Bamboo shoot frozen glaze liquid and frozen storage method for improving bamboo shoot quality

Abstract

The present invention belongs to the technical field of agricultural product storage, and specifically relates to a frozen glaze liquid for bamboo shoots and a frozen storage method for improving the quality of bamboo shoots. The present invention uses glazing technology to treat quick-frozen bamboo shoots, forming a uniform ice layer barrier on the surface of the bamboo shoots, effectively preventing the quality deterioration problems such as browning and water loss during the frozen storage of bamboo shoots. In addition, the present invention uses a natural product chrysanthemum extract as a glaze additive for glazing, which can make the glaze wrapped around the bamboo shoots more uniform and firm, significantly reducing the shedding of the bamboo shoot glaze during frozen storage, and the chrysanthemum extract has antibacterial and antioxidant functions, which can improve the nutritional quality of frozen bamboo shoots.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural product storage, and particularly relates to a bamboo shoot frozen glaze liquid and a frozen storage method for improving the quality of the bamboo shoots. Background Art

[0002] Bamboo shoots are crisp, tender, and delicious. They are rich in functional nutrients such as dietary fiber, high-quality protein, vitamins, and bioactive compounds. They are low in fat and sugar, and have important nutritional value for human health. They are known as the "top vegetarian food." Fresh bamboo shoots are prone to lignification and are not storable, with a shelf life usually limited to less than three days. Therefore, there is an urgent need to take appropriate measures to improve the quality of bamboo shoots and delay their lignification. The quick-frozen bamboo shoots developed in recent years meet this demand. They do not have the sour taste of boiled bamboo shoots, but have the natural flavor of bamboo shoots and their unique fresh, crisp, and fragrant flavor. Therefore, the product has a wide market, high sales price, and good corporate benefits. In addition, this method greatly shortens the process flow. As disclosed in a patent application with publication number CN110074176A, a kind of quick-frozen bamboo shoots and a production process thereof, the process is to first transport the shelled bamboo shoots after plucking to a processing point within two hours, then place the bamboo shoots in a high-pressure killing pot for killing, process the treatment liquid used including calcium chloride, magnesium sulfate and acetic acid, then the bamboo shoots are undressed, the bamboo shoots after undressing are cooled with a brittle agent solution, than the cooled bamboo shoots are put into ice water for pre-cooling treatment, ultrasonic oscillation is carried out simultaneously during the pre-cooling process, finally the bamboo shoots after pre-cooling are put into a liquid nitrogen freezer, and it is -35 DEG C to -40 DEG C to be rapidly cooled to the bamboo shoot surface temperature, completing the preparation of quick-frozen bamboo shoots. The production process in the present invention can fully guarantee the brittleness of bamboo shoots, greatly improving the quality of quick-frozen bamboo shoots. Another example is a patent application with publication number CN107258893A, which discloses a method for preparing quick-frozen bamboo shoots. The method comprises the following steps: washing selected fresh bamboo shoots with clean water, drying the water on the surface of the washed bamboo shoots; soaking the fresh bamboo shoots in 3.2% iodine tincture for 30 minutes, and then soaking them in a sodium chloride aqueous solution for another 20 minutes; brushing a layer of chlorophyll on the surface of the bamboo shoots, and then freezing them to -10°C; taking out the bamboo shoots and thawing them to 5-10°C, and then soaking them in a preservative solution for 1 hour; then rinsing the bamboo shoots with room temperature distilled water, and then naturally drying them to remove any water from the surface. The bamboo shoots are then placed in a quick-freezer and quickly frozen to -15°C, and then tested. After passing the test, the bamboo shoots are packaged and stored in a -20°C cold storage. The method of soaking the bamboo shoots with iodine tincture can ensure that the bamboo shoots do not lose water, the nutrients of the treated bamboo shoots do not lose, and the bamboo shoots are brittle, do not become soft after thawing, and have sufficient elasticity.

[0003] However, during the long-term frozen storage of bamboo shoots, quick-frozen bamboo shoots are prone to problems such as water loss, browning, and lignification, which affect product quality. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention provides a method for freezing bamboo shoots into glaze and improving the quality of bamboo shoots. The purpose is to solve the technical problem that during the long-term frozen storage of bamboo shoots, quick-frozen bamboo shoots are prone to water loss, browning, lignification, etc., which affect the product quality.

