Application of nanocrystallized bamboo leaf cell wall as low-GI food improver, low-GI food improver, preparation method of low-GI food improver and starch-like system containing low-GI food improver

Abstract

The invention provides an application of a nanocrystallized bamboo leaf cell wall as a low-GI food improver, the nanocrystallized bamboo leaf cell wall is edible, cellulose in the nanocrystallized bamboo leaf cell wall has the crystallinity of 70%-95%, the nanocrystallized bamboo leaf cell wall has a one-dimensional characteristic, the transverse size is below 100 nm, the longitudinal size is above 1 mu m, and the cell wall has the advantages of being low in cost and good in stability. The dispersion liquid in water has a viscosity of 200 Pas or more when the mass concentration of the nanocrystallized bamboo leaf cell walls is 0.5%. The invention also provides a low-GI food improver, a preparation method thereof and a starch-like system containing the low-GI food improver.

Description

Technical Field

[0001] This invention relates to the field of food processing, and more specifically, to the use of nano-sized bamboo leaf cell walls as a low-GI food modifier, a low-GI food modifier, its preparation method, and a starch-like system comprising it. Background Technology

[0002] Cellulose, as the most widely distributed and abundant natural polymer in nature, accounts for more than 50% of the carbon content in the plant kingdom and is the main structural component of plant cell walls. As a renewable carbon source, it shows broad application prospects in the fields of energy, materials, and chemical engineering.

[0003] The food industry is another application area for cellulose products. Extracted or synthesized edible cellulose is a typical example of insoluble dietary fiber, which cannot be digested by humans and plays a vital role in promoting intestinal peristalsis and defecation. Because it provides no energy but increases satiety, it is widely used as an additive in weight-loss meals.

[0004] Beyond its basic physiological functions, the understanding of dietary fiber's role in blood sugar control is constantly deepening. Previously, it was recognized that dietary fiber's benefits to blood sugar primarily manifest in slowing sugar absorption, reducing blood sugar fluctuations, and improving insulin sensitivity. It helps maintain stable blood sugar levels by slowing digestion and regulating intestinal function, which is particularly beneficial for people with diabetes or high blood sugar. When it comes into contact with water, it forms a viscous gel-like substance that coats carbohydrates in food, slowing their breakdown and absorption in the intestines. Simultaneously, long-term adequate intake of dietary fiber can improve cellular sensitivity to insulin. Studies have shown that increasing dietary fiber intake can effectively reduce the risk of type 2 diabetes. Fiber promotes the production of short-chain fatty acids (such as butyrate) by regulating the balance of intestinal flora. These substances can directly act on pancreatic β-cells, enhancing insulin secretion function. Therefore, based on the above understanding, dietary fiber has been proposed as a food additive to assist in blood sugar control. For example, Chinese patent application CN202510726682.2 discloses noodles with blood sugar control function and their preparation method, in which dietary fiber is added to flour-based foods as an auxiliary blood sugar regulator.

[0005] Nanocellulose refers to cellulose materials with a scale in the nanometer range. Compared to ordinary cellulose, nanocellulose possesses more unique properties, such as high specific surface area and high hydrophilicity, and has the potential to achieve more unique functions. Several nano-sized dietary fibers have been developed to provide further functionalities. For example, Chinese patent application 202411037355.8 discloses a nano-sized burdock functional dietary fiber and its preparation method, which provides starch digestion inhibition and hypoglycemic activity. This method uses ultrasonic synergistic complex enzyme treatment to effectively decompose the insoluble dietary fiber in burdock, altering the spatial structure of the insoluble dietary fiber to prepare nano-sized burdock functional dietary fiber with a particle size of 200 nm to 600 nm. This fiber can inhibit the activity of amylase and glucosidase, achieving a hypoglycemic effect.

[0006] Current mechanisms for controlling blood sugar using dietary fiber mainly include: (i) replacing starch to provide a feeling of fullness and reduce starch intake; (ii) forming a gel after absorbing water to physically encapsulate starch and slow down its digestion and absorption; (iii) indirectly increasing insulin sensitivity; and (iv) nanostructuring the natural dietary fiber of certain special plants by decomposing and modifying its spatial structure to inhibit the activity of digestive enzymes and reduce starch digestion. However, the inventors of this invention have found that these mechanisms also have corresponding drawbacks. Mechanism (i) requires a large amount of dietary fiber to replace the volume of starch, which alters the taste of food and affects people's appetite. Mechanism (ii) may require the simultaneous intake of a large amount of water, which may lead to increased gastric burden and indigestion. Mechanism (iii) relies on long-term regulation of the endocrine system, and its blood sugar-lowering effect is not significant for a single large intake of starch. Mechanism (iv) has special requirements for plant sources and requires bio-enzymatic hydrolysis and artificial spatial reconstruction or modification of cellulose from specific plant sources, making the process complex.

[0007] In particular, for mechanism iv), the enzymatic hydrolysis method is complex, requires stringent conditions, and has high enzyme reagent costs, making it difficult to achieve large-scale production of nanofibers and limiting its practicality. Although other methods besides enzymatic hydrolysis can be used to prepare nano-cellulose, existing nano-cellulose preparation technologies generally employ strong acids and strong oxidants, which are harmful to human health, posing environmental pollution risks and making it difficult to produce nano-sized dietary fibers suitable for the food industry. To address environmental concerns, Chinese patent application CN202110607105.3 discloses an environmentally friendly method for preparing nano-cellulose and recovering the chemical solution. This application proposes an environmentally friendly preparation method to address the scarcity of nanocellulose varieties. It suggests starting with plant-based raw materials and using a 1:2 to 2:1 volume ratio mixture of 17.5 mol / L glacial acetic acid and 30 wt% hydrogen peroxide as the treatment solution. The raw materials are then soaked, followed by pulverization, homogenization, microfluidization, and grinding to obtain nanocellulose. This nanocellulose can be used in biodegradable plastic reinforcing agents, rheology modifiers, thickeners, and other fields. Anhydrous copper sulfate is used to further recycle the treatment solution. However, this application does not disclose the morphology of the obtained nanocellulose, nor does it mention the ability to obtain food-grade nanocellulose or its application in the food industry.

[0008] Therefore, there is still a need to develop cellulose-based food modifiers that can be used in the food industry to control blood sugar. Summary of the Invention

[0009] The purpose of this invention is to develop the use of cellulose materials as low-GI food modifiers, low-GI food modifiers, their preparation methods, and starch-like systems containing them.

