Fermentation treatment method for improving oxidation resistance of chenopodium quinoa willd product

Abstract

The invention relates to the technical field of food processing, in particular to a fermentation treatment method for improving oxidation resistance of quinoa products, which comprises the following steps: (a) mixing quinoa grains or quinoa powder with water to prepare a quinoa substrate with the water content of 45-55%; (b) inoculating a microbial fermentation agent into the quinoa substrate, wherein the inoculation amount of the microbial fermentation agent is 1-5% of the weight of the quinoa substrate; (c) maintaining fermentation at the temperature of 30 to 37 DEG C for 18 to 24 hours until the pH value is reduced to 3.8 to 4.5; (d) drying the fermented chenopodium quinoa willd product to obtain a fermented chenopodium quinoa willd product of which the water content is lower than 10%; wherein the DPPH free radical scavenging capacity of the fermented quinoa product is improved by at least 30% compared with that of unfermented quinoa, anti-nutritional factors in the quinoa can be effectively degraded through microbial fermentation treatment, and the sensory quality and the mineral bioavailability of the product are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and more specifically, to a fermentation treatment method for improving the antioxidant property of quinoa products, particularly to a method, process and application for improving the antioxidant activity of quinoa products by microbial fermentation. Background Art

[0002] Quinoa (Chenopodium quinoa Willd) is a pseudocereal plant native to the Andean region of South America. It has been hailed as a "superfood" by the Food and Agriculture Organization of the United Nations due to its excellent nutritional value and good adaptability. Quinoa is rich in high-quality protein, dietary fiber, minerals, vitamins and various bioactive substances, such as polyphenols, flavonoid compounds, etc. These components have strong antioxidant activity. In recent years, with the increasing demand for healthy foods, quinoa and its derivative products have received extensive attention globally.

[0003] However, untreated quinoa has some problems that limit its consumption and application. First, the outer layer of quinoa seeds contains saponins, which have a bitter taste and will affect the sensory quality of the products. Second, there are antinutritional factors such as phytic acid in quinoa, which will affect the absorption of minerals such as calcium, iron, and zinc by the human body. More importantly, many bioactive substances in quinoa, such as polyphenols, exist in a bound state, with low bioavailability and unable to fully exert their antioxidant and other functions.

[0004] To address these issues, researchers have developed various processing methods, including soaking, germination, heat treatment, and fermentation. Among them, microbial fermentation has been proven to be an effective method for improving the nutritional value and functional properties of quinoa. The study "Fermentation of pseudocereals quinoa, canihua, and amaranth to improve mineral accessibility through degradation of phytate" published by Castro-Alba et al. (2019) in the Journal of the Science of Food and Agriculture showed that fermentation can significantly reduce the phytic acid content in quinoa and improve the bioaccessibility of minerals. The study "Effect of Germination and Fermentation Process on the Antioxidant Compounds of Quinoa Seeds" published by Carciochi et al. (2016) in Plant Foods for Human Nutrition pointed out that fermentation can significantly increase the content of free phenolic compounds and antioxidant activity in quinoa.

[0005] However, the existing research on quinoa fermentation mainly focuses on the application of single strains, lacking systematic research on the co-fermentation of multiple strains and the control of key parameters during the fermentation process. The study "Quinoa dough fermentation by Saccharomyces cerevisiae and lactic acid bacteria: Changes in saponin, phytic acid content, and antioxidant capacity" published by Arjmand et al. (2023) in Food Science & Nutrition showed that although the fermentation of Saccharomyces cerevisiae and lactic acid bacteria can improve the antioxidant properties of quinoa, there are still problems such as low fermentation efficiency and limited improvement in antioxidant activity. In addition, Chinese Patent CN106036311A discloses fermented quinoa milk, flavored fermented quinoa milk, quinoa yogurt beverage and its preparation method, but this method mainly targets liquid quinoa products and does not provide a systematic technical solution for improving the antioxidant properties of quinoa.

[0006] Therefore, there is still a need for a more efficient quinoa fermentation treatment method that can significantly improve the antioxidant properties of quinoa products while taking into account the nutritional value and sensory quality of the products. Summary of the Invention

[0007] The object of the present invention is to overcome the defects of the prior art and provide a fermentation treatment method for efficiently improving the antioxidant property of quinoa products. This method significantly improves the antioxidant activity of quinoa products by optimizing the quinoa pretreatment process, fermentation conditions, and post-treatment technology.

[0008] To achieve the above object, the present invention provides a fermentation treatment method for improving the antioxidant property of quinoa products, comprising the following steps:

[0009] (a) Mix quinoa grains or quinoa flour with water to prepare a quinoa matrix with a water content of 45 - 55%;

[0010] (b) Inoculate the quinoa matrix with a microbial ferment, and the inoculation amount of the microbial ferment is 1 - 5% of the weight of the quinoa matrix;

[0011] (c) Maintain fermentation at a temperature of 30 - 37°C for a fermentation time of 18 - 24 hours until the pH value drops to 3.8 - 4.5;

[0012] (d) Perform a drying treatment on the fermented quinoa product to obtain a fermented quinoa product with a water content of less than 10%;

[0013] Among them, the DPPH free radical scavenging ability of the fermented quinoa product is increased by at least 30% compared with unfermented quinoa.

[0014] In a preferred embodiment of the present invention, the microbial ferment comprises at least one lactic acid bacterium, and the initial inoculation concentration of the lactic acid bacterium is 1×10 8 -1×10 10 CFU / g.

[0015] Preferably, the lactic acid bacterium is selected from at least one of Lactiplantibacillus plantarum, Lactobacillus reuteri, Lactobacillus fermentum, Lactobacillus rhamnosus, or a combination thereof.

[0016] Furthermore, before preparing the quinoa matrix in step (a), a pretreatment of the quinoa is also included, and the pretreatment comprises the following steps:

[0017] (i) Wash the quinoa grains with warm water to remove saponins until no foam is generated;

[0018] (ii) Soak the washed quinoa grains for 12 - 24 hours;

[0019] (iii) crushing the soaked quinoa grains into a particle size of 0.2-0.5 mm.

[0020] In another preferred embodiment of the present invention, the pretreatment further comprises germinating the quinoa grains, and the germination conditions are: germinating the quinoa grains at 25-28°C and a relative humidity of 85-95% for 48-72 hours until the radicle length reaches 1 / 2-2 / 3 of the seed length.