[0005] The first technical solution provided by the present invention is a bamboo shoot frozen glaze liquid, and the specific technical solution is as follows:

[0006] The bamboo shoot frozen glaze liquid comprises an aqueous solution of chrysanthemum extract, wherein the concentration of the chrysanthemum extract is 5-25 mg / mL.

[0007] In certain embodiments, the chrysanthemum extract is prepared as follows: water is added to chrysanthemum, and the mixture is extracted at 100° C. for 25 minutes, followed by filtration under reduced pressure to obtain the chrysanthemum extract.

[0008] The present invention provides a second technical solution for a frozen storage method for improving the quality of bamboo shoots, which utilizes the bamboo shoot frozen glaze liquid described in the first technical solution to form a completely wrapped glaze on the surface of the bamboo shoots.

[0009] In particular, the following steps are included:

[0010] S1, pre-processing fresh bamboo shoots to obtain processed bamboo shoots;

[0011] S2, pre-cooling the bamboo shoots processed in step S1 to reduce the center temperature of the bamboo shoots to below 5° C., thereby obtaining pre-cooled bamboo shoots;

[0012] S3, quick-freezing the pre-cooled bamboo shoots in step S2 so that the center temperature of the bamboo shoots reaches below -18°C to obtain quick-frozen bamboo shoots;

[0013] S4, immersing the quick-frozen bamboo shoots obtained in step S4 in the bamboo shoot freezing glazing liquid according to claim 1 or 2 for glazing, and then storing the bamboo shoots at a temperature below -18°C.

[0014] In certain embodiments, in step S1, the pretreatment includes washing, pre-cooking and shaping.

[0015] Furthermore, the cleaning process is specifically as follows: rinsing the fresh bamboo shoots with clean water to remove mud, sand and impurities;

[0016] The pre-cooking treatment is as follows: the cleaned bamboo shoots are blanched in boiling water for 25 to 30 minutes and then cooled to room temperature; the shaping treatment is as follows: the bamboo shoots are peeled off from the pre-cooked bamboo shoots, and the aged fiber parts at the base of the stems and the damaged skins are removed.

[0017] In certain embodiments, in step S2, the pre-cooling treatment is specifically as follows: pre-cooling with running water is performed, first cooling the bamboo shoots with 10°C to 15°C water for 5 to 10 minutes, then cooling with running ice water at 0°C to 4°C, until the core temperature of the bamboo shoots is cooled to below 5°C, and then removing moisture from the surface of the bamboo shoots. Air pre-cooling can also be used to quickly cool the bamboo shoots to a core temperature below 5°C.

[0018] In certain embodiments, in step S3, the quick freezing treatment is as follows: freezing the bamboo shoots at a quick freezing temperature of -35°C to -40°C for 10 minutes to 30 minutes until the center temperature of the bamboo shoots reaches below -18°C.

[0019] In some embodiments, in step S4, the glazing treatment is specifically as follows: immersing the quick-frozen bamboo shoots in glazing liquid at a temperature of 0-4°C and shaking for 6-8 seconds, then taking them out and draining off all water droplets.

[0020] The present invention has the following beneficial effects: The present invention uses an ice glazing technology to treat quick-frozen bamboo shoots, forming a uniform ice barrier on the surface of the bamboo shoots, effectively preventing quality deterioration such as browning and water loss during frozen storage. Furthermore, the present invention uses a natural product, chrysanthemum extract, as an ice glaze additive for glazing, which can make the ice coating on the bamboo shoots more uniform and compact, significantly reducing the shedding of the ice glaze during frozen storage. Furthermore, the chrysanthemum extract has antibacterial and antioxidant properties, which can improve the nutritional quality of frozen bamboo shoots. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of a frozen storage method for improving the quality of bamboo shoots. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0023] Example 1

[0024] This embodiment provides a technical solution for freezing bamboo shoots in glaze liquid, which is as follows:

[0025] 1. Preparation of Chrysanthemum Extract

[0026] Weigh 5g of chrysanthemum flowers, add 100mL of water, extract at 100°C for 25min, filter under reduced pressure, and dilute the filtrate to 100mL to obtain a chrysanthemum flower extract with a concentration of 50mg / mL. This extract can be diluted in stages to obtain the desired concentration for testing.

