A double network inulin / KGM-fish protein gel and preparation method thereof

Abstract

The present invention discloses a double network inulin / KGM-fish protein gel and its preparation method and application, which belongs to the field of food processing technology, and comprises the following steps: mixing and homogenizing a myofibrillar protein solution, an inulin / KGM composite polysaccharide solution and sunflower oil, carrying out a gelation reaction under water bath conditions, and obtaining a double network inulin / KGM-fish protein gel after the reaction is completed. The present invention also discloses a double network inulin / KGM-fish protein gel prepared by the above-mentioned preparation method and its application in functional foods. The product obtained by the present invention has a dense network structure, and has the characteristics of easy swallowing and high swallowing safety. In addition, the gel has the nutritional value of high fish protein, and avoids the adverse sensory experience caused by the fishy smell, providing a theoretical basis and reference for the development of new and convenient dysphagia foods.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to a double-network inulin / KGM-fish source protein gel and a preparation method thereof. Background Art

[0002] Swallowing is a basic physiological behavior of human beings. It refers to the process of transporting the chewed food bolus to the back of the mouth through the tongue and finally reaching the esophagus. In the healthy aging process of the elderly, the structure or function of the organs such as the mouth, throat, and esophagus will inevitably degenerate, causing swallowing difficulties. Swallowing difficulties will have a great negative impact on the patient's daily diet and reduce their quality of life and health. With the aggravation of aging, the special food for the elderly with swallowing difficulties has a broad market prospect, and the study of swallowing difficulties diet has also become one of the research hotspots of personalized dietary design. Swallowing difficulties diets include thickened fluids, paste foods, and gels. Thickened fluids and paste foods are widely used in swallowing diets, but they cannot effectively meet the nutritional and sensory needs of consumers, and lack convenience. Gel foods have the advantages of being moist, soft, attractive in appearance, and easy to eat. They can better attract the appetite of people with swallowing difficulties and are also considered to be the mainstream direction of the development of swallowing difficulties foods. At present, some literature has disclosed relevant research on dysphagia foods. For example, Chen et al. (Chen, G., Hu, J., Liang, Y., Huang, X., Seah, GL, Li, J., Liu, D., Tan, C., 2023. Protein gel with designed network and texture regulated via building blocks to study dysphagiadiet classifications. Food Hydrocolloids 140, 108640.) regulated the gel network structure of casein gel by ginger protease and calcium ions to adapt to the dietary needs of people with dysphagia. Min et al. (Min, C., Yang, Q., Pu, H., Cao, Y., Ma, W., Kuang, J., Huang, J., Xiong, YL, 2023a. Textural characterization of calcium salts-induced mung bean starch-flaxseed protein composite gels as dysphagia food. Food Research International 164, 112355.) explored the feasibility of mung bean starch-flaxseed protein composite gels as dysphagia food. Adequate protein intake is beneficial for the elderly to resist immune function decline and chronic diseases caused by aging. However, the elderly have low pepsin levels and are accompanied by gastric acid deficiency, and their ability to digest protein is weak.

[0003] Compared with plant protein, fish-derived myofibrillar protein is rich in essential amino acids, and its digestion characteristics are less affected by the gastric environment (pH), so it is considered an ideal source of protein intake for the elderly. However, fish meat is thorny and myofibrillar protein aggregates and coagulates after cooking, which limits the high-quality fish-derived protein intake of elderly people with dysphagia. In addition, fish-derived myofibrillar protein aggregates under low-salt conditions and cannot form a gel; high salt levels increase the incidence of stroke and hypertension, which is not conducive to the health of the elderly. Therefore, the development of low-salt fish protein gel products is crucial to improving the dietary nutrition of people with dysphagia and promoting their nutritional health.

[0004] Polysaccharides (such as xanthan gum, guar gum, konjac glucomannan, etc.) usually have good thickening, gelling, water holding and stability, and are often used as thickeners and texture improvers. In recent years, the application of protein-polysaccharide gel system in the dietary management of dysphagia has been increasingly studied. However, the current research on protein-polysaccharide gel system for dysphagia diet mainly focuses on the interaction and characteristics between plant protein and polysaccharide, and there is still little research on animal protein-polysaccharide gel system. A large number of studies have shown that hydrogen bonds and electrostatic interactions between polysaccharides and myofibrillar proteins promote the three-dimensional gel structure of protein-polysaccharide and improve the rheological and texture properties of myofibrillar protein gel. Inulin and konjac glucomannan (KGM) are polysaccharides with health benefits and are often used as dietary additives, fat substitutes and texture improvers. Inulin induces the exposure of hydrophobic groups in chicken myofibrillar proteins under low-salt conditions, promotes the formation of hydrophobic interactions, hydrogen bonds and disulfide bonds between myofibrillar protein molecules, and improves its gel properties. Konjac glucomannan is a water-soluble polysaccharide composed of D-glucose and D-mannose linked by β-(1-4) glycosidic bonds. It can regulate intestinal microbial structure and intestinal tissue repair, and improve digestion and metabolism of elderly mice fed a high fish protein diet. At present, most studies focus on the effects of single polysaccharides on myofibril structure, gel network structure and texture properties. Composite polysaccharides can effectively overcome the shortcomings of single polysaccharides and obtain unique gel properties, which is one of the areas of concern in the food industry. However, it is not clear how inulin and KGM composite polysaccharides affect network structure and properties through component interactions, and there is a lack of investigation on the texture and flavor properties of the final composite gel product, which hinders the transition from new product development to market promotion and application.

[0005] Therefore, how to use inulin and KGM complex polysaccharides to provide a protein gel for people with dysphagia is a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a dual-network inulin / KGM-fish protein gel for people with dysphagia, and its preparation method and application. The macro-microstructural characteristics in the polysaccharide-protein gel system are closely related to the food components and the content of each component. Based on this, the present invention explores the molecular interactions between inulin and KGM and myofibrillar protein, as well as the relationship between inulin / KGM-protein interaction and swallowing gel function. Combined SAOS and LAOS tests simulate the evolution of the nonlinear rheological properties of the gel during chewing and swallowing, and the swallowing characteristics of the gel are deeply analyzed. Finally, a comprehensive analysis of the gel products verified by the IDDSI test is conducted from the perspective of texture and flavor characteristics, providing a theoretical basis for the development and application of dysphagia gel products.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a double-network inulin / KGM-fish protein gel comprises the following steps:

[0009] Myofibrillar protein was prepared using fish meat as raw material, and then the myofibrillar protein solution, inulin / KGM complex polysaccharide solution and sunflower oil were mixed and homogenized, and a gelation reaction was carried out in a water bath. After the reaction was completed, a double-network inulin / KGM-fish protein gel was obtained.

[0010] Preferably, the mass concentration of myofibrillar protein in the double network inulin / KGM-fish protein gel is 20%;

[0011] The mass concentration of inulin / KGM composite polysaccharide is 4-8%;

[0012] The mass concentration of sunflower oil is 10%.