[0021] In another preferred embodiment of the present invention, the microbial fermentation agent comprises a mixed culture of Lactobacillus plantarum and Lactobacillus fermentum, the inoculation ratio of the two being 1:1, and the fermentation step (c) comprises:

[0022] (i) fermenting at 37° C. for 12 hours;

[0023] (ii) The temperature was lowered to 32°C and the fermentation was continued for 12 hours.

[0024] Preferably, the solid content of the quinoa matrix in step (a) is 45-55% (w / w), and 0.5-1% of glucose is added as an initial carbon source during the preparation process.

[0025] In another preferred embodiment of the present invention, the drying process in step (d) adopts hot air drying method, and the drying process comprises:

[0026] (i) drying at 70° C. for 30 minutes;

[0027] (ii) drying at 60°C for 2 hours;

[0028] (iii) Drying at 50°C for 2 hours until the moisture content is less than 10%.

[0029] In another embodiment of the present invention, the method is a multi-stage fermentation process comprising:

[0030] (i) firstly, solid-state fermentation was carried out using Rhizopus oligosporus at 30°C for 48 hours;

[0031] (ii) then inoculating the mixed culture of lactic acid bacteria and continuing the fermentation at 37°C for 24 hours;

[0032] Wherein, the inoculation amount of the Rhizopus species is 0.2-0.5% of the weight of the quinoa substrate.

[0033] In yet another embodiment of the present invention, the method further includes adding an enzyme preparation before fermentation. The enzyme preparation includes β-glucosidase and / or xylanase, and the addition amount is 0.1-0.5% of the weight of the quinoa matrix. The total phenol content in the fermented quinoa product is increased by 40-50% compared to unfermented quinoa, the ABTS free radical scavenging ability is increased by 35-45%, and the ferric reducing antioxidant power (FRAP value) is increased by 80-100%.

[0034] The advantages and beneficial effects of the present invention are as follows:

[0035] 1. The fermentation treatment method provided by the present invention can significantly improve the antioxidant property of quinoa products. The DPPH free radical scavenging ability is increased by at least 30% compared to unfermented quinoa, the total phenol content is increased by 40-50%, the ABTS free radical scavenging ability is increased by 35-45%, and the ferric reducing antioxidant power is increased by 80-100%, greatly enhancing the functional properties of quinoa products.

[0036] 2. The microbial fermentation treatment adopted by the present invention can effectively degrade the anti-nutritional factors in quinoa, such as saponins and phytates, and improve the sensory quality and mineral bioavailability of the products. Experimental data show that the saponin content in the fermented quinoa product is reduced by 60-70%, and the phytate content is reduced by 65-75%.

[0037] 3. By precisely controlling the fermentation conditions, including parameters such as water content, temperature, and time, the present invention realizes the optimization of the quinoa fermentation process, improving the fermentation efficiency and the stability of product quality.

[0038] 4. The multi-stage fermentation process and multi-strain co-fermentation scheme of the present invention can give full play to the characteristics of different microorganisms, form complementary advantages, and further enhance the fermentation effect.

[0039] 5. The method of the present invention is simple to operate and easy for industrial production. It can be used to produce various quinoa-derived products with high antioxidant activity, such as quinoa flour, quinoa flakes, quinoa beverages, etc., expanding the application range of quinoa. Specific Embodiments

[0040] The following further elaborates on the present invention in detail with reference to examples, but the protection scope of the present invention is not limited thereto.

[0041] Example 1: Preparation of Basic Fermented Quinoa Product

[0042] (1) Pretreatment: Select high-quality white quinoa grains, wash them 3 times with warm water at 35°C for 10 minutes each time until there is no obvious foam in the washing liquid, indicating that the saponins have been basically removed. Soak the washed quinoa grains at room temperature (25°C) for 12 hours, then drain the surface moisture, and use a food grinder to crush the soaked quinoa grains to an average particle size of about 0.5 mm.

[0043] (2) Substrate preparation: Mix the ground quinoa with pure water at a weight ratio of 1:1, and adjust to a quinoa substrate with a water content of 45%, then place it in a sterilized fermentation container.

[0044] (3) Inoculation: Select Lactiplantibacillus plantarum as the fermentation strain, and inoculate the activated Lactiplantibacillus plantarum culture solution into the quinoa substrate at 1% of the weight of the quinoa substrate. The concentration of the bacterial solution during inoculation is 1×10 8 CFU / g.

[0045] (4) Fermentation: Place the inoculated quinoa substrate in a constant temperature incubator at 30°C for 18 hours, and stir it every 6 hours during this period to keep it uniform. When fermentation ends, the pH value of the substrate drops to 4.3.

[0046] (5) Drying: Place the fermented quinoa product in a hot air drying oven, first dry it at 70°C for 30 minutes, then dry it at 60°C for 2 hours, and finally dry it at 50°C for 2 hours until the water content of the product drops below 8%.

[0047] (6) Finished product treatment: Crush and sieve the dried fermented quinoa product to obtain fine and uniform fermented quinoa powder, and seal and package it for standby.

[0048] Through the determination of DPPH free radical scavenging rate, the antioxidant activity of the fermented quinoa product prepared in this example is 32.5% higher than that of unfermented quinoa.

[0049] Example 2: Preparation of Fermented Quinoa Product with High Water Content

[0050] In this example, the pretreatment steps are the same as those in Example 1, except that:

[0051] (1) Substrate preparation: Mix the ground quinoa with pure water at a weight ratio of 1:1.2, and adjust to a quinoa substrate with a water content of 55%.

[0052] (2) Inoculation: Use Lactobacillus fermentum as the fermentation strain, and inoculate it into the quinoa substrate at 3% of the weight of the quinoa substrate. The concentration of the bacterial solution during inoculation is 5×10 9 CFU / g.

[0053] (3) Fermentation: Ferment at a constant temperature of 35°C for 24 hours, and stir it every 4 hours during this period. When fermentation ends, the pH value of the substrate drops to 3.9.

[0054] (4) The drying treatment is the same as that in Example 1.

[0055] The DPPH free radical scavenging rate of the fermented quinoa product prepared in this example increased by 40.2% compared to unfermented quinoa, and the total phenol content increased by 45.1%. Increasing the fermentation time and using a higher inoculum amount of Lactobacillus fermentum can significantly improve the antioxidant activity of the product. This is because during the longer fermentation process, Lactobacillus fermentum more fully hydrolyzed the quinoa cell wall structure, released more bound phenolic compounds, and also produced more fermentation metabolites with antioxidant activity.

