Sour dough, food quality guarantee product, preparation method and application

Abstract

The invention provides sour dough, a food quality guarantee product, a preparation method and application, and particularly belongs to the technical field of food preservation. The preparation method of the sour dough comprises the following steps: mixing cereal powder with water to obtain cereal pulp; mixing the grain pulp with high-temperature-resistant alpha-amylase, liquefying and sterilizing to obtain sterile grain pulp; mixing the compound bacteria with the sterile grain slurry, and fermenting; the compound bacteria comprise lactic acid bacteria, saccharomycetes and propionibacterium; a degerming compound enzyme is supplemented in the fermentation process; the compound enzyme comprises ligninase, beta-glucosidase, phospholipase, ligninase, pectinase, phytase and aminopeptidase; sterilizing after fermentation, filtering and taking filtrate to obtain the sour dough. The prepared sour dough contains various organic acids, polypeptides and other substances, has an efficient inhibition effect on microorganisms, is antiseptic and antioxidant, is a safe and healthy natural antiseptic product, and can be used for food quality guarantee.

Description

Technical Field

[0001] The present invention belongs to the technical field of food preservation, and particularly relates to a sourdough, a food preservation product, a preparation method and an application thereof. Background Art

[0002] Consumers and national regulatory agencies have been paying increasing attention to food safety issues. Food additives derived from natural sources have also received more and more attention in the food preservation market, not only because of their natural and safe sources and wide applications, but also because in most domestic and foreign markets, consumers have a high acceptance of products with the attribute of "natural", believing that this is a safer and healthier choice. On the one hand, manufacturers need to meet consumers' demand for natural foods, and on the other hand, they need to extend the product shelf life without using chemical additives.

[0003] Taking the baking industry as an example, products such as bread, cakes, and mooncakes are rich in nutrients and have a high water content, providing a natural and excellent medium for the growth of microorganisms. During the long-term preservation process, they are prone to mold and the total number of colonies exceeding the standard, which has a great impact on the safety of baked products. In order to prevent product spoilage and deterioration during production, enterprises usually add preservatives to prevent the growth of microorganisms and extend the product shelf life. However, there is a problem of excessive use of preservatives. The current main anti-corrosion products in the baking industry are still chemically synthesized preservatives. Chemically synthesized preservatives are highly efficient, have a broad antibacterial spectrum, have the advantages of good effect, no peculiar smell, less addition, and low cost, and are widely used in baking enterprises. However, some chemically synthesized preservatives (such as sodium dehydroacetate) have toxicity problems. Preparing highly efficient, safe, and healthy natural anti-corrosion products through microbial fermentation technology has become an important direction for future development. Summary of the Invention

[0004] The purpose of the present invention is to provide a sourdough, a food preservation product, a preparation method and an application thereof. The sourdough obtained by the preparation method of the present invention contains various organic acids and polypeptides and other substances, which have a highly efficient inhibitory effect on microorganisms, have anti-corrosion and antioxidant effects, are safe and healthy natural anti-corrosion products, and can be used for food preservation.

[0005] The present invention provides a preparation method of a sourdough, comprising the following steps:

[0006] Mix cereal flour and water to obtain a cereal slurry; mix the cereal slurry with a thermotolerant α-amylase, perform liquefaction, and first sterilize to obtain a sterile cereal slurry;

[0007] Mix a composite bacterium with the sterile cereal slurry and perform fermentation; the composite bacterium includes lactic acid bacteria, yeast, and propionic acid bacteria; a sterilized composite enzyme is supplemented during the fermentation process; the composite enzyme includes ligninase, β-glucosidase, phospholipase, ligninase, pectinase, phytase, and aminopeptidase;

[0008] After fermentation, perform a second sterilization, filtration, collect the filtrate, concentrate, and dry to obtain the sourdough.

[0009] Preferably, the cereal flour includes one or more of rice flour, wheat flour, millet flour, soybean flour, corn flour, sorghum flour, proso millet flour, and panicled millet flour.

[0010] Preferably, the lactic acid bacteria include Lactococcus lactis subsp. lactis and / or Lactiplantibacillus plantarum; the propionic acid bacteria include Propionibacterium freudenreichii and / or Propionibacterium acidipropionici; the yeast includes Wickerhamomyces membranifaciens and / or Saccharomyces cerevisiae.

