Fresh-keeping processing method of green bamboo shoots

Abstract

The invention relates to the field of food processing, and discloses a fresh-keeping processing method of green bamboo shoots, which comprises the following steps: S1, cleaning collected green bamboo shoots: firstly, manually cleaning impurities on the surfaces of the bamboo shoots, and then carrying out secondary cleaning by using a sodium hypochlorite solution with the concentration of 0.02-0.05%; s2, grading and classifying the cleaned green bamboo shoots according to the appearance color and the tenderness degree; s3, the bamboo shoots are properly aired, ultraviolet rays are used for disinfecting the operation environment, 75% ethyl alcohol is used for spraying treatment on the operation contact surface, and a disinfected cutter is used for removing pollution wounds of the green bamboo shoots. Through manual cleaning and secondary cleaning of the bamboo shoots with a 0.02-0.05% sodium hypochlorite solution, ultraviolet sterilization and disinfection of operation surfaces and tools with 75% ethanol are combined, microorganisms and impurities are effectively removed, the risk of wound pollution is reduced, the wound is soaked with a fresh-keeping solution and packaged with a double-layer paper bag, the fresh-keeping effect is enhanced, the moisture loss of the bamboo shoots is reduced, and the quality of the bamboo shoots is improved. And a plurality of defects of the traditional method are improved.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, in particular to a green bamboo shoot preservation processing method. Background Art

[0002] Green bamboo shoots, commonly known as "horse hoof shoots", are popular among consumers for their white, crisp and tender flesh and sweet taste. This high-fiber, high-protein, low-fat, low-sugar green forest vegetable is not only widely grown and eaten in China, but also has similar eating habits in Asian countries such as Japan and South Korea. However, due to the particularity of green bamboo shoots, they face many challenges in post-harvest processing and preservation.

[0003] The harvested cut surface of green bamboo shoots is large, and the wounds exposed to the air are very susceptible to contamination by microorganisms, leading to corruption and deterioration. At the same time, the cellulose content of bamboo shoots is high, and it is very easy to undergo wood fiberization after harvesting. This fiberization phenomenon not only makes the bamboo shoots hard, but also causes the color to brown, which in turn affects its taste and makes it bitter. Studies have shown that the flavor of green bamboo shoots begins to change within 4-5 hours at room temperature, and the shelf life is only about 1 day; even under refrigerated conditions, its shelf life can only be extended to about 7 days. This makes the storage and transportation of green bamboo shoots a major problem, severely limiting its market sales scope.

[0004] To extend the shelf life of green bamboo shoots, the main methods traditionally used include refrigeration, freezing or drying. However, these methods all have their own shortcomings and limitations. Although refrigeration can delay the deterioration process, the shelf life is still limited; freezing may cause the texture of the bamboo shoots to change, affecting the edible quality; and although drying can extend the shelf life, it will seriously affect the taste and flavor of the bamboo shoots and reduce their nutritional value.

[0005] In addition, green bamboo shoots are prone to browning, fiber dehydration and aging during storage, resulting in the loss of nutrients and a decline in appearance quality. These problems make it difficult for existing preservation technologies to effectively extend the shelf life of bamboo shoots without affecting their quality. In addition, although the shelf life of bamboo shoots can be extended by processing methods such as pickling and canning, these methods often change the natural flavor and taste of bamboo shoots, reducing their appeal as fresh food. At present, the proportion of fresh bamboo shoots on the market is only about 40%, and the remaining 60% of bamboo shoots are processed into products such as dried bamboo shoots, boiled bamboo shoots, fermented bamboo shoots and ready-to-eat seasoned bamboo shoots. This reflects the limitations of existing preservation technologies to a certain extent and cannot fully meet consumers' demand for fresh green bamboo shoots.

[0006] Therefore, the present invention proposes a green bamboo shoot preservation processing method to solve the shortcomings of the prior art. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a green bamboo shoot preservation processing method, which effectively solves the problem of green bamboo shoots being easily perishable and deteriorating during storage and transportation through optimized cleaning steps, wound treatment technology, immersion in a specially formulated preservative solution, innovative packaging method and precise refrigeration control.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions: A green bamboo shoot preservation processing method, comprising the following steps:

[0009] S1, cleaning the collected green bamboo shoots, the cleaning step comprising first manually cleaning impurities on the surface of the bamboo shoots, and then performing a secondary cleaning with a sodium hypochlorite solution having a concentration of 0.02% to 0.05%, the cleaning time being 2 minutes to 5 minutes;

[0010] S2, grading and classifying the cleaned green bamboo shoots according to their appearance color and maturity;

