CN108456711B

CN108456711B - Cold water soluble gel matrix resistant to mesophilic bacteria decomposition and application thereof

Info

Publication number: CN108456711B
Application number: CN201810097490.XA
Authority: CN
Inventors: 蔡芷荷; 滕昆仑; 陈博; 张建明; 卢勉飞; 吴清平; 熊争
Original assignee: Guangdong Huankai Microbial Sci and Tech Co Ltd; Guangdong Huankai Biotechnology Co Ltd
Current assignee: Guangdong Huankai Microbial Sci and Tech Co Ltd; Guangdong Huankai Biotechnology Co Ltd
Priority date: 2018-01-31
Filing date: 2018-01-31
Publication date: 2021-10-15
Anticipated expiration: 2038-01-31
Also published as: CN108456711A

Abstract

The invention discloses a cold water soluble gel matrix capable of tolerating mesophilic bacteria decomposition and application thereof. The gel of the matrix is at least one of carrageenan or modified modifier thereof, and the gel matrix is added with a gel strength regulator and a carrageenase inhibitor. According to the microorganism detection sheet, cold hydrogel which is not easily decomposed directly by mesophilic bacteria is selected, and meanwhile, an enzyme inhibitor and a gel strength regulator which are specially used for inhibiting decomposition of gel enzyme are added, so that normal growth of microorganisms is guaranteed, adverse effects are avoided, and a sample containing bacillus is not liquefied and diffused in the culture process, and a single colony is clear and easy to observe and count. Because of forming agar-like transparent gel with certain gel strength, the colony edges formed after culturing Escherichia coli, pseudomonas aeruginosa and the like are relatively more regular and brighter in color, and the characteristics are close to those of the traditional agar culture medium and are more typical.

Description

Cold water soluble gel matrix resistant to mesophilic bacteria decomposition and application thereof

Technical Field

The invention relates to a gel matrix for a microbial culture medium and application thereof, in particular to a cold water soluble gel matrix resistant to mesophilic bacteria decomposition and application thereof.

Background

The total number of colonies is usually counted by pouring, surface coating, spiral inoculation or membrane filtration, all of which are without exception using agar medium and glass or plastic petri dishes. Agar is a colloid extracted from red purple marine algae such as Eucheuma Gelatinosum. The initial application of agar to microbiology was proposed by fanny hz plug in 1881. Agar began to replace gelatin as the first choice of solidifying agent by the beginning of the 20 th century because it maintained gel strength during high temperature incubation of certain pathogens. Agar is in a gel state at normal temperature and still is a hard gel at the temperature of 65 ℃. Agar melts at about 85 ℃ and begins to solidify at about 32-40 ℃. Bacteriological agar requires good clarity, controlled freezing and melting temperatures, good diffusion, no bacteriostatic toxicity, and a relative lack of metabolically useful minerals and compounds. Agar is generally resistant to microbial enzymatic degradation and is stable to factors such as temperature, ions, pH, etc. Agar is usually used in the coagulation medium to a final concentration of 1-2%. The traditional agar culture medium is dissolved by adding water, boiling, sterilizing with high pressure steam, and cooling to appropriate temperature. The sterilized bottled culture medium still needs to be heated and melted by long-time water bath or flowing steam before being used, then is cooled to about 50 ℃, poured into samples with a plurality of gradients, fully shaken, uniformly mixed and cooled to solidify. The whole process consumes a large amount of water and electricity resources, high-voltage equipment is needed, the preparation time is long, the process is complex, and the working efficiency is low. The subpackaging process needs a space environment with high cleanliness, but the long-time cooling solidification process still easily causes pollution.

The total number of bacterial colonies of samples such as food and the like is counted by adopting a pouring plate method, a culture medium which is sterilized by high-pressure steam and cooled to about 45 ℃ is uniformly mixed with bacterial liquid, and then the mixture is poured into a sterile plate, and the microorganisms, particularly the damaged microorganisms, are further damaged by higher temperature and even die. The surface spiral inoculation needs to be performed by a spiral inoculator, streaking, coating and inoculating, and each time, an inoculating loop is burned or a new disposable inoculating loop is replaced. When a large number of samples are detected, the operation is very inconvenient and the efficiency is low.

