Application of cellulose nanofiber extracted from sargassum fusiforme residues as thickening agent

Abstract

The invention provides application of cellulose nanofibers extracted from sargassum fusiforme residues as a thickening agent, and particularly relates to application of the cellulose nanofibers extracted from sargassum fusiforme residues as the thickening agent in the food field. The sargassum fusiforme-based cellulose nanofiber is added into liquid needing to be thickened, such as apple juice, milk and soda water, an excellent thickening effect can be achieved, and the sargassum fusiforme-based cellulose nanofiber has the advantages of being easy to operate, safe, environmentally friendly and good in stability.

Description

Technical Field

[0001] The present invention relates to the field of cellulose nanofiber extraction, and particularly to the application of cellulose nanofibers extracted from Sargassum fusiforme residues as thickeners, especially as thickeners in the food field. Background Art

[0002] As an important marine biological resource, Sargassum fusiforme is widely distributed in the seas around the world. Due to its rapid growth and many bioactive substances such as polysaccharides, proteins, and trace elements, the components extracted from it have important commercial value in industries such as textiles, biomedicine, chemical engineering, and agriculture and forestry. However, after extracting these high-value products, a large amount of Sargassum fusiforme residues accumulate as by-products. Currently, they are mainly used as fertilizers and fillers after simple mechanical crushing, and their high-value utilization has not been realized.

[0003] In addition, cellulose nanofibers, as one of the most abundant all-green resources on the earth, are nano-building units with a wide range of sources, excellent mechanical properties and thermal stability, and good degradability. However, in traditional cellulose nanofiber extraction processes, some toxic and harmful impurities are often introduced (for example, 2,2,6,6-tetramethylpiperidine oxide, a piperidine-based nitroxide radical), making the prepared cellulose nanofibers difficult to meet the requirements of food safety, thus hindering their wide application in the food field.

[0004] Therefore, the present application provides a high-value application of Sargassum fusiforme-based cellulose nanofibers, that is, Sargassum fusiforme-based cellulose nanofibers are extracted from Sargassum fusiforme residues by a low-energy, simple, efficient, and safe cellulose nanofiber stripping method, and then the Sargassum fusiforme-based cellulose nanofibers are used as thickeners, especially as thickeners in food-related fields. Summary of the Invention

[0005] Another object of the present invention is to apply the food-safe cellulose nanofiber raw material in food-related fields such as liquid thickening, and provide a food-safe liquid thickening raw material for the food field.

[0006] To this end, the present invention provides the following technical solutions.

[0007] <1> An application of Sargassum fusiforme-based cellulose nanofibers extracted from Sargassum fusiforme residues as a liquid thickener, wherein the cellulose nanofibers are obtained from Sargassum fusiforme residues by an extraction method including the following steps:

[0008] A) Adding Sargassum fusiforme residues to a food-grade alkaline degumming solution, heating to a predetermined temperature of 80-120 °C, and maintaining for 5-24 h to obtain degummed Sargassum fusiforme residues;

[0009] B) Add the degummed Sargassum fusiforme residue obtained in step A) to a solution prepared by mixing food-grade hydrogen peroxide and food-grade acetic anhydride in a mass ratio of 1:2 to 1:10, and react at a temperature of 15 to 30 °C for 10 to 24 h to obtain micron-scale Sargassum fusiforme cellulose;

[0010] C) Add the micron-scale Sargassum fusiforme cellulose to acetic acid solution and carry out a decolorization reaction at 23 to 30 °C for 6 to 24 h to obtain bleached micron-scale Sargassum fusiforme cellulose;

[0011] D) Mechanically crush the bleached micron-scale Sargassum fusiforme cellulose to obtain Sargassum fusiforme-based cellulose nanofibrils.

[0012] <2>. According to the application described above, the application is in the food field.

[0013] <3>. According to the application described above, the application includes the following steps:

[0014] Add the Sargassum fusiforme-based cellulose nanofibers to the liquid system to be thickened and mix, where the mass fraction of the Sargassum fusiforme-based cellulose nanofibers in the mixed solution system is 0.1 to 1.0%.

[0015] <4>. According to the application described above, wherein the liquid system is at least one of apple juice, milk, and soda water, and the mixing is carried out by stirring at 1500 to 3000 r / min for 2 to 15 min.

[0016] <5>. According to the application described above, the Sargassum fusiforme-based cellulose nanofibers have at least one of the following properties i) and those selected from ii)-v):

[0017] i). The diameter of the Sargassum fusiforme-based cellulose nanofibers is 5 to 60 nm;

[0018] ii). The aspect ratio of the Sargassum fusiforme-based cellulose nanofibers is 20 to 400;

[0019] iii). The crystallinity of the Sargassum fusiforme-based cellulose nanofibers is 80 to 95%;

[0020] iv). The Sargassum fusiforme-based cellulose nanofibers contain at least one type of hemicellulose component containing carboxyl uronic acid;

[0021] v). The surface charge of the Sargassum fusiforme-based cellulose nanofibers is -60 to -10 mV.

[0022] <6>, According to the application described above, wherein in step A), the alkaline degumming solution is selected from at least one of the following: aqueous solution of food-grade sodium hydroxide, aqueous solution of food-grade potassium hydroxide, aqueous solution of food-grade sodium carbonate and other solvents.

[0023] <7>, According to the application described above, wherein in step A), the mass concentration of the alkaline degumming solution is 5% - 10%, and the mass ratio of the Sargassum fusiforme residue to the food-grade alkaline degumming solution is 1:5 - 1:10.