[0011] Preferably, based on the mass of the sterile cereal slurry, the addition amount of lactic acid bacteria is 0.5 - 1.5%, the addition amount of yeast is 0.2 - 2.0%, and the addition amount of the propionic acid bacteria is 0.8 - 3.0%; the viable count of the lactic acid bacteria > 1.5×10 9 CFU / g; the viable count of the yeast > 2×10 9 CFU / g; the viable count of the propionic acid bacteria > 1×10 9 CFU / g.

[0012] Preferably, the addition amount of ligninase is 1 - 10 ppm, the addition amount of β-glucosidase is 10 - 50 ppm, the addition amount of phospholipase is 1 - 20 ppm, the addition amount of xylanase is 1 - 15 ppm, the addition amount of pectinase is 1 - 20 ppm, the addition amount of phytase is 1 - 5 ppm, and the addition amount of aminopeptidase is 1 - 10 ppm.

[0013] Preferably, the fermentation temperature is 25 - 40 °C; the fermentation time is 90 - 200 h; the stirring rate during fermentation is 0 - 100 rpm.

[0014] Preferably, during the fermentation process, the pH value is controlled to be 4.0 - 8.0.

[0015] The present invention also provides the sourdough prepared by the preparation method described in the above technical solution.

[0016] The present invention also provides a food preservation product, including the sourdough prepared by the preparation method described in the above technical solution and auxiliary materials.

[0017] The present invention also provides the application of the sourdough prepared by the preparation method described in the above technical solution in food anti-corrosion and / or anti-oxidation.

[0018] The present invention provides a method for preparing sourdough. The method for preparing sourdough according to the present invention uses processed cereal flour from natural sources as the fermentation raw material. The fermentation raw material contains various elements and compounds required for the growth and metabolism of lactic acid bacteria, yeasts, and propionic acid bacteria, and there is no need to additionally supplement nutrient media. It has the advantages of wide sources and low price. At the same time, in this method, an enzyme preparation sterilized by filtration is added during the fermentation process to catalytically decompose cellulose, protein, and carbohydrates in the raw materials of the cereal, so that they serve as carbon sources, nitrogen sources, trace elements, etc. required for the fermentation of fermentation bacteria. Therefore, there is no need to additionally supplement carbon sources, nitrogen sources, trace elements, etc. during the fermentation culture process. It has the advantages of high efficiency, safety, energy conservation, environmental protection, and strong controllability, can make full use of the fermentation raw materials, shorten the production time, and is conducive to realizing large-scale industrial production. The sourdough of the present invention contains various organic acids and polypeptides and other substances, which have a good inhibitory effect on microorganisms, have anti-corrosion and antioxidant effects, and can be used for food preservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is the bacteriostatic effect diagram of measuring the total number of colonies by the optical density method provided by the present invention;

[0021] Figure 2 It is the pH value change diagram provided by the present invention;

[0022] Figure 3 It is the comparison diagram of the anti-mold effect in bread toast provided by the present invention;

[0023] Figure 4 It is the comparison diagram of the total number of colonies in bread toast provided by the present invention;

[0024] Figure 5 It is the comparison diagram of the application of the total number of colonies in cakes provided by the present invention;

[0025] Figure 6 It is the comparison diagram of the anti-mold effect in cakes provided by the present invention;

[0026] Figure 7 It is the result diagram of DPPH free radical scavenging and ORAC oxygen free radical absorption capacity in cakes provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention provides a method for preparing sourdough, including the following steps:

[0028] Mix cereal flour and water to obtain a cereal slurry; mix the cereal slurry with a heat-resistant α-amylase and perform liquefaction and the first sterilization to obtain a sterile cereal slurry;

[0029] Mix the composite bacteria with the sterile cereal slurry and perform fermentation; the composite bacteria include lactic acid bacteria, yeast, and propionic acid bacteria; a sterilized composite enzyme is added during the fermentation process; the composite enzyme includes ligninase, β-glucosidase, phospholipase, ligninase, pectinase, phytase, and aminopeptidase;

[0030] After fermentation, perform the second sterilization, filtration, collect the filtrate, concentrate, and dry to obtain a sourdough.

