers the influence of CS, KGM, and tangerine peel total flavonoids extract on the preservation effects of eggs respectively, uniformly coats the surface of eggs, detects the corresponding freshness indexes of the eggs during the storage period of the eggs, and judges the quality of the preservation effect of the composite film on the eggs.

[0022] The present invention optimizes the best coating ratio of CS, KGM and tangerine peel extract through orthogonal experiments, and determines the optimal ratio by measuring the yolk index, Haugh unit, yolk pH, total bacteria count and other indicators of eggs, combined with the effect of the composite coating on the preservation of eggs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is the standard curve of rutin;

[0025] Figure 2 This is the curve showing the effect of tangerine peel extract concentration on egg coating preservation;

[0026] Figure 3 The effect of KGM concentration on the preservation of egg coating;

[0027] Figure 4 The effect of CS concentration on the preservation of egg coating;

[0028] Figure 5 The changes of egg weight loss rate in experimental group and control group;

[0029] Figure 6 The egg-shaped states of the experimental group on the third, ninth, and fifteenth days, where a is the third day, b is the ninth day, and c is the fifteenth day;

[0030] Figure 7 The egg-shaped states of the control group on the third, ninth, and fifteenth days, where a is the third day, b is the ninth day, and c is the fifteenth day;

[0031] Figure 8 is the change of yolk index in the experimental group and the control group;

[0032] Fig. 9 is the Haugh index of the optimal Haugh index group and the Haugh index control group during storage;

[0033] Fig.10 The changes of yolk pH during storage of eggs in the experimental group;

[0034] Fig.11 It is the total number of colonies on the twelfth day of egg storage. DETAILED DESCRIPTION

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0037] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0039] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0040] In the specific implementation scheme of the present invention:

[0041] The preparation steps of the CS solution used are as follows: adding a CS standard to a 1% acetic acid solution, stirring evenly, to prepare a CS solution with a concentration of 0.5 to 2.5 wt %;

[0042] The steps for preparing the KGM solution used are as follows: dissolving a KGM standard in pure water to prepare a KGM solution with a concentration of 0.2 to 1.0 wt %;

[0043] The preparation steps of the tangerine peel extract are as follows: slicing tangerine peel dried fruit, crushing it in a grinder, passing it through a 40-mesh sieve, defatting it with petroleum ether, mixing it with 80% ethanol at a solid-liquid ratio of 1:50, and performing ultrasonic extraction at 80°C for 50 minutes (using the cavitation effect, stirring effect, high acceleration and severe vibration of ultrasound to intensify the rupture of intercellular tissues so that flavonoid compounds can be better and faster dissolved in the extractant), and then concentrating the extract with a rotary evaporator to obtain the tangerine peel extract.

[0044] Example 1

[0045] Preparation of egg coating preservation material (the effect of tangerine peel extract content on egg coating preservation):

[0046] CS solution (2%) and KGM solution (1%) were mixed in a volume ratio of 1:1 and magnetically stirred in a 50°C water bath for 2 h to obtain a KGM-CS composite membrane solution.

[0047] Adding tangerine peel extract to the KGM-CS compound film solution and mixing evenly to obtain the egg coating preservation material;

[0048] The mass fraction of the tangerine peel extract in the egg coating preservation material is 0%, 0.5%, 1%, 1.5%, 2% or 2.5%.

[0049] Example 2

[0050] Preparation of egg coating preservation material (the effect of KGM solution concentration on egg coating preservation):

[0051] CS solution (2%) and KGM solution (0%, 0.2%, 0.4%, 0.6%, 0.8% or 1%) were mixed at a volume ratio of 1:1 and magnetically stirred in a 50°C water bath for 2 h to obtain a KGM-CS composite membrane solution;

[0052] Adding tangerine peel extract to the KGM-CS compound film solution and mixing evenly to obtain the egg coating preservation material;

[0053] The mass fraction of tangerine peel extract in the egg coating preservation material is 1.5%.

[0054] Example 3

[0055] Preparation of egg coating preservation material (the effect of CS solution concentration on egg coating preservation):

[0056] CS solution (0%, 0.5%, 1%, 1.5%, 2% or 2.5%) and KGM solution (1%) were magnetically stirred at a volume ratio of 1:1 in a 50°C water bath for 2 h, and stirred to be uniform to prepare a KGM-CS composite membrane solution;

[0057] Adding tangerine peel extract to the KGM-CS compound film solution and mixing evenly to obtain the egg coating preservation material;

[0058] The mass fraction of tangerine peel extract in the egg coating preservation material is 1.5%.