[0024] <8>, According to the application described above, wherein in step B), the mass concentration of hydrogen peroxide is 10% - 30%, the mass concentration of acetic anhydride is 50% - 90%, the volume ratio of the two solutions is 1:2 - 1:10, and the mass ratio of the degummed Sargassum fusiforme residue raw material to the reaction solution is 1:3 - 1:5.

[0025] <9>, According to the application described above, wherein in step C), the mass concentration of the acetic acid solution is 30% - 90%, the temperature of the oxidation treatment is 23 - 30 °C, and the mass ratio of the micron-scale Sargassum fusiforme cellulose to the acetic acid solution is 1:3 - 1:5.

[0026] <10>, According to the application described above, wherein the thickening effect obtained by the application includes at least one of the following:

[0027] i) Adding the Sargassum fusiforme-based cellulose nanocellulose as a thickening agent to the liquid system to be thickened, when the shear rate of the thickened liquid is 0.01 - 0.05 s -1 the viscosity of the system is measured to be 1200 - 1500 Pa s;

[0028] ii) Adding the Sargassum fusiforme-based cellulose nanocellulose as a thickening agent to the liquid system to be thickened, and the thickened liquid remains stable within 5 - 14 days;

[0029] iii) Adding the Sargassum fusiforme-based cellulose nanocellulose as a thickening agent to the liquid system to be thickened, and the thickened liquid remains stable at 10 - 60 °C. Description of the Drawings

[0030] Figure 1 Digital photo of the untreated Sargassum fusiforme raw material of the present invention;

[0031] Figure 2Digital photos showing different stages in the Sargassum fusiforme stripping process are presented. Respectively: Sargassum fusiforme raw materials, Sargassum fusiforme residues after degumming, Sargassum fusiforme cellulose after bleaching, and Sargassum fusiforme-based cellulose nanofibers. Through comparison, it can be observed that as the stripping process progresses, the size of Sargassum fusiforme cellulose gradually decreases, and finally nano-scale cellulose is obtained.

[0032] Figure 3 Scanning electron microscope photos comparison of Sargassum fusiforme raw materials and Sargassum fusiforme-based cellulose nanofibers is presented, revealing the changes in the structure and component distribution of Sargassum fusiforme during the stripping process.

[0033] Figure 4 The X-ray diffraction curve of the obtained Sargassum fusiforme-based cellulose nanofibers is presented, indicating that the obtained is nano-scale Sargassum fusiforme cellulose; The PANalytical X’pert PRO MRD X-ray diffractometer was used. The sample was evenly placed on a silicon wafer and put into the X-ray diffractometer together to obtain data; Through comparison, it was found that after the nano-sizing of Sargassum fusiforme, the characteristic peaks of nano-cellulose became more obvious.

[0034] Figure 5 The X-ray photoelectron spectroscopy curve of the obtained Sargassum fusiforme-based cellulose nanofibers is presented, indicating that the obtained Sargassum fusiforme-based cellulose nanofibers contain carboxyl groups, providing favorable conditions for its dispersion stability in aqueous solution; The Thermo Scientific K-Alpha+ X-ray photoelectron spectrometer was used, with an Al Kα (hν = 1,486.6 eV) X-ray source and a working power of 72 W.

[0035] Figure 6 The monosaccharide ion chromatography test results of the Sargassum fusiforme-based cellulose nanofibers in three stripping processes are presented. This figure shows the types and contents of hemicellulose in Sargassum fusiforme raw materials, Sargassum fusiforme residues after degumming, and Sargassum fusiforme-based cellulose nanofibers; The ion chromatograph used is ICS5000+, Thermo Fisher Scientific USA, and an electrochemical detector was used to analyze and detect the monosaccharide components.

[0036] Figure 7 Digital photos showing Sargassum fusiforme-based cellulose nanofibers (referred to as cellulose hereinafter, the same below), commercial gelatin, and commercial pectin added to apple juice respectively are presented. The control is apple juice without adding any materials.

[0037] Figure 8 Digital photos showing Sargassum fusiforme-based cellulose nanofibers, commercial gelatin, and commercial pectin added to milk respectively are presented. The control is milk without adding any materials.

[0038] Figure 9Digital photos showing Sargassum-based cellulose nanofibers, commercial gelatin, and commercial pectin added to soda water respectively, with the control being soda water without any added materials.

[0039] Figure 10 Rheological data curves obtained by testing Sargassum-based cellulose nanofibers and gelatin added to apple juice respectively; the HAAKE MARS 60 rotational rheometer was used, relevant data of shear rate and viscosity were obtained through testing, and the corresponding curves were plotted.

[0040] Figure 11 Rheological data curves obtained by testing Sargassum-based cellulose nanofibers and gelatin added to apple juice respectively; the HAAKE MARS 60 rotational rheometer was used, relevant data of rotational speed and storage modulus / loss modulus were obtained through testing, and the corresponding curves were plotted.

[0041] Figure 12 Rheological data curves obtained by testing Sargassum-based cellulose nanofibers and pectin added to apple juice respectively; the HAAKE MARS 60 rotational rheometer was used, relevant data of shear rate and viscosity were obtained through testing, and the corresponding curves were plotted.

[0042] Figure 13 Rheological data curves obtained by testing Sargassum-based cellulose nanofibers and pectin added to apple juice respectively; the HAAKE MARS 60 rotational rheometer was used, relevant data of rotational speed and storage modulus / loss modulus were obtained through testing, and the corresponding curves were plotted.