The microbial paper sheet method developed in recent years takes a high-molecular breathable water-proof material as a carrier, takes cold water soluble gel as a coagulant, is a ready-to-use sterile product, does not need preparation of a culture medium, is simple and convenient to use, only needs three steps of sample adding, culturing and counting, simplifies a test procedure, can greatly simplify the flow of qualitative and quantitative index test of microbes, and obtains a test result in a shorter time. The products can be quickly sold on shelves under the condition of not sacrificing the quality of the products, and the storage cost is reduced. The paper method can be used to count the total number of mesophilic colonies in samples such as food, e.g. 3M petrifilm aerobic plate count.

The total number of colonies is usually the number of colonies formed by mesophilic (30 ℃ or 36 ℃) bacteria grown on plate count agar for 48 or 72 hours under aerobic conditions. The bacillus has strong resistance to external harmful factors and wide distribution, and is commonly present in water, air and soil. The growth and the propagation of the microorganism are rapid, and a large amount of enzyme can be generated in a short culture time to liquefy the paper by the microorganism paper method. Therefore, when a sample such as a food contains Paenibacillus, a 3M paper sheet liquefies during culture, and when there are many colonies, it is difficult to observe and count red continuous sheets.

Other MerrieImpo tvc were counted by MPN method, 16 wells by 3 rows of cards, three rows of wells were 225. mu.l, 22.5. mu.l, 2.25. mu.l, respectively, and incubation after filling with the sample solution decomposed the substrate to generate fluorescent signals, and the computer calculated the maximum possible number by reading the number and position of the signals. Soleristvc production of CO by bacterial growth₂The color of the bottom indicator is changed by the waterproof and breathable film to detect the microbial contamination. After dilution, the template is added into the culture to observe the number of color change wells, and the number is converted into weight through a table and multiplied by the dilution factor. Although the detection effect of the counting methods is equivalent to that of the traditional methods, the counting methods need complex instruments and equipment for matching, are expensive and are difficult to popularize and use in the basic level.

A gel matrix for culturing microorganisms, which is required to have substantially no influence on the growth of microorganisms. This greatly limits the range of choices. Meanwhile, in order to ensure the growth of microorganisms, the gel matrix is required to have proper strength, and the growth of the microorganisms can be inhibited if the strength is too high, so that the detection result is influenced; and the intensity is too low to be observed.

The development of a cold water soluble gel matrix which is resistant to mesophilic bacteria, particularly resistant to the decomposition of paenibacillus is the key to prepare a microorganism detection sheet with a more accurate counting result.

Disclosure of Invention

The invention aims to provide a cold water soluble gel matrix resistant to mesophilic bacterial decomposition and application thereof.

The technical scheme adopted by the invention is as follows:

a cold water soluble gel matrix resisting mesophilic bacteria decomposition is prepared from at least one of carrageenan or modified modifier thereof, and gel strength regulator and carrageenase inhibitor.

In a further improvement of the cold water-soluble gel base, the gel strength modifier is at least one selected from starch and urea.

As a further improvement of the cold water soluble gel matrix, the dosage of the gel strength regulator is 1-5% of the mass of the gel.

As a further improvement of the cold water soluble gel matrix, the carrageenase inhibitor is selected from alkali metal or alkaline earth metal salt, urea, beta mercaptoethanol, sodium dodecyl sulfate, ethylene diamine tetraacetic acid or salt thereof.

As a further improvement of the cold water soluble gel matrix, the dosage of the carrageenase inhibitor is 0.01 to 0.05 percent of the mass of the gel.

A microorganism detection sheet is provided, wherein a culture medium is adsorbed on the detection sheet, and comprises a nutrient substance, a color indicator, a suspending agent and a cold water soluble gel matrix as described above.

