CN107043798B

CN107043798B - Eggshell recovery method and application of recovered material

Info

Publication number: CN107043798B
Application number: CN201710106786.9A
Authority: CN
Inventors: 梁玮彤; 刘佩诗; 朱景基; 何嘉仪
Original assignee: Nano and Advanced Materials Institute Ltd
Current assignee: Nano and Advanced Materials Institute Ltd
Priority date: 2016-03-02
Filing date: 2017-02-27
Publication date: 2021-08-31
Anticipated expiration: 2037-02-27
Also published as: CN107043798A; CN105598138A

Abstract

The invention relates to a method for recovering eggshells and an application of the recovered eggshells, belonging to the field of waste recovery, aiming at providing a method capable of completely recovering eggshells and eggshell membranes simultaneously, directly extracting useful components from the unseparated eggshell waste (the eggshells and the eggshell membranes) without separating the eggshells and the eggshell membranes, recovering the most abundant useful calcified eggshell powder containing calcium carbonate, and increasing the valuable organic content extracted from the eggshells and the eggshell membranes and then dried into the eggshell membrane powder. The invention has the beneficial effects that: 1. the waste can be recycled and utilized to the maximum extent; 2. the eggshells and eggshell membranes are not required to be separated and then recovered, and are hydrolyzed by an enzyme hydrolysis method without destroying organic matters in the eggshells and the eggshells; 3. after the organic part and the inorganic part are respectively dried, substances with different purposes are obtained, and the best use is achieved.

Description

Eggshell recovery method and application of recovered material

Technical Field

The invention belongs to the field of waste recovery, and particularly relates to recovery of eggshells and application of recovered materials.

Background

Eggs are composed of yolk, albumen, two layers of eggshell membranes and eggshells, the consumption of eggs is very large as a staple on each table, the rest is generally disposed of as waste after cooking the yolk and albumen, and is not recovered, but in fact, the value of eggshells is underestimated as waste material, Osuoji et al report that acidic glycosaminoglycans are present in eggshell membranes and that glycosaminoglycans (i.e., hyaluronic acid) are likely to be used for moisture retention and against bacterial attack, and thereafter, more studies report that eggshell membranes contain many valuable compounds such as cross-linked collagen (I, V and X), glycosaminoglycans (i.e., hyaluronic acid, chondroitin sulfate, heparan sulfate and keratan sulfate), albumen proteins (e.g., ovotransferrin, lysozyme) and eggshell matrix proteins (e.g., ovocalcin-36 (ovocaloxin-36).

According to the statistics reported in 2013 from the trade data of hong kong import commodity, about 2,243,000,000 units of shelled eggs are imported to hong kong, which represents a huge amount of waste (about 6 g per egg shell) of the existing eggshell, and because there are a large number of cake and bread manufacturers in china, it is relatively much easier to collect eggshell waste with stable quality than other food waste, and therefore, the eggshell waste should be fully utilized and converted into various kinds of recycled and recycled products which can be widely used.

In order to make better use of the waste eggshells, many researchers and companies have developed different eggshell and eggshell membrane separation methods aimed at obtaining better recovered products by separation. For example, MacNil developed a method and apparatus for removing the membrane portion of the eggshell particles, which membrane could be separated from the eggshells based on preferential flotation. DeJong and Vlad patented for separating eggshell membranes from eggshells by processing the unseparated eggshells in a separation tank containing a fluid and applying a cavitation action to the eggshells in the fluid. Snyder is a method of separating the eggshell membrane from the eggshell by adjusting the water content of the eggshell followed by applying an air current, but, after separation and recycling, even if the eggshell (with the membrane) is dried, crushed, ground and turned over, the eggshell membrane having valuable organic contents such as protein, collagen, elastin and hyaluronic acid on the eggshell membrane may still be firmly attached to the eggshell and not be completely recycled, and the eggshell is discarded as a waste material. Fig. 1 shows a cross-sectional view under a scanning electron microscope of an eggshell without the hydrolysis process provided by the present case, except that the inner and outer membranes are removed by conventional crushing, eggshell membrane removal, washing and drying, and it can be seen that the outer eggshell membrane (1) has a fiber-like cone (2) tip penetrating into the eggshell, and thus, the recovery is not complete.

Disclosure of Invention

The object of the present invention is to provide a method capable of completely recovering both eggshell and eggshell membrane without separating the eggshell from the eggshell membrane, directly extracting useful components such as calcium carbonate, eggshell membrane powder (containing protein, collagen, elastin, hyaluronic acid) from the unseparated eggshell waste (eggshell and eggshell membrane), recovering the most abundant useful calcified eggshell powder containing calcium carbonate, and increasing the amount of valuable organic contents such as protein, collagen, elastin, hyaluronic acid extracted from the eggshell and eggshell membrane and then dried into eggshell membrane powder.