[0013] Preferably, the method for preparing the myofibrillar protein solution comprises the following steps:

[0014] The myofibrillar protein was dispersed in a pre-cooled buffer solution and homogenized for 10 seconds, and the homogenization process was repeated 3 times to obtain the myofibrillar protein solution.

[0015] Preferably, the buffer solution is a sodium chloride solution with a concentration of 0.2 mol / L.

[0016] Preferably, the method for preparing the myofibrillar protein comprises the following steps:

[0017] The golden pomfret meat is minced in an ice bath, and then centrifuged three times in a low phosphate buffer solution, and then the obtained precipitate is centrifuged three times in a high phosphate buffer solution, the obtained supernatant is stored in a 4°C refrigerator for 24 hours, and then centrifuged again at 4°C, the obtained supernatant is mixed with 4°C distilled water and precipitated for 30 minutes, and then centrifuged twice more at 4°C, and the precipitate is collected to obtain the myofibrillar protein.

[0018] Preferably, the pH of the low phosphate buffer is 7.5, which includes 0.005 mol / L NaCl, 3.38 mmol / L NaH 2 PO 4 ·2H 2 O, 15.5mmol / L Na 2 HPO 4 12H 2 O;

[0019] The pH of the high phosphate buffer is 7.0, which includes 0.6 mol / L NaCl, 3.38 mmol / L NaH 2 PO 4 ·2H 2 O, 15.5mmol / LNa 2 HPO 4 12H 2 O.

[0020] Preferably, the method for preparing the inulin / KGM composite polysaccharide solution comprises the following steps:

[0021] After mixing inulin and konjac glucan, water is added and stirred evenly to obtain the inulin / KGM composite polysaccharide solution.

[0022] Preferably, the mass ratio of inulin to konjac glucan is (1-2): (1-2).

[0023] Preferably, the water bath temperature is 90°C and the time is 30 minutes.

[0024] Beneficial effects: The inulin / KGM mixture of the present invention occupies the spatial structure of myofibrillar protein, inhibiting the exposure of hydrophobic groups and the formation of disulfide bonds. During the thermal induction process, the α-helical structure of myofibrillar protein is maintained through hydrophobic interactions and hydrogen bond interactions, promoting the formation of the inulin / KGM-protein gel network structure. The inulin / KGM-protein gel exhibits shear-thinning behavior and solid-state elastic behavior, and the viscoelastic modulus decreases, reducing the difficulty of chewing and swallowing. The creep recovery test results show that the inulin / KGM-protein gel has a low deformation resistance, which can not only ensure the smooth swallowing, but also avoid the gel from breaking during swallowing, and has swallowing safety. In addition, the inulin / KGM-protein gel that meets the IDDSI has low hardness and chewiness, increases flavor substances such as ethanol and 2-octen-ol, and reduces the content of fishy substances such as hexanal and nonanal, so that patients with dysphagia can have a good sensory experience.

[0025] A method for preparing a double-network inulin / KGM-fish-derived protein gel prepares a double-network inulin / KGM-fish-derived protein gel.

[0026] Application of a double network inulin / KGM-fish protein gel in functional food.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] The structure and characteristics of the inulin / KGM-protein gel in the present invention can be regulated by the inulin / KGM ratio, controlling the size and distribution of oil droplets and protein aggregates, promoting the interaction between polysaccharides and myofibrillar proteins, and forming a complete and dense network structure. The conformation of myofibrillar proteins, the moisture state and distribution of the gel, viscoelasticity, creep recovery ability, LAOS behavior and the sensory flavor of the final product are all related to the inulin / KGM ratio. Through the analysis of the above technical effects, it is known that the inulin / KGM gel provided by the present invention can overcome the swallowing difficulties such as the elastic behavior of myofibrillar protein emulsion gel, high deformation resistance, poor cohesion, etc., and has the characteristics of easy swallowing and high swallowing safety. In addition, the gel provided by the present invention has the nutritional value of high fish-derived protein and avoids the adverse sensory experience caused by the fishy smell. The present invention provides a theoretical basis and reference for the development of new and convenient dysphagia foods. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0030] Figure 1The results of the surface hydrophobicity (a) and free thiol content (b) of the double network inulin / KGM-fish protein gel obtained in Examples 1-9 and the control group are shown in FIG.

[0031] Figure 2 FT-IR spectra (a) and secondary structure content (b) of the double network inulin / KGM-fish protein gel obtained in Example 1-9 and the control group;

[0032] Figure 3 This is a comparison diagram of the difference in intermolecular interaction force between the double network inulin / KGM-fish protein gel obtained in Example 1-9 and the control group;

[0033] Figure 4 LF-NMR spectra of the double network inulin / KGM-fish protein gel obtained in Example 1-9 and the control group;

[0034] Figure 5 The apparent viscosity of the double network inulin / KGM-fish protein gel obtained in Example 1-9 and the control group;

[0035] Figure 6 The changes of G', G", and tanδ in the amplitude scan of the double network inulin / KGM-fish protein gel obtained in Example 1-9 and the control group;

[0036] Figure 7 The changes of G', G" and tanδ of the double network inulin / KGM-fish protein gel obtained in Examples 1-9 and the control group in the frequency scan;

[0037] Figure 8 Creep recovery curves of the double network inulin / KGM-fish protein gel obtained in Example 1-9 and the control group;

[0038] Fig. 9 The changes of G' and G" during temperature scanning of the double network inulin / KGM-fish protein gel obtained in Examples 1-9 and the control group;

[0039] Fig.10 The elastic Lissajous curve (a) and the viscosity Lissajous curve (b) of the double network inulin / KGM-fish protein gel obtained in Examples 1-9 and the control group;

[0040] Fig.11 The S factor of the double network inulin / KGM-fish protein gel obtained in Example 1-9 and the control group;

[0041] Fig.12Laser confocal images of the double network inulin / KGM-fish protein gels P4-2:1(a), P4-1:1(b), P4-1:2(c), P6-2:1(d), P6-1:1(e), P6-1:2(f), P8-2:1(g), P8-1:1(h), P8-1:2(i) and the control group (j) obtained in Examples 1-9;

[0042] Fig.13 Fork drop test (a), spoon tilt test (b) and fork squeeze test (c) of the double network inulin / KGM-fish source protein gel obtained in Example 1-9 and the control group;

[0043] Fig.14 This is the flavor heat map of the double network inulin / KGM-fish protein gel obtained in Example 1. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0046] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0047] Among them, inulin was purchased from Orafti HSI Inulin;

[0048] Konjac Glucomannan is purchased from Johnson Food Grade Konjac Glucomannan;

[0049] Sunflower oil was purchased from Guangzhou CR Vanguard Supermarket Doli Sunflower Oil.

[0050] The room temperature or normal temperature in the embodiments of the present invention refers to 25±3°C.