As a further improvement of the above-mentioned microorganism detection sheet, the mixing ratio of the nutrient substance and the cold water-soluble gel matrix is 1: (2-8), preferably 1: (4-8).

As a further improvement of the microorganism detection sheet, the addition amount of the suspending agent is 30-60% of the dry weight of the culture medium.

As a further improvement of the microorganism detection sheet, the suspending agent is a high molecular polymer which can form transparent or semitransparent viscous solution after being dissolved by water or an organic solvent.

As a further improvement of the above-mentioned microorganism detection sheet, the suspending agent is at least one selected from the group consisting of chitosan, dextran, hyaluronic acid, polyvinyl alcohol, polyethylene oxide, and polyethylene glycol.

The invention has the beneficial effects that:

according to the microorganism detection sheet, cold hydrogel which is not easily decomposed directly by mesophilic bacteria is selected, and meanwhile, an enzyme inhibitor and a gel strength regulator which are specially used for inhibiting decomposition of gel enzyme are added, so that normal growth of microorganisms is guaranteed, adverse effects are avoided, and a sample containing bacillus is not liquefied and diffused in the culture process, and a single colony is clear and easy to observe and count.

Because of forming agar-like transparent gel with certain gel strength, the colony edges formed after culturing Escherichia coli, pseudomonas aeruginosa and the like are relatively more regular and brighter in color, and the characteristics are close to those of the traditional agar culture medium and are more typical.

Drawings

FIG. 1 is a photograph of the liquefaction of Bacillus amyloliquefaciens on a 3M colony count sheet of paper;

FIG. 2 shows the growth of Bacillus amyloliquefaciens on the test piece of the present invention.

Detailed Description

A cold water soluble gel matrix resisting mesophilic bacteria decomposition is prepared from at least one of carrageenan or modified modifier thereof, and gel strength regulator and carrageenase inhibitor. In particular, the mesophilic bacterium is a bacillus.

In a further improvement of the above cold water-soluble gel base, the gel strength adjuster is at least one selected from starch, urea, and the like. The starch can be selected from natural starch such as rice, wheat, corn, and potato, and can be soluble starch with straight chain, preferably modified starch completely soluble in food grade cold water.

The solidification assistant may be polysaccharide, starch, small molecular urea, etc., and preferably is modified starch dissolved in cold water.

The carrageenase inhibitor may be SDS, EDTA, EGTA, sodium nitrate, or the like, and preferably at least one of EDTA or a salt thereof.

Suspending agent, nutrient components, color indicator and the like are all common raw materials in the field, and the skilled person can select the suspending agent, the nutrient components, the color indicator and the like correspondingly according to the needs.

The suspending agent can be chitosan, dextran, hyaluronic acid, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, etc., and can be dissolved by water or organic solvent to form transparent or semitransparent solution with certain viscosity.

As the nutritional ingredients, peptone, tryptone, casein peptone, soytone, monthly peptone, beef extract, brain and heart extract, potato extract, malt extract, sucrose, lactose, glycine, tryptophan, sodium pyruvate, etc. can be used.

The chromogenic indicator can make the colony be bright color when the colony is small and difficult to observe by naked eyes, so that the observation is convenient. Common indicators include cytochrome C oxidase indicators such as triphenyltetrazolium chloride, tetrazolium blue, thiazole blue and the like, and microorganisms reduce the cytochrome C oxidase indicators into colored water-insoluble substances in the respiration process. Or neutral red, phenol red, basic fuchsin and the like, the microorganism grows and metabolizes to produce acid or alkali so as to change the pH of the colony and/or the surrounding, and the color of the indicator changes accordingly.

EXAMPLE 1 Effect of different gel Strength aids on gel Strength

Carrageenin (100%) is respectively mixed with 5% water soluble starch, 5% urea, 5% sodium chloride, 2.5% calcium chloride and 1% sodium acetate uniformly, 1.5g is suspended in 20ml 10% (w/v) polyethylene glycol-6000 methanol solution, 2ml is added into the center of the detection tablet and dried. After redissolving overnight with the addition of 1ml of sterile deionized water, the gel strength was observed and measured by hand pressure and the results are shown in Table 1.

