Bamboo shoot preservation method and application thereof

Abstract

The invention discloses a bamboo shoot fresh-keeping method and application thereof, and belongs to the field of bamboo shoot processing. Pretreated fresh bamboo shoots are soaked in a coating liquid of a specific formula to be treated, the treated bamboo shoots are drained to form a film, and then low-dose irradiation treatment is combined to prepare the fresh-keeping bamboo shoots. According to the method, a composite fresh-keeping layer is constructed on the surfaces of the bamboo shoots by utilizing the synergistic effect of coating and irradiation, so that the special quality deterioration problems of exuberant respiration, easiness in fibrosis, easiness in browning and the like of the picked bamboo shoots are solved in a targeted manner, the respiration intensity of the bamboo shoots is remarkably reduced, lignin accumulation and water loss are delayed, and the color, crisp and tender texture and flavor of the bamboo shoots are kept for a long time; the shelf life of commodities is prolonged.

Description

Technical Field

[0001] This invention relates to a method for preserving bamboo shoots and its application, belonging to the field of bamboo shoot processing. Background Technology

[0002] Bamboo shoots, an important forest vegetable, are delicious and rich in dietary fiber, protein, and various trace elements, making them a favorite among consumers. However, after harvesting, bamboo shoots exhibit vigorous physiological activity and high respiration rates, leading to rapid moisture loss, rapid fibrosis, and microbial contamination, resulting in a sharp decline in quality and significant challenges in storage and preservation. Therefore, post-harvest preservation technology is a crucial factor affecting the profitability of the bamboo shoot industry and market supply.

[0003] Currently, bamboo shoot preservation methods mainly include physical preservation (such as low-temperature refrigeration, controlled atmosphere storage, and irradiation preservation) and chemical preservation (such as soaking in preservatives). Among these, coating preservation technology has become a research and application hotspot due to its advantages such as simple operation, low cost, and edible safety. However, existing coating preservation methods still have drawbacks, including difficulty in controlling film thickness, susceptibility of preservation effect to environmental influences, the need for optimization in the selection and ratio of film-forming materials, insignificant antibacterial properties, and the potential for some materials to affect food quality or pose safety hazards. Furthermore, bamboo shoot coating requires high pretreatment standards; the surface of the bamboo shoots must be thoroughly cleaned of mud and impurities before coating, otherwise some residual microorganisms may continue to multiply inside the film, and biodegradable film components may be utilized, thus affecting the long-term storage effect of the bamboo shoots. Unlike fruits and vegetables, which mainly target moisture loss and microbial infection, bamboo shoots require inhibition of lignification and prevention of enzymatic browning. Most coating materials primarily inhibit moisture loss and cannot effectively inhibit lignification of bamboo shoots; therefore, specific treatments must be combined with coating to achieve better preservation results.

[0004] Commonly used coating materials for food preservation include polysaccharides, proteins, and lipids, which have shown good results in blocking moisture evaporation and inhibiting microbial growth. However, current research and applications of coating technologies are mostly designed based on the preservation needs of conventional fruits and vegetables such as apples, citrus fruits, and tomatoes, with their functions focusing on preventing water loss, preventing decay, and protecting color. Bamboo shoots, as a special category with extremely vigorous postharvest respiration and rapid lignification, present a core challenge in preservation: how to effectively regulate their intense respiration. This places significantly higher demands on the gas selective permeability of coating materials compared to traditional fruits and vegetables. Currently, coating systems developed for conventional fruits and vegetables often suffer from insufficient gas (O2 / CO2) exchange capacity due to overly dense film formation. When applied to bamboo shoots, they not only fail to establish a suitable micro-controlled atmosphere required to inhibit respiration but may also accelerate quality deterioration due to internal gas imbalance.

[0005] Bamboo shoots still require normal aerobic respiration after harvesting to sustain their life activities. Existing coatings often prioritize excellent barrier properties, resulting in excessively dense films and an imbalance in oxygen (O2) and carbon dioxide (CO2) permeability. This leads to excessively low O2 concentration and excessive CO2 accumulation in the bamboo shoot's surface microenvironment, forcing it to switch to anaerobic respiration. This process not only accelerates nutrient consumption but also leads to the accumulation of odor-causing substances such as ethanol and acetaldehyde, causing tissue physiological toxicity and producing a "suffocating" effect, thus accelerating spoilage. In other words, existing coatings struggle to achieve a balance between "sealing" and "breathing," and their low permeability has become a key technical obstacle restricting their effectiveness in preserving bamboo shoots.