[0010] In one aspect, the present invention provides the use of nano-sized bamboo leaf cell walls as a low-GI food modifier, wherein,

[0011] The nano-sized bamboo leaf cell walls are edible;

[0012] The cellulose in the nano-sized bamboo leaf cell wall has a crystallinity of 70% to 95%.

[0013] The nano-sized bamboo leaf cell wall has one-dimensional characteristics, with a transverse dimension of less than 100 nm and a longitudinal dimension of more than 1 μm;

[0014] The dispersion of the nano-sized bamboo leaf cell wall in water has a viscosity of over 200 Pa•s when the mass concentration of the nano-sized bamboo leaf cell wall is 0.5%.

[0015] Optionally, the low-GI food improver is a low-GI food improver for starch-like systems.

[0016] Optionally, the starch-like system is a rice flour or wheat flour product, preferably rice noodles, noodles, or biscuits.

[0017] Optionally, the raw material for the nano-sized bamboo leaf cell wall is selected from the leaves of bamboo species such as moso bamboo, nan bamboo, giant dragon bamboo, Ci bamboo, arrow bamboo, yellow bamboo, green skin bamboo, tea pole bamboo, or arrow Ci bamboo.

[0018] In another aspect, the present invention provides a low-GI food modifier, wherein,

[0019] The low-GI food modifier contains nano-sized bamboo leaf cell walls.

[0020] The nano-sized bamboo leaf cell walls are edible;

[0021] The cellulose in the nano-sized bamboo leaf cell wall has a crystallinity of 70% to 95%.

[0022] The nano-sized bamboo leaf cell wall has one-dimensional characteristics, with a transverse dimension of less than 100 nm and a longitudinal dimension of more than 1 μm;

[0023] The dispersion of the nano-sized bamboo leaf cell wall in water has a viscosity of over 200 Pa•s when the mass concentration of the nano-sized bamboo leaf cell wall is 0.5%.

[0024] Optionally, the low-GI food improver is a dispersion of the nano-sized bamboo leaf cell wall in water at a mass concentration of 0.1% to 3%, preferably 0.3% to 2.5%, more preferably 0.4% to 2.5%.

[0025] In another aspect, the present invention provides a method for preparing the aforementioned low-GI food improver, the method comprising preparing the nano-sized bamboo leaf cell wall by the following steps:

[0026] A) Add bamboo leaves to food-grade anhydrous ethanol, heat to 60 to 75°C, and react for 24 to 48 hours;

[0027] B) Add the mixture obtained in step A) to a solution of food-grade hydrogen peroxide and food-grade glacial acetic acid, and react at 60 to 80°C for 24 to 48 h to obtain bleached bamboo leaf cell walls.

[0028] C) The bleached bamboo leaf cell walls obtained in step B) are pulverized using a post-treatment including high-pressure homogenization to obtain the nano-sized bamboo leaf cell walls.

[0029] In another aspect, the present invention provides a starch-like system comprising the aforementioned low-GI food modifier, wherein the low-GI food modifier is a dispersion of the nano-sized bamboo leaf cell wall in water at a mass concentration of 0.1% to 3%, preferably 0.3% to 2.5%, more preferably 0.4% to 2.5%, and the mass ratio of the low-GI food modifier to the starch-like substance in the starch-like system is in the range of 1:1 to 1:5.

[0030] Optionally, the starch-like system is a rice flour or wheat flour product, preferably rice noodles, noodles, or biscuits.

[0031] Optionally, the total mass content of dietary fiber is 0.5% to 1.5%.

[0032] The advantages of the uses discovered in this invention are at least as follows: using unmodified and edible nano-sized bamboo leaf cell walls derived from natural bamboo as a low-GI food modifier expands the applications of bamboo while maintaining its natural structure to a high degree; its high crystalline cellulose exhibits good mechanical, chemical, hygroscopic, biodegradable, and thermal stability, facilitating storage and transportation; its unique morphology exhibits good activity; its high viscosity and high stability in aqueous dispersion facilitate its use in food processing; and it demonstrates a high low-GI effect in practical applications. The low-GI food modifier discovered in this invention has corresponding advantages.

[0033] The advantage of the method for preparing low-GI food modifiers discovered in this invention is that it can simply, efficiently, with low energy consumption and without pollution, prepare the desired nano-sized bamboo leaf cell walls from bamboo leaves.

[0034] The advantages of the starch-like system discovered in this invention are at least as follows: it has excellent low-GI properties, is made of natural ingredients, is easy to process, and provides a good taste. Attached Figure Description

[0035] Figure 1 The proportions of the three components (cellulose, hemicellulose, and lignin) in the raw material of bamboo leaves are shown, as well as the changes in their proportions after bleaching and pulverization.

[0036] Figure 2 An image of a nanostructured bamboo leaf cell wall with one-dimensional features, observed under an atomic force microscope, is shown.

[0037] Figure 3 The UV spectra of the mixture obtained by adding a low-GI food modifier containing 0.5% nano-sized bamboo leaf cell walls to amylase are shown, as well as the UV spectra of the unmodified mixture.

[0038] Figure 4The fluorescence spectra of the mixture obtained by adding a low-GI food modifier containing 0.5% nano-sized bamboo leaf cell walls to amylase are shown, as well as those of the unmodified mixture.

[0039] Figure 5 The data show the activity of porcine pancreatic amylase obtained by adding a low-GI food modifier containing 0.5% nano-sized bamboo leaf cell walls and cellulose nanocrystals obtained by strong acid hydrolysis to amylase.

[0040] Figure 6 The results show the content of rapidly digestible starch, slowly digestible starch, and resistant starch obtained by adding a low-GI food improver with a nano-concentration of 0.5% bamboo leaf cell wall and cellulose nanocrystals obtained by strong acid hydrolysis to starch.

[0041] Figure 7 A scanning electron microscope image of starch gelatinized after a low-GI food modifier was added is shown. Detailed Implementation

[0042] In response to the technical problems existing in related technologies, the inventors of this invention have developed the use of nano-sized bamboo leaf cell walls with specific morphology and properties as a low-GI food modifier.

[0043] For diabetic patients, a core issue in blood sugar control is how to rationally manage the glycemic index (GI) through meals. When attempting to modify food by adding dietary fiber, ideally, the fiber should remain in its natural state so that it can effectively control the GI curve after meals without burdening the digestive system or negatively impacting the taste of the food. Furthermore, as a food improver, it should possess good storage stability, high activity during use, and be easy to apply during food processing.