[0031] In the present invention, cereal flour and water are mixed to obtain a cereal slurry; the cereal slurry is mixed with a heat-resistant α-amylase and liquefied and the first sterilization is performed to obtain a sterile cereal slurry. In a specific embodiment, the cereal flour includes one or more of rice flour, wheat flour, millet flour, soybean flour, corn flour, sorghum flour, proso millet flour, and panicled millet flour. In a specific embodiment, the processed cereal flour is mixed with water for slurry preparation to obtain a cereal slurry. In a specific embodiment, the cereal flour is mixed with 5 to 20 times the mass of water, specifically 10 to 15 times. In a specific embodiment, after the cereal flour and water are mixed, the pH value is further adjusted. In a specific embodiment, the pH value is 5.0 to 7.0, and can be 6.0 to 7.0. The present invention realizes the preliminary liquefaction treatment of raw materials by adding a heat-resistant α-amylase. In a specific embodiment, the heat-resistant α-amylase is purchased from Anhui Greenway Biotech Co., Ltd. After the liquefaction treatment, the present invention stirs evenly, turns on the heating, and performs the first sterilization. In a specific embodiment, the temperature of the first sterilization is 110 to 130 °C. In a specific embodiment, the sterilization time is 10 to 60 min, and can be 20 to 40 min.

[0032] After obtaining the sterile cereal slurry, the present invention mixes the compound bacteria with the sterile cereal slurry and ferments them; the compound bacteria include lactic acid bacteria, yeast, and propionic acid bacteria; during the fermentation process, a sterilized compound enzyme is added; the compound enzyme includes ligninase, β-glucosidase, phospholipase, ligninase, pectinase, phytase, and aminopeptidase. In a specific embodiment, the fermentation temperature is 25-40°C, and can be 30-40°C; the fermentation time is 90-200 h, and can be 120-180 h; the stirring rate of the fermentation is 0-100 rpm, and can be 5-20 rpm. In a specific embodiment, during the fermentation process, the pH value is controlled to be 4.0-8.0, and can be 6.0-7.0. During the fermentation process of the present invention, according to the change of the pH value, an alkali solution with a mass percentage of 10-40% is added dropwise to maintain the stability of the pH value of the fermentation broth. In a specific embodiment, the solute of the alkali solution can be one or more of sodium carbonate, sodium hydroxide, calcium hydroxide, and potassium hydroxide. In a specific embodiment, the lactic acid bacteria include Lactococcus lactis subsp. lactis and / or Lactiplantibacillus plantarum; the propionic acid bacteria include Propionibacterium freudenreichii and / or Propionibacterium acidipropionici; the yeast includes Wickerhamomyces membranifaciens and / or Saccharomyces cerevisiae. In a specific embodiment, the bacterial strains are from the National Center for Bacterial Culture Collection, Propionibacterium freudenreichii CICC10019, Lactiplantibacillus plantarum CICC6009, Lactococcus lactis subsp. lactis CICC6242, Wickerhamomyces membranifaciens CICC33380, Saccharomyces cerevisiae CICC33070. Propionibacterium acidipropionici, DSM4900. In a specific embodiment, based on the mass of the sterile cereal slurry, the addition amount of lactic acid bacteria is 0.5-1.5%, the addition amount of yeast is 0.2-2.0%, and the addition amount of the propionic acid bacteria is 0.8-3.0%; the viable count of the lactic acid bacteria > 1.5×10 9 CFU / g; the viable count of the yeast > 2×10 9 CFU / g; the viable count of the propionic acid bacteria > 1×10 9CFU / g. During the fermentation process of the compound bacteria of the present invention, there will be a mutual promotion effect, and its products can promote the growth of other bacteria. The mixed bacteria fermentation process can effectively increase the yield of the target organic acid. At the same time, during the fermentation process, the compound bacteria, mainly yeast, will produce various enzyme preparations (such as amylase, lipase, cellulase, protease, phytase, etc.). These enzyme preparations will hydrolyze various components in the grains, such as starch, oil, protein, and cellulose, and the products will serve as the nutrients for the fermentation of the compound bacteria. The present invention does not add common enzyme preparations such as saccharifying enzyme, lipase, and protease. It avoids the complex process of first enzymatic hydrolysis, then inactivation, and finally fermentation in the common process, and at the same time can avoid the situation where the excessive sugar content in the initial fermentation broth affects the growth of microorganisms. The present invention relies on the compound enzyme to produce various enzymes during the fermentation process to achieve the process of enzymatic hydrolysis while fermenting, which can maintain an appropriate concentration of sugar in the fermentation broth and is more conducive to fermentation. At the same time, during the entire fermentation process, no additional nutrients need to be supplemented, shortening the operation process of the process (supplementing the fermentation broth operation, enzymatic hydrolysis, and enzyme inactivation operation), and improving the utilization rate of raw materials. In a specific embodiment, the compound enzyme is configured into an aqueous solution and added to the fermentation broth after being filtered and sterilized by a microfiltration membrane. In a specific embodiment, based on the total amount of the grain raw materials, the addition amount of ligninase is 1-10 ppm, the addition amount of β-glucosidase is 10-50 ppm, the addition amount of phospholipase is 1-20 ppm, the addition amount of xylanase is 1-15 ppm, the addition amount of pectinase is 1-20 ppm, the addition amount of phytase is 1-5 ppm, and the addition amount of aminopeptidase is 1-10 ppm. Grains are rich in nutrients. In addition to containing a large amount of protein, fat, and carbohydrates, they also contain a small amount of components such as lignin, phospholipids, phytic acid, protein, cellulose, and colloid. The compound enzyme of the present invention can make full use of each component in the grains. During the fermentation process, the present invention does not add enzyme preparations such as amylase, lipase, and protease because the present invention uses compound bacteria for fermentation and produces amylase, lipase, protease and other enzyme preparations during the fermentation process to decompose the protein, fat, and carbohydrates in the raw materials, and no additional supplementation is required. The addition amount of each enzyme is determined by comprehensively considering the amount of each trace component in the raw materials during fermentation and the utilization rate of the raw materials. An excessive addition amount will result in too high a fermentation cost, and a low addition amount will cause insufficient utilization of the raw materials. The enzymes of the present invention are all purchased from Anhui Greenway Biotechnology Co., Ltd.

