High-fiber low-calorie konjac gel food and preparation method thereof

Abstract

The invention discloses a high-fiber low-calorie konjak gel food and a preparation method thereof, and belongs to the technical field of functional food processing, and the konjak gel food is prepared from the following raw materials: konjak nanowhiskers, apple pectin, lactobacillus plantarum fermentation liquor, a compound sweetening agent, compound prebiotics and vitamin microcapsules. The konjak gel is used for solving three major pain points of alkaline taste residue, rough texture and nutrition loss of traditional konjak gel, and the konjak gel has an elastic taste and an intestinal health function, and is a konjak food with high dietary fiber and ultralow calorie.

Description

Technical Field

[0001] This invention belongs to the field of functional food processing technology, specifically a high-fiber, low-calorie konjac gel food and its preparation method. Background Technology

[0002] Konjac glucomannan (KGM) is widely used in the gelled food industry due to its high dietary fiber and low calorie properties. Currently, the mainstream production processes include: Alkaline gel technology: strong alkaline agents such as Ca(OH)2 or K2CO3 are used to induce the deacetylation of KGM to form a thermally irreversible gel, resulting in a brittle and hard product. Compound colloid thickening technology: adding carrageenan, xanthan gum, etc. to improve elasticity, but requires high temperature (>80℃) processing; Nutritional fortification technology: directly adding prebiotics or vitamins, but it does not solve the problem of processing losses.

[0003] However, existing technologies have the following drawbacks: (1) Texture and stability defects Severe dehydration and shrinkage: Traditional konjac gel has a water holding capacity of <85%, and the water separation rate is >20% after adding fruit juice, because the coarse fiber network (>100μm) cannot lock in free water; Rough texture: Konjac flour is directly gelled, resulting in a gritty texture that fails to meet the taste requirements of high-fiber foods.

[0004] (2) Loss of nutritional activity Decomposition of heat-sensitive components: The retention rate of prebiotics (such as fructooligosaccharides) in alkaline gelation at 80℃ is <50%; Vitamin inactivation: Free vitamin C is oxidatively lost by more than 60% during processing, and fat-soluble vitamins are released from gastric juice by more than 65%.

[0005] (3) Environmental pollution and safety risks Strong alkaline wastewater pollution: The Ca(OH)2 gel process produces wastewater with pH > 12 and COD > 5000 mg / L, with treatment costs as high as $50 / ton; Chemical residues: The product contains residual calcium ions (800-1200mg / kg) and an alkaline taste, requiring multiple washes and increasing resource consumption.

[0006] (4) Uncontrollable release of functions Low colon colonization rate of prebiotics: In traditional processes, the decomposition rate of prebiotics in the acidic environment of the stomach is >55%, and less than 30% of the effective components reach the colon. Vitamins lack targeting: Microcapsule wall materials (such as gelatin) disintegrate prematurely in gastric juice, resulting in bioavailability of <35%.

[0007] The core issues mentioned above lie in: the inherent structural limitations of konjac polysaccharides: acetyl groups hinder molecular cross-linking, requiring strong alkali / high temperature to break them down, but this leads to contamination and nutrient loss; and the defects in the coarse fiber network: micron-sized konjac particles (D... 90 (>100μm) cannot construct a dense water-holding structure; delivery system is inefficient: traditional embedding technology cannot simultaneously protect against gastric juice and target intestinal release. Summary of the Invention