[0043] Figure 14 Rheological data curves obtained by testing Sargassum-based cellulose nanofibers and gelatin added to milk respectively; the HAAKE MARS 60 rotational rheometer was used, relevant data of shear rate and viscosity were obtained through testing, and the corresponding curves were plotted.

[0044] Figure 15 Rheological data curves obtained by testing Sargassum-based cellulose nanofibers and gelatin added to milk respectively; the HAAKE MARS 60 rotational rheometer was used, relevant data of rotational speed and storage modulus / loss modulus were obtained through testing, and the corresponding curves were plotted.

[0045] Figure 16 Rheological data curves obtained by testing Sargassum-based cellulose nanofibers and pectin added to milk respectively; the HAAKE MARS 60 rotational rheometer was used, relevant data of shear rate and viscosity were obtained through testing, and the corresponding curves were plotted.

[0046] Figure 17 Show the rheological data curves obtained by adding Sargassum fusiforme-based cellulose nanofibers and pectin to milk respectively; the HAAKE MARS 60 rotational rheometer was used, and the relevant data of rotational speed and storage modulus / loss modulus were obtained through testing, and the corresponding curves were plotted.

[0047] Figure 18 Show the rheological data curves obtained by adding Sargassum fusiforme-based cellulose nanofibers and gelatin to soda water respectively; the HAAKE MARS 60 rotational rheometer was used, and the relevant data of shear rate and viscosity were obtained through testing, and the corresponding curves were plotted.

[0048] Figure 19 Show the rheological data curves obtained by adding Sargassum fusiforme-based cellulose nanofibers and gelatin to soda water respectively; the HAAKE MARS 60 rotational rheometer was used, and the relevant data of rotational speed and storage modulus / loss modulus were obtained through testing, and the corresponding curves were plotted.

[0049] Figure 20 Show the rheological data curves obtained by adding Sargassum fusiforme-based cellulose nanofibers and pectin to soda water respectively; the HAAKE MARS 60 rotational rheometer was used, and the relevant data of shear rate and viscosity were obtained through testing, and the corresponding curves were plotted.

[0050] Figure 21 Show the rheological data curves obtained by adding Sargassum fusiforme-based cellulose nanofibers and pectin to soda water respectively; the HAAKE MARS 60 rotational rheometer was used, and the relevant data of rotational speed and storage modulus / loss modulus were obtained through testing, and the corresponding curves were plotted. Detailed implementation mode

[0051] To further understand the present invention, the preferred implementation modes of the present invention will be described below in conjunction with embodiments. However, these descriptions are only to further illustrate the specific implementation process and features of the present invention, rather than a limitation on the scope of the claims.

[0052] 1) Preparation of Sargassum fusiforme-based cellulose nanofibers

[0053] As an important marine biological resource, the existing Sargassum fusiforme is widely distributed in the waters around the world. Due to its rapid growth and many bioactive substances such as polysaccharides, proteins, and trace elements, the components extracted from it have important commercial value in industries such as textiles, biomedicine, chemical engineering, and agriculture and forestry. However, after extracting these high-value products, a large amount of Sargassum fusiforme residue accumulates as a by-product. Currently, it is mainly used as fertilizer and filler after simple mechanical crushing, and its high-value utilization has not been achieved.

[0054] In addition, in view of the certain safety problems of nanocellulose prepared by the existing traditional preparation and peeling methods of nanocellulose, the present application provides an edible peeling method for Sargassum fusiforme-based cellulose nanocellulose.

[0055] In the present invention, the term "Sargassum fusiforme" refers to a plant belonging to the genus Sargassum of the family Sargassaceae, with the Latin name Hizikia fusifarme, which can be ingested by the human body as food, and many bioactive substances such as proteins, polysaccharides, and trace elements extracted from it are widely used in the industries of biomedicine, agriculture, and chemical engineering.

[0056] In the present invention, the term "residue" means the solid that precipitates on the filter medium after filtration when Sargassum fusiforme has been extracted of many bioactive substances such as proteins, polysaccharides, and trace elements.

[0057] In the present invention, the term "cellulose nanocellulose" means that the size of the fiber material is in the nanoscale range, that is, the diameter distribution range of the obtained Sargassum fusiforme-based cellulose nanofibers is 5 - 60 nm, and it satisfies at least one of the following properties: the aspect ratio distribution range is 20 - 400, the crystallinity distribution range is 80 - 95%, the surface charge distribution range is -60 - -10 mV, and it contains at least one or more hemicellulose components containing carboxyl uronic acid.

[0058] In the present invention, the term "edible peeling method" refers to a peeling method for safe and edible Sargassum fusiforme-based cellulose nanofibers obtained through degumming with food-grade alkali treatment, oxidation treatment with a mixed solution of food-grade acetic anhydride and food-grade hydrogen peroxide, decolorization treatment with food weak acid, and finally mechanical treatment.

