A straw and a method of making the same

Abstract

The application provides a straw and a preparation method thereof, which comprises: an inner tube, wherein the inner tube comprises first bacterial cellulose and a calcium salt; an intermediate tube, wherein the intermediate tube is sleeved outside the inner tube, and the intermediate tube comprises second bacterial cellulose and a stabilizer; and an outer tube, wherein the outer tube is sleeved outside the intermediate tube and plays a role of isolation. The straw has good thermal stability and hydrolysis resistance, is easy to degrade, and is safe and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the food industry, and more specifically to a straw and its preparation method. Background Technology

[0002] As a widely used disposable tableware in daily life, the choice of materials for straws has a significant impact on the environment and health. Traditional plastic straws are mostly made of petroleum-based materials such as polypropylene (PP). Although they are inexpensive and have good processing performance, their non-degradability leads to serious "white pollution" problems. With the implementation of global plastic bans, biodegradable materials are gradually becoming the mainstream choice for straw manufacturing.

[0003] However, existing biodegradable straw materials, such as polylactic acid (PLA), although biodegradable, have poor heat resistance and hydrolysis resistance, which limits their application in the hot beverage field.

[0004] Therefore, developing a straw with good thermal stability, hydrolysis resistance, and easy degradation is a research hotspot. Summary of the Invention

[0005] This invention provides a straw and its preparation method. The straw has good thermal stability and hydrolysis resistance, is easy to degrade, and is safe and environmentally friendly.

[0006] The present invention provides a straw, comprising: an inner tube comprising a first bacterial cellulose and a calcium salt; a middle tube sleeved on the outside of the inner tube, the middle tube comprising a second bacterial cellulose and a stabilizer; and an outer tube sleeved on the outside of the middle tube, serving as an isolation layer.

[0007] Optionally, in the straw, the thickness of the inner tube is 0.067mm to 0.233mm, the thickness of the middle tube is 0.101mm to 0.350mm, and the thickness of the outer tube is 0.034mm to 0.117mm; and / or, the thickness of the straw wall is 0.18mm to 0.7mm; and / or, the inner diameter of the straw is 1 to 100mm.

[0008] Optionally, in the inner tube, the mass percentage of the first bacterial cellulose is 99.0% to 99.9%, and the mass percentage of the calcium salt is 0.1% to 1%; and / or, in the intermediate tube, the mass percentage of the second bacterial cellulose is 99.0% to 99.8%, and the mass percentage of the stabilizer is 0.2% to 1%.

[0009] Optionally, the calcium salt comprises one or more of calcium lactate and calcium chloride; and / or, the stabilizer comprises modified starch, which comprises one or more of hydroxypropyl distarch phosphate, acetylated starch, and physically modified starch; and / or, the outer tube comprises alginate, citrate, thickener, coagulant, and water, wherein the thickener comprises one or more of agar and pectin, and the coagulant comprises glucono-δ-lactone.

[0010] The present invention also provides a method for preparing the straw as described above, comprising: performing a first molding process on a first raw material system comprising the first bacterial cellulose and the calcium salt to form the inner tube; performing a second molding process on the outer side of the inner tube on a second raw material system comprising the second bacterial cellulose and the stabilizer to form the intermediate tube; and performing a third molding process on the outer side of the intermediate tube on a raw material system of the outer tube to form the outer tube, thereby obtaining the straw.

[0011] Optionally, the moisture content of the first bacterial cellulose is 15% to 25%; and / or, the moisture content of the second bacterial cellulose is 15% to 25%.

[0012] Optionally, in the first raw material system, the mass percentage of the first bacterial cellulose is 99.0% to 99.9%, and the mass percentage of the calcium salt is 0.1% to 1%; and / or, in the second raw material system, the mass percentage of the second bacterial cellulose is 99.0% to 99.8%, and the mass percentage of the stabilizer is 0.2% to 1%; and / or, the raw material system of the outer tube includes, by mass percentage, 1% to 10% alginate, 1% to 10% citrate, 1% to 10% thickener, 1% to 10% coagulant, and the balance being water.

[0013] Optionally, the process of performing a first molding process on the first raw material system comprising the first bacterial cellulose and the calcium salt to form the inner tube, and performing a second molding process on the outer side of the inner tube on the second raw material system comprising the second bacterial cellulose and the stabilizer to form the intermediate tube, includes: simultaneously discharging the first raw material system comprising the first bacterial cellulose and the calcium salt and the second raw material system comprising the second bacterial cellulose and the stabilizer from different outlets, and then simultaneously performing the first molding process and the second molding process to obtain the inner tube and the intermediate tube sleeved on the outer side of the inner tube; and / or, the process of performing a third molding process on the outer side of the intermediate tube on the outer side of the outer tube to form the outer tube, and then obtaining the straw, includes: spraying the raw material system of the outer tube onto the outer side of the intermediate tube to perform a third molding process to form the outer tube, and then obtaining the straw.

[0014] Optionally, the temperature of the first molding process is 170–185°C; and / or, the temperature of the second molding process is 170–185°C.

[0015] Optionally, the first bacterial cellulose and / or the second bacterial cellulose are obtained by a method comprising at least the following process: adding lignocera acetic acid bacteria to coconut water for fermentation to obtain the first bacterial cellulose and / or the second bacterial cellulose; wherein the fermentation temperature is 25-30°C and the fermentation time is 10-14 days.