[0008] To address the above problems, this invention provides a high-fiber, low-calorie konjac gel food and its preparation method, which solves the three major problems of traditional konjac gel: residual alkaline taste, rough texture, and nutrient loss. The product has both an elastic texture and intestinal health benefits, achieving a high-fiber, ultra-low-calorie konjac food.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-fiber, low-calorie konjac gel food is made from the following ingredients: konjac nanofibers, apple pectin, Lactobacillus plantarum fermentation broth, compound sweetener, compound prebiotics, and vitamin microcapsules. In this technical solution, the konjac nanofibers are homogenized under high pressure to form monodisperse nanofibers, which, along with pectin, form a three-dimensional network through hydrogen bonds and van der Waals forces to lock in water and prevent shrinkage, thus improving gel strength and water retention. The organic acids, such as lactic acid, produced by microbial metabolites in the Lactobacillus plantarum fermentation broth, lower the pH, causing partial aggregation of KGM molecular chains to form a weak physical gel. Extracellular polysaccharides (EPS) secreted by lactic acid bacteria bind to KGM through hydrogen bonds or hydrophobic interactions, forming a composite gel network. Divalent ions such as calcium and magnesium in the fermentation broth also promote gelation through ionic cross-linking. The KGM gel in the fermentation broth is a physical gel (reversible) or a composite gel, rather than a traditional irreversible deacetylated gel. Therefore, compared to the traditional alkaline method, the product has no alkaline astringent taste. The layered liquid crystal structure of the vitamin microcapsules achieves zero release of gastric juice and targeted bursting of intestinal juice.

[0010] Under preferred implementation conditions, the raw materials consist of the following parts by weight: 80-100 parts konjac nanofibers, 10-15 parts apple pectin, 200-250 parts Lactobacillus plantarum fermentation broth, 3-5 parts compound sweetener, 10-13 parts compound prebiotic, and 5-8 parts vitamin microcapsules.

[0011] In a preferred embodiment, the konjac nanocrystals are obtained from konjac flour through β-glucomannanase-restricted hydrolysis and high-pressure homogenization exfoliation, wherein the β-glucomannanase activity is 100 U / g, the hydrolysis temperature is 45℃, the hydrolysis time is 1 h, the high-pressure homogenization pressure is 100 MPa, and the cycle is 3 times. The resulting konjac nanocrystals have a length of 1-3 μm, a diameter of 50-100 nm, and an aspect ratio ≥40.

[0012] In a preferred embodiment, the compound sweetener comprises erythritol and steviol glycosides, wherein erythritol comprises 3-4 parts and steviol glycosides comprise 0.1-1 parts. In this technical solution, erythritol provides volumetric sweetness, while steviol glycosides bind to the hydroxyl groups of konjac nanocrystals, masking their metallic aftertaste.

[0013] In a preferred embodiment, the compound prebiotic includes galactooligosaccharides and inulin, wherein there are 6-8 parts of galactooligosaccharides and 4-5 parts of inulin.

[0014] In a preferred embodiment, the wall material of the vitamin microcapsules is a layered liquid crystal structure formed by the self-assembly of konjac nanofibers and lecithin in a 1:1 mass ratio, and the core material contains B vitamins, vitamin C, and lutein. The konjac nanofibers and lecithin self-assemble into a layered liquid crystal, with the hydrophobic regions encapsulating fat-soluble vitamins and the hydrophilic regions binding vitamin C; the hydroxyl groups on the whisker surface form hydrogen bonds with the phosphate groups of lecithin, enhancing the fat-soluble flavor loading rate.

[0015] In a preferred embodiment, the B vitamins include vitamins B1, B2, and B6, wherein the mass ratio of B vitamins, vitamin C, and lutein is 3:5:2.

[0016] In a preferred embodiment, the preparation process of the vitamin microcapsules includes: dispersing konjac nanofibers in water and ultrasonically treating them until completely dispersed; then dissolving lecithin and fat-soluble vitamins in medium-chain triglycerides and heating to 60°C to form a homogeneous oil phase; adding the obtained oil phase to the konjac nanofiber solution and homogenizing it at high speed to form a layered liquid crystal emulsion; injecting supercritical CO2 into the emulsion at a pressure of 12-18 MPa and a temperature of 35-40°C; maintaining the pressure and stirring for 30 minutes; and finally spray drying to obtain microcapsule powder, with the inlet temperature set at 60±2°C and the outlet temperature at 35±1°C.