[0059] The extraction method for extracting food-safe cellulose nanofibers from Sargassum fusiforme residue and applicable to use in the present disclosure includes the following steps:

[0060] A) Add the Sargassum fusiforme residue to a pre-prepared food-grade alkaline degumming solution, heat it to a predetermined temperature of 80 - 120 °C, and maintain it for 5 - 24 h. After the reaction is completed, filter to obtain the degummed Sargassum fusiforme residue;

[0061] B) Add the degummed Sargassum fusiforme residue obtained in step A) to a pre-prepared mixed solution of food-grade hydrogen peroxide and food-grade acetic anhydride, and react at a temperature of 15-30 °C for 10-24 h. After the reaction is completed, filter to obtain micro-scale Sargassum fusiforme cellulose. The diameter of the micro-scale Sargassum fusiforme cellulose is 200-800 μm, preferably 300-500 μm, and more preferably 400-500 μm;

[0062] C) Add the micro-scale Sargassum fusiforme cellulose obtained in step B) to an acetic acid solution with a certain concentration, and carry out a decolorization reaction at room temperature for 6-24 h, and then filter and wash to obtain bleached micro-scale (with a diameter of 200-800 μm) Sargassum fusiforme cellulose;

[0063] D) Mechanically crush the bleached micro-scale Sargassum fusiforme cellulose dispersion obtained in step C) for example for 2-5 h to obtain a cellulose nanofiber dispersion with a mass fraction of 0.5%-3% for storage.

[0064] Preferably, before step A), it may further include: soaking the commercially available Sargassum fusiforme in deionized water multiple times to remove most of the surface salts.

[0065] Preferably, the food-grade alkaline degumming solution includes at least one selected from the following: food-grade sodium hydroxide aqueous solution, food-grade potassium hydroxide aqueous solution, food-grade sodium carbonate aqueous solution and other solvents. In addition, in step A), the concentration of the alkaline degumming solution is 5%-10%, preferably 5%-8%, and the mass ratio of the Sargassum fusiforme raw material to the food-grade alkaline degumming solution is 1:5-1:10, preferably 1:5-1:7.

[0066] Preferably, in step A) of the present invention, the predetermined temperature is 85-110 °C, more preferably 95-105 °C, and the holding time is preferably 6-15 h, more preferably 8-10 h.

[0067] In step B) of the present invention, preferably, the hydrogen peroxide is food-grade, with a concentration of 10%-30%, and the preferred concentration is 15%-20%; the concentration of the acetic anhydride is 50%-90%, and the preferred concentration is 65%-80%; the preferred mass ratio of the two in the mixture is 1:3-1:5, and the more preferred ratio is 1:4. The mass ratio of the Sargassum fusiforme residue raw material to the reaction solution is 1:3-1:5.

[0068] In step C) of the present invention, preferably, the concentration of the acetic acid solution is 30%-90%, and the preferred concentration is 40%-80%; the treatment time of the decolorization reaction is 6-24 h, and the preferred time is 8-15 h; the temperature of the oxidation treatment is 23-30 °C, and the mass ratio of the micro-scale Sargassum fusiforme cellulose raw material to the acetic acid solution is 1:3-1:5.

[0069] In step D) of the present invention, preferably, the mechanical pulverization of the micron-scale Sargassum fusiforme cellulose dispersion includes any one or a combination of a high-pressure homogenizer, a cell ultrasonic disruptor, and a beater. The time of the mechanical pulverization is 1 to 5 h, and the mass fraction of the aqueous solution of Sargassum fusiforme-based cellulose nanofibers is 0.1% to 5%.

[0070] The above aims to enable the Sargassum fusiforme cellulose nanofibers extracted from Sargassum fusiforme residues to have characteristics such as high crystallinity, high aspect ratio, and excellent mechanical and thermal stability, so as to achieve the purpose of the present invention of being used as a thickener. In particular, applying this food-safe cellulose nanofiber raw material in food-related fields such as liquid thickening provides a food-safe liquid thickening raw material for the food field.

[0071] In the present invention, the Sargassum fusiforme-based cellulose nanofibers prepared by the food-grade peeling method have at least property i) and at least one of the following properties ii)-v), preferably at least 2 items, more preferably at least 3 items, more preferably at least 4 items, and more preferably at least 5 items:

[0072] i) The diameter of the Sargassum fusiforme-based cellulose nanofibers is 5 to 60 nm (for example: it can be 5 nm, 8 nm, 10 nm, 20 nm, 25 nm, 30 nm, 35 nm, 45 nm, 58 nm, 60 nm, etc., or it can also be within the range formed by these values, such as 5-8 nm, 35-45 nm, etc.). The diameter is preferably 10 to 50 nm, and more preferably 30 to 40 nm;

[0073] ii) The aspect ratio of the Sargassum fusiforme-based cellulose nanofibers is 20 to 400 (for example: it can be 50, 80, 100, 150, 200, 250, 300, etc., or it can also be within the range formed by these values, such as 80-100, 200-300, etc.). The aspect ratio is preferably 100 to 300, and more preferably 250 to 300;

[0074] iii) The crystallinity of the Sargassum fusiforme-based cellulose nanofibers is 80 to 95% (for example: it can be 85%, 89%, 92%, etc., or it can also be within the range formed by these values, such as 85%-89%, etc.). The crystallinity is preferably 85 to 95%, and more preferably 90 to 95%;

[0075] iv) The Sargassum fusiforme-based cellulose nanofibers contain at least one type of hemicellulose component containing carboxyl uronic acid (for example: it can be at least one selected from Man-UA, Glc-UA, Gul-UA, etc.), preferably containing both Man-UA and Glc-UA, and more preferably containing both Man-UA, Glc-UA and Gul-UA;

[0076] v) The surface charge of the Sargassum fusiforme-based cellulose nanofibers is -60 to -10 mV (for example: it can be -60, -50, -40, -30, -20, -10, etc., or it can be within the range formed by these values, such as -60 to -40, etc.), preferably -50 to -20, and more preferably -40 to -30;

[0077] In addition, it is worth pointing out that in the extraction process of extracting cellulose nanofibers from Sargassum fusiforme used in the present disclosure, no toxic or harmful solvents are added, the environmental pollution is small, the energy consumption is low, the peeling process is simple and efficient, and the obtained Sargassum fusiforme-based cellulose nanofibers have the characteristics of food safety, high crystallinity and rich in various uronic acid hemicelluloses.