[0044] The inventors of this invention, through research, discovered the use of processed bamboo leaf cell walls as a low-GI food modifier for dietary fiber. These bamboo leaf cell walls are nano-sized while retaining some of their natural structure. They provide better low-GI functionality on top of conventional dietary fiber, without burdening the digestive system, and offer the same or better taste. This low-GI food modifier combines good storage stability with high activity during use, and is easy to apply in food processing.

[0045] Bamboo is an abundant plant resource in my country and a forestry economic crop. Based on its intended use, it can be mainly divided into bamboo for shoots, bamboo for timber, bamboo for both shoots and timber, and bamboo for ecological forests. Expanding and developing new uses for bamboo beyond its traditional applications to fully utilize its economic value would greatly benefit my country's economic development. Currently, the edible use of bamboo is primarily limited to bamboo shoots; the development of food uses beyond bamboo shoots remains largely unexplored.

[0046] Among the various parts of bamboo, bamboo leaves, although relatively soft, are unsuitable for consumption even after processing and cooking due to their high impurity content and difficulty in digestion. While bamboo leaves are currently used to make bamboo leaf tea for infusion, for medicinal decoction, for extracting bamboo leaf flavonoids and polysaccharides, and for direct composting, they are rarely eaten and are generally considered unrelated to edible uses. However, the inventors of this invention have noticed that bamboo leaf cells contain a large amount of fiber, making them a rich source of cellulose. Therefore, if edible fiber components could be extracted from natural bamboo leaves and applied to the food industry, it would greatly expand the uses of bamboo and have significant practical implications.

[0047] Bamboo leaves are the main organs for photosynthesis in plants of the genus *Bambusa* in the family Poaceae, and bamboo leaf cells are one of the basic building blocks of bamboo leaves. Bamboo leaf cells are primarily composed of a cell wall and the cytoplasm contained within it. The cell wall mainly contains cellulose, hemicellulose, and lignin, and also contains inorganic matter (ash) and other extracts. Compared to the cell walls of woody products such as timber, the cell walls of unprocessed bamboo leaves have a higher content of silica (inorganic matter) and a higher content of waxes in their extracts.

[0048] Compared to cells in other parts of bamboo, such as the green and yellow parts, bamboo leaf cells store a large amount of flavonoids with antioxidant and lipid peroxidation functions, as well as essential trace elements such as manganese, zinc, and selenium. Some of these substances may remain in the nano-sized bamboo leaf cell walls, which can play a role in antibacterial activity and regulating human immune function after consumption. Moreover, the cell walls of bamboo leaf cells are relatively thin, which is conducive to the extraction of dietary fiber.

[0049] In this invention, the term "nanosized bamboo leaf cell wall" refers to a bamboo leaf cell wall that has been nano-processed, with at least one dimension having a scale in the nanoscale range, while retaining at least part of the natural structure of the bamboo leaf cell wall.

[0050] The term "low-GI food improver" refers to a class of functional food additives that significantly reduce the glycemic index (GI) of food by adjusting its physical structure, chemical composition, or digestible properties. Their core objective is to promote a gradual rise in postprandial blood glucose levels.

[0051] The terms "rapidly digestible starch," "slowly digestible starch," and "resistant starch" generally refer to the classification of starches into three categories based on their digestion speed and absorbability in the small intestine: rapidly digestible starch is quickly broken down and absorbed by the small intestine, leading to a rapid rise in blood sugar (such as white bread and cooked potatoes); slowly digestible starch is completely digested but at a slower rate, providing sustained energy and resulting in a stable rise in blood sugar (such as whole wheat bread and oats); and resistant starch is not digested and absorbed by the small intestine at all, but directly enters the large intestine where it is fermented by gut microbiota, does not raise blood sugar, has prebiotic effects, and can improve gut health and metabolism (such as cold rice, raw bananas, and beans).

[0052] The inventors of this invention have discovered that, compared with existing cellulose-based dietary fibers in related technologies, the nano-sized bamboo leaf cell walls proposed in this invention, as a low-GI food modifier, can not only provide the same or better blood sugar control effects, but also provide other beneficial effects and reduce side effects.

[0053] In one embodiment, the present invention provides the use of nano-sized bamboo leaf cell walls as a low-GI food modifier, wherein...

[0054] The nano-sized bamboo leaf cell walls are edible;

[0055] The cellulose in the nano-sized bamboo leaf cell wall has a crystallinity of 70% to 95%.

[0056] The nano-sized bamboo leaf cell wall has one-dimensional characteristics, with a transverse dimension of less than 100 nm and a longitudinal dimension of more than 1 μm;

[0057] The dispersion of the nano-sized bamboo leaf cell wall in water has a viscosity of over 200 Pa•s when the mass concentration of the nano-sized bamboo leaf cell wall is 0.5%.

[0058] This invention selects a special nano-sized bamboo leaf cell wall for use as a low-GI food modifier.

[0059] The main component of bamboo leaf cell walls is cellulose, and it also contains hemicellulose and lignin. Correspondingly, nano-sized bamboo leaf cell walls are also a type of cellulose product. Compared with other types of cellulose products, one characteristic of the nano-sized bamboo leaf cell walls of this invention is that they consist of bamboo leaf cell walls derived from natural bamboo, rather than artificially synthesized or modified products. They are nano-fragments of bamboo leaf cell walls with most of the lignin and some hemicellulose removed, retaining some of the microstructural characteristics of natural bamboo leaf cell walls, such as their thickness range and the arrangement of cellulose fibers, without reorganization or modification of the fibers. A second characteristic of the nano-sized bamboo leaf cell walls of this invention is that they are edible and can be prepared from low-cost natural bamboo sources using simple, pollution-free methods, thus allowing for economical and safe use as a food improver. A third characteristic of the nano-sized bamboo leaf cell walls of this invention is their high crystallinity, which gives them high mechanical stability, chemical stability, biodegradability stability, and thermal stability, as well as low hygroscopicity in air, resulting in high long-term storage stability, which is beneficial for storage, transportation, and use as an independent low-GI improver. The fourth characteristic of the nano-sized bamboo leaf cell wall of this invention is its one-dimensional nature and high aspect ratio, which allows it to exhibit good activity and performance when used, and facilitates gel formation with low water content. The fifth characteristic of the nano-sized bamboo leaf cell wall of this invention is that it retains high viscosity even when dispersed in water at low doses, thus improving the texture and mouthfeel of food. The sixth characteristic of the nano-sized bamboo leaf cell wall of this invention is its enhanced ability to convert rapidly digestible starch and slowly digestible starch into resistant starch, providing better low-GI performance.