[0011] S3. Dry the bamboo shoots properly, disinfect the operating environment with ultraviolet light, spray the operating contact surface with 75% ethanol, and use a sterilized knife to remove the contaminated wound from the green bamboo shoots;

[0012] S4, soaking the wound surface of the green bamboo shoots after the excision wound in a fresh-keeping solution containing bamboo leaf flavonoids, potassium sorbate, and ascorbic acid for 10 to 15 seconds;

[0013] S5, packing the soaked green bamboo shoots in a double-layer paper bag, and spraying an antibacterial agent composed of tea polyphenols and rosemary extract on the inside of the paper bag;

[0014] S6. Refrigerate the packaged green bamboo shoots at 4°C and a humidity of 90% to 95%.

[0015] Preferably, during the manual cleaning step, the wound of the bamboo shoots is always kept facing upward to prevent bacteria in the external water source from entering the interior of the green bamboo shoots.

[0016] Preferably, in the step of removing the contaminated wound, the UV-C band light intensity of the ultraviolet disinfection is 5W to 10W, the irradiation time is not less than 15 minutes, and the ultraviolet lamp is turned off 30 minutes before the operator enters. The relative humidity of the operating environment is controlled at 60% to 70%.

[0017] Preferably, in the preparation step of the fresh-keeping solution, bamboo leaf flavonoids, potassium sorbate and ascorbic acid are dissolved in water, mixed evenly and then poured into ethanol to make the ethanol content reach 75%, and the prepared solution is filtered through a filter membrane with a pore size of 0.2 micrometers.

[0018] Preferably, the fresh-keeping liquid contains 0.05% bamboo leaf flavonoids, 0.1% potassium sorbate and 0.5% ascorbic acid.

[0019] Preferably, the thickness of the double-layer paper bag is 0.2 mm to 0.3 mm, the spraying amount of the antibacterial agent is 10 ml to 15 ml per square meter of the paper bag surface area, and the bag is left to dry at room temperature of 25° C. for 10 minutes to 20 minutes.

[0020] Preferably, in the antibacterial agent, the concentration of tea polyphenols is 3%, and the concentration of rosemary extract is 2%.

[0021] The present invention provides a green bamboo shoot preservation processing method, which has the following beneficial effects:

[0022] 1. The present invention achieves the technical effect of effectively removing microorganisms and residual impurities on the surface of bamboo shoots by first manually cleaning the impurities on the surface of bamboo shoots and then using a sodium hypochlorite solution with a concentration of 0.02% to 0.05% for secondary cleaning. Compared with the common single physical cleaning method in the prior art, the present invention greatly improves the thoroughness of cleaning, significantly reduces the risk of microbial contamination, solves the shortcomings of incomplete microbial removal and bamboo shoots being susceptible to infection and deterioration in traditional methods, and lays a solid foundation for subsequent preservation treatment.

[0023] 3. The present invention utilizes ultraviolet disinfection, disinfects the operating contact surface, and uses the disinfected knife to treat the contaminated wound of green bamboo shoots, achieving the technical effect of effectively reducing wound microbial contamination and reducing the oxidation rate of bamboo shoots. Compared with the method of directly cutting wounds in the prior art, the present invention significantly reduces the number of microorganisms in the operating environment through ultraviolet disinfection, and the use of disinfected knives effectively controls the contamination of bamboo shoot wounds by microorganisms during the cutting process, solving the shortcomings of traditional methods that wounds are easily infected and oxidation is accelerated, resulting in a rapid decline in the quality of bamboo shoots, significantly extending the shelf life of bamboo shoots, and maintaining their original flavor and texture.

[0024] 4. The present invention adopts a fresh-keeping liquid formula containing bamboo leaf flavonoids, potassium sorbate, and ascorbic acid, and combines it with double-layer paper bag packaging technology to achieve the technical effect of inhibiting the oxidative browning of bamboo shoots and delaying water loss. Compared with the solution of using airtight plastic packaging or a simple single fresh-keeping liquid in the prior art, the present invention avoids the formation of water condensation beads inside the packaging through multiple protection mechanisms, significantly reduces the drying and quality deterioration of bamboo shoots caused by water evaporation, and solves the shortcomings of traditional fresh-keeping methods, such as unsatisfactory fresh-keeping effects and the easy occurrence of browning and fibrosis of bamboo shoots, thereby greatly extending the fresh-keeping time of green bamboo shoots, so that the fresh-keeping period under refrigerated conditions reaches more than 15 days, while maintaining freshness and taste. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The flowchart of the green bamboo shoot preservation processing method is as follows;