[0051] Example 1

[0052] A method for preparing a double-network inulin / KGM-fish protein gel comprises the following steps:

[0053] (1) Extraction of myofibrillar proteins

[0054] The golden pomfret was used as the raw material. The fish meat was minced in an ice bath and diluted in a low phosphate buffer (0.005 mol / L NaCl, 3.38 mmol / L NaH 2 PO 4 ·2H 2 O, 15.5mmol / L Na 2 HPO 4 12H 2 O, pH 7.5) at 8000r / min at 4°C for 10min, and the supernatant was removed. The above centrifugation step was repeated three times to collect the precipitate, and then the precipitate was added to a high phosphate buffer solution (0.6mol / L NaCl, 3.38mmol / L NaH 2 PO 4 ·2H 2 O, 15.5mmol / L Na 2 HPO 4 12H 2 O, pH 7.0) at 4000r / min for 3 times, 10min each time, and store the obtained supernatant in a 4℃ refrigerator for 24h, then centrifuge at 10000r / min for 10min at 4℃, mix the obtained supernatant with 4 times the volume of 4℃ distilled water and precipitate at 4℃ for 30min. After precipitation, centrifuge again at 4℃ and 10000r / min for 15min each time, remove the supernatant from the mixture, collect the precipitate, obtain myofibrillar protein, and store it in a 4℃ refrigerator, and use it within 24h.

[0055] (2) 20% (w / w 菊粉 / KGM-蛋白凝胶 ) The myofibrillar protein obtained in step (1) is dispersed in a buffer solution (0.2 M NaCl) precooled to 4° C. and homogenized for 10 s, and the process is repeated three times to obtain a myofibrillar protein solution.

[0056] (3) After uniformly mixing inulin and konjac glucan in a mass ratio of 2:1, water is added and stirred to obtain a composite polysaccharide solution; then the myofibrillar protein solution obtained in step (2) and the composite polysaccharide solution (wherein the total mass fraction of the composite polysaccharide is 4% (w / w 菊粉 / KGM-蛋白凝胶 )) and shear homogenized at a speed of 10000r / min for 30s, repeated 3 times to obtain a protein-polysaccharide mixed solution; then 10% (w / w 菊粉 / KGM-蛋白凝胶) sunflower oil, homogenize for 10s, repeat 3 times to obtain inulin / KGM-protein emulsion, then put it in a 25℃ water bath, heat to 90℃ at a rate of 5℃ / min, keep it in a 90℃ water bath for 30min for gelation reaction, and cool in an ice bath after the reaction to obtain a double-network inulin / KGM-fish protein gel, recorded as P4-2:1.

[0057] Example 2

[0058] A method for preparing a double-network inulin / KGM-fish protein gel, which is different from that in Example 1 in that the mass ratio of inulin to KGM in step (3) is 1:1, and the other process parameters and steps are the same as those in Example 1, denoted as P4-1:1.

[0059] Example 3

[0060] A method for preparing a double-network inulin / KGM-fish protein gel, which is different from that in Example 1 in that the mass ratio of inulin to KGM in step (3) is 1:2, and the other process parameters and steps are the same as those in Example 1, denoted as P4-1:2.

[0061] Example 4

[0062] A method for preparing a double network inulin / KGM-fish protein gel, which is different from Example 1 in that the total mass fraction of the complex polysaccharide in step (3) is 6% (w / w 菊粉 / KGM-蛋白凝胶 ). Other process parameters and steps are the same as those in Example 1, denoted as P6-2:1.

[0063] Example 5

[0064] A method for preparing a double-network inulin / KGM-fish protein gel, which is different from Example 4 in that the mass ratio of inulin to KGM in step (3) is 1:1, and the other process parameters and steps are the same as Example 4, denoted as P6-1:1.

[0065] Example 6

[0066] A method for preparing a double-network inulin / KGM-fish protein gel, which is different from Example 4 in that the mass ratio of inulin to KGM in step (3) is 1:2, and the other process parameters and steps are the same as Example 4, denoted as P6-1:2.

[0067] Example 7

[0068] A method for preparing a double network inulin / KGM-fish protein gel, which is different from Example 1 in that the total mass fraction of the complex polysaccharide in step (3) is 8% (w / w 菊粉 / KGM-蛋白凝胶 ). Other process parameters and steps are the same as those in Example 1, denoted as P8-2:1.

[0069] Example 8

[0070] A method for preparing a double-network inulin / KGM-fish protein gel, which is different from Example 7 in that the mass ratio of inulin to KGM in step (3) is 1:1, and the other process parameters and steps are the same as Example 7, denoted as P8-1:1.

[0071] Example 9

[0072] A method for preparing a double-network inulin / KGM-fish protein gel, which is different from Example 7 in that the mass ratio of inulin to KGM in step (3) is 1:2, and the other process parameters and steps are the same as Example 7, denoted as P8-1:2.

[0073] Technical effect:

[0074] Unless otherwise specified, the data in each of the following measurements were performed in parallel for at least 3 times, and the data are expressed as mean ± standard deviation. SPSS software was used for ANOVA statistical analysis, and Duncan test was used to compare the mean values ​​(P < 0.05)

[0075] 1. Protein structure and surface hydrophobicity

[0076] (1-1) Free thiol content According to the method of Zhou et al. (Zhou et al., 2024), the absorbance of the sample at 412 mm was determined by the DNTB method, wherein the sample used was the double network inulin / KGM-fish protein gel obtained in Example 1-9.

[0077] (1-2) The method for determining the surface hydrophobicity specifically comprises the following steps:

[0078] Weigh 1g of sample and mix with 1ml of distilled water, vortex homogenize, add 200μL of bromophenol blue solution (1mg / ml), shake in the dark for 10min, centrifuge at 8000rpm for 10min, and collect the supernatant. Dilute the obtained supernatant 10 times with distilled water, and measure the absorbance A at 596nm with a spectrophotometer. 1 Taking distilled water as the control group, the absorbance measured was A 0 The surface hydrophobicity was calculated according to the following formula:

[0079] Bound BPB (μg) = 200 × (A 0 -A 1 ) / A 0

[0080] The results are as follows Figure 1As shown, surface hydrophobicity is related to structural properties (aggregation, dissociation and structural rearrangement), and can effectively reflect the changes in hydrophobic amino acids and the degree of extension of protein structure. During the gel formation process of the double-network inulin / KGM-fish protein gel in the present invention, the structure of myofibrillar protein changes, and the exposure of hydrophobic residues enhances the hydrophobic interactions between protein molecules, causing protein aggregation, leading to increased surface hydrophobicity. In general, compared with the control group, the inulin & KGM mixture can significantly inhibit the increase in surface hydrophobicity. During the heat-induced process of the protein emulsion gel, the protein structure unfolds, the hydrogen bonds between and within the molecules are destroyed, and the non-polar amino acid residues are exposed. Figure 1 As can be seen from part a, when the amount of inulin / KGM mixture added is the same, the surface hydrophobicity of the gel with an inulin to KGM ratio of 2:1 is higher, and the surface hydrophobicity of P4-2:1 and P6-2:1 gels is higher than that of the control group. The α-helical structure containing a hydrophobic center formed by inulin in aqueous solution aggregates with the hydrophobic groups of myofibrillar protein molecules, promotes the exposure of hydrophobic groups in myofibrillar protein, and improves the surface hydrophobicity. However, KGM weakens the hydrophobic interaction of inulin with myofibrillar protein, and excessive KGM masks the exposed hydrophobic groups on the protein surface, reducing the surface hydrophobicity. Therefore, the hydrophobicity of P8-2:1 gel is lower than that of P4-2:1 and P6-2:1. As the proportion of KGM increases, the surface hydrophobicity of inulin / KGM-protein gel decreases. This is because KGM contains hydrophilic groups such as hydroxyl and amino groups and hydrogen bonds, which enhance the interaction with myofibrillar protein, avoid the destruction of the hydrate layer around the polar residues, and inhibit the exposure of hydrophobic residues.