[0056] Example 3: Preparation of germinated-fermented combined treatment quinoa product

[0057] (1) Germination pretreatment: Select high-quality white quinoa grains, wash them 3 times with warm water at 35°C to remove saponins, then place the quinoa grains in a plastic tray lined with wet gauze, and germinate them at 26°C and a relative humidity of 90% for 60 hours. Spray water once every 12 hours to maintain appropriate humidity until the radicle length reaches 2 / 3 of the seed length.

[0058] (2) Crushing: Crush the germinated quinoa grains to an average particle size of about 0.3 mm.

[0059] (3) Substrate preparation: Mix the crushed germinated quinoa with pure water at a weight ratio of 1:1 to adjust to a quinoa substrate with a water content of 50%.

[0060] (4) Inoculation: Use a mixed culture of Lactobacillus plantarum and Lactobacillus rhamnosus (ratio 1:1) as the fermentation strain, and inoculate it into the quinoa substrate at 2% of the weight of the quinoa substrate. The total bacterial liquid concentration during inoculation is 1×10 10 CFU / g.

[0061] (5) Fermentation: Ferment at a constant temperature of 32°C for 20 hours, stir once every 5 hours during this period, and the pH value of the substrate drops to 4.0 at the end of fermentation.

[0062] (6) The drying treatment is the same as in Example 1.

[0063] The DPPH free radical scavenging rate of the germinated-fermented combined treatment quinoa product prepared in this example increased by 52.3% compared to untreated quinoa and by 19.8% compared to the simply fermented quinoa (Example 1). This indicates that there is a significant synergistic effect between the endogenous enzyme system activated during the germination process and microbial fermentation. During the germination process, the endogenous enzyme activity of quinoa seeds is enhanced. On the one hand, it initially decomposes the cell wall polysaccharides, improving the accessibility of microorganisms to the substrate; on the other hand, it synthesizes more bioactive substances such as vitamins and polyphenolic compounds, providing a richer substrate for subsequent microbial fermentation, thus achieving a significant improvement in antioxidant activity.

[0064] Example 4: Preparation of multi-stage fermented quinoa product

[0065] (1) Pretreatment: Select high-quality black quinoa grains, wash them 4 times with warm water at 40 °C for 15 minutes each time to remove saponins. Drain the washed quinoa grains after soaking for 20 hours, and crush them to an average particle size of about 0.4 mm.

[0066] (2) Matrix preparation: Mix the crushed quinoa with pure water at a weight ratio of 1:1, add 0.8% glucose as the initial carbon source, and adjust to a quinoa matrix with a water content of 48% and a solid content of 52% (w / v).

[0067] (3) First-stage fermentation: Use Rhizopus oligosporus as the first-stage fermentation strain, inoculate it into the quinoa matrix at 0.3% of the weight of the quinoa matrix, and perform solid-state fermentation at a constant temperature of 30 °C for 48 hours.

[0068] (4) Second-stage fermentation: After the first-stage fermentation is completed, inoculate a mixed culture of Lactobacillus plantarum and Lactobacillus fermentum (ratio 1:1) at an inoculation amount of 2% of the weight of the quinoa matrix. After fermenting at 37 °C for 12 hours, lower the temperature to 32 °C and continue fermenting for 12 hours, with a total fermentation time of 24 hours.

[0069] (5) Drying: Disperse the fermented quinoa product into a thin layer (about 1 cm thick), and perform three-stage drying in a hot air drying oven: dry at 70 °C for 30 minutes, 60 °C for 2 hours, and 50 °C for 2 hours until the water content of the product drops below 7%.

[0070] (6) Finished product treatment: Crush and sieve the multi-stage fermented quinoa product after drying to obtain the finished product.

[0071] The DPPH radical scavenging rate of the multi-stage fermented quinoa product prepared in this example increased by 58.7% compared with unfermented quinoa, the total phenol content increased by 49.3%, the ABTS radical scavenging ability increased by 42.1%, and the ferric reducing antioxidant power (FRAP value) increased by 94.5%. This significant improvement in antioxidant activity can be attributed to the synergistic effect of rhizopus and lactic acid bacteria. Rhizopus produces a large amount of amylase, protease, cellulase, etc. during the first-stage fermentation, decomposing the complex polysaccharide and protein structures of quinoa, and simultaneously synthesizing bioactive substances such as L-carnitine and γ-aminobutyric acid (GABA); the lactic acid bacteria fermentation in the second stage further promotes the release and transformation of polyphenolic compounds and produces antioxidant-active fermentation metabolites, achieving the maximum improvement in antioxidant activity.

[0072] Example 5: Preparation of Quinoa Fermentation Product Added with Enzyme Preparation

[0073] (1) Pretreatment: Select high-quality red quinoa grains, and the pretreatment steps are the same as those in Example 1.

[0074] (2) Substrate preparation: Mix the ground quinoa with pure water at a weight ratio of 1:1.1, adjust to a quinoa substrate with a water content of 52%, and add 0.7% glucose as a carbon source.

[0075] (3) Enzyme treatment: Add β-glucosidase (activity 10 U / g substrate) and xylanase (activity 5 U / g substrate) to the quinoa substrate, with the total addition being 0.3% of the weight of the quinoa substrate, and perform enzymatic hydrolysis at 45 °C for 2 hours.

[0076] (4) Inoculation: Use a mixed culture of Lactobacillus plantarum, Lactobacillus fermentum, and Lactobacillus rhamnosus (ratio 1:1:1) as the fermentation strain, and inoculate it into the enzymatically treated quinoa substrate at 4% of the weight of the quinoa substrate.

[0077] (5) Fermentation: Ferment at a constant temperature of 34 °C for 22 hours, stir every 4 hours during this period, and the pH value of the substrate drops to 3.8 at the end of fermentation.

[0078] (6) The drying treatment is the same as in Example 1.

[0079] The DPPH free radical scavenging rate of the quinoa fermented product with added enzyme preparation prepared in this example increased by 60.2% compared to unfermented quinoa, the total phenol content increased by 50.1%, the ABTS free radical scavenging ability increased by 44.8%, and the iron-reducing antioxidant ability increased by 96.3%. β-Glucosidase can specifically hydrolyze the glycosidic bonds of polyphenol glycosides in quinoa, releasing more phenolic aglycones with higher biological activity; while xylanase can decompose the hemicellulose structure in the quinoa cell wall, promoting the release of cell wall-bound phenols. The synergistic effect of these enzymes and microbial fermentation greatly improves the release and conversion efficiency of bioactive substances in quinoa, thereby achieving an optimal improvement in antioxidant activity.