[0026] Figure 2 This is the appearance of the bamboo shoots in Example 1 after being left for 18 days;

[0027] Figure 3 This is the appearance of the bamboo shoots in Example 2 after being left for 18 days;

[0028] Figure 4 This is the appearance of the bamboo shoots in Example 3 after being left for 18 days;

[0029] Figure 5 This is an appearance diagram of the bamboo shoots of Example 4 after being left for 18 days. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example:

[0032] Please see attached Figure 1 -Attached Figure 5 :

[0033] Embodiment 1:

[0034] S1, cleaning the collected green bamboo shoots, the cleaning step comprising first manually cleaning impurities on the surface of the bamboo shoots, and then performing a secondary cleaning with a sodium hypochlorite solution having a concentration of 0.02% to 0.05%, the cleaning time being 2 minutes to 5 minutes;

[0035] S6. Place the cleaned and dried green bamboo shoots directly in a refrigerated environment at 4°C and a humidity of 90% to 95%.

[0036] Embodiment 2:

[0037] S1, cleaning the collected green bamboo shoots, the cleaning step comprising first manually cleaning impurities on the surface of the bamboo shoots, and then performing a secondary cleaning with a sodium hypochlorite solution having a concentration of 0.02% to 0.05%, the cleaning time being 2 minutes to 5 minutes;

[0038] S5, packing the washed and dried green bamboo shoots in double-layer paper bags, and spraying an antibacterial agent composed of tea polyphenols and rosemary extract on the inside of the paper bags;

[0039] S6. Refrigerate the packaged green bamboo shoots at 4°C and a humidity of 90% to 95%.

[0040] Embodiment 3:

[0041] S1, cleaning the collected green bamboo shoots, the cleaning step comprising first manually cleaning impurities on the surface of the bamboo shoots, and then performing a secondary cleaning with a sodium hypochlorite solution having a concentration of 0.02% to 0.05%, the cleaning time being 2 minutes to 5 minutes;

[0042] S3. Dry the bamboo shoots properly, disinfect the operating environment with ultraviolet light, spray the operating contact surface with 75% ethanol, and use a sterilized knife to remove the contaminated wound from the green bamboo shoots;

[0043] S5, packing the green bamboo shoots after the incision in a double-layer paper bag, and spraying an antibacterial agent composed of tea polyphenols and rosemary extract inside the paper bag;

[0044] S6. Refrigerate the packaged green bamboo shoots at 4°C and a humidity of 90% to 95%.

[0045] Embodiment 4:

[0046] S1, cleaning the collected green bamboo shoots, the cleaning step comprising first manually cleaning impurities on the surface of the bamboo shoots, and then performing a secondary cleaning with a sodium hypochlorite solution having a concentration of 0.02% to 0.05%, the cleaning time being 2 minutes to 5 minutes;

[0047] S3. Dry the bamboo shoots properly, disinfect the operating environment with ultraviolet light, spray the operating contact surface with 75% ethanol, and use a sterilized knife to remove the contaminated wound from the green bamboo shoots;

[0048] S4, soaking the wound surface of the green bamboo shoots after the excision wound in a fresh-keeping solution containing bamboo leaf flavonoids, potassium sorbate, and ascorbic acid for 10 to 15 seconds;

[0049] S5, packing the soaked green bamboo shoots in a double-layer paper bag, and spraying an antibacterial agent composed of tea polyphenols and rosemary extract on the inside of the paper bag;

[0050] S6. Refrigerate the packaged green bamboo shoots at 4°C and a humidity of 90% to 95%.

[0051] Test experiment:

[0052] After the bamboo shoots of Examples 1 to 4 were placed for 18 days, their crude protein, crude fiber, lignin content and peroxidase and phenylalanine ammonia lyase activities were measured, and the sensory changes of the bamboo shoots were evaluated and appearance photos were collected. The measurement method is as follows:

[0053] Crude protein detection method:

[0054] Refer to GB 5009.5—2016 National Food Safety Standard Determination of Protein in Foods - Method 1 - Kjeldahl Nitrogen Method.

[0055] Crude fiber detection method:

[0056] Refer to GB / T 5009.10—2003 Determination of crude fiber in plant foods

[0057] Detection method of lignin:

[0058] The redox method was used for determination, with reference to the determination of cellulose, hemicellulose and lignin in rice husk by Xiong Sumin et al.

[0059] Detection method of phenylalanine ammonia lyase:

[0060] Refer to the instructions for use of the Plant (P l ant) ​​Phenylalanine Ammonia Lyase (PAL) ELISA Detection Kit for the following steps:

[0061] 1. Take out the required strips from the aluminum foil bag after equilibration at room temperature for 20 minutes, and seal the remaining strips in a ziplock bag and return them to 4°C.