[0016] This invention provides a straw and its preparation method. The straw has a three-layer structure, consisting of an inner tube, a middle tube sleeved outside the inner tube, and an outer tube sleeved outside the middle tube. The three layers work together to improve the straw's strength, hardness, toughness, thermal stability, and hydrolysis resistance. The straw has high bending strength and hardness, capable of puncturing composite films with a thickness of 60μm to 130μm. It also has high toughness, giving it good anti-fragility properties. Furthermore, it has good thermal stability and hydrolysis resistance, maintaining high stability in high-temperature and high-humidity environments. In addition, the straw uses bacterial cellulose as the main material, which is easily degradable and has the characteristics of no environmental pollution and low food safety risk, thus facilitating the industrialization and large-scale application of bacterial cellulose. Attached Figure Description

[0017] 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, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a diagram of an apparatus that can be used to prepare the straws of the embodiments of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. 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.

[0020] Existing biodegradable straw materials, such as polylactic acid (PLA), are biodegradable, but their poor heat resistance and hydrolysis resistance limit their application in the hot beverage industry.

[0021] To overcome the deficiencies in the prior art, in a first aspect, embodiments of the present invention provide a straw, comprising: an inner tube, the inner tube comprising a first bacterial cellulose and a calcium salt; a middle tube, the middle tube being sleeved on the outside of the inner tube, the middle tube comprising a second bacterial cellulose and a stabilizer; and an outer tube, the outer tube being sleeved on the outside of the middle tube, serving as an isolation element.

[0022] The inner tube consists of bacterial cellulose and calcium salt. Cross-linking reactions transform linear or slightly branched macromolecules into a three-dimensional network structure, thereby improving properties such as strength, heat resistance, abrasion resistance, and solvent resistance. The hydroxyl groups in bacterial cellulose and the calcium ions in the calcium salt can form a stable cross-linked network structure through cross-linking reactions, further enhancing the inner tube's strength, heat resistance, abrasion resistance, and solvent resistance. This prevents the inner wall from sticking under pressure and avoids dissolution even after prolonged contact with liquids, contributing to improved straw strength, thermal stability, and hydrolysis resistance.

[0023] The intermediate tube is fitted outside the inner tube and includes a second bacterial cellulose layer and a stabilizer. The bacterial cellulose has strong water retention and toughness, while the stabilizer can repair and connect the network fiber structure of the bacterial cellulose. The synergistic effect of the two gives the intermediate tube good stability, thus providing better stable support for the straw and helping to ensure that the straw's performance remains unchanged during its shelf life.

[0024] The outer tube is fitted over the middle tube to act as an insulator. This helps to isolate the straw from the influence of the external environment (such as oxygen and light).

[0025] According to research and analysis, the inner tube, the middle tube sleeved outside the inner tube, and the outer tube sleeved outside the middle tube form a three-layer structure straw. The three layers work together to improve the straw's strength, hardness, toughness, thermal stability, and hydrolysis resistance. The straw has high bending strength and hardness, capable of puncturing composite membranes with a thickness of 60μm to 130μm. The straw has high toughness, giving it good anti-fragility properties. The straw has good thermal stability and hydrolysis resistance, allowing it to maintain high stability in high-temperature and high-humidity environments. In addition, the straw uses bacterial cellulose as the main material, which is easily degradable and has the characteristics of no environmental pollution and low food safety risk, which helps to realize the industrialization and large-scale application of bacterial cellulose.

[0026] In some specific embodiments of the present invention, the thickness of the inner tube in the straw is 0.067 mm to 0.233 mm, the thickness of the middle tube is 0.101 mm to 0.350 mm, and the thickness of the outer tube is 0.034 mm to 0.117 mm.

[0027] For example, the thickness of the inner tube can be 0.067, 0.070, 0.080, 0.090, 0.100, 0.150, 0.200, 0.233 mm or any combination thereof, the thickness of the middle tube can be 0.101, 0.150, 0.200, 0.250, 0.300, 0.350 mm or any combination thereof, and the thickness of the outer tube can be 0.034, 0.050, 0.100, 0.117 mm or any combination thereof.

[0028] By controlling the thickness of the inner tube, middle tube, and outer tube to meet the above range, the three-layer structure of the straw can work together better to improve the straw's strength, hardness, toughness, thermal stability, and hydrolysis resistance.

[0029] In some embodiments, the thickness of the straw wall is 0.18 mm to 0.7 mm, preferably 0.2 mm to 0.4 mm, and more preferably 0.28 mm to 0.32 mm.

[0030] In some embodiments, the inner diameter of the straw can be 1 to 100 mm.

[0031] For example, the inner diameter of the straw can be a range of 1, 2, 5, 10, 12, 30, 50, 60, 80, 90, 100 mm or any combination thereof.

[0032] Preferably, the inner diameter of the straw can be 2mm-30mm.

[0033] More preferably, the inner diameter of the straw can be 5mm-12mm.

[0034] In specific implementation, the inner diameter (or diameter) of the straw (i.e., the bacterial cellulose-based straw) can be 6 to 7 mm, for example, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0 mm or any combination thereof, preferably 6.6 mm; the length can be 8 to 10 cm, for example, 8, 9, 10 cm or any combination thereof, preferably 9 cm; and the thickness can be 0.2 to 0.4 mm, for example, 0.2, 0.3, 0.4 mm or any combination thereof, preferably 0.3 mm.

[0035] Specifically, in the inner tube, the mass percentage of bacterial cellulose is 99.0% to 99.9%, and the mass percentage of calcium salt is 0.1% to 1%.

[0036] By controlling the mass ratio of bacterial cellulose and calcium salt in the inner tube to meet the above range, the two can undergo a more complete cross-linking reaction, forming a more stable cross-linked network structure, which in turn helps to better improve the strength, hardness, toughness, thermal stability and hydrolysis resistance of the straw.

[0037] Specifically, in the intermediate tube, the mass percentage of the second bacterial cellulose is 99.0% to 99.8%, and the mass percentage of the stabilizer is 0.2% to 1%.