[0081] Compared with the control group, the free thiol content of inulin / KGM-protein gel was significantly increased ( Figure 1 b), which is mainly caused by the exposure of thiol groups and the cleavage of disulfide bonds. Moreover, with the increase of the content of inulin / KGM mixture, the thiol content of inulin / KGM-protein gel generally shows an upward trend. This may be due to the fact that polysaccharides destroy the interaction between protein molecules, resulting in the transfer of thiol groups from the inside of the protein to the outside. In addition, during the gelation process, while the myofibrillar protein structure is unraveled, KGM occupies its spatial structure, exposing more free thiol groups, and inulin can also promote the exposure of thiol groups in myofibrils, and has a certain concentration dependence. In the present invention, the free thiol content in inulin / KGM-protein gel is affected by the ratio of inulin / KGM and the total addition amount. At low concentrations, a high proportion of KGM will promote the exposure of protein thiol groups; but under high concentration conditions, excessive KGM will cover the exposed thiol groups in the protein molecules, causing the free thiol content to decrease. Therefore, when the addition amount of inulin / KGM mixture is 8%, the free thiol content of inulin / KGM-protein gel shows a trend of first increasing and then decreasing.

[0082] 2. FT-IR

[0083] The interaction between myofibrillar protein and inulin & KGM as well as the structural and conformational characteristics of myofibrillar protein were revealed by FT-IR analysis, which specifically included the following steps:

[0084] The sample was placed at -80℃ for 24 hours and then freeze-dried. The dried sample was ground into powder and stored in a desiccator. The sample powder and potassium bromide powder were mixed and ground in a mass ratio of 1:100 to make thin slices for FT-IR detection. The FTIR spectrum range was 400-4000cm -1 , resolution 4cm -1 .

[0085] like Figure 2 As shown in part a, the FT-IR spectra and typical absorption peaks of all inulin / KGM-protein gels in different wavelength ranges are similar, indicating that no new chemical bonds are formed during the gel formation process, that is, no covalent cross-linking occurs between the inulin and KGM mixture and myofibrillar protein. -1 There is a broad OH stretching vibration band at 3200-3700 cm -1 The broad peak is mainly related to the hydration of hydroxyl groups, indicating the existence of hydrogen bonding interactions in the gel. In addition, as the amount of inulin / KGM added increases, the absorption peak shifts to a shorter wave number, indicating that the hydrogen bonding interactions between protein molecules and inulin / KGM are enhanced. 2850-3000cm -1 The peak is caused by the stretching vibration of CH. In the saturated structure, CH 3 and CH 2 The group shows two peaks in this range. 1750cm -1 The narrow peak of 950-1180 cm reflects the presence of carbonyl (C=O) vibration in the gel, which may be derived from the glycosidic bonds in inulin and KGM. In addition, the stretching of CC and CO and the bending of CH make the inulin / KGM-protein gel have a peak at 950-1180 cm -1 Multiple peaks are generated in the range of 993 cm -1 The peak at 1080 cm and KGM -1 When the mixture ratio is 1:1, the peak of inulin / KGM-protein gel is 1010cm -1 The peak intensity at the 40°C position will be significantly reduced. Inulin and KGM can modify the structure of myofibrillar protein, affect its gel behavior, texture and other functional properties, and achieve the regulation of composite gel performance.

[0086] The vibration of the C=O of the polypeptide chain causes the amide I band (1600-1700 cm -1) changes, the amide I segment was deconvoluted and fitted with a Gaussian function to obtain the relative content of the secondary structure of the protein in the gel ( Figure 2 Part b). β-fold is the main secondary structure in the control protein, but in the inulin / KGM-protein gel, α-helix is ​​dominant. The water absorption of KGM causes myofibrillar protein to aggregate in the gel matrix and increase the α-helix structure. β-fold is usually buried inside the protein. The addition of inulin & KGM reduces the β-fold content in the gel protein, indicating that polysaccharides promote the unfolding of protein structure and the exposure of hydrophobic sites, forming more hydrogen bonds between protein molecules. When the addition amount of inulin & KGM is 4%, the β-turn content increases, and as the proportion of KGM increases, the β-turn shows an upward trend. The increase in β-turn is related to the helical structure of the peptide chain, forming a more complex network structure.

[0087] 3. Intermolecular forces

[0088] 0.5g of sample was mixed and homogenized with 4.5ml of S1 (0.6mol / L NaCl), S2 (0.6mol / L NaCl and 1.5mol / L urea), S3 (0.6mol / L NaCl and 8mol / L urea), S4 (0.6mol / L NaCl, 8mol / urea and 0.5mol / L β-mercaptoethanol) solution, and then placed at 4℃ for 1h. The resulting mixture was centrifuged at 10000rpm for 10min at 4℃, and the supernatant was collected. The protein concentration of the supernatant was determined by the biuret method, and the ratio of different chemical bonds in the gel was expressed as the ratio of the content of protein dissolved by different reagents to the total protein concentration.

[0089] The solubility of proteins in various solvents is used to characterize the molecular forces in the gel. The intermolecular forces in the gel system are determined by the physicochemical properties of the gel components and have an important influence on the gel formation and gel properties. The intermolecular forces in the gel system are mainly composed of electrostatic interactions, hydrogen bonds, hydrophobic interactions and disulfide bonds. Among the intermolecular interactions in the gel system, the hydrophobic interaction is dominant, and the hydrophobic interaction of the P4-1:1 gel is the highest. However, excessive hydrophobic interactions may induce the rapid formation of large aggregates of protein molecules, resulting in a rough gel network structure. Compared with the control group, the proportion of hydrogen bonds in the inulin / KGM-protein gel increased, indicating that inulin and KGM can promote myofibrillar protein-water interactions ( Figure 3). The hydrogen bonds formed between the amino and carbonyl groups in the polypeptide chain can effectively stabilize the α-helix structure, which is consistent with the results of the increase in α-helix in the previous article. These results show that hydrophobic interactions and hydrogen bonding interactions play an important role in the formation and maintenance of the inulin / KGM-protein gel structure. The disulfide bond content in the inulin gel was lower than that in the control group, which echoed the previous free thiol results. The electrostatic interaction in the inulin / KGM-protein gel is directly related to the surface charge of protein and polysaccharide molecules, which is affected by multiple factors such as the properties of protein and polysaccharide, concentration ratio, pH and temperature. Inulin and KGM are both neutral polysaccharides and cannot produce electrostatic interactions with myofibrillar protein molecules, but low-content inulin / KGM mixtures enhance the electrostatic interaction between protein molecules and aggregate protein molecules in the gel; while high-concentration inulin / KGM mixtures will be embedded in the myofibrillar protein network structure, blocking and shielding the electrostatic interaction between protein molecules.