[0006] Therefore, given the unique post-harvest physiological characteristics of bamboo shoots, developing a novel coating-based preservation material that combines excellent antibacterial and moisture-resistant properties with suitable and adjustable air permeability is of urgent practical need and significant application value for achieving efficient and safe preservation of bamboo shoots. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for preserving bamboo shoots. The method involves immersing pre-treated fresh bamboo shoots in a coating solution with a specific formulation, draining to form a film, and then combining this with low-dose irradiation treatment to prepare preserved bamboo shoots. This method utilizes the synergistic effect of coating and irradiation to construct a composite preservation layer on the surface of the bamboo shoots. It specifically addresses the unique quality deterioration problems of bamboo shoots, such as vigorous post-harvest respiration, susceptibility to fibrosis, and browning. It significantly reduces respiration intensity, delays lignin accumulation and moisture loss, thereby achieving long-term preservation of the bamboo shoots' color, crisp texture, and flavor, and extending their shelf life.

[0008] The first objective of this invention is to provide a method for preserving bamboo shoots, comprising the following steps: Pre-treated bamboo shoots are immersed in a coating solution, then drained and packaged to obtain coated bamboo shoots; the coated bamboo shoots are then subjected to irradiation treatment to obtain the finished preserved bamboo shoots. The coating solution contains, by weight percentage, 1-3% chitosan, 1-3% hydroxypropyl methylcellulose, 1-3% sodium alginate, and 0.1-0.5% ascorbic acid.

[0009] In one embodiment, the pretreatment involves washing fresh bamboo shoots and then draining them at 0-4°C for 6-8 hours.

[0010] In one embodiment, the soaking is performed at 0-4°C for 5-10 minutes.

[0011] In one embodiment, the radiation dose of the irradiation is 2 to 3 kGy.

[0012] A second objective of this invention is to provide fresh bamboo shoots prepared by any of the methods described above.

[0013] A third objective of this invention is to provide a method for inhibiting the respiration rate, lignin content, and weight loss rate of bamboo shoots, comprising the following steps: Pre-treated bamboo shoots are immersed in a coating solution, then drained and packaged to obtain coated bamboo shoots; the coated bamboo shoots are then subjected to irradiation treatment to obtain the finished preserved bamboo shoots. The coating solution contains, by weight percentage, 1-3% chitosan, 1-3% hydroxypropyl methylcellulose, 1-3% sodium alginate, and 0.1-0.5% ascorbic acid.

[0014] In one embodiment, the pretreatment involves washing fresh bamboo shoots and then draining them at 0-4°C for 6-8 hours.

[0015] In one embodiment, the soaking is performed at 0-4°C for 5-10 minutes.

[0016] In one embodiment, the radiation dose of the irradiation is 2 to 3 kGy.

[0017] A fourth objective of this invention is to provide the application of any of the methods described above in the preservation of bamboo shoots.

[0018] Beneficial effects The bamboo shoot preservation method provided by this invention is simple to operate and has a stable process. Through the synergistic effect of coating and irradiation, it shows a significant comprehensive preservation effect on multiple key quality indicators. Specifically, after 12 days of storage, the respiration rate of bamboo shoots is only 108 mg / (kg·h) and the weight loss rate is 0.15%. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments in the specification. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar with the art.

[0020] Raw material source: The bamboo shoots were provided by the Yunnan Academy of Forestry and Grassland Sciences. Chitosan was purchased from Shanghai Yuanye Biotechnology Co., Ltd. Hydroxypropyl methylcellulose was purchased from Sangon Biotech (Shanghai) Co., Ltd. Sodium alginate was purchased from Shanghai Yuanye Biotechnology Co., Ltd. Ascorbic acid was purchased from Shanghai Yuanye Biotechnology Co., Ltd. Tea polyphenols were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0021] The measurement methods involved in the examples are as follows: 1. Respiratory intensity measurement Take 3 bamboo shoots from each group, divide them into 3 subgroups, and put them into the Micro Pod small fruit post-harvest detection system for measurement. The unit of respiratory intensity is mg / (kg·h).

[0022] 2. Determination of lignin content The Boxbio lignin content detection kit was used, and the operation procedure was performed in accordance with the kit's instructions.

[0023] 3. Determination of weight loss rate The mass (W1, g) of freshly cut bamboo shoots during storage and the mass (W2, g) after a period of storage were determined separately, using the following formula:

[0024] 4. Hardness Measurement The texture of bamboo shoots was assessed using a TA-XT Plus texture analyzer. Uniform bamboo shoot strips were placed under the P36R probe for texture measurement. The following measurement parameters were used: pre-test speed 2 mm / s, test speed 1 mm / s, post-test speed 1 mm / s, 70% compression during the test, pause time 5 s, data acquisition rate 400 pps, and trigger force 5 g.

