A bostriki sweet dracaena bamboo shoot composite biological preservative as well as a preparation method and application thereof

Abstract

This invention provides a compound biological preservative for *Bambusa textilis* shoots, its preparation method, and its application, relating to the field of plant preservation technology. The compound biological preservative comprises, by weight percentage, 1.5%-2.5% chitosan, 0.02%-0.05% nisin, 3%-5% ascorbic acid, and the balance being water. This invention overcomes the shortcomings of existing technologies, effectively delaying the deterioration of the appearance and quality of *Bambusa textilis* shoots, alleviating their fibrosis, and extending their shelf life.

Description

Technical Field

[0001] This invention relates to the field of plant preservation technology, specifically to a compound biological preservative for sweet bamboo shoots, its preparation method, and its application. Background Technology

[0002] *Bambusa breviscapus*, a high-quality bamboo species belonging to the *Bambusa* genus, is mainly distributed in southern and western Yunnan Province at altitudes of 600-2000m, with planting bases covering nine counties and one district in Pu'er City. Its shoots are white and large, with a sweet taste, tender texture, and rich in various essential amino acids and trace elements. It is a high-protein, high-fiber, low-sugar, and low-fat premium forest vegetable, highly favored by consumers. Summer is the peak harvest season for *Bambusa breviscapus* shoots, and the high temperatures make the shoots highly susceptible to temperature changes after harvesting, leading to increased respiration and metabolism. After 48 hours of storage at room temperature, the shoots will severely dehydrate and age; for vegetables, this seriously affects the appearance and quality of the bamboo shoots, even rendering them worthless. Therefore, developing a compound biological preservative formula to delay the storage quality of *Bambusa breviscapus* shoots is of great significance for extending their shelf life.

[0003] Due to their natural materials, safety to humans, and biodegradability, bio-preservatives have become a research hotspot in fruit and vegetable preservation. Using only low storage temperatures or single preservatives is insufficient for achieving good preservation results and fails to maintain appearance, quality, and taste for extended periods. Therefore, combining low temperatures with preservatives is necessary to achieve optimal storage and preservation. Furthermore, bamboo shoots stored at 4℃ exhibit the best quality, as their enzyme activity is inhibited. The combination of low temperatures and natural bio-preservatives has become a research focus in recent years for the post-harvest preservation of bamboo shoots. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a compound biological preservative for Beaufort's sweet bamboo shoots, its preparation method, and its application. This effectively delays the deterioration of the appearance quality of Beaufort's sweet bamboo shoots, alleviates their degree of fibrosis, and extends the shelf life of the bamboo shoots.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A compound biological preservative for sweet bamboo shoots, the biological preservative being composed of the following substances in weight percentage: chitosan 1.5%-2.5%, nisin 0.02%-0.05%, ascorbic acid 3%-5%, and the remainder being water.

[0006] Preferably, the biological preservative is composed of the following substances in weight percentage: 2.5% chitosan, 0.02% nisin, 4% ascorbic acid, and the remainder being water.

[0007] The preparation method of the above-mentioned biological preservative mainly involves dissolving chitosan, nisin, and ascorbic acid in water to prepare chitosan solution, nisin solution, and ascorbic acid solution of a certain concentration, respectively, and then combining the chitosan solution, nisin solution, and ascorbic acid solution to obtain the biological preservative.

[0008] The above-mentioned biological preservative was applied to the preservation of Burley's sweet bamboo shoots.

[0009] Preferably, the application method includes the following steps: (1) Peel, wash and dry the sweet bamboo shoots of Bosch, and prepare the pre-treated bamboo shoots for later use; (2) Coat the surface of the pretreated bamboo shoots with a biological preservative, let them air dry naturally, and then put them into a freezer bag for cold storage.

[0010] Preferably, the natural air-drying environment in step (2) is a cold storage environment at 4±0.5℃.

[0011] Preferably, the food preservation bag in step (2) is a food-grade PE food preservation bag.

[0012] Preferably, the refrigeration and preservation temperature in step (2) is 4±0.5℃.