[0038] By controlling the mass ratio of bacterial cellulose and stabilizer in the intermediate tube to meet the above range, the two can work together better, giving the intermediate tube better stability, which in turn provides better stability support for the straw. This helps to improve the straw's strength, hardness, toughness, thermal stability, and hydrolysis resistance, ensuring that the straw's performance remains unchanged during its shelf life.

[0039] In some specific embodiments of the present invention, the calcium salt includes one or more of calcium lactate and calcium chloride. The calcium ions in the calcium salt crosslink with the hydroxyl groups in bacterial cellulose to form a stable crosslinked network structure. This prevents the inner walls of the inner tube (straw) from sticking together during subsequent processing, avoiding the problem of blockage of internal channels caused by the adhesion of modified starch. Simultaneously, the stable crosslinked network structure makes the inner wall less susceptible to dissolution by the ingested liquid during later use.

[0040] Calcium chloride has a neutral pH, which is similar to that of calcium lactate, which has an acidic pH. However, calcium lactate can adjust the overall acidity of the straw, inhibiting microbial growth and preventing degradation and loss of its physical properties (hardness and toughness) during the later preservation process after the straw is formed.

[0041] In some specific embodiments of the present invention, the stabilizer includes modified starch. Modified starch and bacterial cellulose have a better synergistic effect, which contributes to better straw strength, hardness, toughness, thermal stability and hydrolysis resistance. This is because: First, modified starch has a stabilizing effect, keeping the straw stable during straw preparation processes (such as heating extrusion, molding and drying). Second, modified starch has gelling properties, which can act as an adhesive. The network fiber structure of bacterial cellulose is destroyed by cutting and other actions, but modified starch can repair and connect the destroyed network fiber structure during the extrusion process of the intermediate tube (straw). Third, modified starch also has good film-forming properties, making it easier for the intermediate tube (straw) to become a uniform film structure after extrusion, allowing the intermediate tube to function better and contributing to better straw strength, thermal stability, toughness and hydrolysis resistance.

[0042] Furthermore, the modified starch may include one or more of hydroxypropyl distarch phosphate, acetylated starch, and physically modified starch, preferably hydroxypropyl distarch phosphate.

[0043] In some specific embodiments of the present invention, the outer tube comprises alginate, citrate, thickener, coagulant, and water. The outer tube, comprising the above-mentioned components, has a dense structure. As a dense outer shell of the straw, it can block oxygen, prevent oxidation of the straw, shield it from light, prevent microbial invasion, and also help harden the straw, increase its strength and puncture resistance, and extend its shelf life.

[0044] Alginate can include sodium alginate. Alginate can help harden straws.

[0045] Citrates can include sodium citrate. Citrates can be used to harden pipettes and adjust the pH of the feed material in the outer tube.

[0046] Thickeners may include one or more of agar and pectin. Thickeners can work together with other substances in the outer tube to increase the wall thickness of the straw, thereby increasing its strength and making it less prone to breakage, oxidation, and microbial invasion. This prevents microorganisms from invading the inner tube (inner layer) and middle tube (middle layer) and consuming the bacterial cellulose sodium, thus helping to extend the shelf life of the straw.

[0047] Coagulants can include gluco-δ-lactone. Gluco-δ-lactone is mainly used as a coagulant, stabilizer, preservative, and antiseptic to extend the shelf life of straws.

[0048] The components of the outer tube can combine with the stabilizer (such as modified starch) of the middle tube (e.g., a chemical reaction can occur) to form a strong structure, allowing the outer tube to be evenly adhered to the outer surface of the straw, forming an outer coating of the straw, which helps to better improve the strength, hardness, toughness, thermal stability and hydrolysis resistance of the straw.

[0049] In addition, the outer tube may also include at least one of edible flavorings and edible natural colorings. In practice, it may be added in accordance with GB 2760, the standard for the use of food additives.

[0050] The formula for the outer tube uses food additives for all components, ensuring that the straw is non-toxic. Even if consumers consume the straw, it will not harm their health. By utilizing the inherent properties of each material, it reacts chemically with other materials to form a strong coating (outer tube), ensuring the straw's quality is stable and it can be used for a long time. In addition, flavorings and colorings can be used on the outer coating (outer tube), achieving color and flavor effects while greatly reducing the amount used, thus lowering the possibility of harm to consumers' health.

[0051] The straws of this invention exhibit performance close to polypropylene straws in terms of extended shelf life, brittleness resistance, and heat resistance. Their biodegradability is superior to polylactic acid straws, and they are edible and readily degradable without special conditions, offering advantages such as no environmental pollution and low food safety risk. The straws of this invention have a shelf life of two years or more. During this period, the straws demonstrate antioxidant properties, brittleness resistance, high hardness, good toughness, and stable chemical properties, meeting the usage expectations and environmental protection needs of end consumers. Therefore, the straws of this invention have the potential to replace some non-degradable polypropylene (PP) plastic straws and polylactic acid (PLA) straws that require special degradation conditions.

[0052] Secondly, embodiments of the present invention also provide a method for preparing the above-mentioned straw, comprising: performing a first molding process on a first raw material system comprising a first bacterial cellulose and a calcium salt to form an inner tube; performing a second molding process on the outside of the inner tube on a second raw material system comprising a second bacterial cellulose and a stabilizer to form an intermediate tube; and performing a third molding process on the outside of the intermediate tube on a raw material system of an outer tube to form an outer tube, thereby obtaining a straw.

[0053] The first raw material system, which includes first bacterial cellulose and calcium salt, can be prepared by mixing first bacterial cellulose and calcium salt in a certain proportion.