[0027] 2. Preparation of Ice Glaze Liquid

[0028] Take an appropriate amount of chrysanthemum extract to prepare ice coating liquid. The concentration of chrysanthemum extract in the obtained ice coating liquid is 5-25 mg / mL. Place the ice coating liquid in a refrigerator to cool it down. When the temperature of the ice coating liquid drops to 4°C, it is set aside.

[0029] Example 2

[0030] The present invention provides a frozen storage method for improving the quality of bamboo shoots, and the specific technical solution is as follows:

[0031] 1. Raw Material Processing: Bamboo shoots are purchased from the market and immediately processed in the laboratory. Select fresh bamboo shoots that are free of pests and diseases, mechanical damage, and are of relatively uniform color, age, and size. Rinse with clean water to remove any sand and impurities.

[0032] 2. Pre-cooking: Put the cleaned bamboo shoots into boiling water and blanch them for 25 minutes to inactivate the activity of bamboo shoot enzymes and sterilize them to prevent fibrosis, oxidative discoloration and microbial contamination.

[0033] 3. Cooling: Cool the pre-cooked bamboo shoots with running water at room temperature until the temperature of the bamboo shoots drops to room temperature.

[0034] 4. Shaping: After cooling, quickly peel off the bamboo shoot shells, cut off the aging fiber part at the base of the stem, and wash off the damaged bamboo shoot skins.

[0035] 5. Cutting: Cut into blocks, slices, strips or dices according to processing requirements. No cutting is required for whole bamboo shoots.

[0036] 6. Precooling: Use running water to precool. First cool with 10-15℃ water for 5-10 minutes, then cool with 0℃ running ice water to cool the bamboo shoots to a core temperature below 5℃. Use an air dryer to vibrate and blow air to remove moisture from the surface of the bamboo shoots.

[0037] 7. Quick freezing: Place the bamboo shoots into the quick freezing equipment at a temperature of -40°C and a freezing time of 10 to 30 minutes, until the center temperature of the bamboo shoots reaches -18°C or below.

[0038] 8. Glaze: Place the frozen bamboo shoots in a stainless steel wire basket and quickly immerse them in the glaze solution (chrysanthemum extract concentration is 5 mg / mL) in Example 1 and shake for a while (6-8 seconds). The solution temperature is controlled at 0°C. Lift the bamboo shoots and drain off all the water droplets. At this time, a layer of glaze will form on the surface of the bamboo shoots, covering the entire bamboo shoots with a moderate thickness.

[0039] 9. Online inspection: Remove clumped bamboo shoots and unqualified bamboo shoots in a clean environment below -5℃, and then carry out quantitative packaging.

[0040] 10. Packaging: Put the quick-frozen bamboo shoots into packaging bags and seal them.

[0041] 11. Storage: Bamboo shoots should be stored in a cold storage at a temperature below -18°C, with a temperature fluctuation of no more than ±2°C.

[0042] Example 3

[0043] The present invention provides a frozen storage method for improving the quality of bamboo shoots, and the specific technical solution is as follows:

[0044] 1. Raw Material Processing: Bamboo shoots are purchased from the market and immediately processed in the laboratory. Select fresh bamboo shoots that are free of pests and diseases, mechanical damage, and are of relatively uniform color, age, and size. Rinse with clean water to remove any sand and impurities.

[0045] 2. Pre-cooking: Put the cleaned bamboo shoots into boiling water and blanch them for 30 minutes to inactivate the activity of bamboo shoot enzymes and sterilize them to prevent fibrosis, oxidative discoloration and microbial contamination.

[0046] 3. Cooling: Cool the pre-cooked bamboo shoots with running water at room temperature until the temperature of the bamboo shoots drops to room temperature.