[0033] After fermentation, the present invention performs a second sterilization, filtration, collection of the filtrate, concentration, and drying to obtain a sourdough. The fermentation ends when the sugar content drops below 0.1%, the pH no longer changes during continuous fermentation, and the total organic acid content reaches 50 g / L or more. In a specific embodiment, the temperature of the second sterilization is 80 - 130 °C, and it can be 100 - 121 °C. In a specific embodiment, the time of the second sterilization is 5 - 120 min, and it can be 20 - 50 min. The sourdough of the present invention can be in liquid, solid, or powder form. In a specific embodiment, the concentration includes vacuum distillation concentration. In a specific embodiment, a carrier is added during the concentration. In a specific embodiment, the addition amount of the carrier is 20 - 50% (by mass percentage based on the finished product). In a specific embodiment, the carrier can be starch or dextrin. In a specific embodiment, the drying includes spray drying.

[0034] The preparation method of the present invention adds a complex enzyme, and enzymatic hydrolysis and fermentation are carried out simultaneously. While enzymatic hydrolysis provides nutrients such as carbon sources and nitrogen sources, fermentation consumes them. That is, the nutrients required by microorganisms during the fermentation process are provided by the enzymatic hydrolysis of the complex enzyme, and microorganisms can fully utilize all the nutrients in the cereal raw materials and those produced by enzymatic hydrolysis, including components such as carbon sources, nitrogen sources, and inorganic salts. During the fermentation process of the present invention, there is no need to additionally supplement carbon sources, nitrogen sources, trace elements, etc. At the same time, the present invention can avoid the situation where the initial sugar concentration in the raw materials is too high, causing the microorganisms to grow wildly without producing effective products, which affects the microbial fermentation. The enzymatic hydrolysis process of the present invention proceeds slowly, and the release of the substrate can be controlled, thereby achieving the controllability of each nutrient component in the fermentation tank, controlling the growth rate of microorganisms, and guiding the microbial metabolism of organic acid products. The present invention uses a determined strain for fermentation, and the complex enzyme has been microfiltrated to remove miscellaneous bacteria. Finally, the target fermentation product can be stably obtained, avoiding the situation where the fermentation system and fermentation product get out of control due to the introduction of miscellaneous bacteria, or the fermentation product becomes toxic and harmful due to the introduction of pathogenic bacteria.

[0035] In addition, generally during the fermentation process, enzyme preparations such as amylase and glucoamylase need to be added to decompose starch to produce monosaccharides as the carbon source for microbial fermentation. However, the fermenting bacteria will metabolize and decompose the enzymes for starch, and these enzymes do not need to be added in the present invention. The composite enzyme added in the present invention can mainly make full use of other components in the raw materials, and after enzymatic hydrolysis, it can be used for microbial fermentation. Specifically, α-amylase is added in the present invention for liquefaction, and it is not necessary to completely hydrolyze starch, which can avoid the excessive sugar concentration in the initial fermentation broth from affecting the growth of microorganisms. In the subsequent fermentation process of the present invention, hydrolysis continues during fermentation to keep the sugar concentration from affecting microbial fermentation. The composite enzyme (ligninase, β-glucosidase, phospholipase, xylanase, pectinase, phytase, aminopeptidase) added during the fermentation process can make full use of other trace components of the raw materials. The present invention uses composite bacteria for fermentation, which can produce amylase, lipase, cellulase, and protease. These enzymes will be spontaneously produced by microorganisms during the fermentation process and decompose raw materials such as starch, fat, protein, and cellulose in grains to provide nutrients for microorganisms. There is no need to additionally add these enzyme preparations.