[0059] Example 4

[0060] With the concentration of CS solution being 1%, 1.5%, and 2%, the concentration of KGM solution being 0.6%, 0.8%, and 1%, and the mass fraction of tangerine peel extract in the egg coating preservation material being 1%, 1.5%, and 2%, an orthogonal experiment was designed. The factor level table of the coating ratio orthogonal experiment is shown in Table 1.

[0061] Table 1

[0062]

[0063] Test example

[0064] Drawing of rutin standard curve: accurately weigh 20 mg of rutin standard, dissolve it with 80% ethanol solution and dilute it to a 100 mL volumetric flask, shake it to get a rutin standard solution with a mass concentration of 0.2 mg / mL. Use a pipette to accurately draw 0.00 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, 5.00 mL, 6.00 mL of rutin standard solution, add 1.0 mL of 5.0% sodium nitrite solution to a 25 mL volumetric flask, shake it, let it stand for 5 minutes, then add 1.0 mL of 10% aluminum nitrate solution, shake it, let it stand for 5 minutes, and finally add 4 mL of 4% sodium hydroxide solution, dilute it to 25 mL with 80% ethanol solution, shake it, and let it stand for 10 minutes. Using 80% ethanol solution as reference, the absorbance of the standard solution was measured at a wavelength of 510 nm, and a linear regression was performed on the absorbance versus the mass concentration of rutin to obtain the regression equation. The results are as follows: Figure 1 As shown, Figure 1 The standard curve of rutin is drawn according to the results, and the linear regression equation of the relationship between rutin concentration y and absorbance A is obtained: y = 6.0446x-0.0101, and the correlation coefficient R 2 =0.9904, which shows that there is a good correlation between rutin concentration and absorbance.

[0065] Determination of total flavonoids in tangerine peel extract: Accurately weigh 1 g of tangerine peel powder sample to prepare tangerine peel extract, dilute to 25 mL, measure its absorbance at 510 nm, and finally extract tangerine peel total flavonoids concentration of 139 mg / mL.

[0066] The eggs are commercially available. To ensure the freshness of the raw materials, select fresh eggs from the same batch and produced at the same time (within 2 days of production date). Remove the obvious impurities (egg feces, large dust particles) covering the surface of the eggs. Remember not to wash them with water to maintain the original characteristics of the eggs when they leave the factory, prevent washing from damaging the protective film on the surface of the eggs, prevent bacteria from entering the eggs, and also prevent the evaporation of water inside the eggs.

[0067] Haugh Unit: Crack an egg onto a measuring plate to measure the height of the egg white and calculate its Haugh value.

[0068] The calculation formula of Haugh unit is: HU=100*Lg[h+7.57-1.7*(w^0.37)], where h is the egg white height of concentrated egg white, in mm, and w is the mass of the egg after shelling, in g.

[0069] The calculation of the Haugh Unit takes into account two important quality factors of eggs: the thickness and viscosity of the white. Fresh eggs usually have a higher white height and better viscosity, which helps protect the yolk and maintain the overall quality of the egg. As eggs are stored for a longer time, the white will gradually become thinner and less viscous, causing the Haugh Unit value to decrease. The larger the Haugh Unit value, the fresher the egg, with a thicker and more viscous white.

[0070] Egg grading standards:

[0071] Grade AA: Hough value ≥ 72; Grade A: 60≤Hough value < 72; Grade B: 30<Hough value < 60; Grade C: Hough value ≤ 30.

[0072] Fresh eggs were placed in the coating solution prepared in Example 1 and soaked for 1 min, taken out and dried, and stored at room temperature. The height and diameter of the egg yolk at each coating concentration were measured on the 12th day, and the Haugh unit was calculated. The results are as follows: Figure 2 shown.

[0073] Figure 2 The curve of the effect of tangerine peel extract concentration on egg coating preservation is shown in Figure 2. Figure 2It can be seen that after 12 days of storage at room temperature, the eggs coated at three concentrations of 0%, 0.5%, and 1.0% are all Grade A eggs, while the eggs at 1.5%, 2.0%, and 2.5% extract concentrations are Grade AA fresh eggs. As the extract concentration increases, the Hough index of eggs also increases, and tends to stabilize when the concentration reaches 1.5%. This shows that the best egg preservation effect can be achieved when the amount of tangerine peel extract added is between 1.0% and 2.0%.