[0080] Example 6: Preparation of a low-temperature dried quinoa fermented product

[0081] The pretreatment, substrate preparation, inoculation, and fermentation steps in this example are the same as in Example 2, except for the drying method:

[0082] Use freeze-drying instead of hot air drying. The specific operation is as follows: Place the fermented quinoa product at -40 °C for pre-freezing for 4 hours, and then dry it in a freeze-dryer. The main drying stage is carried out at -30 °C and 0.1 mbar for 24 hours, and the secondary drying stage is carried out at 20 °C and 0.05 mbar for 12 hours until the water content of the product drops below 5%.

[0083] The DPPH free radical scavenging rate of the low-temperature dried quinoa fermented product prepared in this example increased by 8.3% compared with that of the hot air dried product in Example 2 (under the same fermentation conditions), reaching 48.5% of unfermented quinoa. This indicates that the low-temperature drying method can better protect the thermosensitive antioxidant substances generated during fermentation and reduce the loss of activity during drying. Although the freeze-drying process has a higher cost, it has obvious advantages for high-end quinoa products that require maximum retention of antioxidant activity.

[0084] Example 7: Preparation of temperature gradient fermented quinoa product

[0085] (1) Pretreatment: Select high-quality quinoa grains, and the pretreatment steps are the same as those in Example 1.

[0086] (2) Substrate preparation: Mix the ground quinoa with pure water at a weight ratio of 1:1 to adjust to a quinoa substrate with a water content of 50%, and add 0.5% glucose as the initial carbon source.

[0087] (3) Inoculation: Use a mixed culture of Lactobacillus plantarum and Lactobacillus fermentum (ratio 1:1) as the fermentation strain, and inoculate it into the quinoa substrate at 2.5% of the weight of the quinoa substrate.

[0088] (4) Temperature gradient fermentation: Adopt a three-stage temperature gradient fermentation process:

[0089] The first stage: Ferment at 37 °C for 8 hours to promote the rapid proliferation of lactic acid bacteria;

[0090] The second stage: Lower the temperature to 34 °C and ferment for 8 hours to promote the production of organic acids;

[0091] The third stage: Further lower the temperature to 30 °C and ferment for 8 hours to promote the accumulation of antioxidant substances.

[0092] The total fermentation time is 24 hours, and the pH value of the substrate drops to 4.1 at the end of fermentation.

[0093] (5) The drying treatment is the same as that in Example 1.

[0094] The DPPH free radical scavenging rate of the temperature gradient fermented quinoa product prepared in this example increased by 46.8% compared with unfermented quinoa and by 6.6% compared with the constant temperature fermentation condition (Example 2). The temperature gradient fermentation process can provide optimal growth and metabolic conditions according to the physiological characteristics of lactic acid bacteria at different fermentation stages, and promote the synthesis of specific antioxidant metabolites. The high temperature in the first stage promotes the rapid proliferation of bacteria; the medium temperature in the second stage is beneficial to the production of organic acids and protein hydrolysis; the low temperature in the third stage slows down the growth of bacteria and instead promotes the synthesis and accumulation of secondary metabolites, especially antioxidant substances, thus achieving a more effective improvement in antioxidant activity.

[0095] Example 8: Preparation of a Quinoa Fermentation Product with Mineral Adjuvants

[0096] (1) Pretreatment: Select high-quality white quinoa grains. The pretreatment steps are the same as in Example 1.

[0097] (2) Substrate preparation: Mix the crushed quinoa with pure water at a weight ratio of 1:1 to adjust to a quinoa substrate with a water content of 48%. Add 0.6% glucose as a carbon source, and simultaneously add the following mineral adjuvants:

[0098] Manganese sulfate (MnSO4): 30 mg / kg of substrate;

[0099] Magnesium sulfate (MgSO4): 150 mg / kg of substrate;

[0100] Zinc sulfate (ZnSO4): 15 mg / kg of substrate;

[0101] Sodium selenite (Na2SeO3): 1 mg / kg of substrate;

[0102] (3) Inoculation: Use Lactobacillus plantarum as the fermentation strain and inoculate it into the quinoa substrate at 2% of the weight of the quinoa substrate.

[0103] (4) Fermentation: Ferment at a constant temperature of 33 °C for 21 hours, stirring every 7 hours during the period. When fermentation ends, the pH value of the substrate drops to 4.2.

[0104] (5) The drying treatment is the same as in Example 1.

[0105] The DPPH free radical scavenging rate of the quinoa fermentation product with mineral adjuvants prepared in this example is 43.7% higher than that of unfermented quinoa and 11.2% higher than that under the same fermentation conditions (Example 1) without mineral adjuvants. Among the added mineral adjuvants, manganese and magnesium are important cofactors for various antioxidant enzymes, which can activate antioxidant enzyme systems such as superoxide dismutase (SOD) and catalase (CAT) in lactic acid bacteria; zinc is involved in the synthesis of various antioxidant enzymes and enzymes related to polyphenol metabolism; while selenium is an essential element of glutathione peroxidase (GSH-Px) and directly participates in the scavenging of free radicals. The synergistic effect of these minerals significantly enhances the synthesis and accumulation of antioxidant substances during the fermentation process, thereby improving the antioxidant activity of the final product.

[0106] Example 9: Preparation of a Quinoa Fermentation Product with a Composite Carbon Source

[0107] (1) Pretreatment: Select high-quality quinoa grains. The pretreatment steps are the same as in Example 1.

[0108] (2) Substrate preparation: Mix the ground quinoa with pure water at a weight ratio of 1:1, and adjust it to a quinoa substrate with a water content of 47%. Add a composite carbon source:

[0109] Glucose: 0.3%;

[0110] Fructose: 0.2%;

[0111] Sucrose: 0.2%

[0112] Maltodextrin: 0.3%;

[0113] The total addition amount is 1% of the weight of the quinoa substrate.

[0114] (3) Inoculation: Use a mixed culture of Lactobacillus plantarum, Lactobacillus reuteri, and Lactobacillus rhamnosus (ratio 1:1:1) as the fermentation strain, and inoculate it into the quinoa substrate at 3% of the weight of the quinoa substrate.

[0115] (4) Fermentation: Ferment at a constant temperature of 35°C for the initial 6 hours, then reduce the temperature to 32°C and continue fermenting for 16 hours. The total fermentation time is 22 hours. At the end of fermentation, the pH value of the substrate drops to 3.9.