TABLE 1 Effect of gel Strength adjuvants on gel Strength

Remarking: "+" represents gel strength.

The gel strength of the added sodium chloride or sodium acetate is not obviously different from that of the blank carrageenan, and the gel strength is obviously enhanced by the calcium chloride, the urea and the starch, which may be Ca²⁺The gel strength is improved by intermolecular interaction with groups such as sulfate in carrageenan. The interaction of the polyamino group in urea and the group in carrageenan makes the cross-linking area more stable. The high molecular polysaccharide starch may pass through linear chain and branched chain and between carrageenan moleculesA synergistic effect occurs to increase the gel strength.

Example 2 Effect of different factors on the enzymatic Activity of Caraganase

Weighing 45.04mg of D galactose, dissolving with double distilled water to constant volume of 50ml to obtain 5 mu mol/ml standard solution, respectively adding reagents, mixing well, developing under boiling water bath condition for 10min, cooling to room temperature, and adding double distilled water to 5 ml. And measuring the light absorption value at 520nm, and drawing a standard curve by taking the light absorption value as an abscissa and the D galactose content as an ordinate.

The enzyme activity was measured by 3, 5 dinitrosalicylic acid (DNS) method. Taking 50 mu l of carrageenase solution, adding the carrageenase solution into 550 mu l of 0.5 percent carrageenase solution of 0.05M Phosphate (PBS) buffer solution (pH7.0), respectively adding sodium chloride, potassium chloride, calcium chloride, magnesium chloride, EDTA, SDS, beta mercaptoethanol and urea into the solution in a water bath at 60 ℃ for 20min, quickly adding 900 mu l of DNS boiling water bath for 10min, cooling to room temperature, and adding double distilled water to 5 ml. And measuring the light absorption value at 520nm, and calculating the enzyme activity according to the standard curve. The enzyme activity of the original enzyme solution without any substance added was 100%. The results are shown in Table 3.

TABLE 2 Standard Curve preparation

	0	1	2	3	4	5	6	7	8	9	10
												Standard liquid	0	0.2	0.4	0.6	0.8	1	1.2	1.4	1.6	1.8	2
Double distilled water	2	1.8	1.6	1.4	1.2	1	0.8	.06	0.4	0.2	0
												Amount of liquid taken	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6
DNS	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9

TABLE 3 Effect of different factors on the enzymatic Activity of Caraganase

The results show that Na⁺、K⁺No obvious effect on promoting carrageenin, Ca²⁺、Mg²⁺Has obvious promoting effect, and the beta mercaptoethanol and urea have certain inhibition effect on enzyme activityEDTA and SDS have obvious inhibiting effect. However, SDS generally has a more pronounced inhibitory effect on bacterial growth at lower concentrations, and thus low doses of EDTA have a better control of enzyme expression.

In summary, the preferable composition of the cold water soluble gel matrix resistant to the decomposition of mesophilic bacteria is 100% of carrageenan, the gel strength regulator is 3-5% of water soluble starch, and the carrageenase inhibitor is 0.03-0.05% of EDTA or potassium and sodium salts thereof.

EXAMPLE 3 Effect of enzyme inhibitor EDTA-prepared Total colony count test piece

5g of tryptone, 2.5g of yeast extract powder, 1g of glucose and 0.1g of TTC, which are respectively mixed with 34g of carrageenan, 2g of water-soluble starch and 0.015g of EDTA by ball milling, and the dry powder is fixed on a culture device to be made into a detection piece. The cells were sterilized by irradiation with cobalt 60 at a dose of 15 KGy. Escherichia coli ATCC25922, Staphylococcus aureus ATCC6538, Pseudomonas aeruginosa ATCC27853, Bacillus subtilis ATCC6633 were cultured in tryptone soy broth at 36. + -. 1 ℃ for 16-18h, the enrichment broth was shaken up and diluted to about 100CFU/ml with a sterile physiological saline gradient. 1ml of the solution was added to the center of the sterilized test piece, and the whole area was covered with a polyethylene film to diffuse the sample solution. The cells were cultured at 36. + -. 1 ℃ for 24 hours, and the results were observed and shown in Table 4.