[0013] This invention provides a compound biological preservative for *Bretschneidera sinensis* bamboo shoots, its preparation method, and its application. Compared with existing technologies, its advantages are: This invention adopts L9(3) 3 An orthogonal experimental design was used to evaluate the correlation between chitosan, ascorbic acid, and nisin as composite film-forming materials and their postharvest preservation effect on sweet bamboo shoots. The optimal combination was determined through orthogonal experiments to be 2.50% chitosan + 0.02% nisin + 4.00% ascorbic acid. This combination significantly slowed down the moisture loss and quality loss rate of sweet bamboo shoots during storage, controlled the rate of browning, significantly reduced the rate of polysaccharide reduction, and slowed the rate of cellulose content increase, maintaining freshness for up to 15 days without spoilage. Attached Figure Description

[0014] Figure 1 A schematic diagram showing the change in moisture content of Burgh's sweet bamboo shoots under the treatment of compound preservatives; Figure 2 A schematic diagram showing the change in the mass loss rate of Burgh's sweet bamboo shoots under the treatment of compound preservatives; Figure 3 A schematic diagram showing the changes in the appearance of Burgh's sweet bamboo shoots under the treatment of compound preservatives; Figure 4 A schematic diagram showing the change in brightness of Burgh's sweet bamboo shoots under the treatment of compound preservatives; Figure 5A schematic diagram showing the change in yellowness of Burley's sweet bamboo shoots under the treatment of compound preservatives; Figure 6 A schematic diagram showing the change in hardness of Burgh's sweet bamboo shoots under the treatment of compound preservatives; Figure 7 A schematic diagram showing the change in respiration intensity of *Bretschneidera sinensis* bamboo shoots under treatment with a compound preservative. Figure 8 A schematic diagram showing the changes in polysaccharide and crude fiber content in *Bambusa textilis* bamboo shoots under treatment with a compound preservative. Figure 9 A schematic diagram showing the changes in polysaccharide and crude fiber content in *Bambusa textilis* bamboo shoots under treatment with a compound preservative. In the above figure, the same letter indicates that the difference between treatments is not significant (P>0.05), and different letters indicate that the difference is significant (P<0.05). Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1: 1. Materials and Methods 1.1 Sample Collection and Experimental Design 1.1.1 Sample Collection In August 2025, we harvested *Phyllostachys edulis* bamboo shoots from the Yangjiazhai Sweet Bamboo High-Yield Demonstration Base in Simao District, Pu'er City, Yunnan Province. We selected bamboo shoots that were uniform in size and shape and free from pests and diseases, and immediately transported them via cold chain to the Bamboo and Rattan Center of the Yunnan Academy of Forestry and Grassland Sciences.

[0017] 1.1.2 Orthogonal Experimental Design The optimal concentrations of single preservatives—chitosan (1.50%), nisin (0.02%), and ascorbic acid (3.00%)—were determined, and three levels were designed for each of two adjacent concentrations. Then, an orthogonal array L9(3) was applied. 3 Combine them (Table 1): Table 1. Factor Level Table for Orthogonal Experiment 1.2 Test Methods 1.2.1 Preparation of Compound Biological Preservative Using ultrapure water as a solvent, prepare 500 ml of 1.50%, 2.00%, and 2.50% chitosan solutions (7.50 g, 10.00 g, and 12.5 g), 0.02%, 0.03%, and 0.05% nisin solutions (0.10 g, 0.15 g, and 0.25 g), and 3.0%, 4.0%, and 5.0% ascorbic acid solutions (15.00 g, 20.00 g, and 25.00 g). After thorough dissolution, mix them in a 1:1:1 ratio for later use.

[0018] 1.2.2 Coating Treatment Peeled, washed, and dried bamboo shoots were evenly coated with the prepared preservation solution. The control group received no treatment. After treatment, the bamboo shoots were placed in a cold storage to air dry naturally. Then, they were packed into food-grade PE preservation bags and stored at low temperature (4±0.5℃). There were a total of 9 experimental groups, 1 control group, and 1 observation group. Each treatment was repeated 3 times. Samples were taken every 5 days for 15 days.

[0019] 1.2.3 Measurement Indicators (1) Moisture content Determined according to GB / T 5009.3-2003.

[0020] (2) Quality loss rate Weigh the control group and the experimental group before storage and after 5, 10 and 15 days of storage. Calculate the mass loss rate according to formula (1)

[20] .

[0021] W=(M0-M1) / M0×100% (1) Where: W - moisture content, %; M0 - mass before storage, g; M1 - mass after storage, g.

[0022] (3) Color difference value The brightness value L*, yellowness value b*, and color difference value △E of each bamboo shoot cross-section were measured using a colorimeter.

[0023] (4) Hardness Cut bamboo shoots into 2cm length, width, and height pieces and place them under the P36R probe of a texture analyzer. The parameters were set as follows: pre-test speed 2mm / s, test speed 1mm / s; return speed 2mm / s; trigger force 5g; compression degree 40%; data acquisition rate 400pps. Each sample was tested 6 times, and the average value was taken.