[0047] 4. Shaping: After cooling, quickly peel off the bamboo shoot shells, cut off the aging fiber part at the base of the stem, and wash off the damaged bamboo shoot skins.

[0048] 5. Cutting: Cut into blocks, slices, strips or dices according to processing requirements. No cutting is required for whole bamboo shoots.

[0049] 6. Precooling: Use running water to precool. First cool with 10-15℃ water for 5-10 minutes, then cool with 4℃ running ice water to cool the bamboo shoots to a core temperature below 5℃. Use an air dryer to vibrate and blow air to remove moisture from the surface of the bamboo shoots.

[0050] 7. Quick freezing: Place the bamboo shoots into the quick freezing equipment at a temperature of -35°C and a freezing time of 10 to 30 minutes, until the center temperature of the bamboo shoots reaches -18°C or below.

[0051] 8. Glazing: Place the frozen bamboo shoots in a stainless steel wire basket and quickly immerse them in the glazing solution (chrysanthemum extract concentration is 10 mg / mL) described in Example 1 and shake for a while (6-8 seconds). The solution temperature is controlled at 4°C. Lift the basket and drain off all water droplets to obtain a glaze of about 6% (based on the net weight).

[0052] 9. Online inspection: Remove clumped bamboo shoots and unqualified bamboo shoots in a clean environment below -5℃, and then carry out quantitative packaging.

[0053] 10. Packaging: Put the quick-frozen bamboo shoots into packaging bags and seal them.

[0054] 11. Storage: Bamboo shoots should be stored in a cold storage at a temperature below -18°C, with a temperature fluctuation of no more than ±2°C.

[0055] Example 4

[0056] The present invention provides a frozen storage method for improving the quality of bamboo shoots, and the specific technical solution is as follows:

[0057] 1. Raw Material Processing: Bamboo shoots are purchased from the market and immediately processed in the laboratory. Select fresh bamboo shoots that are free of pests and diseases, mechanical damage, and are of relatively uniform color, age, and size. Rinse with clean water to remove any sand and impurities.

[0058] 2. Pre-cooking: Put the cleaned bamboo shoots into boiling water and blanch them for 28 minutes to inactivate the activity of bamboo shoot enzymes and sterilize them to prevent fibrosis, oxidative discoloration and microbial contamination.

[0059] 3. Cooling: Cool the pre-cooked bamboo shoots with running water at room temperature until the temperature of the bamboo shoots drops to room temperature.

[0060] 4. Shaping: After cooling, quickly peel off the bamboo shoot shells, cut off the aging fiber part at the base of the stem, and wash off the damaged bamboo shoot skins.

[0061] 5. Cutting: Cut into blocks, slices, strips or dices according to processing requirements. No cutting is required for whole bamboo shoots.

[0062] 6. Precooling: Use running water to precool. First cool with 10-15℃ water for 5-10 minutes, then cool with 2℃ running ice water to cool the bamboo shoots to a core temperature below 5℃. Use an air dryer to vibrate and blow air to remove moisture from the surface of the bamboo shoots.

[0063] 7. Quick freezing: Place the bamboo shoots into the quick freezing equipment at a temperature of -37°C and a freezing time of 10 to 30 minutes, until the center temperature of the bamboo shoots reaches -18°C or below.

[0064] 8. Glazing: Place the frozen bamboo shoots in a stainless steel wire basket, quickly immerse them in the glazing solution (chrysanthemum extract concentration is 25 mg / mL) prepared in Example 1, and shake for a while (6-8 seconds). The solution temperature is controlled at 2°C, and the basket is lifted and drained of all water droplets.

[0065] 9. Online inspection: Remove clumped bamboo shoots and unqualified bamboo shoots in a clean environment below -5℃, and then carry out quantitative packaging.

[0066] 10. Packaging: Put the quick-frozen bamboo shoots into packaging bags and seal them.

[0067] 11. Storage: Bamboo shoots should be stored in a cold storage at a temperature below -18°C, with a temperature fluctuation of no more than ±2°C.