[0025] 5. Sensory evaluation An evaluation panel of 40 people with sensory evaluation knowledge comprehensively evaluated the changes in sensory characteristics of bamboo shoots treated with different coating solutions during storage and divided them into 4 levels. The evaluation criteria are shown in Table 1. Table 1 Evaluation Criteria

[0026] Example 1: A method for preserving bamboo shoots A method for preserving bamboo shoots includes the following steps: Fresh bamboo shoots without mechanical damage, pests, or diseases, and with intact shape are selected. After rinsing off surface mud and impurities with water, they are placed at 4℃ for 6 hours and then drained. The bamboo shoots are then immersed in a coating solution at 4℃ for 5 minutes, drained, and allowed to dry to form a film. Finally, they are sealed in PE packaging to obtain the coated bamboo shoots.

[0027] An electron beam was used as the irradiation source to irradiate the coated bamboo shoots. The irradiation dose was 3 KGy, and the finished product was obtained.

[0028] The coating solution contains 1.5% chitosan, 1.5% hydroxypropyl methylcellulose, 1.5% sodium alginate, and 0.25% ascorbic acid.

[0029] Comparative Example 1: Using conventional fruit and vegetable coating liquid The specific implementation method is the same as in Example 1, except that the formulation of the coating liquid is changed to 1.5% chitosan, 1.5% citric acid, 0.2% sodium alginate, 0.3% xanthan gum, 2% tea polyphenols, and 94.5% pure water. The remaining steps remain the same, and the finished product is obtained.

[0030] Comparative Example 2: No hydroxypropyl methylcellulose added The specific implementation method is the same as in Example 1, except that hydroxypropyl methylcellulose is not added to the coating liquid formulation. The specific formulation is 3% chitosan, 1.5% sodium alginate, and 0.25% ascorbic acid.

[0031] Comparative Example 3: No sodium alginate added The specific implementation method is the same as in Example 1, except that sodium alginate is not added to the coating liquid formulation. The specific formulation is 3% chitosan, 1.5% hydroxypropyl methylcellulose, and 0.25% ascorbic acid.

[0032] Comparative Example 4: Changing the proportion of the coating liquid formulation The specific implementation method is the same as in Example 1, except that the ratio of chitosan and hydroxypropyl methylcellulose is changed. The specific formula is 2% chitosan, 1% hydroxypropyl methylcellulose, 1.5% sodium alginate, and 0.25% ascorbic acid.

[0033] Comparative Example 5: Changing the proportion of the coating liquid formulation The specific implementation method is the same as in Example 1, except that the ratio of chitosan and sodium alginate is changed. The specific formula is 1% chitosan, 2% hydroxypropyl methylcellulose, 1.5% sodium alginate, and 0.25% ascorbic acid.

[0034] Comparative Example 6: Ascorbic acid was replaced with tea polyphenols The specific implementation method is the same as in Example 1, except that ascorbic acid is replaced with tea polyphenols, while the other steps remain the same, and the finished product is obtained.

[0035] Comparative Example 7: No coating treatment applied. The specific implementation method is the same as in Example 1, except that the bamboo shoots are not coated. The remaining steps are the same to obtain the finished product.

[0036] Example 2: Performance Measurement Eighty freshly picked bamboo shoots were randomly sampled, and their initial properties were measured. The average value was used as a control group stored for 0 days. Subsequently, the remaining 72 bamboo shoots were randomly divided into eight groups and treated using the methods of Example 1 and Comparative Examples 1-7, respectively, to prepare the finished products. Each product was stored at 4°C for 4 days, 8 days, and 12 days, and its corresponding properties were measured.

[0037] 1. Measurement of respiratory intensity The results are shown in Table 2. The results indicate that the respiration intensity of bamboo shoots treated with coating was reduced compared with the uncoated group. However, when conventional fruit and vegetable coating liquid was used to preserve bamboo shoots, although the respiration intensity of bamboo shoots was reduced compared with the uncoated group, it was still at a high level. This shows that the design of existing fruit and vegetable coating liquid is usually based on the general needs of color protection and surface antibacterial properties of common fruits and vegetables, and is not suitable for bamboo shoots, a specific ingredient with extremely high requirements for suppressing respiration intensity.