The method provided by the invention comprises the following steps:

a recycling method of eggshell waste materials comprises the following steps:

(1) selecting the recovered eggshells with membranes, washing and sterilizing to remove dirt and microorganisms;

(2) the eggshell with the membrane is crushed to increase the specific surface area to obtain the eggshell powder with the membrane, the contact area of the crushed eggshell is increased, the enzymatic hydrolysis process in the next step can be accelerated, and the enzymatic hydrolysis time is shortened;

further, in the step (2), the particle size of the crushed eggshells is less than or equal to 2000 microns, preferably 0.1 to 99 microns, the smaller the particles of the eggshell waste, the larger the hydrolysis contact area in the hydrolysis process, the shorter the hydrolysis process and the higher the extraction efficiency;

the appropriate particle size may be reduced before the start of the hydrolysis reaction, i.e. before the start of step (3), e.g. by crushing the eggshells in step (2), which is an efficient way to obtain a substantially unchanged particle size in the hydrolysis reaction.

(3) Performing enzymatic hydrolysis; hydrolyzing the egg shell powder with the membrane, the enzyme and the buffer solution at a weight ratio of 70:0.125:1000 to 150:11:2000, preferably at a temperature of about 20-60 ℃, preferably for about 1-24 hours, preferably at a stirring speed of about 350-1000 rpm, wherein the buffer solution has any suitable pH value matched with the enzyme used, preferably a pH value of 1-8, and obtaining liquid-phase-like organic matter and unhydrolyzed inorganic matter after hydrolysis;

further, more preferred hydrolysis temperatures are about 20-37 degrees Celsius;

further, more preferred hydrolysis times are about 1 to 3 hours;

further, the weight ratio of the eggshell powder with the membrane, the enzyme and the buffer solution is more preferably between 70:0.25:1000 and 70:0.5: 1000;

further, more preferred agitation rates are between about 550 and 1000 revolutions per minute;

further, more preferred pH is 6.8 to 7.3;

further, the buffer solution is PBS buffer solution (PBS-Phosphate-buffered saline), TAE buffer solution or TBE buffer solution;

in order to further accelerate the hydrolysis process, the contact time between the membrane-bearing eggshell powder and the enzyme is increased by increasing the stirring speed of the hydrolysis reaction mixture, so as to reduce the reaction time, and the hydrolysis contact area of the membrane-bearing eggshell powder can be increased by continuously crushing a stirring system during the hydrolysis reaction, wherein the method comprises but is not limited to a homogenizer, a continuous ultrasonic reactor or other reactor/container which comprises stirring and homogenizing or chopping or grinding functions to realize continuous particle size reduction, so as to shorten the total duration of the whole hydrolysis process.

Further, the enzyme used for hydrolysis in step (3) is one or more proteases having at least one thiol group, such as actinidin, bromelain, ficin, papain, pepsin or zingibain, and a single thiol protease or a combination of thiol proteases is used for specific enzymatic hydrolysis to increase the solubility of organic content extracted from eggshell waste (both eggshell and eggshell membrane) without substantial digestion of valuable organic content.

(4) Carrying out solid-liquid phase separation on the hydrolyzed substances;

further, the separation in the step (4) is performed by suction filtration separation and pressure filtration separation, which can be performed at room temperature using a filtration membrane, preferably a filtration membrane having a pore size of 5 to 11 μm.

Further, the separation in step (4) is carried out by centrifugation, preferably at room temperature at a speed of at least 5000 rpm.

(5) Taking the liquid phase, and drying to obtain eggshell membrane powder;

(6) taking the solid phase, and drying to obtain the eggshell powder.

The drying method in the steps (5) and (6) comprises spray drying and freeze drying, wherein the inlet temperature of the spray drying is preferably 95-140 ℃, and the more preferred inlet temperature is 95-115 ℃; preferred suction rates are about 50% to 90%, more preferred suction rates are about 60% to 70%; preferred pump speeds are about 10-50%, more preferably 20-30%; the preferred temperature for freeze drying is between-30 degrees Celsius and 20 degrees Celsius under vacuum, more preferably 8-13 degrees Celsius under vacuum.

Further, the recovery method also comprises the following steps: dissolving the eggshell membrane powder, separating, purifying and drying to obtain the sodium hyaluronate, wherein the purity of the sodium hyaluronate can reach more than 90%.

