Post-harvest green living body preservation method for dendrocalamus brandisii shoots

Abstract

The invention provides a postharvest green living body preservation method for dendrocalamus brandisii shoots, and relates to the technical field of bamboo shoot preservation. The preservation method mainly comprises the following steps: precooling the picked dendrocalamus brandisii shoots in a refrigeration house at 4-10 DEG C for 8-14 hours, soaking the dendrocalamus brandisii shoots in a preservative, wrapping the dendrocalamus brandisii shoots with a preservative film, and refrigerating the dendrocalamus brandisii shoots at 4 DEG C; wherein the dendrocalamus brandisii shoot shell fermentation extracting solution is obtained by cooking dendrocalamus brandisii shoot shell and bamboo shoot trimming residues, grinding into thick liquid, mixing with saccharomyces cerevisiae, fermenting, sterilizing and filtering. The method overcomes the defects in the prior art, effectively prolongs the shelf life of the dendrocalamus brandisii shoots, prevents nutrient loss and browning of the dendrocalamus brandisii shoots, and comprehensively improves the economic value of the dendrocalamus brandisii shoots.

Description

Technical Field

[0001] The present invention relates to the technical field of bamboo shoot fresh-keeping, and particularly relates to a post-harvest green in-vivo fresh-keeping method for sweet dragon bamboo shoots. Background Art

[0002] Sweet dragon bamboo shoots, also known as sweet bamboo shoots, have extremely robust shapes and are good fresh edible bamboo shoot varieties. Sweet dragon bamboo shoots are rich in nutrition, have a refreshing taste, and have high market value. Now, artificial cultivation of sweet dragon bamboo is gradually carried out for bamboo shoot production.

[0003] Since the shoot emergence period of sweet dragon bamboo is mostly in summer and the shoot sprouting period is during the high-temperature season, sweet dragon bamboo shoots need to be eaten as soon as possible after harvesting. Otherwise, the bamboo shoots will gradually age or deteriorate, the nutrient components will be lost, and the whole will turn brown, seriously affecting the edible value and economic value of the bamboo shoots. Based on this, how to carry out in-vivo fresh-keeping of sweet dragon bamboo shoots after harvesting to extend their shelf life is crucial.

[0004] In the literature "Effect of Three Kinds of Biological Preservatives on the Lignification of Post-harvest Dendrocalamus brandisii Bamboo Shoots" published by Zhang Xiongfeng et al., a preservative was prepared by using nisin, lysozyme, and chitosan solution to treat fresh Dendrocalamus brandisii bamboo shoots, which can effectively extend the fresh-keeping period of Dendrocalamus brandisii bamboo shoots, prevent discoloration and lignification. However, in this document, the fresh-keeping effect of Dendrocalamus brandisii bamboo shoots was for 8 days, which is relatively short for the production and sales of sweet dragon bamboo shoots. Therefore, how to further extend the shelf life of sweet dragon bamboo shoots is an important research direction at the present stage. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a post-harvest green in-vivo fresh-keeping method for sweet dragon bamboo shoots, which can effectively extend the shelf life of sweet dragon bamboo shoots, prevent the loss of bamboo shoot nutrients and browning, and comprehensively improve the economic value of sweet dragon bamboo shoots.

[0006] To achieve the above object, the technical solution of the present invention is realized through the following technical solutions: A post-harvest green in-vivo fresh-keeping method for sweet dragon bamboo shoots, the fresh-keeping method comprising the following steps: S1. Bamboo shoot precooling treatment: Take fresh sweet dragon bamboo shoots, peel off the outer bamboo shoot sheaths, trim and shape them, then wash them clean, and place them at a temperature of 4 - 10°C for precooling treatment; or place them at a temperature of 4 - 10°C for precooling after harvesting, and then shell, trim and shape, and wash them. S2. Prepare a preservative according to the following contents: chitosan 10 - 20 g / L + lysozyme 0.5 - 0.8 g / L + fermentation extract of sweet dragon bamboo shoot sheaths 120 - 180 mL / L + tea polyphenols 20 - 40 mg / L + antioxidant 15 - 20 mg / L, and the rest is distilled water; wherein the fermentation extract of sweet dragon bamboo shoot sheaths is obtained by steaming the sweet dragon bamboo shoot sheaths and the remaining bamboo shoot trimming residues, mixing them with Saccharomyces cerevisiae for fermentation, and then sterilizing and filtering. S3. Preservation agent treatment: Soak the pre-cooled bamboo shoots in the preservation agent for 30 - 60 s, then take them out and let them stand at 10 °C to drain the excess preservation agent. S4. Long-term storage: Wrap the above-mentioned bamboo shoots that have stood still with plastic wrap and store them at 4 °C for a long time.