[0060] Practical low-GI food modifiers need to meet a variety of requirements in order to provide more benefits or reduce adverse effects on the resulting food and food preparation process while fully utilizing the glycemic control mechanism, achieving a balance among various desired properties.

[0061] Cellulose includes natural cellulose and synthetic, recombinant, or modified cellulose. For example, the nano-sized burdock functional dietary fiber mentioned earlier belongs to the latter. It involves enzymatic decomposition of insoluble dietary fiber in burdock, altering its spatial structure. Synthetic, recombinant, or modified fibers can achieve specific functions. However, in the food industry, consumers generally prefer purely natural products or products that are not heavily processed and are close to their natural state, even at the cost of some functionality. Therefore, recombinant or modified non-natural dietary fibers often fail to meet consumer demands. The nano-sized bamboo leaf cell wall of this invention does not decompose, alter, recombin, or modify the fibers in the natural cell wall. It retains at least part of the microstructure of the natural bamboo leaf cell wall, more closely resembling the natural state of the raw material, while providing sufficient sugar control functionality, thus meeting consumer demand for natural or near-natural products.

[0062] This invention not only preserves the natural properties of bamboo leaf cell walls but also nanoscales them without introducing toxic or harmful substances, ensuring the edibility of the nanoscaled bamboo leaf cell walls. The nanoscaled bamboo leaf cell walls of this invention can be prepared from low-value plant raw materials using a process that is environmentally friendly, energy-efficient, and simple, offering significant cost advantages.

[0063] In addition to its low-GI functionality, a low-GI food modifier should possess high stability before being added to a food system, and should not easily deteriorate or become ineffective due to environmental factors such as stress during transportation, moisture absorption from the air, or heat during storage. This invention selects a low-GI food modifier based on highly crystalline nano-sized bamboo leaf cell walls, and its product exhibits long-term shelf stability.

[0064] However, high crystallinity can lead to a potential decrease in activity during use. This invention addresses this issue by using nano-sized bamboo leaf cell walls with one-dimensional characteristics, a high aspect ratio, and a lateral dimension below 100 nm. Compared to other granular products, these nano-sized bamboo leaf cell walls, when added to a solvent such as water, exhibit a high specific surface area due to their high aspect ratio, allowing for rapid binding and full activation with water. This enables them to quickly exert their blood sugar control mechanism, thus maintaining their blood sugar control effect despite high crystallinity. The high aspect ratio also makes their one-dimensional fiber characteristics more pronounced, potentially leading to curling or entanglement during use. This facilitates gel formation at low water content, reducing the amount of water required for the gel's blood sugar control mechanism, thus lessening the burden on the digestive system and improving the texture of the food product.

[0065] The nano-sized bamboo leaf cell walls used in this invention can maintain high viscosity even at high water content. This is beneficial for improving the processability of food systems.

[0066] The nano-sized bamboo leaf cell walls used in this invention can maintain good stability in aqueous dispersion systems at room temperature, which is a significant advantage for actual food production, as it allows for more flexible requirements on production time and temperature. For example, it can be easily mixed evenly with water at room temperature before being mixed with flour or other materials for dough kneading.

[0067] Of particular note is that when the nano-sized bamboo leaf cell walls selected in this invention are added to a starch-like system, they not only exert the aforementioned sugar control mechanisms (i) to (iv), but also show particularly good performance in reducing rapidly digested starch, slowly digesting starch, and increasing resistant starch, thereby further improving sugar control performance.

[0068] In summary, this invention selects nano-sized bamboo leaf cell walls with specific sources, crystallinity, morphology, and water dispersibility characteristics as a low-GI food modifier, thereby achieving low-GI modification of food and realizing comprehensive and excellent food performance that meets multiple requirements.

[0069] The nano-sized bamboo leaf cell wall of this invention is edible. It is obtained from natural bamboo leaf cells using the preparation method described later. This preparation method does not decompose, alter, reorganize, or modify the fibers of the bamboo leaf cell wall itself. No toxic or harmful substances are introduced in this preparation method, ensuring food safety.

[0070] The cellulose in the cell walls of nano-sized bamboo leaves has a crystallinity of 70% to 95%. Preferably, the crystallinity is in the range of 90% to 95%. If the crystallinity is too low, the shelf stability may be poor. If the crystallinity is too high, it may affect its activity during use.

[0071] Nanoscaled bamboo leaf cell walls possess a one-dimensional characteristic, clearly distinguishing them from nanoparticles with granular, spherical / ellipsoidal, or two-dimensional sheet-like shapes. The one-dimensional characteristic refers to the fact that its length dimension is significantly larger than its dimensions in the other two directions. The aspect ratio is in the range of 10 to 400, more preferably 10 to 50, and even more preferably 20 to 50. Its lateral dimension is less than 100 nm, and its longitudinal dimension is greater than 1 μm. Preferably, the lateral dimension is 5 to 60 nm. Preferably, the longitudinal dimension is 1 to 10 μm. The lateral dimension refers to the largest scale in the direction perpendicular to the length direction of the one-dimensional characteristic. For example, the nanoscaled bamboo leaf cell wall can be rod-shaped, in which case the lateral dimension is the diameter of the rod. For example, the nanoscaled bamboo leaf cell wall can also be narrow strip-shaped, in which case the lateral dimension is the width of the strip. If the aspect ratio is too low, the nanoscaled bamboo leaf cell wall will have insufficient activity and poor gelation performance during use. If the aspect ratio is too high, the preparation difficulty will be greater, increasing the cost.

[0072] The dispersion of nano-sized bamboo leaf cell walls in water has a viscosity of 200 Pa•s or higher, more preferably 2000 Pa•s or higher, and even more preferably a viscosity range of 4000 to 5000 Pa•s, when the mass concentration of nano-sized bamboo leaf cell walls is 0.5%. This viscosity reflects the stability of the system. Poor viscosity may affect the texture of food. In addition, excessively low viscosity may be detrimental to food processing and shaping.

[0073] In one embodiment, the low-GI food modifier is a low-GI food modifier for starch-like systems. The term "starch-like system" has its well-known meaning in the food industry. The nano-sized bamboo leaf cell walls of the present invention are particularly suitable as a low-GI food modifier for starch-like systems because they have a controlling effect on starch digestion and thus reduce postprandial blood glucose elevation. Of course, the low-GI food modifier can also be used as a low-GI food modifier in other food systems.