[0024] (5) Respiratory intensity For the determination by oxalic acid titration, place 20 mL of 0.2 mol / L NaOH at the bottom of a sealed container, add 20 g of peeled bamboo shoot sample, seal for 8 hours, remove the sample after standing, immediately add 1 drop of phenolphthalein indicator, and titrate with 0.3 mol / L oxalic acid until the red color disappears. Calculate the amount of carbon dioxide absorbed based on the amount of oxalic acid consumed.

[0025] (6) Polysaccharides For the determination using the phenol-sulfuric acid method, with glucose mass concentration (X) as the abscissa and absorbance (Y) as the ordinate, the standard curve obtained is: Y = 0.0084X + 0.0072 (R²⁻¹) 2 = 0.998), calculate the polysaccharide content (ug DE / g FW) in the sample according to the standard curve equation.

[0026] (6) Coarse fiber Determined in accordance with GB / T 5009.10-2003.

[0027] 1.3 Data Analysis The data were organized and statistically analyzed using Excel 2010 and IBM SPSS Statistics 24.0; plotting was performed using Origin 2021.

[0028] 2 Results and Analysis 2.1 Effects of compound biological preservative treatment on moisture content and weight loss rate of *Bambusa textilis* shoots like Figure 1 As shown, the moisture content of each group of *Bambusa textilis* bamboo shoots decreased with increasing storage time. On day 5 of storage, there was no significant difference in moisture loss rate among the groups. On day 10, the moisture loss rate of the bamboo shoots increased in the following order: Group 1 > Group 3 > Group 5 > Group 2 > Group 4 > Group 9 > Group 7 > CK > Group 8 > Group 6. On day 15, the overall moisture loss rate slowed down, showing the following order: Group 3 > Group 1 > Group 4 > Group 2 > Group 5 > CK > Group 9 > Group 8 > Group 7 > Group 6. From the overall trend of moisture change during the storage period, Group 1 showed the slowest moisture loss rate and maintained the highest moisture content.

[0029] like Figure 2As shown, during storage, the bamboo shoot tissue continuously lost water, and the mass loss rate of each group of bamboo shoots generally increased with the increase of storage time. On the 5th day of storage, the mass loss rate of the CK group and the 6th group was significantly higher than that of the other groups (P < 0.05), with the 1st group having the lowest rate and the 3rd group the next highest. By the 10th day of storage, the mass loss rate of the bamboo shoots in each group decreased significantly, in the following order: CK group > 2 group > 5 group > 1 group > 6 group > 7 group > 8 group > 9 group > 3 group > 4 group, with the 4th group having the lowest mass loss rate (P < 0.05). By the 15th day of storage, the mass loss rate of the bamboo shoots slowed down, with the trend being: 8 group > 7 group > 9 group > 6 group > CK group > 1 group > 5 group > 2 group > 3 group > 4 group. In summary, the mass loss rate of the 3rd group of bamboo shoots was the most stable during storage. In addition, the brightness value L* of the bamboo shoots was significantly positively correlated with the mass loss rate, indicating that the 3rd group treatment could effectively delay the mass loss of bamboo shoots.

[0030] 2.2 Effects of compound biological preservative treatment on the color of Burgh's sweet bamboo shoots As storage time increases, the pigments in the *Bambusa textilis* bamboo shoots degrade, leading to a decrease in brightness and an increase in yellowness. The original color and brightness of the shoots gradually fade, and the browning area increases. In groups CK, 3, and 8, browning begins to appear at the outermost edge of the cut surface on day 5. At day 15, although the browning of the shoots intensifies, there is no sign of decay in any of the shoots. Figure 3 ).Depend on Figure 4 It can be seen that the L* and b* values ​​of *Bambusa textilis* bamboo shoots changed significantly with prolonged storage time. The brightness value (L*) decreased overall, with the L* values ​​of the treatment groups all higher than the control group (CK). However, the rate of decrease in L* values ​​of groups 1, 7, 8, and 9 was significantly slower than that of the other treatment groups, with group 1 showing the slowest decrease. The yellowness value (b*) was positive for all groups, indicating that the color of the bamboo shoots was generally yellowish. The change in yellowness value in group 7 was the most stable and significantly lower than that of the other treatment groups. Figure 5 In summary, Group 7 can better control the rate of browning of bamboo shoots, which helps to improve sensory quality.