TABLE 4 results of pure bacteria count by different test pieces

The results show that the Escherichia coli, the staphylococcus aureus, the pseudomonas aeruginosa and the bacillus subtilis grow well on a detection sheet made of carrageenan and EDTA, and the red single colony is clear and calculable. No liquefaction is seen even after the culture is continued for 48 hours, and the carrageenan has stable enzymolysis resistance. The bacillus subtilis is gel-liquefied into a light red tablet on a detection tablet made of carrageenan and 3M, and the count cannot be carried out.

EXAMPLE 4 Effect of test pieces prepared with different proportions of gel and Nutrition

Different proportions of carrageenan and nutritional dry powder were mixed well with 0.1g of TTC. 1.5g of the gel nutrition mixed dry powder is weighed respectively, 20ml of 10% (w/v) polyethylene glycol-6000 methanol solution is added, stirring is carried out continuously to form uniform suspension, and 2ml of the uniform suspension is coated on the lower layer of a detection piece (d is 50mm, h is 1 mm). After drying, the polypropylene film was covered and sterilized with ethylene oxide. And opening the upper layer film, respectively adding 1ml of sterile physiological saline to the center of the detection piece, covering the upper layer film, and observing the absorption and diffusion of the sample solution. Culturing Escherichia coli ATCC8739, Staphylococcus aureus ATCC6538, Pseudomonas aeruginosa ATCC9027 and Bacillus subtilis ATCC6633 in tryptone soybean broth at 36 +/-1 ℃ for 16-18h, shaking the enriched liquid uniformly, and diluting to about 100CFU/ml by using sterile physiological saline in a gradient manner. 1ml was added to the center of the sterilized test piece, and the whole area was filled with the sample solution by diffusion using a polyethylene film, and 3M product was used as a control. The cells were cultured at 36. + -. 1 ℃ for 24 hours, and the results were observed and shown in Table 5.

TABLE 5 Effect of test tablets prepared with gels and nutritional ingredients in different proportions

The result shows that the mixing ratio of the carrageenan and the nutrient components is (1-2): 1, the dry powder is not easy to disperse in the suspension, 1ml of sample solution overflows, and the formed gel is weak; the mixing ratio is (4-8): 1, 1ml of sample liquid basically fills the whole area, the gel strength is good, and the target bacteria grow well; the mixing ratio is 10: 1, the colonies of Escherichia coli and Staphylococcus aureus became significantly smaller, which may be caused by insufficient nutrients. According to the comprehensive gel strength and nutrition conditions, the carrageenan is initially selected to be mixed with the nutritional ingredients in a ratio of (4-8): 1, in particular 4: 1.

example 5 comparison of different dosage effects of mixed dry powder

Taking 1g, 1.5g and 2g respectively according to the weight ratio of 4: the same procedure as in example 3 was used to add 1 part of the gel nutrition mix dry powder to the suspension and 2ml was used to prepare test tablets, and the results are shown in Table 6.

Table 6 comparison of different dosage of mixed dry powder

The results show that about 1.5g 4: 1, the gel nutrient mixed dry powder has the optimal effect, and 1ml of sample liquid can ensure that the dry culture medium layer can be completely absorbed and dissolved to form gel with certain strength, which is better than the proportion of 1g to 2 g.

Example 6 comparison of detection Effect of Bacillus

1) 5g of tryptone, 2.5g of yeast extract powder, 1g of glucose, 0.1g of TTC, 0.015g of EDTA, 2g of water-soluble starch and 34g of carrageenan, and mixing for 2-3 h in a ball milling, grinding or crushing manner to obtain uniform mixed dry powder;

2) weighing 17g of ball-milled gel nutrition mixed dry powder, adding 200ml of 10% (w/v) methanol solution of polyethylene glycol-6000,

continuously stirring to form uniform suspension, and coating the suspension on the lower layer of the detection sheet;

3) after drying, ethylene oxide is sterilized.