[0074] In one implementation, the starch-like system is rice flour or flour products. Flour refers to wheat flour, and rice flour refers to rice flour. Of course, the starch-like system can also be derived from other starch-rich crops. However, flour and rice flour products, as staple foods with particularly high starch content and a large proportion of rapidly digestible starch, especially require the addition of low-GI food improvers. Moreover, the texture of flour and rice flour products is more sensitive to degradation caused by the addition of dietary fiber. More preferably, the starch-like system is rice vermicelli, noodles, or biscuits.

[0075] In one embodiment, the raw material for the nano-sized bamboo leaf cell walls is selected from the leaves of bamboo species such as *Phyllostachys pubescens*, *Phyllostachys aurea*, *Phyllostachys macrocarpa*, *Phyllostachys nigra*, *Phyllostachys nigra*, *Phyllostachys pubescens*, *Phyllostachys nigra*, *Phyllostachys nigra*, or *Phyllostachys nigra*. These bamboo varieties are widely cultivated in my country. The inventors have experimentally verified that they are all suitable as raw materials for this invention. Compared with woody plants, bamboo, as a herbaceous plant, is easier to process, but there are some difficulties in the preparation of nano-sized bamboo leaf cell walls. However, the preparation method of this invention can overcome these difficulties.

[0076] In one embodiment, the present invention provides a low-GI food modifier comprising nano-sized bamboo leaf cell walls having the aforementioned characteristics. This low-GI food modifier possesses the aforementioned beneficial properties. The low-GI food modifier may consist solely of nano-sized bamboo leaf cell walls, such as nano-sized bamboo leaf cell wall powder, or it may contain other components, as long as these components do not degrade the overall performance of the low-GI food modifier. For example, it may contain water.

[0077] In one embodiment, the low-GI food modifier is a dispersion of the nano-sized bamboo leaf cell wall in water at a mass concentration of 0.1% to 3%, preferably 0.3% to 2.5%, more preferably 0.4% to 2.5%. This dispersion allows for full activation of the nano-sized bamboo leaf cell wall powder while maintaining dispersion stability for use in food preparation processes.

[0078] In one embodiment, the present invention provides a method for preparing the low-GI food modifier of the present invention, the method comprising preparing the nano-sized bamboo leaf cell wall by the following steps:

[0079] A) Add bamboo leaves to food-grade anhydrous ethanol, heat to 60 to 75°C, and react for 24 to 48 hours;

[0080] B) Add the mixture obtained in step A) to a solution of food-grade hydrogen peroxide and food-grade glacial acetic acid, and react at 60 to 80°C for 24 to 48 h to obtain bleached bamboo leaf cell walls.

[0081] C) The bleached bamboo leaf cell walls obtained in step B) are pulverized using a post-treatment including high-pressure homogenization to obtain the nano-sized bamboo leaf cell walls.

[0082] Regardless of any theoretical basis, step A) prior to bleaching is crucial in the preparation method of this invention. It promotes the exfoliation of cell walls from the bamboo leaf cells of natural bamboo, while simultaneously removing some ethanol-soluble substances from the bamboo leaf cells that might interfere with the subsequent bleaching process. By implementing step A), compared to the aforementioned Chinese patent application CN202110607105.3, the concentration of glacial acetic acid used can be reduced to approximately 60% to 80%, and the concentration of hydrogen peroxide can be reduced to below 30%, thus simplifying the process requirements.

[0083] In particular, step A) of the preparation method of the present invention can help overcome the difficulties in preparing nano-sized bamboo leaf cell walls from bamboo leaf cells. Compared with wood raw materials, the cell walls of bamboo leaves, as a herbaceous plant, contain a relatively high amount of wax. The presence of wax hinders the reaction of hydrogen peroxide and glacial acetic acid with the cell source on the one hand, and easily remains in the final product after bleaching and pulverization, potentially affecting the properties of the food. Therefore, it is particularly advantageous for bamboo leaves that the present invention effectively dissolves the wax by pre-treating them thoroughly with anhydrous ethanol, reducing their adverse effects in the bleaching step, and also promoting the precipitation of cellulose from natural bamboo. In addition, it also reduces the amount of wax remaining in the food improver, reducing the adverse effects on the final food product.

[0084] In one embodiment, the present invention provides a starch-like system comprising the low-GI food modifier of the present invention, wherein the low-GI food modifier is a dispersion of nano-sized bamboo leaf cell walls in water at a mass concentration of 0.1% to 3%, preferably 0.3% to 2.5%, more preferably 0.4% to 2.5%, and the mass ratio of the low-GI food modifier to starch in the starch-like system is in the range of 1:1 to 1:5, preferably 1:2 to 1:4. The selected range allows for sufficient control of the glycemic index after starch-like system intake while maintaining food properties such as taste and stability.

[0085] In one embodiment, the starch-like system is a rice flour or wheat flour product, preferably rice vermicelli, noodles, or biscuits. Its advantages are as described above.

[0086] In one implementation scheme, the total mass content of dietary fiber in the starch-like system is 0.5% to 1.5%. Besides nano-sized bamboo leaf cell walls, which serve as cellulose dietary fiber, other types of dietary fiber can also be added to the starch-like system. The total mass of dietary fiber should not be too high, otherwise it may affect the taste of the food.

[0087] Regarding the preparation of nano-sized bamboo leaf cell walls, more preferably, the obtained nano-sized bamboo leaf cell walls have a transverse dimension distribution ranging from 5 to 60 nm, a longitudinal dimension distribution ranging from 1 to 10 μm, and an aspect ratio distribution ranging from 10 to 400, more preferably from 10 to 50, and even more preferably from 20 to 50. Furthermore, preferably, their surface charge distribution ranges from -60 to -10 mV. This surface charge distribution range is beneficial for improving stability.

[0088] The preparation method of this invention can also be called an edible peeling method. The term "edible peeling method" refers to a method for preparing safe and edible nanoscale bamboo leaf cell walls through food-grade reagent treatment and mechanical processing, in which most of the lignin and part of the hemicellulose in the cell wall are "peeled" away, preserving as much of the natural microstructure of its cellulose arrangement as possible. In this invention, the food-grade reagents include food-grade anhydrous ethanol, food-grade glacial acetic acid, and food-grade hydrogen peroxide. Without relying on any theory, this invention uses peroxycarboxylic acid obtained from hydrogen peroxide and glacial acetic acid as a highly efficient oxidative separation reagent to selectively oxidize and degrade the phenylpropane structural units of lignin in the bamboo leaf cell wall, followed by a physical fragmentation process to prepare a bamboo leaf cell wall material with nanoscale characteristics. The resulting product exhibits unique ultrafine structural features, and its surface shows no significant chemical modification. This preparation method achieves nanoscale deconstruction of plant cell walls through oxidative-mechanical synergy, and the resulting material retains the excellent crystallinity and high aspect ratio characteristics of bamboo.