[0074] The total flavonoids in tangerine peel extract are a class of natural organic compounds widely present in plants. They have multiple biological activities, including antioxidant, anti-inflammatory and antibacterial properties. When used as coating preservatives, they have broad application prospects in the field of fruit and vegetable preservation because of their natural, safe and effective characteristics. However, too high flavonoid concentrations may affect the sensory qualities of food, such as color and taste, because flavonoids themselves have certain colors and flavors. In addition, too high concentrations may increase costs, so 1.5% was selected as the optimal concentration.

[0075] Yolk index: Crack the eggs and pour them onto a measuring plate. Use a vernier caliper with an accuracy of 0.02 mm to measure the yolk height and diameter. The yolk diameter is the average of the major axis diameter and the minor axis diameter.

[0076] Calculate the yolk index: Yolk index = yolk height / diameter.

[0077] The yolk index is an important indicator for measuring the freshness of eggs. It refers to the ratio of the yolk height to the yolk diameter. The larger the yolk index, the fresher the egg. The yolk membrane of fresh eggs has good toughness and elasticity, and the yolk index is high. As the storage time increases, the toughness and elasticity of the yolk membrane will gradually decrease, and the yolk index will also decrease. Therefore, the size of the yolk index can reflect the strength of the yolk membrane. The stronger the yolk membrane, the larger the yolk index, which indicates that the yolk can maintain a better shape and structure and is not easy to spread. In practical applications, the yolk index is usually used to evaluate the freshness and quality of eggs. The yolk index of fresh eggs is generally around 0.40 to 0.44, and when the yolk index is less than 0.25, it is usually considered to be a loose yolk egg. In addition, the yolk index is also related to the nutritional value of eggs. The larger the yolk ratio, the higher the nutritional level of the egg. Therefore, the yolk index can not only reflect the freshness of eggs, but also indirectly indicate the nutritional value of eggs.

[0078] Fresh eggs were placed in the coating solution prepared in Example 2 and soaked for 1 min, taken out and dried, and stored at room temperature. The yolk height and diameter of the eggs at each coating concentration were measured on the 12th day, and the yolk index was calculated. The results are as follows: Figure 3 shown.

[0079] KGM is a natural polysaccharide extracted from konjac, which has good film-forming, water-holding, emulsifying, thickening and other properties. In the field of food preservation, KGM coating, as a green edible preservative material, can increase the activity of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) in food, enhance the antioxidant capacity of food, reduce the accumulation of active oxygen, and thus delay the aging of food. Figure 3 The effect of KGM concentration on the preservation of egg coating is shown in Table 1. Figure 3 It can be seen that the egg yolk index increases with the increase of KGM concentration. When the KGM concentration reaches 0.8%, it reaches a peak value and then shows a downward trend. The reason may be that when the KGM concentration is too low, the film-forming property is poor, the film-forming quality is poor, and it cannot effectively block the evaporation of water inside the egg, and cannot effectively block the entry of external oxygen. Cell respiration makes the freshness of the egg worse. Similarly, when the KGM concentration is too high, it not only increases the hardness of the coating, but also reduces the air permeability of the eggshell membrane surface, affects the normal breathing of the egg, and affects the preservation effect of the food. Therefore, the KGM concentration of 0.8% is selected as the optimal concentration.

[0080] Fresh eggs were placed in the coating solution prepared in Example 3 and soaked for 1 min, taken out and dried, and stored at room temperature. The yolk height and diameter of the eggs at each coating concentration were measured on the 12th day, and the yolk index was calculated. The results are as follows: Figure 4 shown.

[0081] CS is a natural polysaccharide with multiple biological activities. It is composed of deacetylated derivatives of chitin and has excellent safety, film-forming properties and antibacterial properties. In terms of food preservation, CS mainly has antibacterial, moisturizing and antioxidant effects. Figure 4 The effect of CS concentration on the preservation of egg coating is shown in Table 1. Figure 4 It can be seen that as the CS concentration increases, the egg yolk index also increases, and the egg yolk index reaches a peak value at a concentration of 2%.

[0082] The orthogonal result table of the effect of different coating concentration ratios on the freshness of eggs in Example 4 is shown in Table 2. As can be seen from Table 2, the primary and secondary factors in the coating material are A (CS) concentration > B (KGM) concentration = C (extract mass concentration), and the best conditions for egg coating preservation are: A3B2C1 orthogonal test group 8 is the optimal coating ratio experimental group, that is, the coating ratio concentration CS2%, KGM0.8%, and tangerine peel extract 1%. Under this condition, the eggs are coated and stored for preservation, with the coating ratio concentration CS2%, KGM0.8%, and tangerine peel extract 1% as the experimental group, and the non-coating as the control group, and the relevant freshness indexes are measured.