[0031] 2.3 Effect of compound biological preservative on the firmness of Burgh's sweet bamboo shoots from Figure 6 It can be seen that the hardness of each treatment group (1-9) was generally lower than that of the CK group, with the hardness of most treatment groups concentrated in the range of 550-700 gf. On the 5th day of storage, the CK group, group 3, and group 6 had the highest hardness values ​​(about 720 gf), indicating that the degree of fibrosis of the bamboo shoots was accelerated. Throughout the storage period, groups 1, 2, 4, and 9 showed relatively stable performance, with their hardness all lower than that of the CK group. Group 9 had the lowest hardness value (about 520 gf) and the lowest degree of fibrosis when stored for 15 days. Overall, the hardness and degree of fibrosis showed a positive correlation with the change in storage time.

[0032] 2.4 Changes in respiration intensity of *Bambusa textilis* shoots under treatment with compound biological preservative Depend on Figure 7 It was found that there were significant differences in the trend of respiration intensity changes during the storage of *Bamboo Buddleja officinalis* shoots among different treatment groups. Overall, groups 1, 2, 4, 5, 7, 8, and the control group showed an initial decrease followed by an increase, while groups 3, 6, and 9 showed an initial increase followed by a decrease. Specifically, the respiration intensity of groups 4 and 5 decreased significantly at 5 days of storage (P < 0.05), and increased somewhat in the later stages of storage. In contrast, the respiration intensity of group 9 remained stable throughout the storage period, and the value at 15 days was significantly lower than that at 0 days (P < 0.05), followed by group 1. This indicates that these two treatments had a certain inhibitory effect on respiration during the storage of *Bamboo Buddleja officinalis* shoots.

[0033] 2.5 Effects of compound biological preservatives on the polysaccharide and crude fiber content of *Bambusa textilis* bamboo shoots With prolonged storage, the polysaccharide content of bamboo shoots in all groups showed a gradual decreasing trend. For example... Figure 8 As shown, the polysaccharide content in group 1 bamboo shoots exhibited the most stable trend. With storage time extended to 15 days, the polysaccharide content in the control group (CK) decreased significantly. The polysaccharide content in groups 4, 5, 7, and 8 showed no significant difference from the CK group. Group 8 showed good results from 5 to 10 days, but its effect was not significant at 15 days, making it suitable for short-term storage. The effects of different treatments on polysaccharide content dynamically changed with storage time. The polysaccharide content in group 1 remained stable at the highest value, indicating that group 1 helped delay polysaccharide degradation during bamboo shoot storage.

[0034] Depend on Figure 9 It was found that the crude fiber content of bamboo shoots increased with prolonged storage time. After 5 days of storage, the control group (CK) had the highest crude fiber content, while group 1 had the lowest (P < 0.05). Groups 2-9 fluctuated between 11.2% and 12.5%, and groups 4, 6, and 9 showed no significant difference from the CK group. After 10 days of storage, the trend of crude fiber content in the CK and group 1 was consistent with that at 5 days, while treatment groups 2-9 maintained a content between 12.0% and 13.0%, with a relatively small overall coefficient of variation. After 15 days of storage, the crude fiber content in treatment groups 1, 4, and 7 was significantly lower than that in the CK group. In conclusion, the degree of fibrosis in bamboo shoots intensifies during natural storage. Group 1 exhibited better storage and preservation effects during the storage period and can be considered a preferred treatment condition for delaying bamboo shoot fibrosis.

[0035] 2.6 Comprehensive Evaluation and Range Analysis of Orthogonal Experiment Results As shown in Table 2, the order of influence of the three factors on the overall quality (total score) of bamboo shoots is: nisin > ascorbic acid > chitosan. Based on the principle of maximizing the K-value, the optimal combination for storing *Bambusa textilis* bamboo shoots is K3Ni1Vc2, i.e., 2.5% chitosan + 0.02% nisin + 4.0% ascorbic acid. Among these, the 0.02% nisin concentration is the key factor in the combination. Combined with 2.5% chitosan and 4.0% ascorbic acid for oxidative protection, it can delay the increase in water content, respiration rate, yellowing, and weight loss rate of the bamboo shoots, thereby improving the storage quality of *Bambusa textilis* bamboo shoots.

[0036] Table 2 Evaluation and Range Analysis of Orthogonal Experiment Results In this invention, when *Bauhinia purpurea* bamboo shoots treated with a composite coating of chitosan, ascorbic acid, and nisin at different mass concentrations were stored for 15 days, the moisture loss and mass loss rates of groups 1-9 were significantly lower than those of the control group. This indicates that the composite preservative treatment can effectively inhibit the evaporation of water and the consumption of nutrients in bamboo shoots, thus maintaining their commercial quality.