[0089] Preferably, before step A), the process may further include: repeatedly soaking commercially available bamboo leaves in deionized water to remove most of the surface salt.

[0090] Preferably, in step A), the mass ratio of bamboo leaves to anhydrous ethanol is 1:3 to 1:15, more preferably 1:5 to 1:10.

[0091] More preferably, the temperature in step A) of the present invention is 70 to 75°C, and the holding time is more preferably 36 to 48 h.

[0092] Preferably, in step B) of the present invention, the concentration of hydrogen peroxide solution is 15% to 40%; the concentration of glacial acetic acid solution is 60% to 80%, and the mass ratio of the two is 1:5 to 1:20; the mass ratio of bamboo leaves to reaction solution is 1:3 to 1:5.

[0093] In step C) of this invention, a post-processing method including high-pressure homogenization is used. The high-pressure homogenization crushing method relies on the pressurization and depressurization process of liquid to complete the material crushing through effects such as shearing, cavitation, and impact. The inventors have discovered that when plant cells are derived from bamboo leaves, they contain a relatively high content of silica, a high-hardness substance, compared to those derived from woody plants. Mechanical crushing using methods such as high-speed rotating cutters may result in rapid cutter wear, leading to reduced processing efficiency and potentially introducing impurity particles. High-pressure homogenization avoids these drawbacks and is therefore particularly suitable for preparing nano-sized bamboo leaf cell walls from bamboo leaves. Preferably, the mechanical pulverization of the bleached bamboo leaf cell wall dispersion includes any one or more combinations of a high-pressure homogenizer, a cell ultrasonic disruptor, and a pulper, with a pulverization time of 1 to 5 hours. Preferably, the mass concentration of the bamboo leaf cell wall dispersion in water is 0.4% to 2.5%. Preferably, the high-pressure homogenization process can be carried out for 2 to 5 hours.

[0094] The purpose of the above preparation method is to enable the nano-sized bamboo leaf cell walls extracted from natural bamboo to have the required high crystallinity, high aspect ratio and excellent mechanical and thermal stability, so as to realize the use of the present invention as a low-GI food improver.

[0095] The method of this invention extracts nano-sized bamboo leaf cell walls from natural bamboo without adding toxic or harmful solvents, resulting in minimal environmental pollution, low energy consumption, a simple and efficient peeling process, and food safety features.

[0096] The low-GI food improver of the present invention uses nano-sized bamboo leaf cell walls with special properties. When used in food systems, especially starch-like substances, it also has the function of reducing rapidly digested starch, slowing down the digestion of starch, and increasing resistant starch.

[0097] In this invention, the process of combining low-GI food modifiers with starch and characterizing their properties may include the following steps:

[0098] Step a): Add a certain amount of deionized water or remove a certain amount of water to the prepared nano-sized bamboo leaf cell wall aqueous dispersion to adjust the mass concentration, so as to prepare a nano-sized bamboo leaf cell wall aqueous dispersion with a mass concentration of 0.1% to 3%, preferably 0.3% to 2.5%, more preferably 0.4% to 2.5%;

[0099] Step b): Add the nano-sized bamboo leaf cell wall aqueous dispersion obtained in step a) to starch. The nano-sized bamboo leaf cell wall aqueous dispersion and starch are compounded in a mass ratio of 1:1 to 1:5, preferably 1:2 to 1:4. Then, the mixture is uniformly mixed and dispersed by mechanical means, and then it can be left to stand in the freezer for 30 to 60 minutes.

[0100] Step c): Take out 5 to 10 mL or 5 to 10 g of the well-dispersed solution obtained in step b) and place it in a glass beaker. Perform rheological property testing on the material using a viscosity measurement method. For example, a Waters HR20 rheometer from TA Instruments (USA) can be used. Use a parallel plate with a diameter of 60 mm and measure the shear rate from 0.01 to 100 s⁻¹ at 8°C. -1 The change in solution viscosity and the frequency from 1 to 100 rad / s -1 Changes in the storage modulus and loss modulus of the solution.

[0101] The mechanical stirring described in step b) above can be performed using a magnetic stirrer, ultrasonic stirrer, PTFE stirrer, or cell disruptor, preferably a magnetic stirrer or cell disruptor, and more preferably a cell disruptor; the mechanical stirring rate range is 1500 to 3000 r / min. -1 Stir for 2 to 15 minutes, and let stand in the refrigerator for 10 to 15 minutes.

[0102] In this invention, nano-sized bamboo leaf cell walls are added to starch, forming a dense network structure with good stability between the nano-sized bamboo leaf cell walls and starch, which can exhibit one or more of the following effects:

[0103] i) Adding the low-GI food modifier to the desired starch-like system results in a more compact starch-like system structure;

[0104] ii) When the low-GI food modifier is added to the desired starch-like system, the viscosity and storage modulus are significantly improved;

[0105] iii) After adding the low-GI food modifier to the starch-like system and gelatinizing it, an in vitro simulated digestion experiment was conducted. As the concentration of nano-sized bamboo leaf cell walls extracted from natural bamboo increased, the content of rapidly digestible starch and slowly digestible starch decreased, while the content of resistant starch increased.

[0106] When low-GI food modifiers are added to a liquid system of porcine pancreatic amylase, they can interact with amylase and reduce its activity.

[0107] To further understand the present invention, the application and corresponding inhibitory effect of nano-sized bamboo leaf cell walls in inhibiting starch digestion are further illustrated below with reference to embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0108] Example

[0109] In this embodiment, bamboo leaves were used as a natural plant source to provide the cell walls of bamboo leaves, and were purchased from the bamboo product store on Taobao.

[0110] The characterization experiments of the target performance parameters in the embodiments all use methods commonly used in the art.

[0111] Example 1 of preparation of nano-sized bamboo leaf cell walls

[0112] Nanoscale bamboo leaf cell walls were prepared using the following steps.

[0113] First, soak 1000g of bamboo leaves in deionized water multiple times to remove most of the salt from the surface.

[0114] Subsequently, the desalted bamboo leaves were added to food-grade anhydrous ethanol and reacted at 70°C for 12 h in a reaction vessel to promote the bleachability of the cell walls of the bamboo leaves. The ratio of the two was 1:6.