[0090] 4. LF-NMR

[0091] 4 g of gel sample was weighed and equilibrated to room temperature, and then placed in a nuclear magnetic resonance tube for measurement.

[0092] SR-CPMG sequence: SW=2000KHz, SF=19MHz, O1=453037.23Hz, P1=6.6us, P2=11.04us, RFD=0.02ms, RG1=10.0db, DRG1=3, PRG=2, TE=0.6ms, NECH=9000, number of inversion times=20, NS=8.

[0093] The water state, water distribution and water-macromolecule binding state inside the gel have an important influence on the properties of protein gel. T2i refers to the transverse relaxation time, which corresponds to the different water states in the gel system and the interaction between water and gel components. T21 represents bound water, with a peak distribution of 1-10ms; while T22 and T23 represent fixed water (10-100ms) and free water (100-1000ms), respectively. Figure 4As shown in the figure, the moisture content of the gel sample is mainly fixed water and free water. Compared with the control group, the relaxation time of the inulin / KGM-protein gel shifts to the left, indicating that the water molecules are more tightly bound to the macromolecules in the gel matrix, the mobility of water is reduced, and the water retention of the gel system is improved (Fei et al., 2024). In addition, the free water content in the inulin / KGM-protein gel is higher than that in the control group, and increases with the increase of the KGM ratio, but the fixed water shows the opposite trend; this indicates that part of the fixed water is converted into free water. The water absorption of KGM causes the protein to aggregate in the matrix, promotes the interaction between polysaccharide molecules and proteins, and forms a denser gel network structure. The network structure formed by the inulin / KGM mixture can effectively capture water molecules, limit their freedom, improve the water holding capacity of the composite gel, maintain wettability, and facilitate the swallowing process.

[0094] 6. Rheological properties

[0095] (6-1) Apparent viscosity

[0096] At 25°C, in 0.1s -1 ~100s -1 The viscosity is collected over a range of shear rates.

[0097] In the steady-state shear test, the shear force applied by the external environment is gradually increased to observe its effect on the internal structure of the gel system. Usually, shear thinning behavior is one of the characteristics that swallowing disorder foods must have, which makes it have a higher viscosity in a steady state and prolongs the swallowing time, but it is easy to swallow when the shear rate during the oral processing is low. All gel samples were tested at a shear rate of 0.1-100s -1 The apparent viscosity in the range Figure 5 As shown. With the increase of shear rate, the apparent viscosity of inulin / KGM-protein gel continues to decrease, showing shear thinning behavior. The shear thinning behavior of the gel can prolong the reflex reaction time of the nervous system during swallowing, reduce the risk of choking, and improve swallowing safety. In addition, the shear thinning behavior of inulin / KGM-protein gel allows patients with dysphagia to feel stickiness during chewing, bringing a pleasant taste. The apparent viscosity of inulin / KGM-protein gel is higher than that of the control group, which can be attributed to the non-covalent interaction between inulin and KGM and protein molecules, forming a transient network structure, inhibiting the fluidity of protein molecules, and leading to an increase in viscosity.

[0098] (6-2) Amplitude scan

[0099] Amplitude scanning refers to testing the gel sample at an appropriate constant frequency and applying varying strains, which is used to characterize the structural strength of the gel. Specifically, the stress range of 0.1% to 100% is scanned at a frequency of 1 Hz to detect the changes in storage modulus (G') and loss modulus (G") with strain.

[0100] The viscoelastic characteristics of the gel directly affect the pleasure during swallowing. The storage modulus (G') is an elastic index that characterizes the viscoelasticity of the gel system and reflects the strength of the gel; while the loss modulus (G") is a viscosity index. In addition, the LVR region of strong gels is wider than that of weak gels. The results are as follows Figure 6 As shown, it can be seen that at the same polysaccharide addition level, when Inulin:KGM=2:1, the LVR value is the lowest, indicating that the gel is easy to break under less pressure, and the increase in inulin content will increase the brittleness of the gel. Gels with high brittleness tend to form food boluses with uneven structures when chewing. When Inulin:KGM=1:2 or 2:1, the LVR decreases with the increase in the amount of inulin / KGM mixture added, indicating that this ratio of inulin / KGM mixture will weaken the strength of the gel and is more conducive to intake by people with dysphagia. From Figure 6 It can be seen that within the linear viscoelastic region (LVR) of strain, the elastic modulus (G') and viscous modulus (G") remain constant, and G' is higher than G", indicating that the inulin / KGM-protein gel exhibits elasticity-dominated rheological characteristics and presents a semisolid gel state. When the strain is higher than the LVR, G' and G" decrease and G" is higher than G', indicating that the intermolecular interaction of the gel is destroyed, resulting in the rupture of the gel network structure. Compared with the control group, the elastic modulus of the inulin / KGM-protein gel is reduced, proving that the formed physical entanglement network structure is weak and has poor mechanical resistance to strain, which is convenient for people with dysphagia to eat. The KGM double helix aggregates to form a network structure. Increasing the proportion of all KGM can effectively increase the G' and G" of the gel and increase the elasticity of the composite gel.

[0101] (6-3) Frequency Scan

[0102] In the linear viscoelastic region, the changes of G' and G" of inulin / KGM-protein gel with frequency at constant amplitude were observed, and the structure and mechanical properties of the gel system were studied in depth. Specifically, at a strain of 1%, a frequency scan was performed at a frequency of 0.1Hz to 100Hz to measure the elastic modulus G' and viscous modulus G".

[0103] The results are as follows Figure 7 As shown, from Figure 7It can be seen that G' and G" increase with the increase of frequency, showing a slight frequency dependence, indicating that appropriately increasing the frequency can enhance the emulsion gel structure and present the weak gel behavior of the gel (Yousefi and Ako, 2020). The increase in amplitude frequency will cause an increase in molecular friction in the gel, resulting in an increase in G". Within the frequency scanning range of 0.1-100 Hz, the G' of all samples is greater than G" and there is no intersection between the G' and G" change curves, indicating that the elastic characteristics of the gel samples are more prominent in viscoelasticity and exhibit solid-like behavior. An interconnected network structure is formed in the gel, which has the ability to resist mechanical stress and maintain the stability of the gel system. In addition, G'>G" meets the rheological properties requirements for the design of dysphagia foods. The G' and G" of the control group gel are significantly higher than those of the inulin / KGM-protein gel, indicating that the inulin / KGM mixture can reduce the elasticity of the collagen fibril gel network, but keep it in a solid elastic state. The mixture of inulin and KGM can reduce the viscoelastic modulus of the gel, thereby reducing the difficulty of chewing during food swallowing and meeting the special needs of people with dysphagia during the oral process, which will be beneficial for people with dysphagia. At the same time, this also proves that the mixture of inulin and KGM can improve the viscoelasticity of myofibrillar protein gel and form a gel that is easy to swallow. In addition, the tanδ of all gel samples is <1, indicating that the gel has solid properties. At low shear frequency, the tanδ of the control group is lower than that of the inulin / KGM-protein gel group; while at high shear rate, the opposite is true. When the polysaccharide addition amount is 4% and 6%, tanδ increases with the increase of KGM ratio; among them, the higher the tanδ, the weaker the elasticity and network structure of the gel system, and the easier it is to chew and swallow.