[0116] (5) The drying treatment is the same as that in Example 1.

[0117] The DPPH free radical scavenging rate of the composite carbon source quinoa fermentation product prepared in this example is 45.3% higher than that of unfermented quinoa and 5.1% higher than that under the same fermentation conditions with a single carbon source (Example 2). The composite carbon source can meet the different preferences of different lactic acid bacteria strains for carbon sources and promote the synergistic growth of multiple strains; at the same time, the different metabolic pathways of different sugars will also affect the intracellular redox state and the synthesis of secondary metabolites, thereby affecting the production of antioxidant substances. In addition, as a complex carbohydrate, maltodextrin can slowly degrade and release glucose, maintain the carbon source supply in the later stage of fermentation, extend the active period of lactic acid bacteria, and is conducive to the continuous synthesis and accumulation of antioxidant substances.

[0118] Example 10: Preparation of a quinoa fermentation product with ultrafine grinding pretreatment

[0119] (1) Pretreatment: Select high-quality quinoa grains, wash them 3 times with warm water at 35°C to remove saponins, soak them for 16 hours, and then use ultrafine grinding technology to grind the quinoa grains to an average particle size not exceeding 0.2 mm.

[0120] (2) Substrate preparation: Mix the ultrafinely ground quinoa with pure water at a weight ratio of 1:1.1, and adjust it to a quinoa substrate with a water content of 53%. Add 0.8% glucose as the carbon source.

[0121] (3) Inoculation: Use a mixed culture of Lactobacillus plantarum and Lactobacillus fermentum (ratio 1:1) as the fermentation strain, and inoculate it into the quinoa substrate at 5% of the weight of the quinoa substrate. The concentration of the bacterial liquid during inoculation is 1×10 10 CFU / g.

[0122] (4) Fermentation: Adopt the temperature gradient fermentation process of Example 7. The total fermentation time is 24 hours, and the pH value of the substrate drops to 3.8 at the end of fermentation.

[0123] (5) Drying treatment: First, dry at 70°C for 30 minutes, and then dry at 55°C for 4 hours until the water content of the product drops below 6%.

[0124] The DPPH free radical scavenging rate of the ultrafine comminution pretreated quinoa fermentation product prepared in this example is 55.4% higher than that of unfermented quinoa, and 8.6% higher than that under the same fermentation conditions (Example 7) with conventional comminution pretreatment. The ultrafine comminution technology can significantly increase the specific surface area of quinoa particles, improve the permeability of water and microorganisms to the quinoa cell structure, and at the same time destroy more cell wall structures, release more cell contents, providing a more sufficient substrate contact surface and richer nutrients for microbial fermentation. In addition, the mechanical energy generated during ultrafine comminution also causes structural changes in some polyphenolic compounds, further improving their biological activity. These factors work together to significantly enhance the antioxidant activity of the final product.

[0125] Comparative Example 1: Unfermented quinoa product

[0126] Select high-quality white quinoa grains, wash them 3 times with warm water at 35°C for 10 minutes each time to remove saponins. Directly dry the washed quinoa grains until the water content is below 10%, and then crush and sieve them to obtain unfermented quinoa powder.

[0127] The unfermented quinoa powder prepared in this comparative example is used as the reference control sample for each example of the present invention. Its DPPH free radical scavenging rate, total phenol content, ABTS free radical scavenging ability, and ferric reducing antioxidant power (FRAP value) are all set as the reference values (100%).

[0128] Comparative Example 2: Quinoa product with simple soaking treatment

[0129] Select high-quality white quinoa grains, wash them 3 times with warm water at 35°C for 10 minutes each time to remove saponins. Soak the washed quinoa grains at room temperature (25°C) for 24 hours, and then directly dry them until the water content is below 10%, crush and sieve them to obtain soaked quinoa powder.

[0130] The DPPH free radical scavenging rate of the quinoa powder prepared by this comparative example after soaking treatment increased by 8.3% compared with untreated quinoa (Comparative Example 1), and the total phenol content increased by 5.7%. This indicates that simple soaking treatment can dissolve some water-soluble antioxidant substances, but the improvement effect is limited, far lower than the microbial fermentation treatment method of the present invention.

[0131] Comparative Example 3: Quinoa product treated with enzymes alone

[0132] Select high-quality white quinoa grains, and the pretreatment steps are the same as those in Example 1. Mix the ground quinoa with pure water at a weight ratio of 1:1 to adjust to a quinoa matrix with a water content of 50%, add β-glucosidase and xylanase (the total addition amount is 0.3% of the weight of the quinoa matrix), and carry out enzymatic hydrolysis treatment at 45 °C for 6 hours, but do not carry out microbial fermentation. After enzymatic hydrolysis, directly carry out drying treatment to obtain quinoa powder treated with enzymes alone.

[0133] The DPPH free radical scavenging rate of the quinoa powder treated with enzymes alone prepared by this comparative example increased by 20.4% compared with untreated quinoa (Comparative Example 1), and was 39.8% lower than that of the fermentation treatment (Example 5). This indicates that enzymatic treatment can release some bound antioxidant substances, but its effect is significantly lower than the combined process of enzymatic treatment combined with microbial fermentation. Without microbial fermentation, the further transformation of antioxidant substances and the synthesis of metabolites cannot be achieved, thus limiting the improvement of antioxidant activity.

[0134] Comparative Example 4: Quinoa product with short-term fermentation

[0135] The pretreatment, matrix preparation and inoculation steps of this comparative example are the same as those in Example 2, except for the fermentation time:

[0136] Ferment only for 6 hours at a constant temperature of 35 °C, and then directly carry out drying treatment to obtain quinoa powder with short-term fermentation.

[0137] The DPPH free radical scavenging rate of the quinoa powder with short-term fermentation prepared by this comparative example increased by 15.6% compared with untreated quinoa (Comparative Example 1), and was 24.6% lower than that of the complete fermentation time (Example 2, 24 hours). This indicates that although short-term fermentation can initiate microbial metabolism, the fermentation time is insufficient, the number of microorganisms and the accumulation of metabolites are limited, and the antioxidant substances in quinoa cannot be fully released and transformed, resulting in limited improvement of antioxidant activity.

[0138] Comparative Example 5: Quinoa product fermented with a single strain

[0139] The pretreatment and matrix preparation steps of this comparative example are the same as those in Example 9, except that only a single strain is used:

[0140] Only Lactobacillus plantarum was used as the fermentation strain and inoculated into the quinoa substrate at 3% of the weight of the quinoa substrate, and the remaining fermentation conditions were the same as those in Example 9.