Bacillus subtilis CMCC (B)63501, FICC (B) 115039-115049, Bacillus subtilis var niger ATCC9372, Bacillus cereus ATCC11778, CMCC (B)63303, CMCC (B)63301, Bacillus circulans FICC (B)115011, FICC (B)115056, Bacillus firmus FICC (B)115012, Bacillus lentus FICC (B)115014, FICC (B)115015, Bacillus coagulans FICC (B)115059, FICC (B)115122, bacillus megaterium ATCC14945, FICC (B)115026, Bacillus licheniformis FICC (B)115017, 115028, Bacillus mycoides ATCC10206, Bacillus pumilus FICC (B)115031, FICC (B)115032, Bacillus thuringiensis ATCC10792, FICC (B)115263, Bacillus amyloliquefaciens FICC (B)11502334, FICC (B)11502335, Bacillus alvei FICC (B)11502336 and 11502337 are cultured in tryptic soy broth at 36 +/-1 ℃ for 16-18h, and the enrichment broth is shaken up and diluted to about 100CFU/ml by a sterile saline gradient. 1ml was added to the center of the sterilized test piece, and the whole area was filled with the sample solution by diffusion using a polyethylene film, and 3M product was used as a control. The cells were cultured at 36. + -. 1 ℃ for 24 hours, and the results were observed and shown in Table 7.

TABLE 7 comparison of the specific detection results of Bacillus

The results show that the colonies of 13 strains of bacillus subtilis and 2 strains of bacillus amyloliquefaciens are liquefied into light red on a 3M paper sheet and fused together, and single colonies cannot be counted (figure 1), while the colonies are not liquefied on the culture medium of the invention, and the red color of the colonies is larger and clearly counted (figure 2). Other bacilli are not obviously liquefied on the invention and 3M, and bacterial colonies are red and large, so that the bacilli can be counted clearly and easily.

Example 7 evaluation of the Effect of simulated surface swab sampling

Sterile stainless steel table 100cm²Artificial contamination was carried out with 5ml (about 100CFU/ml) of a mixed bacterial suspension of Escherichia coli ATCC25922, Staphylococcus aureus ATCC6538, Pseudomonas aeruginosa ATCC9027 and Bacillus subtilis ATCC 6633.

Open package the cotton swab was dipped into a test tube containing 10ml of buffered peptone water and the swab was squeezed on the test tube wall to remove excess water. The swab is placed at an angle of 30 ° of 10cm²The surface to be measured is wiped back and forth for 10 times in the forward direction, the test tube is placed back to fully oscillate and extrude redundant moisture, the surface is wiped back and forth for 10 times in the reverse direction by rotating 90 degrees, the test tube is placed back to fully oscillate and extrude redundant moisture, and the surface is wiped back and forth for 10 times in the lateral direction by rotating 45 degrees. Shaking with ultrasonic wave for 1min to releaseMicroorganisms, squeeze excess water out of the swab. 1ml of the stock solution is added into the center of the detection piece, and a cover membrane is covered. The preparation of the test piece is the same as that of example six. 1ml of pour Plate Count Agar (PCA) was also taken. The cells were cultured at 37 ℃ for 48 hours, and the results are shown in Table 8.

Table 8 agar counting results for invention and plate count after swab sampling

The results show that there is no significant difference in the counting results of the cotton swab surface samples on the present invention versus the PCA.

EXAMPLE 8 comparison of the detection Effect of pure strains in the present invention with 3M colony count sheets and PCA

Test pieces were prepared as in example 6.