[0104] (6-4) Creep recovery

[0105] During swallowing, the tongue needs to provide continuous driving force for the food bolus to enter the throat smoothly, and the deformation and recovery ability of the food bolus during oral processing is considered to be an important factor in judging safe swallowing. The specific test method for creep recovery is:

[0106] A stress of 10 Pa was applied to the gel sample for 300 s, and then the applied stress was removed for 300 s before recovery, and the strain recovery was observed.

[0107] The results are as follows Figure 8 As shown, it can be seen that when a certain external force is applied, the strain of the gel gradually increases. When the external force is removed, the elasticity of the material itself gradually recovers and the strain gradually decreases. However, the internal structure of the gel is irreversibly damaged, so it cannot be restored to its initial state. The lower the strain value, the stronger the deformation resistance, the more obvious the elastic characteristics of the gel, and the more stable the structure. However, for the swallowing process, the tongue needs to provide corresponding force to deform the food bolus and enter the throat. If the food bolus has low strain and strong deformation resistance, it will be unfavorable for smooth swallowing. Figure 8It can be seen that the strain of the inulin / KGM-protein gel obtained by the present invention is higher than that of the control group, indicating that the inulin / KGM-protein gel structure is softer, and the mixture of inulin and KGM can effectively improve the swallowing safety of the food bolus. When the content level of the inulin / KGM mixture is consistent, and Inulin:KGM=1:2, the strain value of the gel is higher, indicating that the inulin / KGM-protein gel of this ratio is more likely to deform, and the gel structure at this time is not enough to resist deformation. When the ratio of inulin to KGM is 1:1, as the polysaccharide content increases, the deformation degree of the gel decreases, and it has a strong network structure, which can maintain its shape during swallowing, prevent any residual matter from remaining in the mouth, and reduce the risk of suffocation.

[0108] (6-5) Temperature scan

[0109] The changes of G' and G" during heating, constant temperature and cooling of the gel are used to explore the formation process of the gel. The specific steps include:

[0110] The samples were subjected to temperature scanning test, and the samples successively went through heating stage (25-90℃, 5℃ / min), insulation stage (90℃, 15min) and cooling stage (95-20℃, 5℃ / min).

[0111] The results are as follows Fig. 9As shown in the figure, it can be seen that G' is higher than G" and there is no intersection in the whole temperature range, which is consistent with the easy-to-swallow DOP / XG gel. During the heating process, G' and G" of inulin / KGM-protein gel first decrease and then increase, indicating that heat induction first weakens the hydrogen bond interaction in the gel system, destroys the initial weak viscoelastic structure of the polysaccharide-protein gel system, and then reconstructs a new gel network. Alternatively, this may also be due to the dissociation of myofibrillar protein, which enhances the fluidity of the gel solution and leads to a decrease in G' value. In the early stage of heating, the G' of inulin / KGM-protein gel is higher than that of the control group. This is mainly because the mixture of inulin and KGM has a higher viscosity, which makes the system of inulin / KGM mixture more stable than the control group. When the amount of inulin / KGM mixture added is the same, the higher the proportion of inulin, the lower the G', which is speculated to be weaker cross-linking between inulin and myofibrillar protein molecules. When the temperature rises to 50℃, the myofibrillar protein structure stretches, forms a three-dimensional network structure under heat induction, and G' rises rapidly. The time when the G' inflection point of the inulin / KGM-protein gel appeared increased with the increase of the amount of inulin / KGM mixture added. It is speculated that this is mainly due to the inhibition of the cross-linking effect between the inulin / KGM mixture and the myofibrillar protein molecules. With the increase of temperature, the G' of the inulin / KGM-protein gel gradually decreased compared with the control group, indicating that polysaccharides weaken the gel-forming ability of myofibrillar protein and obtain soft gels suitable for people with dysphagia. In the constant temperature stage of 90℃, the G' and G" values ​​of the inulin / KGM-protein gel continued to rise. Myofibrillar protein denatured during continuous heating, the disulfide bonds and thiol groups in the protein began to oxidize under heat, the covalent interaction between protein molecules was enhanced, the gel network structure was further strengthened, and the viscoelastic modulus was enhanced. In the cooling stage, the G' and G" of the inulin / KGM-protein gel continued to increase, the protein molecules were cross-linked with each other through non-covalent interactions, and the formation of the gel network structure was promoted through hydrogen bonds and hydrophobic interactions, which enhanced the viscoelasticity of the gel. When the polysaccharide addition amount was 4% and 6%, the G' of the gel increased with the increase of KGM ratio, which was beneficial to improve the stability and storage of the gel. The tanδ of the heat-treated-cooled inulin / KGM gel was higher than that of the control group and tanδ<1, which was consistent with the previous frequency scanning results.

[0112] (6-6) LAOS analysis

[0113] Nonlinear rheological properties can effectively analyze the relationship between the microstructure and rheology of composite gels, as well as the structural evolution of gels under the influence of large amplitudes. Plotting stress against strain or strain rate, usually called elastic or viscous Lissajous curves, can effectively reflect the LAOS behavior of gels. The specific LAOS analysis method is: measuring at 25°C and a frequency of 1Hz, collecting strain-stress data of samples in the strain range of 1%-1000%.

[0114] The strain response formula under linear conditions is as follows:

[0115] γ(t)=γ 0 cos(ωt+δ)

[0116] Where, γ is strain (%);

[0117] ω is the input frequency (rad / s);

[0118] t is time (s);

[0119] δ is the difference between the phase angles of the input strain and stress waveforms;

[0120] Under nonlinear conditions, the discrete Fourier series is used to expand and decompose into apparent elastic strain and apparent shear rate viscous strain.