[0078] 2) The Sargassum fusiforme-based cellulose nanofibers are used in the field of food thickening

[0079] The purpose of this application is to provide an application of the obtained food-safe Sargassum fusiforme-based cellulose nanofibers in liquid thickening, and adding the obtained food-safe Sargassum fusiforme-based cellulose nanofibers with a certain concentration to milk, juice and soda water.

[0080] The food field generally refers to various substances for human consumption, including animal and plant foods, processed foods and various condiment fields.

[0081] The term "thickening" means its usual meaning. Thickening refers to the operation of making the solid particles suspended in the liquid become thick slurry and separating them from the liquid, also known as precipitation concentration or sedimentation concentration. Specifically, in the present invention, it refers to adding the obtained edible Sargassum fusiforme-based cellulose nanofibers to the liquid in a certain proportion to improve the stability of the added liquid, increase the viscosity of the liquid, and change the rheological form of the liquid.

[0082] In the present disclosure, the application of thickening includes the following steps:

[0083] a) Adding a certain amount of deionized water to the above-mentioned extracted Sargassum fusiforme-based cellulose nanofiber suspension to prepare a cellulose nanofiber dispersion with a mass concentration of 0.1 to 3%, preferably 0.5 to 2.5%, and more preferably 0.8 to 2%;

[0084] b) adding the Sargassum-based cellulose nanofibers obtained in step a) to a desired thickening liquid system (e.g., apple juice, milk, or soda water), the Sargassum-based cellulose nanofibers and the thickening liquid are compounded in a mass ratio of 1:50 to 1:1000, preferably 1:100 to 1:800, more preferably 1:200 to 1:500, and then uniformly mixed and dispersed by mechanical means, and allowed to stand in a freezer for 10 to 20 minutes;

[0085] c) taking out 5-10 mL of the uniformly dispersed mixed solution obtained in step B) and placing it in a glass beaker, and performing a rheological test according to the test method mentioned in the document (Gao H, Duan B, Lu A, et al. Fabrication of cellulose nanofibers from waste brown algae and their potential application as milkthickeners [J]. Food Hydrocolloids, 2018, 79: 473-481.);

[0086] d) According to the characteristics of the test mixed solution, the viscosity measurement method is selected: using a rheometer, the rheometer model: HR20 from TA Instruments Waters, USA. A parallel plate with a diameter of 60 mm is selected, and the shear rate is measured from 0.01-100 s at 8°C. -1 The change of solution viscosity under the condition of rotation speed 1-100rad s -1 Changes in the storage modulus and loss modulus of the solution.

[0087] In the present invention, the mechanical stirring in step b) is carried out using a magnetic stirrer, an ultrasonic stirrer, a polytetrafluoroethylene stirrer and a cell disruptor, etc., preferably a magnetic stirrer and a cell disruptor, and more preferably a cell disruptor; the rate range of the mechanical stirring is 1500-3000 r / min for 2-15 min, preferably 2000-2500 r / min for 5-10 min, and more preferably 2500 r / min for 8 min; the standing time in the refrigerator is preferably 10-15 min, and more preferably 10-12 min.

[0088] In the present invention, the Sargassum-based cellulose nanofibers are added to the thickening liquid system, and the Sargassum-based cellulose nanofibers form good stability with the thickening system, and have a good thickening effect; so that the thickening system has at least one of the following properties, preferably at least two, more preferably at least three, and most preferably has all of the following properties at the same time:

[0089] i) The thickener is added to the liquid. When the shear rate of the thickened liquid is 0.01 - 0.05 s -1 , the viscosity of the system is measured to be 1200 - 1500 Pa s;

[0090] ii) The thickener is added to the liquid, and the thickened liquid remains stable within 5 - 14 days;

[0091] iii) The thickener is added to the liquid, and the thickened liquid remains stable at 10 - 60 °C;

[0092] To further understand the present invention, the application of Sargassum fusiforme - based cellulose nanofibers in the field of food thickening and their corresponding thickening effects are further elaborated below in conjunction with examples. The protection scope of the present invention is not limited by the following examples.

[0093] Examples

[0094] The Sargassum fusiforme was purchased from Yun Sheng Seafood Co., Ltd., Laoshan, Rongcheng City.

[0095] Raw material preparation example 1

[0096] A) 1000 g of Sargassum fusiforme was soaked in deionized water multiple times to remove most of the surface salts;

[0097] B) The washed Sargassum fusiforme was added to a sodium carbonate aqueous solution with a mass concentration of 6%, and reacted at 80 °C for 5 hours;

[0098] C) The reacted material was washed repeatedly until neutral, and then put into a pre - prepared mixed solution of hydrogen peroxide and acetic anhydride. The concentration of hydrogen peroxide was 10%, the concentration of acetic anhydride was 50%, the volume ratio of the two mixtures was 1:3, the reaction time was 8 hours, and the reaction temperature was 30 °C;

[0099] D) Subsequently, the reactant was added to an acetic acid solution with a mass concentration of 30%. The oxidation and bleaching treatment time was 6 hours, the oxidation treatment temperature was 25 °C, and the mass ratio of the micron - level Sargassum fusiforme cellulose raw material to the acetic acid solution was 1:3;

[0100] E) The obtained bleached micron - level Sargassum fusiforme cellulose was pulverized in a beater for 1 hour, and then broken by a high - speed shear machine for 30 minutes to obtain Sargassum fusiforme - based cellulose nanofibers.

