A method for preparing a starch-based straw by bio-enzyme cooperation and extrusion shearing

Abstract

The application provides a method for preparing a starch-based straw by using biological enzyme and synergistic extrusion and shearing, and the method uses starch as a main material, water as a plasticizer and TG as an enzyme preparation, and utilizes a double-screw extruder for melt blending, and then is cooled and formed after extrusion through a mold. The method has the advantages of low production cost and safety and greenness, and the starch-based straw obtained by using the method has the advantages of high strength, strong water resistance, strong heat resistance, no swelling and no deformation in hot drinks, good use feeling, degradability and edibility.

Description

Technical Field

[0001] This invention relates to the field of starch derivative production technology, specifically to a method for preparing starch-based straws by bio-enzyme synergistic extrusion shearing. Background Technology

[0002] As people become more health-conscious and environmentally conscious, their awareness of the problems associated with using plastic products is also gradually increasing. Besides the hazards of traditional plastic straws being small, highly polluting, and difficult to recycle, some plastic straws floating in the ocean degrade into microplastics as they age. Microplastics accumulate through the food chain and may eventually enter the human body, threatening human health. Therefore, banning the use of non-degradable single-use plastic straws has become an inevitable trend, thus promoting the use of biodegradable straws.

[0003] Biodegradable straws mainly include paper straws, polylactic acid (PLA) straws, bamboo straws, glass straws, and straw straws. Among them, paper straws have problems such as deforming easily when bitten, softening or even falling apart when soaked in hot drinks, and lacking resilience. PLA straws have problems such as being not heat-resistant and being expensive. Bamboo straws have problems such as being not durable, easily cracking, easily moldy, having limited resources, being complex to process, and requiring hand washing and manual polishing. Glass straws have problems such as being fragile, difficult to store, and relatively expensive. Metal straws have problems such as being difficult to clean and having a metallic taste. Straw straws have problems such as being not strong and easily breaking. The above-mentioned problems make it difficult for current biodegradable straws to replace traditional plastic straws in terms of performance and cost. Therefore, providing a biodegradable straw that has low production cost, good product performance, is easy to completely degrade, and can completely replace traditional plastic straws is an urgent task that the industry needs to solve.

[0004] Starch is a natural high-molecular-weight polysaccharide containing multiple hydroxyl groups. It boasts advantages such as wide availability (grains, potatoes, beans, etc.), low price, edibility, strong carbon reduction capabilities, and rapid complete degradation in the natural environment. Therefore, starch-based biodegradable plastics have become a widely researched class of bio-based biodegradable plastics both domestically and internationally. However, the weak hydrophobic properties (poor water resistance) and poor mechanical properties (high brittleness, low elongation at break, etc.) of starch severely limit the practical production and application of starch-based biodegradable straws. Therefore, improving the hydrophobic properties and mechanical properties of starch-based biodegradable straws is currently a major technical bottleneck.

[0005] Studies have shown that the mechanical properties and water resistance of starch-based materials are largely related to the degree of starch aging (recrystallization). During the thermoplastic extrusion of starch, shear force has a significant impact on the molecular chain structure of amylopectin (Ap), but little effect on amylose (Am). Therefore, changes in the molecular chain structure of Ap in the starch melt play a decisive role in the degree of starch aging. Ap branches that are too short (DP < 9) or too long (DP > 60) are less likely to form molecular chain entanglement, making it difficult to form a double helix and hindering aging and crystallization. High branching degree leads to greater steric hindrance, making it difficult for the molecular chain to rotate internally around the σ single bond (CC), resulting in low chain flexibility, low aging degree, and low crystallinity. However, if the branched side chains are uniformly distributed, the molecules have high stereoregularity, and the molecular chains move and align fully, resulting in high aging degree and high crystallinity.

[0006] It is evident that providing a starch-based straw with excellent mechanical properties and water resistance is of great significance to the industry. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing starch-based straws using a bio-enzyme synergistic extrusion shearing process. This method uses starch as the main material, water as a plasticizer, and TG as an enzyme preparation. The materials are melt-blended using a twin-screw extruder, extruded through a die, and then cooled to form the straw. This method offers advantages such as low production cost, safety, and environmental friendliness. The starch-based straws obtained using this method exhibit high strength, strong water resistance, biodegradability, and edibility.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing starch-based straws by bio-enzyme synergistic extrusion shearing uses starch as the main material, water as the plasticizer, and TG as the enzyme preparation. The materials are melt-blended using a twin-screw extruder, extruded through a die, and then cooled to form the straw.

[0010] Preferably, the above method includes the following steps:

[0011] (1) Add starch, water and TG to a mixer and mix evenly. Then put it into a sealed container and let it stand until the water is evenly distributed to obtain a mixture.