[0007] Preferably, the pre-cooling treatment time in step S1 is 8 - 14 h, with the aim of finally reducing the central temperature of the bamboo shoots to below 6 °C, and optimally 4 °C.

[0008] Preferably, the preparation method of the fermentation extract of Tianlong bamboo shoot shells in step S2 includes the following steps: S2-1. Rinse the fresh bamboo shoot shells and the remaining parts of the trimmed bamboo shoots, then steam them at 110 - 120 °C for 30 min. Collect the juice during steaming and mix it with the bamboo shoot shells, then add water to control the solid-liquid ratio to 1:2 - 3 and grind it into a slurry to obtain the mixed slurry for standby. S2-2. Inoculate 0.1% - 0.2% of the total mass of the mixed slurry with Saccharomyces cerevisiae and ferment for 30 - 40 h to obtain the fermented material for standby. S2-3. Sterilize the above-mentioned fermented material and then press and filter it. The filtrate is the fermentation extract of Tianlong bamboo shoot shells.

[0009] Preferably, the viable count of Saccharomyces cerevisiae in step S2-2 is 1×10 9 -2×10 9 CFU / g.

[0010] Preferably, the sterilization method in step S2-3 is to raise the temperature to 115 °C, increase the pressure to 1.85 Mpa, and perform heat and pressure preservation sterilization for 15 min.

[0011] Preferably, the storage and use temperatures of the fermentation extract of Tianlong bamboo shoot shells and the prepared preservation agent are both controlled below 10 °C.

[0012] Preferably, the antioxidant in step S2 is citric acid.

[0013] Preferably, the temperature of the preservation agent is controlled at 2 - 10 °C during the soaking treatment in step S3.

[0014] Preferably, the standing time in step S3 is 1 - 2 h.

[0015] Preferably, the plastic wrap used in step S4 is PE plastic wrap.

[0016] The present invention provides a post-harvest green in-vivo preservation method for Tianlong bamboo shoots. Compared with the prior art, its advantages are as follows: The present invention adopts early low-temperature treatment, followed by pre-cooling and then treatment with a mixed preservative to effectively extend the shelf life of fresh and sweet dragon bamboo shoots. Moreover, the low-temperature and pre-cooling treatments can effectively inhibit the respiration of bamboo shoots, reduce the nutritional loss of bamboo shoots during subsequent low-temperature storage, and the preservative prepared by compounding chitosan, lysozyme, the fermentation extract of dragon bamboo shoot shells, tea polyphenols, and antioxidants is used to treat the bamboo shoots and then wrapped with plastic wrap and refrigerated, which can effectively antioxidize and prevent the browning of bamboo shoots, further reduce the loss of total sugar during storage, reduce the generation of lignin, delay the lignification degree of bamboo shoots, and extend the shelf time to 35 days. Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the surface browning of bamboo shoots stored for 10 days in Experimental Group 1 of the present invention; Figure 2 It is a schematic diagram of the surface browning of bamboo shoots stored for 35 days in Experimental Group 1 of the present invention; Figure 3 It is a schematic diagram of the surface browning of bamboo shoots stored for 10 days in Experimental Group 2 of the present invention; Figure 4 It is a schematic diagram of the surface browning of bamboo shoots stored for 35 days in Experimental Group 2 of the present invention; Figure 5 It is a schematic diagram of the surface browning of bamboo shoots stored for 10 days in Experimental Group 3 of the present invention; Figure 6 It is a schematic diagram of the surface browning of bamboo shoots stored for 35 days in Experimental Group 3 of the present invention; Figure 7 It is a schematic diagram of the surface browning of bamboo shoots stored for 10 days in Experimental Group 4 of the present invention; Figure 8 It is a schematic diagram of the surface browning of bamboo shoots stored for 35 days in Experimental Group 4 of the present invention; Figure 9 It is a schematic diagram of the surface browning of bamboo shoots stored for 10 days in Experimental Group 5 of the present invention; Figure 10 It is a schematic diagram of the surface browning of bamboo shoots stored for 35 days in Experimental Group 5 of the present invention; Figure 11 It is a schematic diagram of the surface browning of bamboo shoots stored for 10 days in Experimental Group 6 of the present invention; Figure 12 It is a schematic diagram of the surface browning of bamboo shoots stored for 35 days in Experimental Group 6 of the present invention; Figure 13 It is a schematic diagram of the surface browning of bamboo shoots stored for 10 days in the control group of the present invention; Figure 14 It is a schematic diagram of the surface browning of bamboo shoots stored for 35 days in the control group of the present invention. Detailed Description of the Invention