The sodium hyaluronate is a biochemical drug with high clinical value, is widely applied to various ophthalmic surgeries such as crystal implantation, corneal transplantation, anti-glaucoma surgery and the like, can be used for treating arthritis and accelerating wound healing, can play a unique role in protecting skin when being used in cosmetics, can keep the skin moist, smooth, fine, tender and elastic, and has the functions of preventing wrinkles, resisting wrinkles, beautifying and protecting health and restoring the physiological functions of the skin.

The eggshell powder prepared by the method has the particle size of less than or equal to 800 micrometers, can reach 0.1-45 micrometers, has the calcium carbonate content of 90-99 percent, contains little or no organic content, and can be used for replacing the existing calcium carbonate polymer filler to be mixed into a thermoplastic product by using a single-screw or double-screw extruder.

Further, the thermoplastic is prepared from polyethylene, polylactic acid, polypropylene, poly (ethylene vinyl acetate) or/and polyvinyl chloride and the eggshell powder prepared in the present application, wherein the weight of the eggshell powder is 15% to 60%, and other additive components such as antimicrobial agents, antistatic agents, coupling agents, dyes and pigments, fillers, flame retardants, foaming agents, heat stabilizers, nucleating agents, odor releasing agents, ultraviolet light or light stabilizers may also be included, and the thermoplastic polymer composite may be further processed by extrusion, injection molding, blow molding and fused deposition molding to produce thermoplastic products.

The invention has the beneficial effects that: 1. the waste can be recycled and utilized to the maximum extent; 2. the eggshells and eggshell membranes are not required to be separated and then recovered, and are hydrolyzed by an enzyme hydrolysis method without destroying organic matters in the eggshells and the eggshells; 3. after the organic part and the inorganic part are respectively dried, substances with different purposes are obtained, and the best use is achieved.

Drawings

FIG. 1 is a cross-sectional view under a scanning electron microscope of ground eggshell after separation of the eggshell membrane using conventional methods;

FIG. 2 is a process flow diagram of the present application;

FIG. 3 is a cross-sectional view under a scanning electron microscope of the eggshell powder with membrane after hydrolysis in example 1;

FIG. 4 is a graph of the relationship between the protein extractable per gram of eggshell and the primary particle size of the eggshell powder;

FIG. 5 is a graph comparing particle size distribution before reaction and after hydrolysis in example 2;

FIG. 6 is a graph comparing particle size distribution before reaction and after hydrolysis in example 3;

FIG. 7 is a cross-sectional view of an electron microscope of ground eggshell after hydrolysis in example 4;

FIG. 8 is an analysis diagram of solid-phase eggshell powder treated with membrane eggshell, eggshell membrane, ficin by Fourier transform infrared spectrometer;

FIG. 9 is an electron microscopic sectional view of the hydrolyzed eggshell powder of example 5;

FIG. 10 shows polymer filler particles mixed with polyethylene having a ground eggshell content of 30 wt% at various particle size ranges.

FIG. 11 shows ground eggshell, in the particle size range of 22-45 microns, with varying amounts of polymeric filler blended separately with polyethylene.

Detailed Description

Example 1

As shown in the flow chart of fig. 2, the recycling method of eggshell waste comprises the following steps:

(1) selecting a recycled eggshell with a membrane, flushing the eggshell with sterile water for 3 minutes, and removing dirt and microorganisms;

(2) grinding eggshells by using a grinding seed to increase the specific surface area of the eggshells, wherein the particle size of the crushed eggshells is equal to or less than 2000 microns to obtain eggshell powder with a membrane;

(3) specific enzymatic hydrolysis with ficin: hydrolyzing for 24 hours at 30 ℃, and mixing the egg shell powder with the membrane: ficin: hydrolyzing the buffer solution with the pH value of 6.9 at a weight ratio of 70:0.5:1000, and stirring the hydrolysis mixture at 1000 revolutions per minute by using a stirring magnetic stirrer;

(4) centrifuging the hydrolyzed substance for solid-liquid phase separation, namely centrifuging at room temperature for 3 minutes at 5000 rpm, taking a liquid phase after centrifugation is finished, and drying to obtain eggshell membrane powder; and taking the solid phase, and drying at 80 ℃ to obtain the eggshell powder.

The eggshell powder was subjected to electron microscopy characterization and liquid phase protein content analysis and figure 3 shows a scanning electron microscopy image of the surface of the eggshell after the hydrolysis process in this example, it can be seen that most of the analogous fiber of the eggshell membrane inserted into the tip of the cone (2) of the eggshell had disappeared, indicating that the enzymatic hydrolysis had been substantially completed.