[0012] (2) The mixture is added to a twin-screw extruder. The temperature of the I-V section of the twin-screw extruder is 30-60℃. Within this temperature range, TG enzymatically hydrolyzes the starch. The temperature of the VI-VIII section is 80-110℃. Within this temperature range, the starch melts into a solution. Then, the extrusion tube is extruded through the die.

[0013] (3) Use a cooling system to cool and lower the temperature of the extruded straw, so that the molecules inside the straw can be arranged in an orderly and dense crystalline structure to improve the mechanical strength and water resistance of the straw.

[0014] (4) Cut the straw and then let it age to obtain the product.

[0015] Transglucosidase (TG) is a transglycosidase that specifically modifies the branched structure of Ap molecules. TG cleaves the α-1,4 glycosidic bonds of the Am molecular chain, and then the cleaved linear short chains are linked to the Ap molecular chain via α-1,6 glycosidic bonds through transglycosylation to form new branch points, increasing the degree of branching. This invention employs dynamic shearing synergistic TG-directed modification of the Ap molecular chain structure in starch melt. During the thermoplastic extrusion of starch, the Am and Ap molecular chains are first partially degraded under shear force to form relatively short linear chains. Secondly, TG directionally links these linear short chains to the Ap molecular chain via α-1,6 glycosidic bonds to generate a highly branched Ap molecular chain structure with uneven branch distribution. Finally, the longer branched side chains in the Ap continue to be dynamically sheared and broken, forming an Ap molecular chain structure with a high degree of branching and relatively uniform branch distribution.

[0016] The straws prepared using the above method have high strength and heat resistance, and do not swell or deform in hot drinks, resulting in a better user experience.

[0017] Preferably, in step (1), the starch is tapioca starch.

[0018] Preferably, for every 100 parts of starch, 25-30 parts of water and 5-10 parts of TG are added; the starch, TG and water are placed in a mixer and semi-wet-stirred for 5-20 minutes, and then placed in a sealed container to stand and equilibrate for 12-48 hours.

[0019] Preferably, for every 100 parts of starch, 28 parts of water and 6 parts of TG are added; the starch, TG and water are placed in a mixer and semi-wet-stirred for 10 minutes, and then placed in a sealed container to stand and equilibrate for 24 hours.

[0020] Preferably, in step (2), the feeding speed of the twin-screw extruder is 1-10 g / min and the extrusion speed is 1-10 g / min.

[0021] Preferably, the temperature of the twin-screw extruder is 35℃ in zone I, 40℃ in zone II, 46℃ in zone III, 52℃ in zone IV, 58℃ in zone V, 80℃ in zone VI, 90℃ in zone VII, and 110℃ in zone VIII, with a feeding speed of 8g / min and an extrusion speed of 7g / min.

[0022] Preferably, in step (3), the extruded straw is cooled immediately by cold air for 5-10 minutes.

[0023] Preferably, the cooling time is 8 minutes.

[0024] Preferably, in step (4), the straw is cut to 10-13cm and then placed in an environment of 4-15℃ for starch aging and crystallization, with an aging time of 1-7 days.

[0025] Preferably, the straw is cut to 13cm and then aged at 4℃ for 5 days.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The main ingredient used in this invention is starch, which not only has the advantages of being widely available, inexpensive, edible, and having strong carbon reduction capabilities, but also has the advantage of being able to completely degrade in the natural environment at a rapid rate. The straws made using this main ingredient have a white, semi-transparent surface, no unpleasant odor, and are edible. The straws have high mechanical strength, water resistance, and heat resistance, and do not swell or deform in hot drinks, providing a good user experience.

[0028] 2. The method of the present invention is simple, has a short preparation cycle, low production cost, simple equipment, is suitable for industrial production, and is safe and pollution-free during production. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is an appearance diagram of the starch-based straw prepared in Example 1.

[0031] Figure 2 The image shows the water immersion experiment of the starch-based straws prepared in Example 1; in the image, 1 and 2 are photos after soaking in room temperature water for 30 minutes, and 3 and 4 are photos after soaking in 85°C for 30 minutes.

[0032] Figure 3 This is a comparison chart of straw water absorption rates.

[0033] Figure 4 This is a comparison chart of the mechanical properties of straws. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0035] Example 1

[0036] A method for preparing starch-based straws by bio-enzyme synergistic extrusion shearing includes the following steps:

[0037] (1) Weigh 100g of cassava starch, 28g of water and 6g of TG, add them to a mixer, stir semi-wet for 10 minutes, mix evenly, then put them into a sealed container and let them stand and balance for 24 hours. The water is evenly distributed to obtain the mixture.