[0121] Fig.10 Figure 2 is the elastic Lissajous curve and elastic Lissajous curve of inulin / KGM-protein gel at a specific strain amplitude. Fig.10 It can be seen that at low strain amplitude, the elastic LB curves of the gel samples are all elliptical, reflecting the elastic response of the gel, which is an ideal viscoelastic behavior. However, the viscosity LB curve of the inulin / KGM-protein gel is elliptical at low strain. As the strain increases, the curve area gradually increases, indicating that the input of strain energy causes the gel nonlinear behavior to enhance, resulting in energy dissipation. The increase in the content of the inulin / KGM mixture will gradually increase the elliptical area of ​​the elastic LB curve, proving that high concentrations of inulin / KGM can enhance the elasticity of the composite gel. The shape of the elastic LB curve gradually distorts from an ellipse to a parallelogram as the strain amplitude continues to increase. At this time, the viscoelastic response of the gel is transferred from the linear region to the nonlinear region, and the rheological behavior is transformed from elasticity-dominated to viscosity-dominated. At the same time, the ellipse in the viscosity LB curve gradually narrows and then distorts. Under high strain (1000%), the viscosity LB curve of the inulin / KGM-protein gel system is a "self-intersecting ring" structure, indicating that the time scale of the rearrangement of the microstructure is smaller than the time scale of deformation, that is, the strong nonlinear viscoelastic shear stress overshoot leads to the rearrangement of the gel network structure. With the increase of inulin / KGM mixture, the structural transition from linear to nonlinear behavior in the gel system occurred at lower strain values, indicating that the gel strength and ability to resist deformation decreased, which is beneficial for dysphagia foods.

[0122] Under dynamic change environments such as large deformation, the destruction and reorganization of the gel structure also give the gel rheological properties different from those under small deformation. The nonlinear viscoelastic behavior of the gel is evaluated by the nonlinear parameter, the strain thickening coefficient (S). Fig.11). At low strain, the S values ​​of all gel samples are lower than 0 (within the linear viscoelastic region). As the strain increases, the S values ​​of all samples show an increasing trend, and finally S>1, indicating that the gel gradually changes from strain softening to strain hardening. In the nonlinear rheological region, the strain hardening behavior of inulin / KGM is caused by the rearrangement of the destroyed gel network structure under large amplitude strain. When the gel is subjected to a large chewing force, the gel exhibits hardening behavior. This property can provide chewing satisfaction for patients with mild dysphagia or people who still have a certain chewing ability.

[0123] 7. Laser Confocal

[0124] Laser confocal microscopy (CLSM) was used to observe the microstructure of the emulsion gel and to image and analyze the distribution of proteins and oil droplets in the gel. Fluorescent dyes (Calcofluor White Strain 100μl, 1mg / ml Nile Blue ethanol solution 100μl, 1mg / ml Nile Red isopropanol solution 100μl)) were used to stain the polysaccharide, myofibrillar protein and oil phase. The stained samples were placed on a slide and observed and photographed under a laser confocal microscope as soon as possible.

[0125] The blue, green and red areas in the laser confocal microscope represent myofibrillar protein, konjac glucan & inulin mixture and oil phase, respectively. Fig.12 It can be seen that the inulin / KGM-protein gel exhibits a non-uniform microstructure. The incompatibility of myofibrillar protein and polysaccharide forms a bicontinuous gel network structure. The P4-2:1 and P4-1:1 gel structures are loose, the protein voids are large, the oil droplets are not tightly filled, and the lipid particles are easy to move and re-aggregate to form large oil droplets. The large oil droplets are unevenly distributed in the gel network, and protein aggregation is prone to occur, which weakens the supporting effect of the gel network, resulting in low strength of P4-2:1 and P4-1:1 gels, which is consistent with the rheological results. With the increase in the amount of polysaccharide added, the oil droplet size is smaller and the distribution is more uniform, and the protein aggregates are more evenly dispersed in the inulin & KGM network. The oil droplets are evenly filled in the myofibrillar protein gel network, which is conducive to the formation of a dense and uniform gel structure and improved gelation. The P8-1:2 gel forms a concentrated and clearly visible microscopic network structure. The increase in the proportion of KGM can effectively absorb excess water in myofibrillar protein and distribute it evenly, promote the combination of polysaccharide hydrogel and myofibrillar protein gel network, and improve the gelling ability of myofibrillar protein. A small amount of inulin & KGM mixture will promote the aggregation of myofibrillar protein, and KGM will promote the formation of dense and rigid protein aggregates. A high concentration of inulin / KGM mixture can reduce the size distribution of myofibrillar protein aggregates in the gel system, and the protein aggregates become denser, forming a continuous and tighter double network gel structure.

[0126] 8.IDDSI test

[0127] Fork drip test: Use a smooth fork to lift the gel sample and observe its stacking state on the fork and its dripping state between the teeth.

[0128] Spoon tilt test: Use a standard smooth spoon to scoop up the sample and observe the state of the food bolus on the spoon. Then slowly tilt the spoon to the side and observe the sliding state of the sample and the state of the spoon surface after the sample slides down.

[0129] Fork squeeze test: Cut a gel sample of appropriate size and use a fork to squeeze the gel sample with the thumb for testing. The degree of squeezing is determined by the whitening of the thumb nail. Based on the IDDSI standard description, the texture grade of the gel deformation and particle size is divided.

[0130] The swallowing performance and texture classification of gel samples were verified according to the IDDSI framework to evaluate the feasibility of inulin / KGM-protein gel as a food for dysphagia. Fig.13 As can be seen from part a), the inulin / KGM-protein gel can be piled up on the fork without dripping from the fork. This result indicates that the gel samples all belong to IDDSI solid food level 4-fine mud type and above. When the amount of polysaccharide added is low, the gel will form a fishtail shape under the fork, indicating that the gel texture is soft. In the spoon tilt test, the inulin / KGM-protein gel can accumulate in the spoon and maintain its shape. However, the control group, P4-2:1, P4-1:1, P4-1:2, P6-2:1 and P6-1:1 gels have more residues after falling in the spoon, which does not meet the IDDSI standard. These gels are prone to form food residues in the throat, and the tongue force required for swallowing is large, or they cannot fall smoothly into the esophagus during swallowing, resulting in pharyngeal blockage. The gels P6-1:2, P8-2:1, P8-1:1, and P8-1:2 can maintain their shape in the spoon, and they will fall off the spoon in the spoon tilt test, leaving little residue on the spoon, which is conducive to safe swallowing for people with dysphagia. In the fork squeeze test, the P6-1:2 gel is soft and can be flattened with a fork, but the indentation is not very obvious. The P8-2:1, P8-1:1, and P8-1:2 gels are easily flattened under the pressure of the thumb nail turning white, and the gel samples will not return to their original shape after the pressure is removed, and can be classified as Class 6 foods in the IDDSI. When these three gels are eaten, they only require chewing force and tongue strength to form a suitable food bolus and move it to the pharynx to complete the safe swallowing process, and are suitable for people with moderate dysphagia.

[0131] 9.Texture characteristics

[0132] TPA was used to analyze the effect of different ratios of inulin / KGM mixtures on the texture properties of the composite gel. The specific steps include:

[0133] A cylindrical gel sample (25 nm in diameter and 25 nm in height) was placed in a texture analyzer (BROOKFIELD CT3-4500) to determine its texture characteristics. Test parameters: pre-test speed 1 mm / s, test speed 1 mm / s, post-test speed 1 mm / s, displacement distance 3.0 mm, dwell time 5 s, trigger force 5 g, secondary compression mode, repeated 5 times per group.