[0017] A method for preparing a high-fiber, low-calorie konjac gel food includes the following steps: (a) According to the above weight proportions, konjac nanocrystals and apple pectin were dry-mixed, and then compound sweetener, compound prebiotics and Lactobacillus plantarum fermentation liquid were added. The mixture was homogenized under high pressure at 60±5MPa and circulated twice to obtain the mixture. (b) The mixture was gelled by ultrasonic assistance at a frequency of 40 kHz, a power of 150 W, a temperature of 40-45 °C, and a time of 30 min. Then it was poured into a mold and refrigerated at 4 °C for 12 h. (c) Finally, vacuum freeze-dry until the moisture content is ≤8%, and then spray vitamin microcapsules on the surface to obtain konjac gel food.

[0018] In the above technical solution, konjac nanofibers are mixed with apple pectin, and a high-pressure homogeneous dispersion of the nanofiber-pectin composite is adopted. The ultrasonic cavitation effect promotes hydrogen bond cross-linking, and cold refrigeration and ripening cause the double network to solidify slowly. Pectin molecules slowly form a zinc ion bridging network, which can remain stable in gastric juice. When the intestinal pH is >7, the zinc ions dissociate to achieve colon-targeted release. Vacuum freeze drying preserves the porous structure.

[0019] Compared with the prior art, the technical effects of the present invention are: (1) The present invention achieves high dietary fiber, ultra-low calories, and clean label food, while solving the three major pain points of traditional konjac gel: alkaline residue, rough texture, and nutrient loss. The product has both elastic taste and intestinal health function. (2) The konjac nanofibers used in this invention eliminate the gritty / rough feel of traditional high-fiber foods, achieving the paradoxical structure of "melts in the mouth + chewy texture". The aspect ratio ≥40 is the basis for maintaining the orderly arrangement of liquid crystals and forming a dense network. Short whiskers (aspect ratio <30) will cause the structure to collapse. The vitamin microcapsules used have konjac nanofibers as the hydrophilic skeleton, and the surface is rich in active hydroxyl groups to form a rigid network. Lecithin is used as a hydrophobic carrier. The amphiphilic molecules, the hydrophilic head (phosphate group) and the whisker hydroxyl group are anchored by hydrogen bonds, and the hydrophobic tail self-assembles into a bilayer. The membrane, a mixture of konjac whiskers and lecithin, forms a layered liquid crystal through a hydrophobic-hydrophilic balance. Fat-soluble vitamins (lutein) are embedded in the hydrophobic layer, while water-soluble vitamins (Vc, B vitamins) are adsorbed in the hydrophilic region. Supercritical CO2 permeates the liquid crystal layer to dissolve lipids. After depressurization, the CO2 vaporizes and expands, forming micropores within the wall material. Through oral chewing and friction, heat is generated, causing the gas within the micropores to expand and the wall material to rupture, achieving an explosive release effect. This microcapsule, through "bio-based liquid crystal self-assembly + supercritical precision pore formation" technology, achieves "zero loss in the stomach, targeted release in the intestine, and controllable explosion in the mouth" of vitamins, providing an irreplaceable core carrier for the functional enhancement of high-fiber foods. (3) This invention utilizes the synergistic effects of three technologies: “konjac nanocrystal network framework + microbial low-temperature gelation + liquid crystal intelligent encapsulation”. The nanocrystals (50-100nm) eliminate the gritty feel of high-fiber foods, and the supercritical microcapsules achieve targeted release of vitamins into the colon, resulting in zero nutrient loss. The fermentation liquid of Lactobacillus plantarum replaces strong alkali, reducing wastewater discharge and achieving green manufacturing. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0021] In the following examples, konjac nanocrystals were obtained from konjac flour by β-glucomannanase-restricted hydrolysis and high-pressure homogenization. The β-glucomannanase activity was 100 U / g, the hydrolysis temperature was 45℃, the hydrolysis time was 1 h, the high-pressure homogenization pressure was 100 MPa, and the cycle was repeated 3 times. The resulting konjac nanocrystals had a length of 1-3 μm, a diameter of 50-100 nm, and an aspect ratio ≥40.