[0036] The present invention also provides a sourdough prepared by the preparation method described in the above technical solution. The main components of the sourdough of the present invention are organic acid salts (such as lactic acid, acetic acid, propionic acid, succinic acid, etc.), as well as a small amount of components such as polypeptides, polysaccharides, and amino acids. The raw material of the sourdough is grains, and various flavor substances can be produced during the fermentation process, which will be more compatible with grain processing products and endow the products with unique fermentation flavors and textures.

[0037] The present invention also provides a food preservation product, including the sourdough prepared by the preparation method described in the above technical solution and auxiliary materials. The product of the present invention has good antibacterial and antioxidant effects, so the shelf life can be extended. In a specific embodiment, the food includes baked foods, rice products, or flour products.

[0038] The present invention also provides the application of the sourdough prepared by the preparation method described in the above technical solution in food preservation and / or antioxidant.

[0039] In order to further illustrate the present invention, the following will describe in detail a sourdough, a food preservation product, a preparation method, and an application provided by the present invention with reference to the drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1

[0041] Add water with a mass 10 times that of rice flour, adjust the pH value of the slurry to 6.5, add thermotolerant α-amylase (purchased from Anhui Greenway Biotechnology Co., Ltd.), and the addition amount is 10 u / g of raw material. After stirring evenly, directly start heating for sterilization treatment, the sterilization temperature is 121 °C, and the sterilization time is 30 min.

[0042] The addition amount of Lactococcus lactis subsp. lactis CICC6242 is 1.0%, the addition amount of Propionibacterium acidipropionici DSM 4900 is 2.5%, and the addition amount of Saccharomyces cerevisiae CICC33070 is 0.8%, based on the mass of the grain slurry.

[0043] The viable count of Lactococcus lactis subsp. lactis is (1.5 - 2.0)×10 9 CFU / g; the viable count of Saccharomyces cerevisiae > (2.0 - 2.5)×10 9 CFU / g; the viable count of Propionibacterium acidipropionici is (2.5 - 3.0)×10 9 CFU / g;

[0044] The temperature of fermentation culture is 30°C, the stirring rate is 10 rpm, and the fermentation time is 120 h. Add 10% calcium hydroxide solution according to the change of the pH value of the fermentation broth, and control the pH value of the fermentation broth between 6.5 - 7.0;

[0045] Prepare the complex enzyme (ligninase, β-glucosidase, phospholipase, xylanase, pectinase, phytase, aminopeptidase) into an aqueous solution with a mass percentage content of 5%, and filter and sterilize it through a microfiltration membrane (the filter membrane is sterilized with steam at 121°C, and after the enzyme filtration is completed, the filter membrane is rinsed with sterile water, and the filtrate is added to the storage tank). During the fermentation process, add the complex enzyme aqueous solution according to the fermentation situation, and control the amount added to the fermentation broth through the valve flow rate.

[0046] The addition amount of ligninase is 5 ppm, the addition amount of β-glucosidase is 30 ppm, the addition amount of phospholipase is 10 ppm, the addition amount of xylanase is 5 ppm, the addition amount of pectinase is 10 ppm, the addition amount of phytase is 2 ppm, and the addition amount of aminopeptidase is 3 ppm; the addition amount of the enzyme is based on the total amount of rice flour.

[0047] When the sugar content drops below 0.1% and the pH value of the continued fermentation no longer changes and the total organic acid content reaches more than 50 g / L, the fermentation ends. After the fermentation ends, the sterilization temperature of the fermentation broth is 100°C and the time is 50 min. After sterilization, filter to remove the bacterial residue, carry out vacuum distillation concentration, add 30% dextrin carrier (based on the finished product), mix evenly and then spray dry to obtain the finished product.

[0048] The obtained sourdough mainly contains organic acids (calcium lactate, calcium acetate, calcium propionate and calcium succinate), as well as a small amount of polypeptides, amino acids and polysaccharide substances. Among them, the calcium lactate content is 15 - 25%, the calcium propionate content is 25 - 30%, the calcium acetate is 5 - 15%, the calcium succinate content is 2 - 4%, the dextrin is 30%, the moisture content is less than 5%, and the total of the remaining trace components is less than 5%. This product has good anti-corrosion, anti-mildew and antioxidant effects, and can be applied to products such as bakery products and rice and flour products, greatly extending the shelf life and improving the food safety.