[0054] Because the inner tube (or inner layer) is squeezed by external forces generated by guide rails or rollers during subsequent processing after extrusion molding, the inner walls of the straw may come into contact with each other, easily leading to adhesion. However, in the first raw material system of this embodiment (i.e., the raw material of the inner tube), calcium ions can undergo a cross-linking reaction with the hydroxyl groups in bacterial cellulose under high temperature to form a stable cross-linked network structure. This effectively avoids the adhesion problem caused by extrusion, and also effectively avoids the problem of adhesion and blockage of internal channels caused by extrusion when the straw only has a middle layer material. In addition, the stable cross-linked network structure of the inner tube (or inner layer) improves the straw's resistance to dissolution, making the inner wall of the straw less likely to dissolve during later use.

[0055] Similarly, a second raw material system comprising a second bacterial cellulose and a stabilizer can be prepared by mixing the second bacterial cellulose and the stabilizer in a specific ratio.

[0056] Both the first molding process and the second molding process described above can be performed using conventional processes in the art, such as extrusion using a straw extruder.

[0057] Understandably, the middle tube needs to be formed on the outer layer of the inner tube, and the outer tube needs to be formed on the outer layer of the middle tube, so that the straw with the three-layer structure of the present invention can be prepared.

[0058] The above preparation method is simple to operate and can produce straws with excellent strength, hardness, toughness, thermal stability and hydrolysis resistance.

[0059] It is understood that the above preparation method may also include a mixing process, such as mixing the first bacterial cellulose and calcium salt in a certain proportion to obtain a first raw material system, and mixing the first bacterial cellulose and calcium stabilizer in a certain proportion to obtain a second raw material system.

[0060] To improve processing performance, the moisture content of the first raw material system can be adjusted to make it a semi-dry paste, which facilitates subsequent production.

[0061] Since the moisture in the first raw material system can come from the first bacterial cellulose, the moisture content of the first raw material system can be adjusted by controlling the moisture content of the first bacterial cellulose.

[0062] In some specific embodiments of the present invention, the moisture content of the first bacterial cellulose is 15% to 25%. The moisture in the first bacterial cellulose can be utilized by calcium salts, thereby making the first raw material system a semi-dry paste, which facilitates subsequent production.

[0063] Similarly, in order to improve processing performance, the moisture content of the second raw material system can be adjusted so that the second raw material system is in a semi-dry paste form, which is convenient for subsequent production.

[0064] In practice, since the moisture in the second raw material system can come from the second bacterial cellulose, the moisture content of the second raw material system can be adjusted by controlling the moisture content of the second bacterial cellulose.

[0065] In some specific embodiments of the present invention, the moisture content of the second bacterial cellulose is 15% to 25%. The moisture in the second bacterial cellulose can be utilized by the stabilizer, thereby making the second raw material system a semi-dry paste, which is convenient for subsequent production.

[0066] In some specific embodiments of the present invention, in the first raw material system, the mass percentage of the first bacterial cellulose is 99.0% to 99.9%, and the mass percentage of the calcium salt is 0.1% to 1%.

[0067] In some embodiments, in the second raw material system, the mass percentage of the second bacterial cellulose is 99.0% to 99.8%, and the mass percentage of the stabilizer is 0.2% to 1%.

[0068] In some embodiments, the raw material system of the outer tube comprises, by mass percentage, 1% to 10% alginate, 1% to 10% citrate, 1% to 10% thickener, 1% to 10% coagulant, and the balance being water.

[0069] In some specific embodiments of the present invention, the process of performing a first molding process on a first raw material system comprising a first bacterial cellulose and a calcium salt to form an inner tube, and performing a second molding process on the outer side of a second raw material system comprising a second bacterial cellulose and a stabilizer to form an intermediate tube includes: simultaneously discharging the first raw material system comprising a first bacterial cellulose and a calcium salt and the second raw material system comprising a second bacterial cellulose and a stabilizer from different outlets, and then simultaneously performing the first molding process and the second molding process to obtain an inner tube and an intermediate tube sleeved on the outer side of the inner tube.

[0070] That is, in the above-mentioned method for preparing straws, the inner tube and the middle tube can be prepared simultaneously.

[0071] In practice, a double-layer co-extrusion molding process can be adopted to extrude the first raw material system and the second raw material system at the same time, thereby forming the inner tube and the intermediate tube at the same time. During this process, the first raw material system and the second raw material body are discharged from different outlets at the same time to ensure that the intermediate tube is sleeved on the outer layer of the inner tube.

[0072] Unlike the traditional method of directly extruding straws in one step, this invention employs a two-layer co-extrusion molding process to simultaneously form an inner tube and an intermediate tube sleeved on the outside of the inner tube. Then, a third molding treatment (coating treatment) is applied to the outer side (outer wall) of the intermediate tube, thereby forming a straw with a three-layer composite structure. This effectively solves the problem of the inner wall's resistance to dissolution during continuous straw production. The coating process improves the hardness and oxidation resistance of the straw's outer wall, which further facilitates the cross-linking of the second bacterial cellulose in the intermediate tube and the calcium salt in the inner tube at the interface. This enhances the connection strength between the inner tube and the intermediate tube, allowing the two layers to work together better, thus improving the straw's strength and other properties.

[0073] In practical applications, the following methods can be adopted: Figure 1 The straw extruder shown (the mainstream straw manufacturing equipment in the field) performs the above-mentioned double-layer co-extrusion molding process. Specifically, the straw extruder can be started and heated first. After reaching the production conditions, the first raw material system is added to hopper B, and the second raw material system is added to hopper A. Production is carried out according to the set parameters to produce an inner tube and an intermediate tube (i.e., straw blank) that is sleeved on the outside of the inner tube in a double-layer co-extrusion manner.