[0018] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following clearly and completely describes the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0019] The Saccharomyces cerevisiae used below is commercially available, with a viable count of 1×10 9 cfu / g, and the preservation number of the Saccharomyces cerevisiae is CCTCC NO: M2014019; the antioxidant is citric acid. Example 1:

[0020] Raw material preparation: 1. Raw material preparation: 1.1 Select the same batch of mature sweet dragon bamboo shoots, remove the bad shoots, and reserve them as experimental materials; 1.2 Preparation of preservatives: Preservative 1: Chitosan 10 g / L + Lysozyme 0.5 g / L + Extract A 1200 mL / L + Tea polyphenols 20 mg / L + Antioxidant 15 mg / L, and the rest is distilled water; Preservative 2: Chitosan 20 g / L + Lysozyme 0.8 g / L + Extract A 180 mL / L + Tea polyphenols 40 mg / L + Antioxidant 20 mg / L, and the rest is distilled water; Preservative 3: Chitosan 10 g / L + Lysozyme 0.5 g / L + Extract B 120 mL / L + Tea polyphenols 20 mg / L + Antioxidant 15 mg / L, and the rest is distilled water; Preservative 4: Chitosan 10 g / L + Lysozyme 0.5 g / L + Extract C 120 mL / L + Antioxidant 15 mg / L, and the rest is distilled water; 1.2-1 The preparation method of Extract A is as follows: (1) After rinsing the fresh bamboo shoot shells (including the residues remaining after trimming the bamboo shoots) thoroughly, steam them for 30 min, collect the juice during steaming and mix it with the bamboo shoot shells, then add water to control the solid-liquid ratio to 1:2 and grind it into a slurry to obtain a mixed slurry; (2) Inoculate the mixed slurry with 0.2% of Saccharomyces cerevisiae based on the total mass of the mixed slurry, and ferment it for 35 h to obtain a fermented material; (3) Heat the above fermented material to 115°C, increase the pressure to 1.85 Mpa, sterilize it for 15 min, and then press and filter it. The filtrate is Extract A.

[0021] 1.2-2 The preparation method of Extract B is as follows: (1) Rinse the fresh bamboo shoot sheaths (including the residues remaining after trimming the bamboo shoots) thoroughly, then steam them for 30 minutes. Collect the juice during steaming and mix it with the bamboo shoot sheaths. Add clear water to control the solid-liquid ratio at 1:2, and then grind it into a slurry to obtain a mixed slurry. (2) Heat the mixed slurry to 115 °C, increase the pressure to 1.85 Mpa, sterilize it for 15 minutes, then press and filter. The filtrate is Extract B.

[0022] 1.2 - 3. The preparation method of Extract C is as follows: (1) Inoculate 0.2% of Saccharomyces cerevisiae into YPD liquid medium and culture it under suitable conditions for 35 hours to obtain a fermentation material. (2) Heat the above fermentation material to 115 °C, increase the pressure to 1.85 Mpa, sterilize it for 15 minutes, then press and filter. The filtrate is Extract C.