[0068] Comparative Example 1

[0069] Pretreatment: Bamboo shoots purchased from the market are immediately processed in the laboratory. Fresh square bamboo shoots without mechanical damage, good color, and of relatively uniform age and size are selected. Boil them in water for 30 minutes, quickly cool them in cold water, remove the shells, and air-dry them. After pre-cooling to 4°C, place them in a -35°C freezer for 10-30 minutes, until the core temperature reaches -18°C or below, without forming an ice layer. Place them in a sealed plastic bag and store them in a -18°C freezer.

[0070] Comparative Example 2

[0071] Pretreatment: Bamboo shoots purchased from the market are immediately processed in the laboratory. Fresh square bamboo shoots without mechanical damage, good color, and relatively uniform in age and size are selected. Boil them in water for 30 minutes, quickly cool them in cold water, remove the shells, and air-dry them. After pre-cooling to 4°C, they are quickly frozen at -35°C for 10-30 minutes, until the center temperature reaches -18°C or below. Then, they are immersed in ice water (no additives) at approximately 4°C for approximately 6-8 seconds, resulting in a coated product with a glaze content of approximately 6% (by net weight).

[0072] Test Case

[0073] The frozen bamboo shoots of Example 3, Comparative Example 1 and Comparative Example 2 were sampled after storage for 0, 6 and 9 months, respectively, and the quality-related indicators of the bamboo shoots were analyzed.

[0074] 1. Hardness test: The hardness of bamboo shoots was measured using a texture analyzer. The results are shown in Table 1.

[0075] Table 1 Changes in hardness of bamboo shoots during frozen storage

[0076]

[0077] Unlike most fruits and vegetables, bamboo shoots tend to steadily increase in firmness after harvest. As shown in Table 1, bamboo shoot firmness gradually increases with frozen storage time. After nine months of frozen storage at -18°C, the bamboo shoots in Comparative Example 1 increased in firmness by 19.58%, while those in Comparative Example 2 and Example 3 increased in firmness by 9.41% and 6.66%, respectively. The increase in firmness of the bamboo shoots coated with glaze was suppressed. In Example 3, the addition of chrysanthemum extract provided a good glaze protection, minimizing hardness change and effectively maintaining the texture and quality of the bamboo shoots.

[0078] 2. Weight loss rate: The weight loss rate was determined by weighing method. The results are shown in Table 2.

[0079] Table 2 Changes in weight loss rate of bamboo shoots during frozen storage

[0080]

[0081] Water loss and nutrient consumption during storage affect the weight loss rate of bamboo shoots. As shown in Table 2, the weight loss rates of bamboo shoots in Example 3, Comparative Example 1, and Comparative Example 2 all showed an upward trend during storage. The rate of increase in the weight loss rate of bamboo shoots in Example 3 and Comparative Example 2 was significantly lower than that in Comparative Example 1. The results show that the glaze technology can significantly improve the water loss of bamboo shoots during frozen storage. The glaze in Example 3 is firm and uniform due to the addition of chrysanthemum extract. It is not easy to crack or fall off during storage, which inhibits the loss of water and nutrients in the bamboo shoots. Therefore, the bamboo shoots in Example 3 retain a good amount of water and nutrients.

[0082] 3. Vitamin C: Refer to GB 5009.86-2016 Determination of ascorbic acid in foods. The results are shown in Table 3.

[0083] Table 3 Changes in VC of bamboo shoots during frozen storage

[0084]

[0085] Vitamin C content represents the nutritional level of fruits and vegetables and is an important indicator for measuring their nutritional value. As shown in Table 3, the vitamin C content of each group of bamboo shoots showed a downward trend during frozen storage. Among them, the rate of decline of the vitamin C content of the bamboo shoots in Comparative Example 1 was significantly higher than that in Comparative Example 2 and Example 3. The results show that the ice coating treatment can effectively inhibit the loss of vitamin C during storage. The addition of chrysanthemum extract contains polysaccharides, flavonoids and other substances, which have certain antioxidant activity and can inhibit the oxidative deterioration of substances such as vitamin C in bamboo shoots, effectively maintaining the nutritional value and quality of bamboo shoots.

[0086] 4. Lignin: The sulfuric acid hydrolysis-titration method was used for determination. The results are shown in Table 4.