[0074] like Figure 1 As shown, hopper B and hopper A each have a discharge port. During production, the two inlets supply material simultaneously. However, because hopper A is at the front of hopper B (according to the material flow direction), the inner tube formed by the first raw material system is in the inner layer, and the intermediate tube formed by the second raw material system is attached to the outside of the inner tube. This effectively solves the problem of adhesion of the inner tube (suction tube).

[0075] Understandably, the process parameters of the straw extruder can be adjusted appropriately according to the actual production situation.

[0076] Furthermore, the straw preparation process, i.e., the straw extrusion process, can be divided into a feeding section, a compression section, a melting section, and a metering section. Specific temperature parameters can be set as follows:

[0077] Feeding section: 175℃~195℃, depending on the extruder's shear performance and extrusion volume, ensuring the displayed temperature >170℃; Compression section: 170℃~190℃; Melting section: 170℃~190℃; Metering section: 170℃~180℃, depending on the extruder's shear performance and extrusion volume, ensuring the displayed temperature ≤185℃.

[0078] If necessary, the screw temperature, feed rate, and other methods can be used to adjust them separately.

[0079] In addition, the die head temperature is 175℃~195℃ and the die temperature is 190℃~200℃, which should be adjusted accordingly depending on the profile cross-section forming and wall thickness.

[0080] In addition, the temperature of the first molding process can be 170-185℃, and the temperature of the second molding process can be 170-185℃.

[0081] For example, the temperature of the first molding process can be a range of 170, 175, 180, 185°C or any combination thereof, and the temperature of the second molding process can be a range of 170, 175, 180, 185°C or any combination thereof.

[0082] In some specific embodiments of the present invention, the process of performing a third molding process on the outside of the middle tube to form an outer tube and then obtaining a straw includes: spraying the raw material system of the outer tube onto the outside of the middle tube to perform a third molding process to form an outer tube and then obtaining a straw.

[0083] In other words, the outer tube can be formed by spraying. This helps to form a uniform coating on the outer tube, thereby improving the performance of the straw and extending its shelf life.

[0084] In practice, the straw blank (inner tube and intermediate tube sleeved outside the inner tube) can be passed through the water tank to coat its surface evenly with a coating, forming the outer tube. The time the straw blank spends in the soaking tank can be adjusted according to the sensory condition of the coating; for example, the time can be 3 to 5 seconds.

[0085] Next, the coated straws (including the inner, middle, and outer tubes) can be dried, for example, in the hot air duct of a dryer. The drying (hot air) temperature and time can be adjusted according to the sensory condition of the straws; for example, the temperature can be 40–150°C and the time can be 20–30 seconds.

[0086] Generally, in the actual production process, it also includes: cutting the straws, ensuring that the cuts are neat and burr-free, and that the length meets the requirements.

[0087] It is understood that bacterial cellulose (BC) in the embodiments of the present invention refers to the general term for cellulose synthesized by certain microorganisms such as Acetobacter, Agrobacterium, Rhizobium, and Sarcina under different conditions. For example, coconut water can produce a milky white or transparent edible cellulose gel through the fermentation of specific microorganisms, commonly known as "coconut jelly" or "nata", which belongs to bacterial cellulose.

[0088] In some specific embodiments of the present invention, the first bacterial cellulose and / or the second bacterial cellulose are obtained by a method comprising at least the following process: adding lignocera acetic acid bacteria into a raw material system comprising monosaccharides for fermentation to obtain the first bacterial cellulose and / or the second bacterial cellulose; wherein the fermentation temperature is 25-30°C and the fermentation time is 10-14 days.

[0089] In some embodiments, the process flow for preparing the first bacterial cellulose and / or the second bacterial cellulose is as follows:

[0090] The process includes: receiving the monosaccharide raw material system (liquid raw material) → filtration (100-mesh filter) → sterilization (75±2℃ / 15s) → cooling → acidification (adjusting pH=6.0±0.5) → inoculation → fermentation (25-30℃ / 10-14d) → passing inspection → sterilization (84-86℃ / 33min) → preservation of soaking solution for later use → raw material removal and dicing → dehydration by filter press → mixing → extrusion molding → outer surface soaking coating → drying by dryer (150℃ / 30s) → slitting → packaging → inspection and shipment.

[0091] The aforementioned raw material system including monosaccharides (liquid raw materials) should comply with the food safety regulations of GB 15203. Specifically, it can include at least one of coconut water, watermelon rind juice, soybean juice, orange juice, and pineapple juice. In addition, sucrose, glucose, fructose, yeast extract, peptone, disodium hydrogen phosphate, citric acid, ethanol, and water can be used as the main components to prepare the culture medium for *Acetobacter xylinum* (i.e., the raw material system including monosaccharides). Alternatively, tea water and white sugar can be used to prepare the raw material system for producing bacterial cellulose. Furthermore, the nitrogen source, carbon source, and inorganic salts required by specific microorganisms that produce bacterial cellulose can be added to water in proportion to prepare a culture medium, which can be used as the raw material system for fermentation to produce bacterial cellulose. A wide range of raw material sources helps reduce the production cost of bacterial cellulose and expands the prospects for edible bacterial cellulose.

[0092] In some embodiments, the sensory requirements of the above-mentioned raw material system including monosaccharides are shown in Table 1, and the physicochemical properties are shown in Table 2.

[0093] Table 1 Sensory Requirements

[0094]

[0095] Table 2 Physicochemical Indicators

[0096]

[0097] The specific steps are explained below.