[0141] The DPPH free radical scavenging rate of the single-strain fermented quinoa powder prepared in this comparative example was 33.1% higher than that of the untreated quinoa (Comparative Example 1) and 12.2% lower than that of the multi-strain fermentation (Example 9). This indicates that although single-strain fermentation can also improve the antioxidant activity of quinoa, its effect is significantly lower than that of multi-strain co-fermentation. In multi-strain fermentation, the metabolic characteristics and enzyme system compositions of different strains are complementary, which can decompose the complex structure of quinoa more comprehensively, release more types of antioxidant substances, and produce richer metabolites, thus maximizing the improvement of antioxidant activity.

[0142] In order to objectively evaluate the antioxidant activity of the quinoa products prepared in each example and comparative example, the following standardized test methods were adopted in the present invention:

[0143] Determination method of DPPH free radical scavenging rate:

[0144] The determination of DPPH free radical scavenging rate was carried out by the Brand-Williams method, and the specific steps were as follows:

[0145] 1. Sample preparation: Take 1.0 g of the quinoa fermentation sample and add it to 10 mL of 70% ethanol, ultrasonically extract for 30 minutes, centrifuge at 4000 rpm for 10 minutes, and take the supernatant as the test solution.

[0146] 2. Standard reaction: Take 100 μL of the sample extract at different concentrations, add 3.9 mL of DPPH methanol solution with a concentration of 0.1 mmol / L, mix well and react in the dark for 30 minutes.

[0147] 3. Determination: Use a UV-1800 ultraviolet-visible spectrophotometer to measure the absorbance at a wavelength of 517 nm, denoted as A sample.

[0148] 4. Control: Replace the sample extract with 70% ethanol, operate according to the same method, measure the absorbance, and denote it as A control.

[0149] 5. Calculation: DPPH free radical scavenging rate (%) = (1 - A sample / A control) × 100%

[0150] Determination method of total phenol content:

[0151] The total phenol content was determined by the Folin-Ciocalteu method, using gallic acid (GA) as the standard:

[0152] 1. Sample extraction: Take 1.0 g of the quinoa fermentation sample, add it to 25 mL of 70% ethanol, extract ultrasonically for 20 minutes, centrifuge at 4500 rpm for 15 minutes, and take the supernatant and dilute it to an appropriate concentration.

[0153] 2. Color reaction: Take 1.0 mL of the sample extract, add 5.0 mL of the Folin-Ciocalteu reagent diluted tenfold, mix well and let stand for 3 - 5 minutes, then add 4.0 mL of 7.5% Na2CO3 solution, and react in the dark for 60 minutes.

[0154] 3. Determination: Measure the absorbance at a wavelength of 765 nm.

[0155] 4. Standard curve: Using gallic acid as the standard, prepare a standard curve of 0 - 100 μg / mL, calculate the total phenolic content of the sample, and express the results as mg GAE / 100 g dry weight.

[0156] Determination method for ABTS radical scavenging ability:

[0157] The ABTS radical scavenging ability was determined by the Trolox equivalent antioxidant capacity (TEAC) method:

[0158] 1. Preparation of ABTS radical solution: Mix ABTS and potassium persulfate at a concentration ratio of 7.4 mmol / L:2.6 mmol / L, react in the dark at room temperature for 12 - 16 hours, and dilute with PBS buffer (pH 7.4) to an absorbance of 0.70 ± 0.02 at 734 nm.

[0159] 2. Sample determination: Take 20 μL of the sample extract, add it to 2.0 mL of the ABTS radical solution, mix well and react in the dark for 6 minutes, and measure the absorbance at a wavelength of 734 nm.

[0160] 3. Standard curve: Using Trolox as the standard, prepare a standard curve of 0 - 2000 μmol / L, calculate the Trolox equivalent antioxidant capacity of the sample, and express the results as μmol TE / g dry weight.

[0161] Determination method for ferric reducing antioxidant power (FRAP value)

[0162] The FRAP determination was carried out using the method of Benzie and Strain, and the specific steps are as follows:

[0163] 1. Preparation of FRAP reagent: Mix 300 mmol / L acetate buffer (pH 3.6), 10 mmol / L TPTZ (2,4,6 - tris(2 - pyridyl)-s - triazine), and 20 mmol / L FeCl3 solution in a volume ratio of 10:1:1, and preheat at 37 °C for standby.

[0164] 2. Sample determination: Take 100 μL of the sample extract and add 3.0 mL of the FRAP reagent. After mixing, react at 37 °C for 30 minutes, and measure the absorbance at a wavelength of 593 nm.

[0165] 3. Standard curve: Using FeSO4 as the standard product, prepare a standard curve of 0 - 1000 μmol / L, calculate the FRAP value of the sample, and express the result in μmol Fe 2+ / g dry weight.

[0166] Based on the above method for determination, the test results of each example and comparative example are shown in Table 1:

[0167] Table 1: Determination results of the antioxidant activities of quinoa products in each example and comparative example

[0168]

[0169]

[0170] The test results clearly show that various fermentation treatment methods of the present invention significantly improve the antioxidant activity of quinoa products. Among them, Example 5 (quinoa fermented product added with enzyme preparation) is the most prominent, with the DPPH free radical scavenging rate reaching 44.5%, the total phenol content reaching 278.1 mg GAE / 100 g, the ABTS free radical scavenging ability reaching 66.0 μmol TE / g, and the FRAP value reaching 134.8 μmol Fe 2+ / g, which are respectively 16.7 percentage points, 92.8 mg GAE / 100 g, 20.4 μmol TE / g, and 66.1 μmol Fe 2+ / g higher than those of unfermented quinoa (Comparative Example 1).

[0171] Through in-depth research, it is found that the synergistic effect of various factors during the fermentation process leads to a significant increase in the antioxidant activity of quinoa. The present invention has systematically analyzed these mechanisms, mainly including the following aspects:

[0172] Approximately 85% of the phenolic compounds in quinoa exist in a bound form, mainly connected to macromolecular structures such as cell wall polysaccharides, cellulose, and hemicellulose through ester bonds or glycosidic bonds. During the fermentation process, various enzymes produced by microorganisms, such as β-glucosidase, esterase, and hemicellulase, can specifically cut these linkage bonds and convert the bound phenolic compounds into free forms. Experiments have proved that the content of free phenolic compounds in quinoa after fermentation is increased by 3 - 5 times compared with that before fermentation, and free phenols have higher biological activity and bioavailability.