[0115] After the bamboo leaves were washed with deionized water, they were bleached in a pre-prepared mixed solution of food-grade hydrogen peroxide aqueous solution and food-grade glacial acetic acid aqueous solution at a ratio of 1:4. The concentration of the hydrogen peroxide aqueous solution was 20%, the concentration of the glacial acetic acid aqueous solution was 60%, the mass ratio of the two solutions was 1:10, the reaction time was 24 h, and the reaction temperature was 60℃.

[0116] The mixture obtained after the bleaching step separated into layers upon standing. The upper layer was a floating slurry, the lower layer was a liquid, and the bottom layer was sediment. The upper slurry was separated and washed with water, an appropriate amount of water was added, and then the mixture was pulverized in a pulper for 1 hour, followed by crushing in a high-pressure homogenizer for 120 minutes to obtain a nano-sized bamboo leaf cell wall dispersion.

[0117] Figure 1 The proportions of the three components (cellulose, hemicellulose, and lignin) in the raw material of bamboo leaves and their changes after bleaching and mechanical treatment are shown. It can be seen that after bleaching, the lignin proportion decreases significantly, the cellulose proportion increases significantly, and the hemicellulose proportion remains relatively unchanged. This indicates that the bleaching process removes most of the lignin and some of the hemicellulose from the bamboo leaves. After mechanical treatment, the proportions of the three components do not change significantly further.

[0118] Figure 2 This image shows a nanostructured bamboo leaf cell wall with one-dimensional features observed under an atomic force microscope. The scale bar is at the bottom of the image, and the gradient color bar on the right represents the sample height in terms of brightness. It can be seen that it has one-dimensional features, with a lateral dimension of approximately 80 nm and a longitudinal dimension of approximately 5 μm.

[0119] Repeated experiments showed that the aqueous dispersion of the obtained nano-sized bamboo leaf cell wall had a viscosity of over 200 Pa•s when the mass concentration of the nano-sized bamboo leaf cell wall was 0.5%.

[0120] Example 2 of preparation of nano-sized bamboo leaf cell walls

[0121] Nanoscale bamboo leaf cell walls were prepared in a manner essentially the same as in Example 1, with the following differences: during the treatment with food-grade anhydrous ethanol, the reaction time was 24 h; during the bleaching process, the concentration of hydrogen peroxide aqueous solution was 30%, the concentration of glacial acetic acid aqueous solution was 80%, the volume ratio of the two was 1:20, the reaction time was 48 h, and the reaction temperature was 80 °C; during the pulverization process, the cells were pulverized in a pulper for 2 h, and then crushed in a high-pressure homogenizer for 90 minutes.

[0122] The product was subjected to the aforementioned detection and characterization, and the results were consistent with those of Example 1, which was used to prepare nano-sized bamboo leaf cell walls.

[0123] Example 1 of food improver performance

[0124] The product obtained from Example 1 of the preparation of nano-sized bamboo leaf cell walls was used as a low-GI food modifier in an experiment added to a starch-like system. Before addition, the content ratio of the low-GI food modifier in the dispersion was adjusted. Specifically, the product from Example 1 of the preparation of nano-sized bamboo leaf cell walls was dried, weighed, and its solid content was calculated. Based on the calculation result, a certain amount of water was added or evaporated to obtain an aqueous dispersion with a predetermined mass concentration of nano-sized bamboo leaf cell walls. An aqueous dispersion of nano-sized bamboo leaf cell walls with a mass concentration of 0.5% was prepared in this manner as a low-GI food modifier sample.

[0125] The low-GI food improver sample and porcine pancreatic amylase were mixed at a mass ratio of 10:1, stirred at room temperature, and allowed to stand at room temperature for 20 minutes after being stirred evenly to obtain a homogeneous mixed solution system.

[0126] Figure 3 The ultraviolet spectrum of this mixture, measured using a SOLID 3700 ultraviolet-visible-near-infrared spectrophotometer, is shown.

[0127] Figure 4 The fluorescence spectrum of this mixture, measured using an XRF-1800 X-ray fluorescence spectrometer, is shown.

[0128] Figure 3 , 4 Microscopically, it was shown that the nano-sized bamboo leaf cell walls reduced enzyme activity, thereby inhibiting digestion.

[0129] Take 1 mL of the supernatant from the obtained mixed solution system and place it in a glass beaker. Measure the activity of porcine pancreatic amylase using an enzyme-linked immunosorbent assay (ELISA) reader to calculate the data.

[0130] Figure 5The data on porcine pancreatic amylase activity and enzyme activity curves of this mixture, measured using an ST-360 microplate reader, are shown. Figure 5 Macroscopically, this indicates that the nano-sized bamboo leaf cell walls reduce enzyme activity, thereby inhibiting digestion.

[0131] Without relying on any theory, the low-GI food improver of this invention can inhibit the activity of α-amylase and hinder starch digestion through physicochemical interactions and steric hindrance effects, achieving a low-GI effect. Specifically, the hydroxyl and carboxyl functional groups on the surface of the nano-bamboo leaf cell wall in the low-GI food improver can directly adsorb α-amylase molecules through electrostatic interactions and hydrogen bonds, resulting in the masking of the enzyme's active site or a conformational change. In addition to inhibiting the activation of amylase molecules, the three-dimensional network structure formed by the nano-bamboo leaf cell wall in the starch matrix can physically block the contact between α-amylase and starch molecules, significantly reducing the enzymatic hydrolysis efficiency. Furthermore, the nano-bamboo leaf cell wall can also affect the gelatinization and retrogradation properties of starch by preferentially binding to amylose, further reducing the exposure of enzymatic hydrolysis sites. These synergistic effects ultimately lead to a significant reduction in the rate and extent of starch digestion. In particular, the nano-bamboo leaf cell wall of this invention may have a better effect on inhibiting amylase than cellulose nanocrystals obtained by conventional strong acid hydrolysis due to the retention of some natural cell wall structure and specific morphology.

[0132] Example 2 of food improver performance

[0133] The low-GI food improver sample was prepared using the same method as in Example 1 of the food improver performance test. The low-GI food improver sample and starch were mixed at a mass ratio of 1:2 and gelatinized by heating at 60 to 80°C for 30 min.

[0134] Figure 6 The contents of rapidly digestible starch, slowly digestible starch, and resistant starch in this mixture are shown, as measured using an ST-360 microplate reader.

[0135] Figure 6 This demonstrates that the addition of low-GI food improvers reduces the content of rapidly digestible and slowly digestible starches while increasing the content of resistant starches, thus achieving a low-GI effect.

[0136] When the low-GI food improver of the present invention is added to starch, due to the high specific surface area and network structure formed by the nanoscale and one-dimensional characteristics of the nano-sized bamboo leaf cell walls, it can effectively reduce the proportion of rapidly digestible starch and slowly digestible starch in starch, increase the proportion of resistant starch, and further improve the low-GI effect.