Figure 4 shows that as the particle size of most of the recovered membrane-bearing eggshells decreased, the extracted protein content increased.

Example 2

(1) Selecting and recycling eggshells with membranes, flushing the eggshells with sterile water, and removing dirt and microorganisms;

(2) grinding eggshells by using a grinder to increase the specific surface area of the eggshells, wherein the particle size of the crushed eggshells is equal to or less than 2000 microns, and thus the eggshell powder with the membrane is obtained;

(3) specific enzymatic hydrolysis with ficin: hydrolysis was carried out at room temperature (-25 degrees celsius) for 24 hours with an eggshell: ficin: the weight ratio of PBS buffer solution with pH value of 7.3 is 70:0.25:1000, the reaction mixture is stirred by an overhead electronic stirrer with 1000 r/min;

(4) and (3) performing solid-liquid phase centrifugal separation on the hydrolyzed substance, centrifuging for 3 minutes at room temperature at 5000 rpm to obtain a solid phase, drying at 80 ℃ to obtain the eggshell powder, and performing particle size analysis on the obtained eggshell powder by using a vibrating screen.

Fig. 5 shows that the particle size distribution of the crushed eggshells with membranes was not substantially changed in the reaction of this example, and the particle size was substantially unchanged before the reaction (hydrolysis) and after 24 hours of reaction.

Example 3

(1) Selecting and recycling eggshells with membranes, flushing the eggshells with sterile water for 3 minutes, and removing dirt and microorganisms;

(2) grinding eggshell with a grinder to increase its specific surface area, the eggshell having a particle size equal to or less than 2000 μm after grinding to obtain eggshell powder with membrane;

(3) specific enzyme hydrolysis was performed using a round bottom reaction kettle, while using a magnetic stirrer which ground and recovered eggshells with membranes continuously reduced particle size, hydrolyzed at 30 ℃ for 6 hours, wherein the eggshells: ficin: the weight ratio of TAE buffer solution with pH value of 6.8 is 70:0.5:1000, the reaction mixture is stirred by a magnetic stirrer at 1000 r/min;

FIG. 6 shows that most of the solid particles above 315 microns were reduced to around 22 microns by hydrolysis in example 3.

Example 4

(2) firstly, grinding eggshells by using a grinder to increase the specific surface area of the eggshells, wherein the particle size of the crushed eggshells is equal to or less than 1000 microns, and thus the eggshell powder with the membrane is obtained;

(3) specific enzymatic hydrolysis with actinidin to increase extraction from eggshell waste (both eggshell and eggshell membrane): hydrolysis was carried out at 37 ℃ for 24 hours, where the shell: kiwi fruit proteinase: after the buffer solution with the pH value of 6.8 is mixed according to the weight ratio of 150:11:2000, the hydrolysis mixture is stirred by an overhead electronic stirrer at 1000 revolutions per minute;

(4) carrying out solid-liquid phase suction filtration separation on the hydrolyzed substance, wherein the suction filtration separation is carried out by adopting a filter membrane with the aperture of 8 microns at room temperature;

(5) taking a liquid phase, and carrying out spray drying to obtain eggshell membrane powder, wherein the inlet air temperature of spray drying is 135 ℃, the suction rate and the pump speed are 65% and 25% respectively, the obtained eggshell membrane powder contains about 60ppm of protein and about 18.7ppm of hyaluronic acid;

(6) after separation by suction filtration, the solid phase was taken, ground eggshell was obtained after drying at 80 ℃ and was subjected to electron microscopic characterization (see fig. 7), fig. 7 shows a cross-sectional view of the ground eggshell after hydrolysis according to this example, no fibers were found which were similar at the tip of the cone (2) which penetrates the eggshell from the outer eggshell membrane, and the size of the majority of the solid particles was unchanged in this example.