[0101] The obtained Sargassum fusiforme - based cellulose nanofibers have a diameter of 10 - 30 nm, an aspect ratio of 20 - 100, a crystallinity of 90%, and contain hemicellulose components such as Man - UA uronic acid and Glc - UA uronic acid.

[0102] Raw material preparation example 2

[0103] A) Soak 1000 g of Sargassum fusiforme in deionized water multiple times to remove most of the surface salts.

[0104] B) Add the soaked Sargassum fusiforme raw material to an aqueous sodium carbonate solution with a mass concentration of 8%, and react in an oven at 80 °C for 12 hours.

[0105] C) Wash the reacted material repeatedly until it is neutral, filter it with a filter bag, and then put it into a pre-prepared mixed solution of hydrogen peroxide and acetic anhydride. The mass concentration of hydrogen peroxide is 15%, the mass concentration of acetic anhydride is 55%, the volume ratio of the two mixtures is 1:3, the reaction time is 10 hours, and the reaction temperature is 25 °C.

[0106] D) Subsequently, wash the reacted material repeatedly until it is neutral, filter it with a filter bag, and then put it into an acetic acid solution with a mass concentration of 50%. The oxidation bleaching treatment time is 5 hours, the oxidation treatment temperature is 25 °C, and the mass ratio of the micron-sized Sargassum fusiforme cellulose raw material to the acetic acid solution is 1:4.

[0107] E) Pulverize the obtained bleached micron-sized Sargassum fusiforme cellulose in a beater for 2 hours, and then perform high-pressure homogenization treatment for 1.5 hours to obtain Sargassum fusiforme-based cellulose nanofibers.

[0108] Figure 2 D is a digital photo of the prepared food-safe Sargassum fusiforme-based cellulose nanofibers. Figure 2 As can be seen from D, the cellulose solution is a uniformly dispersed, semi-transparent white emulsion, and there are no any harmful impurities remaining in it.

[0109] The obtained Sargassum fusiforme-based cellulose nanofibers have a diameter of 15 - 40 nm, an aspect ratio of 50 - 250, a crystallinity of 90%, and contain hemicellulose components such as Man-UA uronic acid.

[0110] Example 1

[0111] a) First, add a certain amount of deionized water to the Sargassum fusiforme-based cellulose nanofibers obtained in the above raw material preparation example 1 to make a cellulose nanofiber solution with a mass concentration of 0.8%.

[0112] b) Mix the Sargassum fusiforme cellulose nanofibers with a mass concentration of 0.8% and apple juice according to a mass ratio of 1:300, stir with a magnetic stirrer at room temperature, and let it stand in a freezer for 15 min to obtain a uniformly mixed apple juice mixed solution system.

[0113] c) Take out 10 mL of the uniformly dispersed mixed solution obtained in step B) and place it in a glass beaker, and conduct tests with reference to the test method mentioned in this literature (Gao H, Duan B, Lu A, et al. Fabrication of cellulose nanofibers from waste brown algae and their potential application as milk thickeners[J]. Food Hydrocolloids, 2018, 79: 473-481.).

[0114] d) According to the characteristics of the test apple juice mixed solution, select the viscosity measurement method: measure with a rheometer, rheometer model: HR20 of TA Instruments Waters Corporation, USA. Select a parallel plate with a diameter of 60 mm, and measure the change in the solution viscosity at a shear rate from 0.01 - 100 s -1 under the condition of 8 °C, as well as the change in the storage modulus and loss modulus of the solution at a rotational speed of 1 - 100 rad s -1 under.

[0115] After adding Sargassum fusiforme cellulose nanofibers to apple juice, excellent thickening effect and stability are shown. From the curve of shear rate and viscosity, it can be seen that compared with commercial gelatin, the Sargassum fusiforme cellulose nanofibers of this application show higher viscosity. The viscosity at a shear rate of 0.01 s -1 is 341 Pa s, far greater than 4.93 Pa s of gelatin and 3.54 Pa s of pectin, and has a better thickening effect. The storage modulus and loss modulus respectively reflect the elasticity and viscosity of the material. When the storage modulus is greater than the loss modulus, the material mainly undergoes elastic deformation, showing the characteristics of a solid state. From the curve of rotational speed and storage modulus / loss modulus, it can be seen that compared with commercial gelatin, the storage modulus of Sargassum fusiforme cellulose nanofibers is much greater than the loss modulus, and the difference is about 7.8 MPa. At this time, the solid characteristics of apple juice are more obvious, indicating that the thickening effect of Sargassum fusiforme cellulose nanofibers is more obvious.

[0116] Example 2

[0117] a) First, add a certain amount of deionized water to the Sargassum fusiforme-based cellulose nanofibers obtained in the above raw material preparation example 2 to make a cellulose nanofiber solution with a mass fraction of 0.8%.