[0038] (2) Add the mixture into the twin-screw extruder and set the temperature of zone I of the twin-screw extruder to 35℃, zone II to 40℃, zone III to 46℃, zone IV to 52℃, zone V to 58℃, zone VI to 80℃, zone VII to 90℃, and zone VIII to 110℃. The feeding speed is 8g / min, the extrusion speed is 7g / min, and then the mixture is extruded through the die and suction tube.

[0039] (3) The extruded straw is cooled immediately by cold air for 8 minutes, so that the molecules inside the straw are arranged in an orderly and dense crystalline structure to improve the mechanical strength and water resistance of the straw.

[0040] (4) After cutting the straw to 13cm, place it at 4℃ for 5 days to age and obtain the product.

[0041] The starch-based straws prepared in this embodiment were tested and found to have a maximum bending force of 54.06 N, a bending elastic modulus of 42.15 N / cm, a water absorption rate of 46.97%, and did not swell or soften after being soaked in hot water at 85°C for 30 minutes.

[0042] Example 2

[0043] A method for preparing starch-based straws by bio-enzyme synergistic extrusion shearing includes the following steps:

[0044] (1) Weigh 100g of cassava starch, 25g of water and 5g of TG, add them to a mixer and stir semi-wet for 20 minutes until they are evenly mixed. Then put them into a sealed container and let them stand for 12 hours to balance the water distribution and obtain the mixture.

[0045] (2) Add the mixture into the twin-screw extruder and set the temperature of zone I of the twin-screw extruder to 30℃, zone II to 35℃, zone III to 40℃, zone IV to 45℃, zone V to 50℃, zone VI to 80℃, zone VII to 95℃, and zone VIII to 100℃. The feeding speed is 10g / min, the extrusion speed is 7g / min, and then the mixture is extruded through the die and suction tube.

[0046] (3) The extruded straw is cooled immediately by cold air for 10 minutes, so that the molecules inside the straw are arranged in an orderly and dense crystalline structure to improve the mechanical strength and water resistance of the straw.

[0047] (4) After cutting the straw to 13cm, place it at 5℃ for 7 days to age and obtain the product.

[0048] The starch-based straws prepared in this embodiment were tested and found to have a maximum bending force of 51.32 N, a bending elastic modulus of 46.34 N / cm, a water absorption rate of 51.28%, and slight swelling and softening after soaking in 85°C hot water for 30 minutes.

[0049] Example 3

[0050] A method for preparing starch-based straws by bio-enzyme synergistic extrusion shearing includes the following steps:

[0051] (1) Weigh 100g of cassava starch, 30g of water and 8g of TG, add them to a mixer, stir semi-wet for 15 minutes, mix evenly, then put them into a sealed container and let them stand for 24 hours to balance, so that the water is evenly distributed and the mixture is obtained.

[0052] (2) Add the mixture into the twin-screw extruder, set the temperature of zone I of the twin-screw extruder to 30℃, zone II to 40℃, zone III to 50℃, zone IV to 55℃, zone V to 60℃, zone VI to 85℃, zone VII to 95℃, zone VIII to 110℃, feed rate to 10g / min, extrusion rate to 10g / min, and then extrude through the die through the suction tube;

[0053] (3) The extruded straw is cooled immediately by cold air for 5 minutes, so that the molecules inside the straw are arranged in an orderly and dense crystalline structure to improve the mechanical strength and water resistance of the straw.

[0054] (4) After cutting the straw to 13cm, place it at 10℃ for 7 days to age and obtain the product.

[0055] The starch-based straws prepared in this embodiment were tested and found to have a maximum bending force of 48.96 N, a bending elastic modulus of 48.11 N / cm, a water absorption rate of 56.52%, and to swell and soften after being soaked in hot water at 85°C for 30 minutes.

[0056] Combination Figure 2 As can be seen, compared with commercially available starch-based straws, the quality of this Example 1 product (starch content ≥95%, maximum bending force (strength) 54.06N, bending modulus of elasticity (toughness) 42.15N / cm, water absorption rate 46.97%, no swelling or softening after soaking in 85℃ hot water for 30 minutes) is superior to similar commercially available products (starch content ≥70%, maximum bending force 6.76N, bending modulus of elasticity 19.32N / cm, water absorption rate 72.06%, swelling and softening with flocculent leaching after soaking in 85℃ hot water for 30 minutes). This indicates that the starch-based straw prepared by this invention has higher mechanical strength and high-temperature and water resistance than commercially available starch-based straws, and offers better cost performance.