[0098] Filtration: The qualified liquid raw materials are filtered, and the filter mesh can be 100 mesh;

[0099] Sterilization: The filtered liquid raw material is sterilized by passing it through a pasteurization system at 75±2℃ / 15s;

[0100] Cooling: After sterilization, the liquid raw material is cooled to 30±2℃ via a cooling plate heat exchanger;

[0101] Acidity adjustment: Use food-grade lactic acid or sodium hydroxide to adjust the pH of the liquid raw material to 6.0±0.5;

[0102] Inoculation: In a clean room (air cleanliness level of 10,000), add woody acetic acid bacteria to the fermentation tray, stir for 15-20 minutes, then stop stirring, place on a three-dimensional shelf, ensure good ventilation on the surface of each fermentation tray, and let it ferment statically.

[0103] The strain used is expanded acetic acid bacteria of wood, or, if conditions permit, glucosamine acetobacterium xylanum;

[0104] Fermentation trays, measuring 600mm × 900mm × 60mm, can be made of thin stainless steel. The automated shelving system can hold 20 shelves, with spacing between shelves for ventilation.

[0105] Heat the liquid raw material to (32±2)°C, then pour it into fermentation trays. After each fermentation tray is half filled (50%), pour 100ml of the liquid expanded cultured fermentation bacteria into it, and stir evenly with a clean and sterilized stirring rod (it is sufficient that the fermentation bacterial liquid is basically uniform in the fermentation tray as observed with the naked eye, then place it stably on the fermentation shelf. After the shelves are fully loaded, push them into the fermentation chamber for standing;

[0106] Fermentation: Ferment for 10-14 days at a temperature of 25-30°C, and observe the forming state of the fermentation product starting from the 10th day;

[0107] Qualified by inspection: Visually inspect that the fermentation product is in good forming state, and has a firm feeling when pressed by hand, then it is qualified;

[0108] Squeeze the clot with hands sterilized by alcohol. If it feels very elastic and does not break easily when squeezed with a little force, it meets the requirements (if it breaks when squeezed with a little force, the fermentation time needs to be extended);

[0109] Sterilization: Fish out the fermentation product with a tool, put it into a sterilization pot, start timing when the temperature reaches 85°C (temperature range 84-86°C), keep the temperature for 33 minutes, then take it out with a tool, place it in a sterile soaking solution for storage for later use; the soaking solution is composed of 55%-65% sucrose solution, which is boiled at 100°C for 300s before being used for soaking.

[0110] Bacterial cellulose is prepared through the above process.

[0111] Before using the above bacterial cellulose to produce straws, the bacterial cellulose raw material can be taken out and diced: before production, use a tool to take the fermentation product (bacterial cellulose) out of the soaking solution, rinse it with production water and drain it, then cut it into pieces with a dicing machine, with a diameter of 15±1mm; then use a filter press to remove water: put the cut raw bacterial cellulose into the filter press to squeeze out water, stop when the weight is reduced to 75% to 85% of the original weight, that is, when the water content is 15% to 25%, and take it out for later use.

[0112] Based on the characteristic that bacterial cellulose (commonly known as coconut cellulose) can absorb up to 100% of its own weight in water, it cannot be completely dried or too wet during subsequent processing. If the bacterial cellulose is too dry, water must be added during extrusion molding. Furthermore, in the step of removing water in the filter press, once more than 80% of the water in the bacterial cellulose has been removed, further pressing becomes very difficult, resulting in high energy consumption, significant equipment wear and tear, and increased clogging and damage to the filter cloth. After comprehensive testing, it is considered that removing 75%–85% of the water content yields the best results. Additionally, before the raw material for the straws enters the extruder, drying stabilizers (such as powdered modified starch) and calcium salts (such as calcium lactate and / or calcium chloride) must be added. The 15%–25% water content in the bacterial cellulose can be utilized by the two added drying stabilizers and calcium salts, resulting in a semi-dry paste-like raw material system suitable for subsequent production.

[0113] In some embodiments, edible bacterial cellulose containing glucose and fructose monosaccharides, produced by the fermentation of acetic acid bacteria, is used as a raw material. After filtering out the moisture from the bacterial cellulose, calcium salts (such as calcium lactate and / or calcium chloride) are added to obtain a first raw material system. A stabilizer (such as modified starch) is added to obtain a second raw material system. Then, a double-layer co-extrusion process is used to form a straw blank with a double-layer structure, including an inner tube and an intermediate tube sleeved on the outer layer of the inner tube. The outer wall of the straw blank is then coated with the raw material of the outer tube (such as an soaking solution containing agar, pectin, sodium alginate, glucono-δ-lactone, and sodium citrate). After drying and molding, a biodegradable and edible straw with a three-layer composite structure is obtained.

[0114] The present invention will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0115] Example 1

[0116] This embodiment provides a method for preparing a straw, including:

[0117] 1) Preparation of bacterial cellulose,

[0118] Acetic acid bacteria were added to a raw material system containing monosaccharides for fermentation. After fermentation, the raw materials were sterilized and then filtered to obtain first bacterial cellulose and second bacterial cellulose, respectively. The fermentation temperature was 25°C and the fermentation time was 10 days. During the filtration process, the moisture content of both the first and second bacterial cellulose was controlled to be 20%.

[0119] The first bacterial cellulose, calcium lactate, and calcium chloride are mixed to obtain the first raw material system. In the first raw material system, the mass percentage of the first bacterial cellulose is 99.9%, the mass percentage of calcium lactate is 0.05%, and the mass percentage of calcium chloride is 0.05%.

[0120] The second bacterial cellulose and hydroxypropyl distarch phosphate were mixed to obtain the second raw material system. In the second raw material system, the mass percentage of the second bacterial cellulose was 99.8% and the mass percentage of hydroxypropyl distarch phosphate was 0.2%.

[0121] Prepare the raw material system for the outer tube, which includes, by mass percentage, 4% agar, 2% pectin, 2% sodium alginate, 1% glucose-δ-lactone, 1% sodium citrate, and the remainder being water.