[0062] 2. Set up standard wells and sample wells, and add 50 μL of standards of different concentrations to each standard well;

[0063] 3. First add 10μL of the sample to be tested to the sample well, then add 40μL of sample diluent; do not add to the blank well.

[0064] 4. Except for the blank wells, add 100 μL of horseradish peroxidase (HRP)-labeled detection antibody to each well of the standard well and sample well, seal the reaction wells with a sealing film, and incubate in a 37°C water bath or incubator for 60 min.

[0065] 5. Discard the liquid, pat dry on absorbent paper, fill each well with washing solution, let it stand for 1 minute, shake off the washing solution, pat dry on absorbent paper, and repeat this process 5 times (you can also use a plate washer to wash the plate).

[0066] 6. Add 50 μL of substrate A and B to each well and incubate at 37°C in the dark for 15 min.

[0067] 7. Add 50 μL of stop solution to each well and measure the OD value of each well at a wavelength of 450 nm within 15 minutes.

[0068] Result judgment:

[0069] Draw a standard curve: In the Excel worksheet, use the standard concentration as the horizontal axis and the corresponding OD value as the vertical axis to draw the standard linear regression curve, and calculate the concentration value of each sample according to the curve equation.

[0070] Peroxidase (POD) detection method:

[0071] Preparation of phosphate buffer:

[0072] Solution A: 0.2M KH2PO4 solution: Analytical pure KH2PO4 27.216 g, dilute to 1000 mL with distilled water.

[0073] Solution B: 0.2M KH2PO4 solution: 5.644 g of analytically pure KH2PO4·3H2O4, dilute to 1000 mL with distilled water.

[0074] or:

[0075] Solution A: 0.2M NaH2PO4 solution Analytical pure NaH2PO4·2H2O 31.21g, dilute to 1000mL with distilled water.

[0076] Solution B: 0.2M NaH2PO4 solution Analytical pure Na2HPO4·12H2O 71.64g, dilute to 1000mL with distilled water.

[0077] Sample processing:

[0078] Weigh 0.5 g into a mortar, add 10 mL of pH 7.8 phosphate buffer, grind in an ice bath, pour the homogenate into a centrifuge tube, centrifuge for 20 min (10,000 × g), pour the supernatant (enzyme solution) into a test tube, and store at 0-4°C for later use.

[0079] Determination of POD (peroxidase):

[0080] (1) Preparation of 0.1 M pH 6.0 phosphate buffer: 219.25 mL of solution A + 30.75 mL of solution B, dilute to 500 mL;

[0081] (2) Preparation of POD reaction solution: 50 mL of 0.1 M pH 6.0 phosphate buffer was placed in a beaker, 28 μL of guaiacol was added, and the mixture was heated and stirred with a magnetic stirrer to completely dissolve. After cooling, 19 μL of 30% H2O2 was added and mixed, and the mixture was stored in a refrigerator.

[0082] (3) Determination of POD: 20 μL enzyme solution + 3 mL reaction solution were placed in a cuvette and the colorimetric reading was taken at 470 nm every 1 minute. The absorbance change per minute (ΔA470 / min·mg pr or ΔA470 / mgFW) was used to represent the enzyme activity.

[0083] Enzyme activity calculation:

[0084] A change (increase) of 0.01 in OD value per min was defined as 1 unit (u) of enzyme activity.

[0085]

[0086] in:

[0087] ΔA470——The change in absorbance during the reaction time;

[0088] W——fresh weight of sample (g);

[0089] t——reaction time (min);

[0090] Vt——total volume of the extracted enzyme solution (ml);

[0091] Vs——The volume of enzyme solution used for determination (ml).

[0092] Sensory evaluation:

[0093] The evaluation criteria are shown in the table below. Eight professionals who have received sensory evaluation training will conduct a comprehensive evaluation according to the sensory scoring standard table of the product. At the same time, appearance photos of different treatment groups during storage were collected under the same conditions.