[0083] Table 2

[0084]

[0085] Water retention / weight loss rate: Weigh the eggs before storage, and weigh them every 3 days thereafter. The weight loss rate is calculated as follows: weight loss rate = (weight before storage - weight after storage) / weight before storage × 100%. Over time, eggs will gradually lose water through the eggshell, causing the eggs to become lighter and drier.

[0086] Figure 5 is the change of egg weight loss rate in the experimental group and the control group. Figure 5 It can be seen that the coating preservation group (experimental group) retains water better than the uncoated group (control group). During the period of 3 to 6 days, the weight loss rate of the experimental group and the control group was roughly the same. However, starting from the 9th day, the gap gradually became obvious, and the water retention effect of the experimental group was more obvious. This shows that the experimental group has better water retention for eggs. The weight loss rate of eggs in the first 12 days, the weight loss rate of eggs in both groups changed slowly, but the weight loss rate rose sharply after the 12th day of storage. This phenomenon may be due to the fact that with the extension of storage time, the quality of the eggshell, such as shell thickness, number of pores and integrity of the eggshell membrane, changes, and these factors will affect the loss of water from eggs. The ratio of concentrated and diluted protein is also closely related to the weight loss rate of eggs. The ratio of concentrated and diluted protein in egg white is also related to water retention, and the water in diluted egg white is easy to lose. The extension of the preservation time causes more concentrated protein to be converted into diluted protein, resulting in faster water loss.

[0087] Sensory indicators: The appearance, egg white, yolk and ligament condition of eggs were evaluated respectively. The evaluation criteria are shown in Table 3.

[0088] Table 3

[0089]

[0090] Among them, +++ means excellent; ++ means relatively good; + means good; - means poor.

[0091] The sensory evaluation results of the experimental group and the control group are shown in Table 4.

[0092] Table 4

[0093]

[0094] Figure 6 The egg-shaped states of the experimental group on the third, ninth, and fifteenth days, where a is the third day, b is the ninth day, and c is the fifteenth day; Figure 7 The egg-shaped state of the control group on the third, ninth and fifteenth days, where a is the third day, b is the ninth day, and c is the fifteenth day. Figures 6-7It can be seen that on the third and ninth days, the eggs in the experimental group had normal yolks, a shape close to a sphere, dense and non-dispersible protein, and complete and coarse white ligaments. On the fifteenth day, the concentrated protein was relatively reduced, and the protein was not full enough and tended to disperse. The yolk was not elastic, flat in shape, and the ligaments were incomplete and fell off. On the third day, all indicators of the eggs in the control group were fresh. On the ninth day, it was found that the concentrated protein was less, dispersed, and the ligaments fell off. On the fifteenth day, the eggs were measured to have loose yolks. It can be shown that the composite film made with a CS concentration of 2%, a KGM concentration of 0.8%, and a tangerine extract concentration of 1% has a significant preservation effect on eggs. In addition, with the increase of storage time, the color of the yolk also changes, and the protein in the yolk may denature, which may affect the texture and color of the yolk. Fresh yolks are mostly orange-red, and with the extension of storage period, the color of the yolk mostly changes to yellow.

[0095] Figure 8 is the change of yolk index in the experimental group and the control group. Figure 8 It can be seen that the overall yolk index of the experimental group has a smaller range of change and a lower amplitude than that of the control group. The overall change tends to be relatively stable. The yolk index of the control group dropped sharply from the 6th to the 9th day, and the freshness of the eggs dropped sharply after the twelfth day. The yolk index of the control group fell by 0.3 on the 15th day. The above phenomenon shows that the composite film of the experimental group has a significant effect on the yolk index of eggs. The composite film with the optimal coating ratio can make the yolk index of eggs more stable, maintain the stability of the yolk membrane, and make it less likely to loosen the yolk.

[0096] The coating ratio of CS2%, KGM 0.8%, and tangerine peel extract 1% was used as the optimal Haff index group, and the coating ratio of CS1%, KGM 0.6%, and tangerine peel extract 1% was used as the Haff index control group. The changes of Haff index of eggs after coating are as follows: Fig. 9 shown.

[0097] Fig. 9 is the Haugh index of the optimal Haugh index group and the Haugh index control group during storage. Fig. 9 It can be seen that the Haff value of the optimal Haff index group has a smaller range of change and a lower amplitude than that of the Haff index control group. Due to the number of testing days, the Haff values ​​of the two coating groups were both shown at level A and above, but the optimal Haff index group had a better protection effect on the concentrated egg white in the same period of time.