[0122] The first raw material system and the second raw material system are discharged from different outlets at the same time, and then extruded simultaneously (first molding process and second molding process) to obtain an inner tube and an intermediate tube sleeved on the outside of the inner tube, and to obtain a straw blank. The temperature of the first molding process and the second molding process is 180°C.

[0123] Then, the raw material system of the outer tube is sprayed onto the outside of the straw blank (intermediate tube) for a third molding process to form the outer tube, thereby obtaining the straw.

[0124] During the process of adjusting the first molding process, the second molding process, and the third molding process, the thickness of the three layers of the straw is as shown in Table 3.

[0125] Example 2

[0126] This embodiment is basically the same as Embodiment 1, except that:

[0127] The moisture content of both the first and second bacterial cellulose was controlled at 15% during the pressure filtration process, while other conditions remained unchanged.

[0128] Example 3

[0129] This embodiment is basically the same as Embodiment 1, except that:

[0130] The moisture content of both the first and second bacterial cellulose was controlled at 25% during the pressure filtration process, while other conditions remained unchanged.

[0131] Example 4

[0132] This embodiment is basically the same as Embodiment 1, except that:

[0133] The moisture content of both the first and second bacterial cellulose was controlled at 14% during the pressure filtration process, while other conditions remained unchanged.

[0134] Example 5

[0135] This embodiment is basically the same as Embodiment 1, except that:

[0136] The moisture content of both the first and second bacterial cellulose was controlled at 26% during the pressure filtration process, while other conditions remained unchanged.

[0137] Example 6

[0138] This embodiment is basically the same as Embodiment 1, except that:

[0139] In the first raw material system, the mass percentage of the first bacterial cellulose is 99.0%, the mass percentage of calcium lactate is 0.5%, and the mass percentage of calcium chloride is 0.5%. In the second raw material system, the mass percentage of the second bacterial cellulose is 99.0%, and the mass percentage of hydroxypropyl distarch phosphate is 1%. The temperature of both the first molding treatment and the second molding treatment is 185℃.

[0140] All other conditions remain unchanged.

[0141] Example 7

[0142] This embodiment is basically the same as Embodiment 1, except that:

[0143] In the first raw material system, the mass percentage of the first bacterial cellulose is 99.5%, the mass percentage of calcium lactate is 0.25%, and the mass percentage of calcium chloride is 0.25%. In the second raw material system, the mass percentage of the second bacterial cellulose is 99.4%, and the mass percentage of hydroxypropyl distarch phosphate is 0.6%. The temperature of both the first and second molding treatments is 170℃. Other conditions remain unchanged.

[0144] Example 8

[0145] This embodiment is basically the same as Embodiment 1, except that:

[0146] In the first raw material system, the mass percentage of the first bacterial cellulose is 99.7%, the mass percentage of calcium lactate is 0.15%, and the mass percentage of calcium chloride is 0.15%. In the second raw material system, the mass percentage of the second bacterial cellulose is 99.6%, and the mass percentage of hydroxypropyl distarch phosphate is 0.4%. The fermentation time is adjusted to 14 days. Other conditions remain unchanged.

[0147] Example 9

[0148] This embodiment is basically the same as Embodiment 1, except that:

[0149] In the first raw material system, the mass percentage of cellulose from the first bacteria is 99.9%, and the mass percentage of calcium lactate is 0.1%; other conditions remain unchanged.

[0150] Example 10

[0151] This embodiment is basically the same as Embodiment 1, except that:

[0152] In the first raw material system, the mass percentage of cellulose from the first bacteria is 99.9%, and the mass percentage of calcium chloride is 0.1%; other conditions remain unchanged.

[0153] Comparative Example 1

[0154] Paper straws.

[0155] Comparative Example 2

[0156] Plastic straws.

[0157] Comparative Example 3

[0158] Polylactic acid (PLA) straws.

[0159] Test case

[0160] The following parameters of the straws in each embodiment and comparative example were tested:

[0161] 1) Mass percentage of the first bacterial cellulose and calcium salt in the inner tube: Chemical analysis methods, such as elemental analysis and gravimetric analysis, were used to analyze the composition of the inner tube of the pipette and determine the mass percentage of each component.

[0162] 2) Mass percentage of cellulose from the second bacterial strain and mass percentage of stabilizer in the intermediate tube: The intermediate tube of the pipette was analyzed using the same chemical analysis method.

[0163] 3) The mass percentage of the inner tube, middle tube, and outer tube in the straw: After separating each layer of the straw, weigh them separately and calculate the percentage of each layer's mass to the total mass of the straw.

[0164] 4) Bending strength (MPa): Tested using a universal testing instrument;

[0165] 5) Aging time (standard ≥ 15 hours) Temperature 85℃ / humidity 85%RH: Place the straw in the aging test chamber, set the temperature to 85℃ and the humidity to 85%RH, observe the appearance and performance changes of the straw regularly, and record the time when the straw is obviously damaged or its performance deteriorates.

[0166] 6) Maximum temperature resistance: Place the straw in a high-temperature test chamber and raise the temperature at a certain rate. The temperature at which the straw begins to deform or melt is the maximum temperature resistance.

[0167] 7) Film puncture test (film material PET7 / AL40 / PE80): Place the straw vertically above the film and press the straw down at a certain speed. Record the maximum number of times the straw can puncture the film.

[0168] 8) Straw drop test (room temperature) pass rate: Place the straw horizontally on a hard surface, and use an object of a certain weight to drop freely from a certain height onto the straw. Check whether the straw breaks, and calculate the percentage of qualified straws out of the total number of tests.

[0169] 9) Pass rate of straw smashing test (-11℃): Place the straw in a low temperature environment of -11℃ for a certain period of time, and then test it according to the method of straw smashing test at room temperature, and calculate the pass rate.