[0022] The *Lactobacillus plantarum* fermentation broth used in the following examples was obtained from *Lactobacillus plantarum* Lp3a fermentation, which was purchased from Puruting Biotechnology (Beijing) Co., Ltd. The specific preparation process of the *Lactobacillus plantarum* fermentation broth was as follows: After culturing Lp3a to the logarithmic growth phase, 20% sterile glycerol was added and mixed well, then frozen at -80℃ to obtain glycerol culture. 5 mL of glycerol culture was then placed in 100 mL of MRS medium and incubated at 37℃ for 12 h. Then, 100 mL of the seed culture was poured into 900 mL of fresh medium (45 g sucrose, 20 g yeast extract, 10 g peptone, 5 g trisodium citrate, 1 L water, pH 7.0, sterilized), and incubated at 37℃ for 16 h until the pH dropped to 4.0. Finally, the mixture was centrifuged at 4℃ and 6000 rpm for 10 min, and the supernatant was collected and sterilely filtered through a 0.22 µm filter to obtain the *Lactobacillus plantarum* fermentation broth.

[0023] In the following embodiments, the wall material of the vitamin microcapsules is a layered liquid crystal structure formed by self-assembly of konjac nanocrystals and lecithin in a 1:1 mass ratio. The core material contains B vitamins, vitamin C, and lutein. The B vitamins include vitamins B1, B2, and B6, wherein the mass ratio of B vitamins, vitamin C, and lutein is 3:5:2.

[0024] The preparation process of vitamin microcapsules in the following examples includes: dispersing konjac nanofibers in water and sonicating them until completely dispersed; then dissolving lecithin and fat-soluble vitamins in medium-chain triglycerides and heating to 60°C to form a homogeneous oil phase; adding the obtained oil phase to the konjac nanofiber solution and homogenizing it at high speed to form a layered liquid crystal emulsion; injecting supercritical CO2 into the emulsion at a pressure of 18 MPa and a temperature of 38°C; maintaining the pressure and stirring for 30 min; and finally spray drying to obtain microcapsule powder, with the inlet temperature set at 60°C and the outlet temperature at 35°C.

[0025] Example 1:

[0026] A high-fiber, low-calorie konjac gel food is made from the following ingredients: 90 parts konjac nanocrystals, 12 parts apple pectin, 220 parts Lactobacillus plantarum fermentation broth, 3.5 parts erythritol, 0.3 parts steviol glycosides, 7 parts galactooligosaccharides, 4.5 parts inulin, and 6 parts vitamin microcapsules.

[0027] A method for preparing a high-fiber, low-calorie konjac gel food includes the following steps: (a) According to the above weight proportions, konjac nanocrystals and apple pectin were dry-mixed, and then compound sweetener, compound prebiotics and Lactobacillus plantarum fermentation liquid were added. The mixture was homogenized under high pressure at 65 MPa and circulated twice to obtain a mixture. (b) The mixture was gelled by ultrasonic assistance at a frequency of 40 kHz, a power of 150 W, a temperature of 45 °C, and a time of 30 min. Then it was poured into a mold and refrigerated at 4 °C for 12 h. (c) Finally, vacuum freeze-dry until the moisture content is ≤8%, and then spray vitamin microcapsules on the surface to obtain konjac gel food.

[0028] Example 2:

[0029] A high-fiber, low-calorie konjac gel food is made from the following ingredients: 85 parts konjac nanocrystals, 15 parts apple pectin, 250 parts Lactobacillus plantarum fermentation broth, 3 parts erythritol, 0.8 parts steviol glycosides, 8 parts galactooligosaccharides, 5 parts inulin, and 5 parts vitamin microcapsules.