[0098] Fig.10The figure shows the changes in the yolk pH during the storage of the experimental group of eggs. The storage time of eggs will affect the pH value of their egg white and yolk. In newly laid eggs, the egg white contains more carbon dioxide produced by metabolism, so the pH value is lower. As the storage time increases, the carbon dioxide in the egg gradually diffuses to the outside of the egg and is accompanied by the loss of some water, the pH value of the egg white will increase. At the same time, the egg liquid is not as full as before, and the contact between the egg white and the inner shell membrane is no longer as close, which reduces the adhesion. When fresh eggs are just laid, the pH value of the yolk is usually close to 6.0. However, as the storage time increases, the pH value of the yolk will gradually increase, reaching a maximum of 6.4-6.9. Fig.10 It can be seen that the pH of egg yolk gradually increases with the storage time, reaching a maximum of 6.5. It may be that as the storage time increases, the water and carbon dioxide inside the egg are lost through the gaps in the eggshell, and the reduction of carbon dioxide leads to a decrease in bicarbonate ions, thus affecting the pH value of the egg. On the other hand, as time goes by, the protein in the egg decomposes to produce alkaline substances, which increases the pH value of the egg.

[0099] Total bacteria count: Remove dirt from fresh eggshells, wash the eggs under running water, and disinfect the eggshells with 75% alcohol cotton after drying. Then, according to the inspection requirements, open the eggshells, take out the egg whites, egg yolks or whole egg liquid, put them into a sterilized bottle with glass beads, and shake them well for inspection. According to the national standard GB4789.19-2024, dilute at 1:40 to reduce the influence of lysozyme.

[0100] The coating ratio was CS2%, KGM 0.8%, and tangerine peel extract 1.5%, which was the coating group 2:0.8:1.5; the coating ratio was CS1%, KGM 0.6%, and tangerine peel extract 1%, which was the coating group 1:0.6:1. The changes in the total colony count were measured, and the control groups were supplemented with normal saline control and uncoated group.

[0101] Fig.11The total number of colonies on the twelfth day of egg storage. During the storage of eggs, the change in the total number of colonies is affected by many factors, including storage temperature, time, the condition of the protective film on the surface of the eggs, and the environment in which the eggs are located. Effective monitoring and prediction of changes in the total number of colonies is essential to ensure the safety and quality of eggs. The experiment found that no significant difference in the total number of colonies was detected in the first 9 days. On the 12th day, a large difference in the total number of colonies was detected. The natural protective film on the surface of fresh, unwashed eggs has a certain self-defense ability, but this ability gradually weakens with the extension of time and temperature changes. Low-temperature storage can effectively control the number of bacteria in various parts of the eggs, while high temperature will accelerate the growth of bacteria. The reason for this phenomenon may be that the lysozyme content in fresh eggs is rich and active. It has a strong inhibitory effect on bacteria inside the eggs. In the early stage, the total number of colonies was not detected. The egg structure was relatively complete, the eggshell strength was high, and the eggshell membrane tissue was complete, isolating most of the miscellaneous bacteria in the air. On the twelfth day, the total number of colonies in the coating group was significantly better than that of the coating group and the control group with a coating ratio of 1:0.6:1. The results showed that CS concentration of 2%, KGM concentration of 0.8%, and orange peel flavonoids extract concentration of 1.5% had better protection effect on eggs and stronger antibacterial ability. It may be that the membrane with this composite ratio has lower air permeability to eggs, reducing the entry of oxygen into the eggs and isolating the entry of external bacteria, making the total colony count of eggs better than other groups.

[0102] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing an egg coating preservation material, characterized in that the steps include: The chitosan solution and the konjac glucomannan solution are stirred to prepare a KGM-CS composite membrane solution; The tangerine peel extract is added to the KGM-CS composite film solution and mixed evenly to obtain the egg coating preservation material.

2. The preparation method according to claim 1, characterized in that: The concentration of the CS solution is 0.5-2.5 wt %.

3. The preparation method according to claim 1, characterized in that: The concentration of the KGM solution is 0.2-1.0 wt %.

4. The preparation method according to claim 1, characterized in that: The volume ratio of the CS solution to the KGM solution is 1:

1.

5. The preparation method according to claim 1, characterized in that: The stirring time is 2 hours and the temperature is 50°C.

6. The preparation method according to claim 1, characterized in that: The mass fraction of the tangerine peel extract in the egg coating preservative material is 0 to 2.5%, and is not 0.

7. An egg coating preservative material prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the egg coating fresh-keeping material as claimed in claim 7 in egg preservation.

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