[0118] b) Mix 0.8% Sargassum fusiforme cellulose nanofibers and milk according to a mass ratio of 1:400, stir with a magnetic stirrer at room temperature, and let it stand in a freezer for 20 min to obtain a composite and uniform thickened milk mixed solution system.

[0119] c) Take out 5 mL of the uniformly dispersed mixed solution obtained in step B) and place it in a glass beaker, and conduct tests with reference to the test method mentioned in this literature (Gao H, Duan B, Lu A, et al. Fabrication of cellulose nanofibers from waste brown algae and their potential application as milk thickeners [J]. Food Hydrocolloids, 2018, 79: 473-481.).

[0120] d) According to the characteristics of the test milk mixed solution, select the viscosity measurement method: measure with a rheometer, rheometer model: HR20 of TA Instruments Waters Company, USA. Select a parallel plate with a diameter of 60 mm and measure the change in the solution viscosity at a shear rate from 0.01 - 100 s -1 under the condition of 8 °C, as well as the change in the storage modulus and loss modulus of the solution at a rotational speed of 1 - 100 rad s -1 under.

[0121] After adding Sargassum fusiforme cellulose nanofibers to milk, excellent thickening effect and stability are shown. From the curve of shear rate and viscosity, it can be seen that compared with commercial gelatin, the Sargassum fusiforme cellulose nanofibers of this application show higher viscosity. The viscosity at a shear rate of 0.01 s -1 is 1364.96 Pa s, far greater than 8.64 Pa s of pectin, and has a better thickening effect. From the curve of rotational speed and storage modulus / loss modulus, it can be seen that compared with commercial gelatin, the storage modulus of Sargassum fusiforme cellulose nanofibers is much greater than the loss modulus, and the difference is about 51.5 MPa, while that of gelatin is about 3.8 MPa. At this time, the solid characteristics of the milk thickened by Sargassum fusiforme cellulose nanofibers are more obvious, and the thickening effect of Sargassum fusiforme cellulose nanofibers is more obvious.

[0122] Example 3

[0123] a) First, add a certain amount of deionized water to the Sargassum fusiforme-based cellulose nanofibers obtained in the above raw material preparation example 1 to make a 1.0% Sargassum fusiforme-based cellulose nanofiber solution;

[0124] b) Mix 1.0% Sargassum fusiforme cellulose nanofibers and soda water according to a mass ratio of 1:100, stir with a polytetrafluoroethylene stirring paddle at room temperature, and let it stand at room temperature for 20 min after stirring evenly to obtain a composite and uniform soda water mixed solution system;

[0125] c) Take out 5 mL of the uniformly dispersed mixed solution obtained in step B) and place it in a glass beaker. Refer to the test method mentioned in this literature (Gao H, Duan B, Lu A, et al. Fabrication of cellulose nanofibers from waste brown algae and their potential application as milk thickeners[J]. Food Hydrocolloids, 2018, 79: 473-481.) for rheological testing;

[0126] c) According to the characteristics of the test soda water mixed solution, select the viscosity measurement method: measure with a rheometer, rheometer model: HR20 of TA Instruments Waters Corporation, USA. Select a parallel plate with a diameter of 60 mm and measure the change in the solution viscosity at a shear rate from 0.01 - 100 s -1 under the condition of 8 °C, as well as the change in the storage modulus and loss modulus of the solution at a rotational speed of 1 - 100 rad s -1 under the condition of 8 °C.

[0127] After adding Sargassum fusiforme cellulose nanofibers to milk, excellent thickening effect and stability are shown. From the curve of shear rate and viscosity, it can be seen that compared with commercial gelatin, the Sargassum fusiforme cellulose nanofibers of this application show higher viscosity. The viscosity at a shear rate of 0.01 s -1 is 335.5 Pa s, which is much greater than 1.35 Pa s of gelatin and 3.2 Pa s of pectin, and has a better thickening effect. From the curve of rotational speed and storage modulus / loss modulus, it can be seen that compared with commercial gelatin, the storage modulus of Sargassum fusiforme cellulose nanofibers is much greater than the loss modulus, and the difference is about 14.85 MPa. At this time, the solid characteristics of milk are more obvious, and the thickening effect of Sargassum fusiforme cellulose nanofibers is more obvious.

[0128] Comparative Example 1

[0129] This comparative example is the same as Example 1, except that commercial gelatin material is added to apple juice, and its thickening effect is difficult to meet the actual application requirements.

[0130] Figure 7 and Figure 10 and Figure 11 are the digital photos and rheological data obtained by using different thickening materials in Example 1 and Comparative Example 1.

[0131] Comparative Example 2

[0132] This comparative example is the same as Example 1, except that commercial pectin material is added to apple juice, and its thickening effect is difficult to meet the actual application requirements.

[0133] Figure 7 , Figure 12 and Figure 13 The digital photos and rheological data obtained by using different thickening materials in Example 1 and Comparative Example 2 are shown.

[0134] Comparative Example 3

[0135] This comparative example is the same as Example 2, except that commercial gelatin material is added to milk, and its thickening effect is difficult to meet actual application requirements.

[0136] Figure 8 , Figure 14 and Figure 15 The digital photos and rheological data obtained by using different thickening materials in Example 2 and Comparative Example 3 are shown.

[0137] Comparative Example 4

[0138] This comparative example is the same as Example 2, except that commercial pectin material is added to milk, and its thickening effect is difficult to meet actual application requirements.

[0139] Figure 8 , Figure 16 and Figure 17 The digital photos and rheological data obtained by using different thickening materials in Example 2 and Comparative Example 4 are shown.