[0030] A method for preparing a high-fiber, low-calorie konjac gel food includes the following steps: (a) According to the above weight proportions, konjac nanocrystals and apple pectin were dry-mixed, and then compound sweetener, compound prebiotics and Lactobacillus plantarum fermentation liquid were added. The mixture was homogenized under high pressure at 60 MPa and circulated twice to obtain a mixture. (b) The mixture was gelled by ultrasonic assistance at a frequency of 40 kHz, a power of 150 W, a temperature of 40 °C, and a time of 30 min. Then it was poured into a mold and refrigerated at 4 °C for 12 h. (c) Finally, vacuum freeze-dry until the moisture content is ≤8%, and then spray vitamin microcapsules on the surface to obtain konjac gel food.

[0031] Example 3:

[0032] A high-fiber, low-calorie konjac gel food is made from the following ingredients: 100 parts konjac nanocrystals, 14 parts apple pectin, 210 parts Lactobacillus plantarum fermentation broth, 4 parts erythritol, 1 part steviol glycoside, 6 parts galactooligosaccharides, 4 parts inulin, and 8 parts vitamin microcapsules.

[0033] A method for preparing a high-fiber, low-calorie konjac gel food includes the following steps: (a) According to the above weight proportions, konjac nanocrystals and apple pectin were dry-mixed, and then compound sweetener, compound prebiotics and Lactobacillus plantarum fermentation liquid were added. The mixture was homogenized under high pressure at 55 MPa and circulated twice to obtain a mixture. (b) The mixture was gelled by ultrasonic assistance at a frequency of 40 kHz, a power of 150 W, a temperature of 43 °C, and a time of 30 min. Then it was poured into a mold and refrigerated at 4 °C for 12 h. (c) Finally, vacuum freeze-dry until the moisture content is ≤8%, and then spray vitamin microcapsules on the surface to obtain konjac gel food.

[0034] The konjac gel foods obtained in Examples 1-3 above were subjected to quality testing, and the test results are shown in the table below.

[0035] Table 1

[0036] To verify the impact of critical parameter deviation on performance, comparative examples 1-3 were set with different conditional parameters than example 1. The specific parameters are shown in the table below.

[0037]

[0038] The performance of Example 1 was compared with that of Comparative Examples 1-3. According to the National Food Safety Standard GB 5009.82-2016 and an in vitro simulated digestion model, the vitamin retention rate in konjac gel food was detected, and the results are shown in the table below.

[0039]

[0040] Comparative Example 4: The difference between this comparative example and Example 1 is that the traditional alkali method was used to make konjac jelly, and Ca(OH)2 was used instead of Lactobacillus plantarum fermentation broth in the raw materials. In terms of process, the gel was heated at 80°C, and the konjac jelly was washed three times with water to remove alkali residue. Then, the performance of the obtained konjac jelly was tested. Its dehydration shrinkage rate was 26.5%, calcium ion residue was 1050 mg / kg, wastewater COD was 4200, and prebiotic retention rate was 48%.

[0041] Comparative Example 5: The difference between this comparative example and Example 1 is that the compound colloidal konjac gel is prepared by using konjac flour instead of konjac nanocrystals in the raw materials, while the other technical contents are the same.

[0042] Comparative Example 6: The difference between this comparative example and Example 1 is that the compound colloidal konjac gel is prepared by using carrageenan instead of apple pectin in the raw materials, while the other technical contents are the same.

[0043] The konjac gel foods obtained in Example 1 and Comparative Examples 5-6 were subjected to performance testing, and the test results are shown in the table below.

[0044]

[0045] Note: In the gritty feeling rating, 1-4 points indicate a strong foreign body sensation, making swallowing difficult; 4-8 points indicate a significant gritty sensation, with frictional pain or obvious granular feel but not irritating; and 8-10 points indicate a slight granular feel that disappears or becomes completely absent after chewing 5 times, with a smooth texture like mousse.