Example 5

(2) firstly, grinding eggshells by using a grinder to increase the specific surface area of the eggshells, wherein the particle size of the crushed eggshells is equal to or less than 2000 microns, and thus the eggshell powder with the membrane is obtained;

(3) adopt round bottom reation kettle, ficin carries out the hydrolysis of specificity enzyme, uses the magnetism stirring seed to grind the recovery simultaneously and takes the membrane eggshell in order to reduce the particle diameter in succession, hydrolyzes 1 hour under 30 ℃, wherein the eggshell: ficin: the weight ratio of the buffer solution with the pH value of 7.4 is 70:0.5:1000, and the hydrolysis mixture is stirred at 1000 revolutions per minute;

(5) taking the liquid phase, and freeze-drying to obtain eggshell membrane powder, wherein the freeze-drying is to carry out freeze-drying at 10 ℃ in a vacuum state, and in the embodiment, the finally obtained protein content of each gram of the eggshell powder with the membrane is 7.50mg, the sodium hyaluronate is 35.68 mu g, and the elastin is 0.0812 mu g;

(6) after separation by suction filtration, a solid phase was obtained, which was dried at 80 ℃ to obtain ground eggshell, which was then characterized by infrared (FIG. 8) and electron microscopy (FIG. 9).

FIG. 8 shows the Fourier transform infrared spectrometer analysis of the membrane-coated eggshells, eggshell membranes, and ficin-treated solid eggshell powder, in which no characteristic signal of eggshell membrane was observed in the solid eggshell powder after ficin hydrolysis.

Figure 9 shows an electron microscopic cross-sectional view of an egg shell undergoing the hydrolysis process of example 5, where no similar fibers were found at the tip of the cone (2) inserted into the egg shell from the outer egg shell membrane, and a majority of solid particles above 315 microns were reduced to above 22 microns.

Example 6

After six steps in example 1, the resultant eggshell powder was analyzed by X-ray fluorescence, and the calcium content was more than 92%. Then, the egg shell powder is divided into different particle size ranges by a size sieve: 500- < 800 > microns, 150- < 315 > microns, 90-150 microns and 22-45 microns.

As shown in FIG. 10, eggshell powders having different particle size ranges, in a content of 30%, were mixed with polyethylene at 150 ℃ in an extruder, respectively, to form a polymer filler.

As shown in FIG. 11, eggshell powders having particle sizes ranging from 22 to 45 μm in weight percentages of 15 wt%, 30 wt%, 45 wt% and 60 wt%, respectively, were mixed with polyethylene at 150 ℃ using an extruder to form a polymer filler. Since eggshell powder in this particle size range of 22 to 45 microns is sufficiently small, a polymeric filler can be made which mixes relatively uniformly up to 60% by weight of eggshell powder.

Example 7

Table 1 below shows the soluble proteins extracted after hydrolytic treatment of eggshell membranes of brown eggs at different temperatures using different proteases having at least one thiol group, the extracted soluble proteins were analyzed using Pierce BCA protein quantitative assay, the extracted Elastin was analyzed using chicken Elastin (Elastin) ELISA kit from MyBioSource, and the extracted Hyaluronic acid was analyzed using Hyaluronic acid (hydrauronic acid) ELISA kit from Corgenix.

TABLE 1

Claims

1. The eggshell recovery method is characterized by comprising the following steps:

(1) selecting eggshells with membranes, and removing dirt and microorganisms;

(2) grinding eggshell with membrane to obtain eggshell powder with membrane particle size less than or equal to 2000 μm;

(3) and (3) enzymatic hydrolysis: selecting membrane-bearing eggshell powder with the weight ratio of 150:11:2000 or 70:0.5:1000, enzyme and buffer solution to carry out hydrolysis reaction, wherein the hydrolysis temperature is about 20-37 ℃, the hydrolysis time is 1-24 hours, the pH value is 6.8-7.3 or 7.4, the enzyme is protease with at least one sulfydryl, and liquid-phase organic matter and solid-phase inorganic matter are obtained after hydrolysis; stirring the hydrolysis mixture at the speed of 350-1000 rpm; the protease is actinidin, bromelin, ficin, papain, pepsin or ginger protease; the buffer solution is PBS buffer solution, TAE buffer solution or TBE buffer solution;

(4) separating organic matters and inorganic matters by suction filtration, wherein the suction filtration separation is carried out at room temperature by adopting a filter membrane with the aperture of 8 microns;

(5) taking the liquid phase, and drying to obtain eggshell membrane powder;

(6) taking the solid phase, and drying to obtain the eggshell powder.

2. The egg shell recycling method of claim 1, wherein the particle size after pulverization in step (2) is 0.1 to 99 μm.

3. The eggshell recovery method as claimed in claim 1, wherein the drying process in steps (5) and (6) is spray drying or freeze drying.

4. The egg shell recycling method of claim 1, further comprising dissolving said egg shell membrane powder, separating, purifying, and drying to obtain sodium hyaluronate.

5. A thermoplastic material prepared from ground eggshell recovered according to the method of any one of claims 1 to 4, wherein said thermoplastic material comprises from 15% to 60% by weight of ground eggshell.