[0140] Comparative Example 5

[0141] This comparative example is the same as Example 3, except that commercial gelatin material is added to soda water, and its thickening effect is difficult to meet actual application requirements.

[0142] Figure 9 , Figure 18 and Figure 19 The digital photos and rheological data obtained by using different thickening materials in Example 3 and Comparative Example 5 are shown.

[0143] Comparative Example 6

[0144] This comparative example is the same as Example 3, except that commercial pectin material is added to soda water, and its thickening effect is difficult to meet actual application requirements.

[0145] Figure 9 , Figure 20 and Figure 21 The digital photos and rheological data obtained by using different thickening materials in Example 3 and Comparative Example 6 are shown.

[0146] Industrial Applicability

[0147] The Sargassum fusiforme-based cellulose nanofibers obtained in the present disclosure were added to liquids such as apple juice, milk, and soda water, and it was verified that the material has good dispersibility and thickening stability. Therefore, it will have broad application prospects especially in related fields such as food thickening.

[0148] The above descriptions of the specific embodiments and examples are only used to help understand the method of the present invention and its core idea. It should be noted that for those of ordinary skill in the art, without departing from the principles and spirit of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. Use of Sargassum fusiforme - based cellulose nanofibers extracted from Sargassum fusiforme residues as a liquid thickener, wherein the Sargassum fusiforme - based cellulose nanofibers are obtained from Sargassum fusiforme residues by an extraction method comprising the following steps: A) Adding Sargassum fusiforme residues to a food - grade alkaline degumming solution, heating to a predetermined temperature of 80 - 120 °C, and maintaining for 5 - 24 h to obtain degummed Sargassum fusiforme residues; B) Adding the degummed Sargassum fusiforme residues obtained in step A) to a solution in which food - grade hydrogen peroxide and food - grade acetic anhydride are mixed in a mass ratio of 1:2 - 1:10, reacting at a temperature of 15 - 30 °C for 10 - 24 h to obtain micron - scale Sargassum fusiforme cellulose; C) Adding the micron - scale Sargassum fusiforme cellulose to acetic acid solution, performing a decolorization reaction at 23 - 30 °C for 6 - 24 h to obtain bleached micron - scale Sargassum fusiforme cellulose; D) Mechanically pulverizing the bleached micron - scale Sargassum fusiforme cellulose to obtain Sargassum fusiforme - based cellulose nanofibers.

2. The use according to claim 1, wherein the use is in the food field.

3. The use according to claim 1, wherein the use comprises the following steps: Adding Sargassum fusiforme - based cellulose nanofibers to a liquid system to be thickened and mixing, wherein the mass fraction of the Sargassum fusiforme - based cellulose nanofibers in the mixed solution system is 0.1 - 1.0%.

4. The application according to claim 3, wherein The liquid system is selected from at least one of apple juice, milk, and soda water, and the mixing is carried out by stirring at 1500 - 3000 r / min for 2 - 15 min.

5. The use according to claim 1, wherein the Sargassum fusiforme - based cellulose nanofibers have the following property i) and at least one of the properties selected from ii) - v): i). The diameter of the Sargassum fusiforme - based cellulose nanofibers is 5 - 60 nm; ii). The aspect ratio of the Sargassum fusiforme - based cellulose nanofibers is 20 - 400; iii). The crystallinity of the Sargassum fusiforme - based cellulose nanofibers is 80 - 95%; iv). The Sargassum fusiforme - based cellulose nanofibers contain at least one type of hemicellulose component containing carboxyl uronic acid; v). The surface charge of the Sargassum fusiforme - based cellulose nanofibers is - 60 - - 10 mV.

6. The use according to claim 1, wherein in step A), the alkaline degumming solution is selected from at least one of the following: food - grade aqueous sodium hydroxide solution, food - grade aqueous potassium hydroxide solution, and food - grade aqueous sodium carbonate solution.

7. The use according to claim 1, wherein in step A), the mass concentration of the alkaline degumming solution is 5% - 10%, and the mass ratio of the Sargassum fusiforme residues to the food - grade alkaline degumming solution is 1:5 - 1:

10.

8. The use according to claim 1, wherein in step B), the mass concentration of hydrogen peroxide is 10% - 30%, the mass concentration of acetic anhydride is 50% - 90%, the volume ratio of the two solutions is 1:2 - 1:10, and the mass ratio of the degummed Sargassum fusiforme residue raw material to the reaction solution is 1:3 - 1:

5.

9. The application according to claim 1, wherein in step C), the mass concentration of the acetic acid solution is 30% to 90%, the temperature of the oxidation treatment is 23 to 30 °C, and the mass ratio of the microscale Sargassum fusiforme cellulose to the acetic acid solution is 1:3 to 1:

5.

10. The application according to claim 1, wherein the thickening effect obtained by the application includes at least one of the following: i) Add the Sargassum fusiforme-based cellulose nanofibrils as a thickening agent to the liquid system to be thickened. When the shear rate of the thickened liquid is 0.01 - 0.05 s -1 , the viscosity of the system is measured to be 1200 - 1500 Pa s; ii) adding the Sargassum fusiforme-based cellulose nanocellulose as a thickener to the liquid system to be thickened, and the thickened liquid remains stable within 5 to 14 days; iii) adding the Sargassum fusiforme-based cellulose nanocellulose as a thickener to the liquid system to be thickened, and the thickened liquid remains stable at 10 to 60 °C.

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