[0046] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A high-fiber, low-calorie konjac gel food product, characterized in that, Made from the following ingredients: konjac nanocrystals, apple pectin, Lactobacillus plantarum fermentation broth, compound sweetener, compound prebiotics, and vitamin microcapsules.

2. The high-fiber, low-calorie konjac gel food product according to claim 1, characterized in that, It is composed of the following raw materials in parts by weight: 80-100 parts konjac nano crystals, 10-15 parts apple pectin, 200-250 parts Lactobacillus plantarum fermentation broth, 3-5 parts compound sweetener, 10-13 parts compound prebiotics, and 5-8 parts vitamin microcapsules.

3. The high-fiber, low-calorie konjac gel food product according to claim 1, characterized in that, The konjac nanocrystals are obtained from konjac flour through β-glucomannan-restricted hydrolysis and high-pressure homogenization. The β-glucomannan activity is 100 U / g, the hydrolysis temperature is 45℃, the hydrolysis time is 1 h, the high-pressure homogenization pressure is 100 MPa, and the cycle is 3 times. The resulting konjac nanocrystals have a length of 1-3 μm, a diameter of 50-100 nm, and an aspect ratio of ≥40.

4. The high-fiber, low-calorie konjac gel food product according to claim 1, characterized in that, The compound sweetener includes erythritol and steviol glycosides, wherein erythritol is 3-4 parts and steviol glycosides are 0.1-1 parts.

5. The high-fiber, low-calorie konjac gel food product according to claim 1, characterized in that, The compound prebiotics include galactooligosaccharides and inulin, wherein there are 6-8 parts of galactooligosaccharides and 4-5 parts of inulin.

6. The high-fiber, low-calorie konjac gel food product according to claim 1, characterized in that, The wall material of the vitamin microcapsules is a layered liquid crystal structure formed by self-assembling konjac nanocrystals and lecithin in a 1:1 mass ratio, and the core material contains B vitamins, vitamin C, and lutein.

7. A high-fiber, low-calorie konjac gel food product according to claim 6, characterized in that, The B vitamins include vitamins B1, B2, and B6, wherein the mass ratio of B vitamins, vitamin C, and lutein is 3:5:

2.

8. A high-fiber, low-calorie konjac gel food product according to claim 1 or 6, characterized in that, The preparation process of the vitamin microcapsules includes: dispersing konjac nanofibers in water and ultrasonically treating them until completely dispersed; then dissolving lecithin and fat-soluble vitamins in medium-chain triglycerides and heating to 60°C to form a homogeneous oil phase; adding the obtained oil phase to the konjac nanofiber solution and homogenizing it at high speed to form a layered liquid crystal emulsion; injecting supercritical CO2 into the emulsion at a pressure of 12-18 MPa and a temperature of 35-40°C; maintaining the pressure and stirring for 30 minutes; and finally spray drying to obtain microcapsule powder, with the inlet temperature set at 60±2°C and the outlet temperature at 35±1°C.

9. A method for preparing a high-fiber, low-calorie konjac gel food, characterized in that, Includes the following steps: (a) According to the above weight proportions, konjac nanocrystals and apple pectin were dry-mixed, and then compound sweetener, compound prebiotics and Lactobacillus plantarum fermentation liquid were added. The mixture was homogenized under high pressure at 60±5MPa and circulated twice to obtain the mixture. (b) The mixture was gelled by ultrasonic assistance at a frequency of 40 kHz, a power of 150 W, a temperature of 40-45 °C, and a time of 30 min. Then it was poured into a mold and refrigerated at 4 °C for 12 h. (c) Finally, vacuum freeze-dry until the moisture content is ≤8%, and then spray vitamin microcapsules on the surface to obtain konjac gel food.

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