[0137] Figure 7 A scanning electron microscope image of starch gelatinized after a low-GI food modifier was added is shown.

[0138] As can be seen, the gelatinized starch has a denser structure after the addition of low-GI food improvers. These low-GI food improvers form a three-dimensional network structure, thereby reducing the contact between enzymes and starch, inhibiting starch digestion, and thus controlling glycemic output.

[0139] Comparative Example 1

[0140] This comparative example is the same as Example 1, except that the nano-sized bamboo leaf cell walls were replaced with cellulose nanocrystals (CNCs) obtained by hydrolysis with a strong acid at a mass concentration of 0.5%. The CNCs used in this comparative example were obtained from wood by conventional methods through strong acid hydrolysis, retaining only the cellulose crystalline region.

[0141] Figure 5 The graph shows the amylase activity data obtained in Example 1 and Comparative Example 1 using cellulose nanocrystals and nano-sized bamboo leaf cell walls at a mass concentration of 0.5%. The amylase activity was lower after adding nano-sized bamboo leaf cell walls compared to adding cellulose nanocrystals.

[0142] Comparative Example 2

[0143] This comparative example is the same as Example 2, except that the nano-sized bamboo leaf cell walls were replaced with cellulose nanocrystals with a mass concentration of 0.5%. Figure 6 The figures represent the contents of rapidly digestible starch, slowly digestible starch, and resistant starch obtained in Example 2 and Comparative Example 2 using nano-sized bamboo leaf cell walls and cellulose nanocrystals at a mass concentration of 0.5%. Compared to the addition of cellulose nanocrystals, the addition of nano-sized bamboo leaf cell walls resulted in less rapidly digestible starch and less slowly digestible starch, and more resistant starch.

[0144] Comparative Example 3

[0145] The preparation was carried out in the same manner as in Example 1 of the preparation of nano-sized bamboo leaf cell walls, except that the anhydrous ethanol reaction step was not performed.

[0146] The same characterization of the product showed that its hemicellulose and lignin residues were high and its one-dimensional characteristics were poor.

[0147] As can be seen, the nano-sized bamboo leaf cell walls obtained in this invention, when added to starch, verify that this material has the effect of inhibiting the increase of glycemic index (GI) through multiple mechanisms, and therefore has broad application prospects, especially in low-GI foods and related fields. The nano-sized cell walls extracted from natural bamboo leaves in this invention, when added to starch-like systems, not only reduce the glycemic index and obtain low-GI products, but also have other comprehensive and excellent effects. This product has significant advantages and broad application prospects. In food systems, it can not only be used to develop low-glycemic index foods, help control blood sugar levels, and reduce the risk of chronic diseases, but also as a liquid thickener and stabilizer to improve the taste and stability of food. Its preparation method is simple, non-toxic, efficient, and environmentally friendly in obtaining the desired nano-sized bamboo leaf cell walls, with anhydrous ethanol treatment improving the preparation effect.

[0148] The above descriptions of specific embodiments and examples are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles and spirit, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. Use of nano-sized bamboo leaf cell wall as a low GI food improver, characterized in that, the nano-sized bamboo leaf cell wall is edible; the cellulose in the nano-sized bamboo leaf cell wall has a crystallinity of 70% to 95%; the nano-sized bamboo leaf cell wall has a one-dimensional feature, with a lateral size of less than 100 nm and a longitudinal size of more than 1 μm; a dispersion of the nano-sized bamboo leaf cell wall in water has a viscosity of more than 200 Pa-s at a nano-sized bamboo leaf cell wall mass concentration of 0.5%.

2. The use according to claim 1, characterized in that, the low GI food improver is a low GI food improver for starch-like systems.

3. The use according to claim 2, characterized in that, the starch-like system is a rice flour or flour product, preferably rice noodles, noodles or biscuits.

4. The use according to claim 1, characterized in that, the cell source of the nano-sized bamboo leaf cell wall is selected from the bamboo leaves of Phyllostachys edulis, Phyllostachys pubescens, Dendrocalamus giganteus, Dendrocalamus latiflorus, Dendrocalamus strictus, Pleioblastus amarus, Pleioblastus graminacus, Bambusa pachinensis or Dendrocalamus farinosus.

5. A low GI food improver, characterized in that, the low GI food improver comprises a nano-sized bamboo leaf cell wall, the nano-sized bamboo leaf cell wall is edible; the cellulose in the nano-sized bamboo leaf cell wall has a crystallinity of 70% to 95%; the nano-sized bamboo leaf cell wall has a one-dimensional feature, with a lateral size of less than 100 nm and a longitudinal size of more than 1 μm; a dispersion of the nano-sized bamboo leaf cell wall in water has a viscosity of more than 200 Pa-s at a nano-sized bamboo leaf cell wall mass concentration of 0.5%.

6. The low GI food improver according to claim 5, characterized in that, the low GI food improver is a dispersion of the nano-sized bamboo leaf cell wall in water at a mass concentration of 0.1% to 3%, preferably 0.3% to 2.5%, more preferably 0.4% to 2.5%.

7. A method of preparing a low-GI food modifier according to claim 5 or 6, characterised in that, the method comprises the following steps to prepare the nano-sized bamboo leaf cell wall: A) adding bamboo leaves to food-grade anhydrous ethanol, heating to 60 to 75 °C, and reacting for 24 to 48 h; B) adding the mixture obtained in step A) to a solution of food-grade hydrogen peroxide and food-grade glacial acetic acid mixed together, reacting at 60 to 80 °C for 24 to 48 h to obtain bleached bamboo leaf cell wall; C) using post-treatment including high-pressure homogenization to crush the bleached bamboo leaf cell wall obtained in step B) to obtain the nano-sized bamboo leaf cell wall.

8. A starch-like system comprising the low GI food improver according to claim 5 or 6, characterized in that, the low GI food improver is a dispersion of the nano-sized bamboo leaf cell wall in water at a mass concentration of 0.1% to 3%, preferably 0.3% to 2.5%, more preferably 0.4% to 2.5%, and the mass ratio of the low GI food improver to starch-like in the starch-like system is in the range of 1:1 to 1:

5.

9. Starch-like system according to claim 8, characterised in that the starch-like system is a rice flour or flour product, preferably rice noodles, noodles or biscuits.

10. The starch-like system according to claim 8, characterized in that, wherein the total mass content of dietary fiber is 0.5% to 1.5%.

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