[0023] 2. Preservation treatment of Dendrocalamus brandisii:

[0024] (1) For fresh Dendrocalamus brandisii, peel off the outer bamboo shoot sheaths, trim and shape them, then wash them thoroughly. Place them at 4 °C for precooling treatment for 8 hours, and then take them out. (2) Immerse the precooled bamboo shoots in a preservative at 5 °C for 50 seconds, then take them out and let them stand at 10 °C for 1.5 hours to drain the excess preservative. Then wrap them with PE plastic wrap and store them at 4 °C. Detection:

[0025] 1. Detect the preservation effect of different preservatives on Dendrocalamus brandisii: Referring to the above preservation treatment method, a total of 5 groups of preservation experiments are set up (10 bamboo shoots in each group). Each group is treated with different preservatives according to Table 1 below, and the weight loss rate, total sugar content, lignin content, crude fiber content (the main component is cellulose, and also contains some hemicellulose, pentosan, and nitrogen-containing substances), and vitamin C content of the bamboo shoots in each group are detected at 0 d, 5 d, 15 d, and 35 d of preservation. Among them, the browning grade is divided into 0 - 5 levels, and the classification standard is: level 0 is no browning, level 1 is slight browning (browning area ≤ 10%), level 2 is mild browning (browning area 10% - 20%), level 3 is moderate browning (browning area 20% - 30%), level 4 is severe browning (browning area 30% - 40%), and level 5 is extreme browning (browning area > 50%); Weight loss rate = (weight before storage - weight after storage) / weight before storage; The total sugar content is determined by the direct titration method with Fehling's reagent; The detection of lignin content is as follows: Cut 5 g (M1) of bamboo shoots, crush them, and mix them with 10 mL of 72% H 2 SO 4Stir evenly, then let it stand at a constant temperature of 20 °C for 4 h, and then H 2 SO 4 is diluted to 3%, boiled for 2 h, then filtered by suction and washed until neutral, and then dried in an oven at 105 °C, cooled and weighed, recorded as M2, and the final lignin content = M2 / M1; The detection of crude fiber content is as follows: Referring to the method of GB / T 5009.10 - 2003, it is measured using a Fibertc 8000 cellulose analyzer.

[0026] The vitamin C content is determined by the 2,6 - dichlorophenol indophenol method.

[0027] The specific detection results are shown in Table 1 below: Table 1

[0028] As can be seen from the above table, the overall weight loss rate, lignin content, and crude fiber content of the bamboo shoots treated with preservative 1 and preservative 2 are lower after 35 days of storage, and the total sugar content and vitamin C content are higher. On the 5th day of storage, the total sugar content of experimental groups 1 - 4 and the control group all increased. Subsequently, the total sugar content of the control group decreased significantly, while the total sugar content of experimental groups 1 - 4 decreased less, and the decrease amplitude of experimental groups 1 - 2 was the smallest. That is, treating bamboo shoots with preservative 1 and preservative 2 in experimental groups 1 - 2 has a better preservation effect.

[0029] 2. Use preservative 1 to preserve sweet dragon bamboo shoots, and set different preservation treatment methods according to the following experimental groups: Experimental group 5: (1) For fresh sweet dragon bamboo shoots, peel off the outer bamboo shoot sheaths, trim and shape them, and then wash them clean; (2) Soak the washed bamboo shoots in preservative 1 at 5 °C for 50 s, then take them out and let them stand at 10 °C for 1.5 h to drain the excess preservative, and then wrap them with PE fresh - keeping film and store them at 4 °C.

[0030] Experimental group 6: (1) For fresh sweet dragon bamboo shoots, peel off the outer bamboo shoot sheaths, trim and shape them, and wash them clean, then pre - cool them at 5 °C for 8 h; (2) Soak the pre - cooled bamboo shoots in preservative 1 at room temperature for 50 s, then take them out and let them stand at room temperature for 1.5 h to drain the excess preservative, and then wrap them with PE fresh - keeping film and store them at 4 °C.

[0031] Detect the weight loss rate, total sugar content, lignin content, crude fiber content, and vitamin C content of the above experimental group 5 and experimental group 6 at 0 d, 5 d, 15 d, and 35 d of storage. The specific results are shown in Table 2 below Table 2

[0032] By comparing Experimental Groups 5 - 6 in the above table with the above Experimental Group 1, it can be seen that the weight loss rate, total sugar content, lignin content, crude fiber content, and vitamin C in Experimental Groups 5 - 6 and Experimental Group 1 during storage have little difference, but the overall flatness is slightly worse than that of Experimental Group 1.