[0170] 10) Drop test: Drop the straw freely from a certain height and observe whether the straw breaks or is damaged.

[0171] 11) Fluorescence: Use a fluorescence detector to test the pipette and observe whether any fluorescent substances are emitted.

[0172] 12) Straw inner diameter: Use calipers or an inner diameter measuring instrument to directly measure the inner diameter of the straw.

[0173] 13) Wall thickness: Use a thickness gauge to measure the thickness of each layer of the straw.

[0174] The test results are shown in Tables 3 and 4.

[0175] Table 3

[0176]

[0177]

[0178] Table 4

[0179]

[0180] The test results show that the straws of the present invention outperform the straws of the comparative examples in all performance indicators. In terms of bending strength, the straws of the present invention are significantly stronger than paper straws, plastic straws, and polylactic acid straws, indicating that the straws of the present invention have better strength and toughness. The straws of the present invention also perform well in terms of aging time and maximum temperature resistance, indicating that they have better thermal stability and hydrolysis resistance. The results of the puncture test, drop test, and impact test show that the straws of the present invention have a high pass rate, indicating that they are more durable in actual use. Furthermore, all straws of the present invention are free of fluorescence, ensuring safety in use. Within the examples, Examples 1-3, with a bacterial cellulose moisture content in the range of 15%-25%, have similar and good performance, while Examples 4 and 5, with moisture content exceeding this range, show a slight decrease in performance, indicating that the moisture content of bacterial cellulose has a certain impact on straw performance.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A straw, characterized in that, include: Inner tube, the inner tube comprising a first bacterial cellulose and calcium salt; An intermediate tube, which is sleeved on the outside of the inner tube, includes a second bacterial cellulose and a stabilizer; The outer tube is sleeved on the outside of the middle tube and serves as an isolation device.

2. The straw according to claim 1, characterized in that, In the straw, the thickness of the inner tube is 0.067mm to 0.233mm, the thickness of the middle tube is 0.101mm to 0.350mm, and the thickness of the outer tube is 0.034mm to 0.117mm. And / or, the thickness of the straw wall is 0.18 mm to 0.7 mm; And / or, the inner diameter of the straw is 1 to 100 mm.

3. The straw according to claim 1, characterized in that, In the inner tube, the mass percentage of the first bacterial cellulose is 99.0% to 99.9%, and the mass percentage of the calcium salt is 0.1% to 1%. And / or, in the intermediate tube, the mass percentage of the second bacterial cellulose is 99.0% to 99.8%, and the mass percentage of the stabilizer is 0.2% to 1%.

4. The straw according to any one of claims 1-3, characterized in that, The calcium salt includes one or more of calcium lactate and calcium chloride; And / or, the stabilizer comprises modified starch, which includes one or more of hydroxypropyl distarch phosphate, acetylated starch, and physically modified starch; And / or, the outer tube comprises alginate, citrate, thickener, coagulant and water, the thickener comprising one or more of agar and pectin, and the coagulant comprising glucono-δ-lactone.

5. A method for preparing a straw according to any one of claims 1-4, characterized in that, include: The first raw material system, comprising the first bacterial cellulose and the calcium salt, is subjected to a first molding process to form the inner tube; The second raw material system, including the second bacterial cellulose and the stabilizer, is subjected to a second molding process on the outside of the inner tube to form the intermediate tube; The raw material system of the outer tube is subjected to a third molding process on the outside of the middle tube to form the outer tube, thereby obtaining the straw.

6. The method for preparing a straw according to claim 5, characterized in that, The moisture content of the first bacterial cellulose is 15% to 25%; And / or, the moisture content of the second bacterial cellulose is 15% to 25%.

7. The method for preparing a straw according to claim 5 or 6, characterized in that, In the first raw material system, the mass percentage of the first bacterial cellulose is 99.0% to 99.9%, and the mass percentage of the calcium salt is 0.1% to 1%. And / or, in the second raw material system, the mass percentage of the second bacterial cellulose is 99.0% to 99.8%, and the mass percentage of the stabilizer is 0.2% to 1%; And / or, the raw material system of the outer tube comprises, by mass percentage, 1% to 10% alginate, 1% to 10% citrate, 1% to 10% thickener, 1% to 10% coagulant, and the balance being water.

8. The method for preparing a straw according to claim 5 or 6, characterized in that, The process of performing a first molding process on a first raw material system comprising the first bacterial cellulose and the calcium salt to form the inner tube, and performing a second molding process on the outer side of the inner tube on a second raw material system comprising the second bacterial cellulose and the stabilizer to form the intermediate tube, includes: A first raw material system comprising the first bacterial cellulose and the calcium salt and a second raw material system comprising the second bacterial cellulose and the stabilizer are simultaneously discharged from different outlets, and then simultaneously subjected to a first molding process and a second molding process, thereby obtaining the inner tube and the intermediate tube sleeved on the outside of the inner tube; And / or, the process of performing a third molding process on the outside of the intermediate tube to form the outer tube and thus obtain the straw includes: spraying the raw material system of the outer tube onto the outside of the intermediate tube to perform a third molding process to form the outer tube and thus obtain the straw.

9. The method for preparing a straw according to claim 5 or 6, characterized in that, The temperature of the first molding process is 170–185°C; And / or, the temperature of the second molding process is 170–185°C.

10. The method for preparing a straw according to claim 5 or 6, characterized in that, The first bacterial cellulose and / or the second bacterial cellulose are obtained by a method comprising at least the following processes: Acetic acid bacteria are added to coconut water for fermentation to obtain the first bacterial cellulose and / or the second bacterial cellulose; wherein the fermentation temperature is 25-30℃ and the fermentation time is 10-14 days.

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