[0094] Table 1 Sensory evaluation standards for bamboo shoots

[0095] Fraction Evaluation Criteria 80-100 The cut is tender, the meat is fresh, the color is bright, and the fragrance is strong 60-80 The cut is slightly wrinkled, the color is white, the meat is fresh and has a fresh fragrance 30-60 The cut surface is wrinkled, the cut surface turns brown and darkens, the meat quality deteriorates, and there is no fragrance. 0-30 The cut surface is obviously wrinkled, severely browned, or even moldy, the meat is rotten, and has a strange smell

[0096] The results are shown in Table 2 and Figure 2-Figure 5 :

[0097] The experimental results showed that the bamboo shoots that were only washed without other treatments and stored at 4℃ had the worst preservation effect, the highest degree of browning, obvious wound shrinkage, severe water loss, and the highest crude fiber and lignin content. Among them, phenylalanine ammonia lyase and peroxidase were positively correlated with the accumulation of lignin in bamboo shoot tissues, which could promote the synthesis of lignin in bamboo shoots. It was found that the phenylalanine ammonia lyase activity in treatment 1 was the highest; the crude protein content in treatment 1 was the lowest, which may be due to the highest degree of microbial contamination, which may lead to accelerated protein decomposition. Using double-layer paper bags for packaging and disinfection of cut bamboo shoots can delay water loss and inhibit the growth of lignin and crude fiber content to a certain extent. Among them, only adding double-layer packaging still cannot effectively inhibit the browning of bamboo shoots. Cutting bamboo shoots under disinfection conditions can effectively reduce microbial contamination and inhibit wound browning, but the wound still loses water and shrinks. Treatment 4 added preservative liquid treatment, and it was obviously found that it was the treatment group with the best preservation effect. It had the highest protein content, the lowest lignin and crude fiber content, the lowest phenylalanine ammonia lyase and peroxidase activities, and no browning or shrinkage on the wound. This shows that adding preservative liquid treatment can improve the preservation effect of bamboo shoots and enhance the effect of inhibiting lignification and browning of bamboo shoots. The shelf life of bamboo shoots was extended to 18 days, while maintaining the excellent taste of bamboo shoots.

[0098] Table 2 Comparison of the quality of different bamboo shoots after 18 days of storage

[0099]

[0100] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preserving green bamboo shoots, characterized in that: The following steps are involved: S1, cleaning the collected green bamboo shoots, the cleaning step comprising first manually cleaning impurities on the surface of the bamboo shoots, and then performing a secondary cleaning with a sodium hypochlorite solution having a concentration of 0.02% to 0.05%, the cleaning time being 2 minutes to 5 minutes; S2, grading and classifying the cleaned green bamboo shoots according to their appearance color and maturity; S3. Dry the bamboo shoots properly, disinfect the operating environment with ultraviolet light, spray the operating contact surface with 75% ethanol, and use a sterilized knife to remove the contaminated wound from the green bamboo shoots; S4, soaking the wound surface of the green bamboo shoots after the excision wound in a fresh-keeping solution containing bamboo leaf flavonoids, potassium sorbate, and ascorbic acid for 10 to 15 seconds; S5, packing the soaked green bamboo shoots in a double-layer paper bag, and spraying an antibacterial agent composed of tea polyphenols and rosemary extract on the inside of the paper bag; S6. Refrigerate the packaged green bamboo shoots at 4°C and a humidity of 90% to 95%.

2. A method for preserving green bamboo shoots according to claim 1, characterized in that: During the manual cleaning step, the wound of the bamboo shoots is always kept facing upward to prevent bacteria in the external water source from entering the interior of the green bamboo shoots.

3. A method for preserving green bamboo shoots according to claim 1, characterized in that: In the step of removing the contaminated wound, the UV-C band light intensity of the ultraviolet disinfection is 5W to 10W, the irradiation time is not less than 15 minutes, the ultraviolet lamp is turned off 30 minutes before the operator enters, and the relative humidity of the operating environment is controlled at 60% to 70%.

4. A method for preserving green bamboo shoots according to claim 1, characterized in that: In the preparation step of the fresh-keeping solution, bamboo leaf flavonoids, potassium sorbate and ascorbic acid are dissolved in water, mixed evenly, and then ethanol is poured into the water to make the ethanol content reach 75%, and the prepared solution is filtered through a filter membrane with a pore size of 0.2 microns.

5. A method for preserving green bamboo shoots according to claim 4, characterized in that: The fresh-keeping liquid contains 0.05% bamboo leaf flavonoids, 0.1% potassium sorbate and 0.5% ascorbic acid.

6. A method for preserving green bamboo shoots according to claim 1, characterized in that: The thickness of the double-layer paper bag is 0.2 mm to 0.3 mm, and the spraying amount of the antibacterial agent is 10 ml to 15 ml per square meter of the surface area of ​​the paper bag, and the paper bag is left to dry at room temperature of 25° C. for 10 minutes to 20 minutes.

7. A method for preserving green bamboo shoots according to claim 7, characterized in that: In the antibacterial agent, the concentration of tea polyphenols is 0% to 3%, and the concentration of rosemary extract is 0% to 2%.

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