[0033] Grade the browning of the bamboo shoots in the above Experimental Groups 1 - 6 and the control group after 10 days and 35 days of storage (take 3 bamboo shoots from each group to calculate the average value). The specific calculation results are shown in Table 3 and the appendix Figure 1-14 As shown, and the browning is divided into grades 0 - 5. The grading standard for each grade is: Grade 0 is no browning, Grade 1 is slight browning (browning area ≤ 10%), Grade 2 is mild browning (browning area 10% - 20%), Grade 3 is moderate browning (browning area 20% - 30%), Grade 4 is severe browning (browning area 30% - 40%), and Grade 5 is extreme browning (browning area > 50%).

[0034] Table 3

[0035] As can be seen from the above table, Experimental Groups 1 - 2 have lower browning grades and still have higher quality after 35 days of storage, while Experimental Groups 5 - 6 have a relatively higher degree of browning.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preserving green live bamboo shoots after harvest, characterized in that: The fresh-keeping method comprises the following steps: S1. Precooling bamboo shoots: Take fresh sweet dragon bamboo shoots, peel off the outer shell, trim and shape them, clean them, and precool them at 4-10°C; or precool them at 4-10°C after harvesting, then peel, trim and shape them, and wash them; S2. Prepare a preservative according to the following contents: chitosan 10-20g / L + lysozyme 0.5-0.8g / L + sweet bamboo shoot shell fermentation extract 120-180mL / L + tea polyphenols 20-40mg / L + antioxidant 15-20mg / L, and the rest is distilled water; wherein the sweet bamboo shoot shell fermentation extract is obtained by steaming the sweet bamboo shoot shell and the trimmed bamboo shoot residue, mixing them with brewer's yeast for fermentation, and then sterilizing and filtering; S3, preservative treatment: soak the pre-cooled bamboo shoots in a preservative for 30-60 seconds, then take them out and let them stand at 10°C to drain out excess preservative; S4. Long-term storage: Wrap the bamboo shoots after standing still with plastic wrap and store them at 4°C for a long term.

2. The preservation method according to claim 1, characterized in that: The precooling treatment time in step S1 is 8-14 hours, so that the final center temperature of the bamboo shoots drops below 6°C.

3. The preservation method according to claim 1, characterized in that: The method for preparing the fermented extract of sweet bamboo shoot shells in step S2 comprises the following steps: S2-1, rinse the fresh bamboo shoots and the trimmed bamboo shoots, and then steam them at 110-120° C. for 30 min, collect the juice during steaming and mix it with the bamboo shoots, add clean water to control the material-liquid ratio to 1:2-3, and grind into slurry to obtain a mixed slurry for later use; S2-2, inoculating 0.1%-0.2% of the total mass of the mixed slurry with brewer's yeast, fermenting for 30-40 hours, and obtaining a fermented material for use; S2-3, sterilizing the fermented material, squeezing and filtering it, and the filtrate is the fermented extract of sweet bamboo shoot shell.

4. The preservation method according to claim 3, characterized in that: The number of live yeast cells in step S2-2 is 1×10 9 -2×10 9 Pieces / g.

5. The preservation method according to claim 3, characterized in that: The sterilization method of step S2-3 is to increase the temperature to 115°C, increase the pressure to 1.85 MPa, and maintain the temperature and pressure for sterilization for 15 minutes.

6. The preservation method according to claim 1, characterized in that: The storage and use temperatures of the sweet bamboo shoot shell fermentation extract and the prepared preservative are both controlled below 10°C.

7. The preservation method according to claim 1, characterized in that: The antioxidant in step S2 is citric acid.

8. The preservation method according to claim 1, characterized in that: During the soaking process in step S3, the temperature of the preservative is controlled to be 2-10°C.

9. The preservation method according to claim 1, characterized in that: The standing time in step S3 is 1-2 hours.

10. The preservation method according to claim 1, characterized in that: The cling film used in step S4 is a PE cling film.

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