[0173] In addition, the microbial metabolic process also leads to the modification of the structure of phenolic compounds, such as methylation, hydroxylation, polymerization, etc. These modifications further enhance the antioxidant activity of phenolic compounds. For example, in Examples 4 and 5, the contents of specific phenolic compounds such as catechin, quercetin, and ferulic acid in fermented quinoa increased, and these compounds all have strong antioxidant capabilities.

[0174] There is a significant synergistic effect between the exogenous enzyme system produced during the microbial fermentation process and the endogenous enzyme system in quinoa. This is particularly evident in the germination-fermentation combined treatment (Example 3). During the germination process, endogenous enzymes in quinoa seeds such as amylase, protease, lipase, polyphenol oxidase, etc. are activated, initially changing the biochemical components of quinoa; subsequent microbial fermentation further catalyzes a series of biochemical reactions through the exogenous enzyme system, and the synergistic effect of the two significantly improves the release and conversion efficiency of antioxidant substances.

[0175] The synergistic mechanism between the microbial enzyme system and plant endogenous enzymes includes:

[0176] 1. Cascade catalysis: The reaction product of one enzyme becomes the substrate of another enzyme, forming a continuous catalytic chain

[0177] 2. Structural pretreatment: The endogenous enzyme partially decomposes the macromolecular structure, providing more accessible reaction sites for the microbial enzyme

[0178] 3. Complementary catalysis: Different enzyme systems have complementary selectivity for specific chemical bonds, and their combined action covers a wider range of substrates

[0179] During the fermentation process, the protease produced by the microorganism hydrolyzes quinoa proteins to produce a variety of small peptides. These bioactive peptides not only have higher bioavailability, but some peptides also have direct antioxidant activity. Analysis by liquid chromatography-mass spectrometry showed that a large number of small peptides with molecular weights in the range of 500 - 1500 Da were produced in Examples 4 and 5, and about 15% of the peptide segments had antioxidant activity.

[0180] These antioxidant peptides mainly act through the following mechanisms:

[0181] 1. Directly scavenging free radicals, such as hydroxyl radicals (·OH), superoxide anion radicals (O2 - ·), etc.;

[0182] 2. Chelating metal ions to prevent them from catalyzing the generation of free radicals;

[0183] 3. Inhibiting lipid peroxidation reactions;

[0184] 4. Acting as a hydrogen atom donor and participating in the free radical termination reaction;

[0185] It was experimentally observed that the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in fermented quinoa products were significantly increased. This is due to two reasons: one is that these antioxidant enzymes are produced by the microorganisms themselves; the other is that certain metabolites produced during the fermentation process act as signal molecules, activating the expression of endogenous antioxidant enzyme genes in quinoa.

[0186] Especially in Example 8 with the addition of mineral adjuvants, trace elements such as manganese, zinc, and selenium, as cofactors of antioxidant enzymes, significantly enhanced the enzyme activities. The measurement results showed that in Example 8, the SOD activity was 56.3% higher than that in Comparative Example 1, the CAT activity was 43.8% higher, and the GSH-Px activity was 72.5% higher. This increase in the enzyme system level provides additional antioxidant defense capabilities for quinoa products.

[0187] Microorganisms produce various metabolites during the fermentation process, such as organic acids (lactic acid, citric acid, etc.), vitamins (especially B vitamins), polyphenolic compounds, exogenous antioxidant enzymes, etc. These substances themselves have antioxidant activity and directly improve the antioxidant capacity of the products.

[0188] Particularly noteworthy is that in multi-stage fermentation (Example 4) and multi-strain fermentation (Example 9), a mutualistic symbiotic relationship is formed between different microorganisms, resulting in a synergistic metabolic effect. For example, the amylase and protease produced by Rhizopus fungi provide more available nutrients for subsequent lactic acid bacteria; while the lactic acid produced by lactic acid bacteria provides a suitable acidic environment for Rhizopus, inhibiting the growth of miscellaneous bacteria. This mutualistic relationship promotes the formation of more abundant metabolites and further improves the antioxidant activity.

[0189] Quinoa contains anti-nutritional factors such as phytic acid and saponins. These substances not only affect the sensory quality but also reduce the bioavailability of minerals. During the fermentation process, phytase produced by microorganisms can effectively degrade phytic acid, releasing chelated mineral ions such as iron, zinc, and calcium. These mineral ions, especially iron and zinc, as important cofactors of the antioxidant enzyme system, further enhance the antioxidant defense capabilities.

[0190] Through measurement, in Examples 4 and 5, the bioavailability of minerals such as iron, zinc, and manganese increased by 65.2%, 58.7%, and 71.4% respectively. These released minerals not only directly participate in antioxidant physiological processes but also activate the expression of antioxidant-related genes through metal response elements (MREs), forming a positive feedback loop.

[0191] The fermentation treatment method for improving the antioxidant properties of quinoa products provided by the present invention has broad industrial application prospects, mainly reflected in the following fields:

[0192] With the improvement of health awareness, consumers' demand for functional foods rich in antioxidants is increasing continuously. The fermented quinoa products of the present invention can be developed into various functional foods, such as:

[0193] 1. High-antioxidant breakfast cereals: Mix fermented quinoa with other grains to make ready-to-eat breakfast cereals, oat bars and other products, providing rich antioxidants for breakfast. Market research shows that the annual growth rate of high-functional breakfast foods reaches 8.5%, having huge market potential.

[0194] 2. Functional beverages: Using fermented quinoa as the base material, adding appropriate flavoring agents and sweeteners to develop antioxidant quinoa beverages. Adopting the low-temperature drying method of Example 6 can maximize the retention of antioxidant activity, providing high-quality raw materials for the functional beverage market.

[0195] 3. Sports nutrition foods: Fermented quinoa is rich in high-quality protein and antioxidants, suitable for developing nutritional supplements for sports recovery to help athletes relieve exercise-induced oxidative stress.

[0196] 4. Diets for special populations: Aiming at the nutritional needs of special populations such as the elderly and pregnant women, developing antioxidant-enhanced quinoa meal powder, nutrition bars and other products to provide convenient antioxidant nutrition supplements.

[0197] Antioxidant components have important application values in the cosmetics industry, which can protect the skin from free radical damage and delay skin aging. The fermented quinoa extract of the present invention can be used as a natural antioxidant raw material in various cosmetics:

[0198] 1. Anti-aging skin care products: Using the high-antioxidant fermented quinoa extract of Example 5 to develop anti-aging essences, creams and other products to resist oxidative stress caused by environmental pollution and ultraviolet rays.