[0087] Table 4 Changes in lignin in bamboo shoots during frozen storage

[0088]

[0089] Lignin is a complex polymer that significantly contributes to the rigidity of fruit and vegetable cell walls. As shown in Table 4, during storage, the lignin content of the bamboo shoots prepared in Comparative Example 1 steadily increased, while the lignin content in Comparative Example 2 and Example 3 increased relatively slowly, with Example 3 experiencing the slowest increase. This suggests that the chrysanthemum extract ice coat effectively inhibited the increase in lignin content during bamboo shoot storage, reducing its hardness and improving its edible quality.

[0090] In summary, the present invention provides a method for improving the frozen storage quality of bamboo shoots. By adopting ice coating technology and adding natural substances such as chrysanthemum extract, the ice coating of quick-frozen bamboo shoots can be effectively prevented from cracking and falling off during frozen storage, thereby solving the quality deterioration problems of bamboo shoots such as water loss, browning, and lignification during frozen storage, extending the frozen storage time of bamboo shoots, and improving the nutritional quality and edible quality of bamboo shoots during frozen storage.

[0091] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. The present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. The application of chrysanthemum extract ice coat in suppressing the increase of lignin content during bamboo shoot storage, characterized in that: A bamboo shoot glaze solution is used to form a completely coated glaze on the surface of the bamboo shoots. The bamboo shoot glaze solution includes a chrysanthemum extract having a concentration of 10 mg / mL. The chrysanthemum extract is prepared as follows: 5 g of chrysanthemum is weighed, 100 mL of water is added, and the mixture is extracted at 100° C. for 25 minutes, followed by vacuum filtration to obtain the chrysanthemum extract. The steps include: S1, pre-processing fresh bamboo shoots to obtain processed bamboo shoots; S2, pre-cooling the bamboo shoots processed in step S1 to reduce the center temperature of the bamboo shoots to below 5° C., thereby obtaining pre-cooled bamboo shoots; S3, quick-freezing the pre-cooled bamboo shoots in step S2 so that the center temperature of the bamboo shoots reaches below -18°C to obtain quick-frozen bamboo shoots; S4, immersing the quick-frozen bamboo shoots from step S3 in a bamboo shoot freezing glaze liquid for glazing, and then storing at a temperature below -18°C; On the one hand, using chrysanthemum extract to coat bamboo shoots with ice not only inhibits the increase in hardness of bamboo shoots and the loss of water and nutrients, but also inhibits the oxidation and deterioration of vitamin C in bamboo shoots and the increase in the lignin content of bamboo shoots. On the other hand, using chrysanthemum extract to coat bamboo shoots with ice can make the ice coating on the bamboo shoots uniform and firm, preventing the ice coating from cracking and falling off.

2. The use according to claim 1, characterized in that In step S1, the pretreatment includes cleaning, pre-cooking and shaping.

3. The use according to claim 2, characterized in that The cleaning process is specifically as follows: rinsing the fresh bamboo shoots with clean water to remove mud, sand and impurities; The pre-cooking treatment is as follows: the cleaned bamboo shoots are blanched in boiling water for 25 to 30 minutes and then cooled to room temperature; the shaping treatment is as follows: the bamboo shoots are peeled off from the pre-cooked bamboo shoots, and the aged fiber parts and damaged bamboo shoot skins at the base of the stems are removed.

4. The use according to claim 1, characterized in that In step S2, the pre-cooling process is specifically as follows: Use running water pre-cooling, first cool with 10℃~15℃ water for 5min~10min, then cool with 0℃~4℃ flowing ice water to cool the center temperature of the bamboo shoots to below 5℃, and then remove the moisture on the surface of the bamboo shoots.

5. The use according to claim 1, characterized in that In step S3, the quick freezing treatment is as follows: freezing the bamboo shoots at a quick freezing temperature of -35°C to -40°C for 10 minutes to 30 minutes until the center temperature of the bamboo shoots reaches below -18°C.

6. The use according to claim 1, characterized in that In step S4, the glazing treatment is specifically as follows: immersing the quick-frozen bamboo shoots in glazing liquid at a temperature of 0-4°C and shaking for 6-8 seconds, then taking them out and draining off all water droplets.

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