Fresh Escherichia coli ATCC25922, Escherichia coli ATCC35218, Escherichia coli CMCC (B)44102, Escherichia coli O157: H712900, Citrobacter freundii ATCC43864, Enterobacter cloacae CMCC (B)45301, Proteus mirabilis CMCC (B)49005, Enterobacter sakazakii ATCC29544, nitrate-negative Acinetobacter CMCC (B)25001, Klebsiella pneumoniae CMCC (B)46117, Salmonella typhi ATCC14028, Shigella flexneri CMCC (B)51572, Shigella intracellularis CMCC (B)51592, Pseudomonas aeruginosa ATCC27853, Staphylococcus aureus ATCC 2066538, Staphylococcus epidermidis ATCC 206659, enterococcus faecalis ATCC29212, etc. were made into a suspension of 0.5McF strain, diluted 10-fold gradient to 100CFU/ml, 1ml was added to the center of the test piece of the present invention and 3M, and 1ml of TTC-containing liquid was poured into the test piece, and the test piece was cultured at 48 ℃ as a control (see Table 48, PCA) for 48, for aerobic culture.

TABLE 9 comparison of the detection effects of the pure strains

The result shows that the detection result of the non-bacillus bacteria on the detection sheet of the invention is consistent with the detection result of a 3M paper sheet and plate counting agar, and the non-bacillus bacteria have more typical colony characteristics, but in PCA, the growth of pseudomonas aeruginosa and the like is slow and is in a small red dot shape. However, the growth of Pseudomonas aeruginosa on the detection sheet and the 3M paper sheet of the invention is faster, and the red colony is larger in 24 hours.

EXAMPLE 9 Effect of testing actual samples comparison of the present invention with 3M and PCA

Test pieces were prepared as in example 6. Respectively weighing 25g (ml) of rice flour, fushou fish, chicken, pork, milk powder and cake samples in an aseptic operation mode, adding the rice flour, the fushou fish, the chicken, the pork, the milk powder and the cake samples into 225ml of bagged phosphate buffer solution, carrying out pulse homogenization for 1min, then diluting the rice flour, the milk powder and the cake samples by 10 times of the phosphate buffer solution, taking 1ml of the PCA plates, respectively pouring the PCA plates into the PCA plates, adding the detection sheets and the 3M paper sheets, carrying out aerobic culture at 36 +/-1 ℃ for 48h, carrying out aerobic culture at 30 +/-1 ℃ for 72h on the fish, observing and counting red colonies, wherein the results are shown in a table 10.

TABLE 10 comparison of the results of the actual sample measurements

Estimate of 24 h.

The result shows that the detection result of the detection piece of the invention is basically consistent with 3M and PCA when the total number of the bacterial colonies is detected by the actual food sample. When the rice flour and pork samples are detected, other bacteria growing around the bacillus cannot form clear single colonies due to liquefaction of the bacillus-containing 3M paper sheets during counting for 48 hours, and become red sheets. The detection sheet of the invention has no liquefaction phenomenon, single colony is regular and typical, the limit among colonies is obvious, and the detection sheet can be easily observed and counted.

Claims

1. A cold water soluble gel matrix resistant to decomposition by mesophilic bacteria, characterized by: the gel is carrageenan, a gel strength regulator and a carrageenase inhibitor are added into a gel matrix, and the carrageenase inhibitor is ethylenediamine tetraacetic acid or salt thereof; the dosage of the carrageenase inhibitor is 0.03 to 0.05 percent of the mass of the gel; the gel strength regulator is at least one of starch and urea; the dosage of the gel strength regulator is 1-5% of the mass of the gel.

2. A microorganism detection sheet, characterized in that: a culture medium is adsorbed on the detection sheet, and the culture medium comprises nutrient substances, a color indicator, a suspending agent and the cold water soluble gel matrix of claim 1; wherein the content of the first and second substances,

the mixing ratio of the nutrient substance and the cold water soluble gel matrix is 1: (4-8);

the addition amount of the suspending agent is 30-60% of the dry weight of the culture medium;

the suspending agent is at least one selected from chitosan, dextran, hyaluronic acid, polyvinyl alcohol, polyethylene oxide and polyethylene glycol.