[0037] After treatment with the compound preservative of this invention, the rate of decrease in L* value and increase in b* value of bamboo shoots was significantly slowed down, while the brown color of the cut surface of the bamboo shoots in the CK group began to deepen from the outside to the inside on day 5. This indicates that the compound preservative treatment can effectively delay the browning time and area of ​​bamboo shoots, maintain their good appearance quality, and extend their shelf life.

[0038] The bamboo shoots after harvesting were still "living" and their respiration rate increased rapidly. The respiration intensity of the CK group showed an upward trend, while the treatment groups (1-9 groups) showed a slow downward trend, indicating that the compound preservative could effectively inhibit the respiratory metabolism of bamboo shoots and reduce the consumption of nutrients. At the same time, as the storage time increased, the bamboo shoots gradually hardened due to the increase in respiration and fibrosis

[20]

[28] . In addition, the polysaccharides in the bamboo shoots were continuously consumed, resulting in softening of texture and an increase in crude fiber content, forming a chain reaction of "increased respiratory metabolism → aggravated water loss → simultaneous occurrence of softening and browning". During the storage period (0-15 days), the polysaccharide content of each group decreased overall, while the hardness value and crude fiber content increased. However, the polysaccharide content of bamboo shoots treated with the compound preservative was consumed less, and the texture was better maintained, which was better than that of the CK group.

[0039] Treatment with three compound preservatives—chitosan, ascorbic acid, and nisin—effectively improved the water retention, antibacterial effect, and antioxidant properties of bamboo shoots. With prolonged storage, the moisture content, brightness (L*), and polysaccharide content of bamboo shoots in each treatment group showed a decreasing trend, while the weight loss rate, yellowness (b*), and crude fiber content showed an increasing trend, and the rate of change in the treatment groups was lower than that in the control group (CK group). Respiration intensity exhibited different fluctuation patterns (groups 1, 2, 4, 5, 7, 8, and CK group showed an initial decrease followed by an increase, while groups 3, 6, and 9 showed an initial increase followed by a decrease). Group 1 showed the best performance in moisture retention, stable polysaccharide content, fiber control, and brightness maintenance; Group 4 showed the best mid-term weight loss control; Group 7 showed the best browning control; and Group 9 had the most stable respiration intensity.

[0040] Furthermore, the order of influence of various preservatives on the overall quality of *Bambusa bougainvillea* bamboo shoots was nisin > ascorbic acid > chitosan. The appropriate treatment combination for post-harvest storage and preservation of *Bambusa bougainvillea* bamboo shoots is 2.5% chitosan + 0.02% nisin + 4.0% ascorbic acid. This combination can significantly slow down the rate of moisture loss and quality loss during storage, control the rate of browning of the bamboo shoots, significantly reduce the rate of reduction of bamboo shoot polysaccharides, and delay the rate of increase of cellulose content. Even after 15 days of preservation, there are still no signs of spoilage.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A compound biological preservative for Dendrocalamus latiflorus Beesley, characterized in that, The biological preservative is composed of the following substances in weight percentage: chitosan 1.5%-2.5%, nisin 0.02%-0.05%, ascorbic acid 3%-5%, and the remainder is water.

2. The bio-preservation agent of claim 1, wherein: The biological preservative is composed of the following substances in weight percentage: 2.5% chitosan, 0.02% nisin, 4% ascorbic acid, and the remainder is water.

3. A method of preparing the biological preservative according to any one of claims 1-2, characterized by, The preparation method mainly involves dissolving chitosan, nisin, and ascorbic acid in water to prepare chitosan solutions, nisin solutions, and ascorbic acid solutions of a certain concentration, respectively, and then combining the chitosan solutions, nisin solutions, and ascorbic acid solutions to obtain a biological preservative.

4. The application of the biopreservative as described in any one of claims 1-2 in the preservation of Burgh's sweet bamboo shoots.

5. Use according to claim 4, characterized in that, The application method includes the following steps: (1) Peel, wash and dry the sweet bamboo shoots of Bosch, and prepare the pre-treated bamboo shoots for later use; (2) Coat the surface of the pretreated bamboo shoots with a biological preservative, let them air dry naturally, and then put them into a freezer bag for cold storage.

6. Use according to claim 5, characterized in that: The natural air-drying environment in step (2) is a cold storage environment at 4±0.5℃.

7. Use according to claim 5, characterized in that: The preservation bag used in step (2) is a food-grade PE preservation bag.

8. Use according to claim 5, characterized in that: The refrigeration and preservation temperature in step (2) is 4±0.5℃.

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