[0134] Inulin and KGM are evenly distributed in the protein network and fill the cavities of the myofibrillar protein gel network during the gelation process, which enhances the cross-linking between polysaccharides and protein molecules and improves the gel hardness. As shown in Table 1, P8-1:2 gel has the highest hardness, followed by P8-1:1 and P8-2:1, which is consistent with the change trend of G' in the frequency scan. The increase in gel hardness will increase the number of chewing and swallowing times during oral processing, which can be attributed to the formation of a stronger network structure due to the double helix aggregation of high concentrations of KGM. Adhesion refers to the ability required to overcome the adhesion between teeth and gel. Foods with strong adhesion will increase the difficulty of the tongue to push the food bolus into the throat, increase the risk of choking, and are not friendly to people with swallowing disorders. The adhesion of the gel increases with the increase in the proportion of KGM, which is consistent with the change trend of viscosity, but the adhesion and viscosity of the three groups of gels are generally at low values, which can form a food bolus that is easy to swallow during oral processing. Cohesion represents the internal interaction force of the gel network, which is conducive to the formation of a moist and cohesive food bolus. P8-2:1 has the strongest cohesion, which can effectively prevent the gel from breaking down into fine particles during swallowing and causing aspiration and choking, thus ensuring swallowing safety. The hardness of inulin-MP gel is lower than that of KGM-MP gel, and its elasticity and cohesion are higher than that of KGM-MP gel. Generally speaking, the chewiness of a gel increases with increasing hardness, but the results are the opposite. This may be because the chewiness of a gel is also related to its adhesiveness, and increased adhesiveness of the gel leads to increased chewiness. P8-1:2 gel with lower chewiness may be suitable for patients with more severe dysphagia.

[0135] Table 1 Texture characteristics of gel

[0136]

[0137] 10. Flavor Testing

[0138] Flavor characteristics directly affect consumer acceptance and play a vital role in the promotion and application of gel products. GC-MS was used to determine the flavor components of four groups of gels, which specifically included the following steps:

[0139] Take 5g of sample and place it in a headspace bottle, place it in a 60℃ water bath, equilibrate for 20min, insert the extraction needle activated at 250℃ for 20min into the headspace bottle, extract for 30min, and inject and analyze.

[0140] The gas chromatography-mass spectrometry conditions were as follows: INNOWAX (0.25 mm × 0.25 um × 60 m); temperature program: initially 40 °C, hold for 5 min, heat to 240 °C at 5 °C / min and hold for 0 min; heat to 250 °C at 10 °C / min and hold for 6 min; ion source temperature 230 °C, quadrupole temperature 150 °C, EI ionization 70 eV, full scan 29-550 da.

[0141] The detected components were compared and analyzed through the NIST mass spectral library, and the aroma compounds with a matching degree >80 were quantified by the peak area normalization method.

[0142] The results are as follows Fig.14 As shown in the figure, a total of 92 volatile compounds were detected in the four groups of gel samples, of which 54 were common compounds. The types of volatile compounds in inulin / KGM-protein gel were higher than those in the control group, indicating that inulin and KGM can give the gel unique flavor components and form new flavor characteristics. These volatile compounds include acids, alcohols, esters, acids, aromatics and hydrocarbon compounds. The thresholds of hydrocarbon compounds and aromatic compounds are higher and have less effect on the flavor of the gel; while the thresholds of aldehyde compounds are lower and are generally considered to be important flavor compounds; hexanal, heptanal, octanal and nonanal are the main compounds that produce fishy smell and are considered to be unpleasant odors. The content of these four aldehydes in inulin / KGM-protein gel is significantly lower than that in the control group, indicating that the mixture of inulin and KGM can effectively reduce the fishy smell components in fish myofibrillar protein gel and improve the overall flavor of the gel. This may be attributed to the enhanced hydrophobic interaction in inulin / KGM-protein gel, which improves the adsorption capacity of myofibrillar protein for aldehyde flavor substances. Acidic substances include acetic acid, valeric acid, octanoic acid and nonanoic acid, but the control group only contains acetic acid, and its proportion in the flavor content is relatively low. Compared with the control group, inulin / KGM-protein gel adds flavor compounds such as ethanol, 2-octen-ol, methyl acetate, and methyl butyrate, among which ethanol and 2-octen-ol account for a relatively high proportion in the volatile compounds. Therefore, it is speculated that ethanol and 2-octen-ol play an important role in improving the flavor characteristics of the gel.

[0143] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing a double network inulin / KGM-fish protein gel, characterized in that: The following steps are involved: Myofibrillar protein is prepared by using fish meat as a raw material, and then the myofibrillar protein solution, inulin / KGM composite polysaccharide solution and sunflower oil are mixed and homogenized, and a gelation reaction is carried out in a water bath. After the reaction is completed, a double network inulin / KGM-fish protein gel is obtained; The preparation method of the inulin / KGM composite polysaccharide solution comprises the following steps: After mixing inulin and konjac glucan, add water and stir evenly to obtain the inulin / KGM composite polysaccharide solution; The mass ratio of inulin to konjac glucan is (1-2): (1-2).

2. The method for preparing a double network inulin / KGM-fish source protein gel according to claim 1, characterized in that: The preparation method of the myofibrillar protein solution comprises the following steps: The myofibrillar protein was dispersed in a precooled buffer solution and homogenized for 10 seconds, and the homogenization process was repeated 3 times to obtain the myofibrillar protein solution.

3. The method for preparing a double network inulin / KGM-fish source protein gel according to claim 2, characterized in that: The buffer solution is a sodium chloride solution with a concentration of 0.2 mol / L.

4. The method for preparing a double network inulin / KGM-fish source protein gel according to claim 2, characterized in that: The preparation method of the myofibrillar protein comprises the following steps: The golden pomfret meat is minced in an ice bath, and then centrifuged three times in a low phosphate buffer solution, and then the obtained precipitate is centrifuged three times in a high phosphate buffer solution, the obtained supernatant is stored in a 4°C refrigerator for 24 hours, and then centrifuged again at 4°C, the obtained supernatant is mixed with 4°C distilled water and precipitated for 30 minutes, and then centrifuged twice more at 4°C, and the precipitate is collected to obtain the myofibrillar protein.

5. The method for preparing a double network inulin / KGM-fish source protein gel according to claim 4, characterized in that: The pH of the low phosphate buffer is 7.5, which includes 0.005 mol / L NaCl, 3.38 mmol / L NaH2PO4·2H2O, and 15.5 mmol / L Na2HPO4·12H2O; The pH of the high phosphate buffer is 7.0, which includes 0.6 mol / L NaCl, 3.38 mmol / L NaH2PO4·2H2O, and 15.5 mmol / L Na2HPO4·12H2O.

6. The method for preparing a double network inulin / KGM-fish source protein gel according to claim 1, characterized in that: The water bath temperature was 90°C and the time was 30 min.

7. Double-network inulin / KGM-fish-derived protein gel prepared by the method for preparing a double-network inulin / KGM-fish-derived protein gel according to any one of claims 1 to 6.

8. Use of the double network inulin / KGM-fish source protein gel as claimed in claim 7 in functional food.

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