[0038] Among them, the respiration intensity of Example 1 was the lowest compared to Comparative Examples 1-7, indicating that the coating liquid formulation can effectively inhibit the respiration of bamboo shoots. However, when the formulation and ratio of the coating liquid were changed, the air permeability regulation performance and structural integrity of the coating liquid were significantly insufficient, failing to establish a stable microenvironment that effectively inhibited respiration in bamboo shoots, resulting in a preservation effect far inferior to that of Example 1.

[0039] Table 2 Respiratory Intensity Measurement

[0040] 2. Lignin content determination The results are shown in Table 3. The results indicate that the lignin content of bamboo shoots continuously increases during storage. Among them, the increase in lignin content in Example 1 is the slowest during storage. This is because the bamboo shoot coating solution formulation and irradiation effectively inhibit respiration, thereby effectively prolonging the storage time of bamboo shoots.

[0041] Table 3. Determination of Lignin Content

[0042] 3. Determination of weight loss rate The results are shown in Table 4. The results indicate that the weight loss rate of bamboo shoots increases with storage time, which is due to water loss caused by respiration during storage. The bamboo shoots in Example 1 showed a weight loss rate of only 0.15% after 12 days of storage, demonstrating excellent water retention performance. However, while the weight loss rate of bamboo shoots in Comparative Example 4 was similar to that of Example 1 in the early stages, it rose sharply to 0.48% in the later stages of storage, indicating that the water retention performance of the formula in Comparative Example 4 decreased during long-term storage.

[0043] In summary, the optimized formulation of Example 1 effectively inhibits respiration and reduces moisture loss by forming a stable, dense coating with good gas selectivity, thus performing best in maintaining the weight and freshness of bamboo shoots, further confirming the effectiveness of the formulation in preserving bamboo shoots.

[0044] Table 4. Weight Loss Rate Measurement

[0045] 4. Hardness Measurement The results are shown in Table 5. The results indicate that the hardness of bamboo shoots gradually increases with storage time, mainly due to the increased lignin content in the bamboo shoots, which affects the hardness. Among them, Example 1 showed the slowest increase in hardness compared to the other treatment groups, indicating that the bamboo shoot preservation method used in Example 1 can effectively delay the increase in bamboo shoot hardness.

[0046] Table 5 Hardness Measurement

[0047] 5. Sensory evaluation The results are shown in Table 6. The results indicate that the sensory evaluation scores of bamboo shoots decreased with the extension of storage time. Among them, the sensory evaluation of Example 1 was the best, indicating that the coating liquid formulation can maintain the taste of bamboo shoots well.

[0048] Table 6 Sensory Evaluation

[0049] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preserving bamboo shoots, characterized in that, Including the following steps: Pre-treated bamboo shoots are immersed in a coating solution, then drained and packaged to obtain coated bamboo shoots; the coated bamboo shoots are then subjected to irradiation treatment to obtain the finished preserved bamboo shoots. The coating solution contains, by weight percentage, 1-3% chitosan, 1-3% hydroxypropyl methylcellulose, 1-3% sodium alginate, and 0.1-0.5% ascorbic acid.

2. The method according to claim 1, characterized in that, The pretreatment involves washing fresh bamboo shoots and then draining them at 0-4℃ for 6-8 hours.

3. The method according to claim 1, characterized in that, The soaking process involves soaking at 0-4℃ for 5-10 minutes.

4. The method according to claim 1, characterized in that, The radiation dose of the irradiation is 2~3 KGy.

5. Fresh bamboo shoots prepared by any one of claims 1 to 4.

6. A method for inhibiting the respiration rate, lignin content, and weight loss rate of bamboo shoots, characterized in that, Including the following steps: Pre-treated bamboo shoots are immersed in a coating solution, then drained and packaged to obtain coated bamboo shoots; the coated bamboo shoots are then subjected to irradiation treatment to obtain the finished preserved bamboo shoots. The coating solution contains, by weight percentage, 1-3% chitosan, 1-3% hydroxypropyl methylcellulose, 1-3% sodium alginate, and 0.1-0.5% ascorbic acid.

7. The method according to claim 6, characterized in that, The pretreatment involves washing fresh bamboo shoots and then draining them at 0-4℃ for 6-8 hours.

8. The method according to claim 6, characterized in that, The soaking process involves soaking at 0-4℃ for 5-10 minutes.

9. The method according to claim 6, characterized in that, The radiation dose of the irradiation is 2~3 KGy.

10. The application of the method according to any one of claims 6 to 9 in the preservation of bamboo shoots.

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