[0057] Method for determining water absorption rate:

[0058] Weigh the starch pipettes using an electronic balance with an accuracy of 0.1%, and record the mass as M1. Immerse the starch pipettes in centrifuge tubes containing deionized water at the desired temperature. Place all centrifuge tubes with starch pipettes in a beaker and maintain a constant temperature for 30 minutes. After the specified time, remove the starch pipettes and wipe off any excess moisture with absorbent paper. Weigh the pipettes on the electronic balance after water absorption. Record this as M2. Take the average of three measurements. The formula for determining the water absorption rate is as follows:

[0059]

[0060] Methods for determining mechanical properties:

[0061] The bending mechanical properties of starch straws were determined using a universal testing machine. According to GB / T 14452-93, the three-point bending test method was used to determine the mechanical properties of materials with circular cross-sections. The starch straw (diameter d) was fixed on a base with clamps spaced L = 40 mm apart. The indenter was pressed firmly against the straw wall. The displacement (x) and normal force (F) were zeroed. The measurement was started, and the indenter applied normal force to the straw, causing it to bend until it broke or underwent irreversible deformation. The normal force at which the straw broke was defined as the maximum bending stress. The material's toughness (flexural modulus, E) was also measured. b The ratio of normal force to displacement is defined as the ratio of the two when the normal force and displacement are linearly related.

[0062]

[0063]

[0064] The test results are shown in Table 1 below:

[0065] Table 1. Statistics on characteristics of straws

[0066]

[0067] This invention utilizes a bio-enzyme synergistic twin-screw extrusion shearing technology to prepare a starch-based biodegradable straw (starch content ≥95%). The raw material cost is low (0.029 yuan / straw), and it is a green and biodegradable product that can be consumed directly.

[0068] Although the present invention has been described in detail with reference to preferred embodiments, it is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A method of producing starch-based straws by bio-enzyme synergistic extrusion shear, characterized in that, The starch is used as the main material, water is used as the plasticizer, and TG is used as the transfer glucoside enzyme, and a double-screw extruder is used for melt blending, and the extruded product is cooled and formed through a mold; The method for preparing the starch-based straw by using the biological enzyme and the extrusion shearing comprises the following steps: (1) The starch, water and TG are mixed uniformly in a blender, and then are loaded into a sealed container to stand and balance until the water is uniformly distributed, so as to obtain a mixed material; (2) The mixed material is loaded into a double-screw extruder, the temperature of the I zone of the double-screw extruder is 35 DEG C, the temperature of the II zone is 40 DEG C, the temperature of the III zone is 46 DEG C, the temperature of the IV zone is 52 DEG C, the temperature of the V zone is 58 DEG C, the temperature of the VI zone is 80 DEG C, the temperature of the VII zone is 90 DEG C, and the temperature of the VIII zone is 110 DEG C; the feeding speed is 8 g / min, and the extrusion speed is 7 g / min; then the straw is extruded through a die; (3) The extruded straw is cooled and cooled by using a cooling system; (4) The straw is cut and then is placed to age, so as to obtain a product.

2. The method of claim 1, wherein the bio-enzyme synergistic extrusion-shearing preparation of starch-based straws is characterized by, The starch-based straw comprises 25-30 parts of water and 5-10 parts of TG per 100 parts of starch; the starch, the TG and the water are placed in a blender and are half-wetly stirred for 5-20 min, and then are placed in a sealed container to stand and balance for 12-48 h.

3. The method of claim 2, wherein the bio-enzyme synergistic extrusion-shearing preparation of starch-based straws is characterized by, The starch-based straw comprises 28 parts of water and 6 parts of TG per 100 parts of starch; the starch, the TG and the water are placed in a blender and are half-wetly stirred for 10 min, and then are placed in a sealed container to stand and balance for 24 h.

4. The method of claim 1, wherein the bio-enzyme synergic extrusion-shearing preparation of starch-based straws is characterized by, In step (1), the starch is cassava starch.

5. The method of claim 1, wherein the bio-enzyme synergic extrusion-shearing preparation of starch-based straws is characterized by, In step (3), the extruded straw is immediately cooled by using cold air, and the cooling time is 5-10 min.

6. The method of claim 1, wherein the bio-enzyme synergic extrusion-shearing preparation of starch-based straws is characterized by, In step (4), the straw is cut to 10-13 cm, and then is placed in an environment with a temperature of 4-15 DEG C to age and crystallize the starch, and the aging time is 1-7 days.

7. The method of claim 6, wherein the bio-enzyme synergic extrusion-shearing preparation of starch-based straws is characterized by, After the straw is cut to 13 cm, the straw is placed in an environment with a temperature of 4 DEG C to age for 5 days.

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