[0199] 2. Sensitive skin care: The fermentation process not only improves antioxidant activity but also reduces irritating components such as saponins, suitable for developing sensitive skin care products.

[0200] 3. Scalp care products: The bioactive peptides and antioxidants in quinoa have a regulatory effect on the scalp environment, and antioxidant-enhanced shampoos, hair conditioners and other products can be developed.

[0201] Experiments show that the skin care formula added with 2% fermented quinoa extract has 35% higher antioxidant capacity than the formula added with the same amount of synthetic antioxidant (BHT), and has higher safety, meeting the needs of the natural cosmetics market.

[0202] Quinoa is a recognized plant with both edible and medicinal properties, and its fermented products have broad prospects in the health product market:

[0203] 1. Antioxidant dietary supplement: The fermented quinoa extract is made into dosage forms such as capsules and tablets, serving as a daily antioxidant dietary supplement to meet the health care needs of sub-healthy people.

[0204] 2. Immunomodulatory product: Antioxidants are closely related to immune function. Fermented quinoa products can be developed into health care products for immunomodulation to enhance the body's resistance.

[0205] 3. Metabolic health product: Aiming at the common metabolic problems faced by modern people, fermented quinoa health care products for regulating blood sugar and blood lipids are developed, and their antioxidant properties are used to improve metabolic health.

[0206] The industrial production of the present invention has good feasibility, which is mainly reflected in the following aspects:

[0207] 1. Stable raw material source: With the expansion of quinoa planting scale, the raw material supply is gradually stable, and the price tends to be reasonable, providing a basic guarantee for industrial production.

[0208] 2. Simple process operation: The fermentation treatment method of the present invention is simple to operate, does not require special equipment, and is easy to realize industrial production. The key parameters (temperature, time, pH value, etc.) during the fermentation process are easy to control, ensuring the stability of product quality.

[0209] 3. Adaptability to large-scale equipment: The fermentation process of the present invention can be carried out on existing fermentation equipment, such as solid-state fermentation tanks and liquid fermentation tanks, and the equipment investment cost is relatively low.

[0210] 4. Advantage of industrial chain integration: The present invention can be integrated with the existing quinoa processing industrial chain to achieve industrial upgrading and increase the added value of products. For example, quinoa processing enterprises can upgrade ordinary quinoa flour to highly antioxidant fermented quinoa flour by adding a fermentation process link, significantly increasing the product value.

[0211] 5. Analysis of production cost: Preliminary calculation shows that the cost of producing highly antioxidant fermented quinoa products by the method of the present invention increases by about 30 - 50%, while the product value can be increased by 100 - 200%, showing obvious economic benefits.

Claims

1. A fermentation treatment method for improving the antioxidant property of quinoa products, characterized in that, Comprising the following steps: (a) Mix quinoa grains or quinoa flour with water to prepare a quinoa matrix with a water content of 45 - 55%; (b) Inoculate the quinoa matrix with a microbial ferment, and the inoculation amount of the microbial ferment is 1 - 5% of the weight of the quinoa matrix; (c) Maintain fermentation at a temperature of 30 - 37 °C for a fermentation time of 18 - 24 hours until the pH value drops to 3.8 - 4.5; (d) Dry the fermented quinoa product to obtain a fermented quinoa product with a water content of less than 10%; Among them, the DPPH free radical scavenging ability of the fermented quinoa product is increased by at least 30% compared with unfermented quinoa.

2. The method according to claim 1, wherein The microbial ferment includes at least one lactic acid bacterium, and the initial inoculation concentration of the lactic acid bacterium is 1×10 8 -1×10 10 CFU / g.

3. The method according to claim 2, wherein The lactic acid bacteria are selected from at least one of Lactiplantibacillus plantarum, Lactobacillus reuteri, Lactobacillus fermentum, Lactobacillus rhamnosus, or a combination thereof.

4. The method according to claim 1, characterized in that, Before preparing the quinoa matrix in step (a), pretreatment of quinoa is also included, and the pretreatment includes the following steps: (i) Wash the quinoa grains with warm water to remove saponins until no foam is produced; (ii) Soak the washed quinoa grains for 12 - 24 hours; (iii) Grind the soaked quinoa grains to a particle size of 0.2 - 0.5 mm.

5. The method according to claim 4, characterized in that, The pretreatment also includes germinating the quinoa grains, and the germination conditions are: at 25 - 28 °C, germinate the quinoa grains under a relative humidity of 85 - 95% for 48 - 72 hours until the radicle length reaches 1 / 2 - 2 / 3 of the seed length.

6. The method according to claim 1, wherein The microbial ferment includes a mixed culture of Lactiplantibacillus plantarum and Lactobacillus fermentum, and the inoculation ratio of the two is 1:1, and fermentation step (c) includes: (i) Ferment at 37 °C for 12 hours; (ii) Lower the temperature to 32 °C and continue fermentation for 12 hours.

7. The method according to claim 1, characterized in that In step (a), the solid content of the quinoa matrix is 45 - 55% (w / w), and 0.5 - 1% of glucose is added as an initial carbon source during the preparation process, and 0.5 - 1% of glucose is added as an initial carbon source during the preparation process.

8. The method according to claim 1, characterized in that, The drying treatment in step (d) adopts the hot air drying method, and the drying process includes: (i) Dry at 70 °C for 30 minutes; (ii) Dry at 60 °C for 2 hours; (iii) Dry at 50 °C for 2 hours until the water content is less than 10%.

9. The method according to claim 1, wherein The method is a multi-stage fermentation process, including: (i) First, use Rhizopus oligosporus for solid-state fermentation at 30 °C for 48 hours; (ii) Subsequently, inoculate a mixed culture of lactic acid bacteria and continue fermentation at 37 °C for 24 hours; Among them, the inoculation amount of the Rhizopus oligosporus strain is 0.2 - 0.5% of the weight of the quinoa matrix.

10. The method according to claim 1, wherein The method further includes adding an enzyme preparation before fermentation. The enzyme preparation includes β-glucosidase and / or xylanase, and the addition amount is 0.1-0.5% of the weight of the quinoa matrix; the total phenolic content in the fermented quinoa product is increased by 40-50% compared with unfermented quinoa, the ABT S free radical scavenging ability is increased by 35-45%, and the ferric reducing antioxidant power (FRAP value) is increased by 80-100%.

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