[0049] Example 2

[0050] Add water with a mass 15 times that of wheat flour and adjust the pH value of the slurry to 6.5. Add thermotolerant α - amylase with an addition amount of 10 u / g of raw materials. After stirring evenly, directly start heating for sterilization treatment, with a sterilization temperature of 120 °C and a sterilization time of 35 min.

[0051] The addition amount of Lactiplantibacillus plantarum CICC6009 is 2.0%, the addition amount of Propionibacterium freudenreichii CICC10019 is 1.5%, and the addition amount of Pichia membranifaciens CICC33380 is 1.0%, based on the mass of the cereal slurry.

[0052] The viable count of Lactiplantibacillus plantarum is (1.5 - 3.0)×10 9 CFU / g; the viable count of Pichia membranifaciens is (3 - 5)×10 9 CFU / g; the viable count of Propionibacterium freudenreichii is (1 - 1.5)×10 9 CFU / g;

[0053] The temperature for fermentation culture is 28 °C, the stirring rate is 10 rpm, and the fermentation time is 140 h. Add 10% potassium hydroxide solution according to the change of the pH value of the fermentation broth to control the pH value of the fermentation broth between 6.5 - 7.0;

[0054] Prepare a 5% aqueous solution by mass of a complex enzyme (ligninase, β - glucosidase, phospholipase, xylanase, pectinase, phytase, aminopeptidase) and filter and sterilize it through a microfiltration membrane (prepared in the same way as in Example 1). During the fermentation process, add the aqueous solution of the complex enzyme according to the fermentation situation, and control the amount added to the fermentation broth through the valve flow rate.

[0055] The addition amount of ligninase is 5 ppm, the addition amount of β - glucosidase is 25 ppm, the addition amount of phospholipase is 20 ppm, the addition amount of xylanase is 5 ppm, the addition amount of pectinase is 5 ppm, the addition amount of phytase is 5 ppm, and the addition amount of aminopeptidase is 8 ppm; the addition amount of the enzyme is based on the total amount of wheat flour.

[0056] When the sugar content drops below 0.1%, and the pH value no longer changes during continuous fermentation and the total organic acid content reaches 50 g / L or more, the fermentation ends. After fermentation ends, the sterilization temperature of the fermentation broth is 120 °C and the time is 20 min. After sterilization, filter to remove bacterial residues, residual cellulose, etc., carry out vacuum distillation and concentration, add 30% wheat starch carrier (based on the finished product), mix evenly and then spray - dry to obtain the finished product.

[0057] The obtained sourdough mainly consists of organic acids (potassium lactate, potassium acetate, potassium propionate, and potassium succinate), as well as a small amount of polypeptides, amino acids, and polysaccharides. Among them, the potassium lactate content is 20 - 30%, the potassium propionate content is 13 - 18%, the potassium acetate is 15 - 25%, the potassium succinate is 1 - 3%, the wheat starch is 30%, the moisture content is less than 5%, and the total of the remaining trace components is less than 5%. This product has good anti-corrosion, anti-mildew, and antioxidant effects, and can be applied to products such as baked goods and flour and rice products, greatly extending the shelf life and improving the food safety.

[0058] Example 3

[0059] The antibacterial effects of the sourdough (sourdough 1 prepared in Example 1 and sourdough 2 prepared in Example 2) were compared using the optical density method, and the antibacterial effect on the complex bacteria (the complex bacteria were obtained from newly purchased fresh pork tenderloin. After chopping, 25 g was added to 225 g of sterile physiological saline and homogenized evenly with a beating homogenizer to obtain the complex bacteria) was measured: the initial total colony count of the nutrient broth was 1.5×10 5 CFU / mL, and the culture temperature was 36°C;

[0060] The comparison operation of the optical density method is as follows:

[0061] 5% tap water was added to the sterilized NB medium and cultured in a constant temperature shaking water bath at 36°C for 6 - 8 h to make the colony concentration reach 10 7 ~10 8 CFU / g. Then it was added to the sterilized NB medium and the addition amount was adjusted to make the colony concentration reach 10 5 ~10 6 CFU / g. After mixing evenly, it was divided into three groups on average. The first group was added with sourdough 1, the second group was added with sourdough 2, and the third group was used as the blank group without addition. It was cultured in a constant temperature shaking water bath at 36°C, and samples were taken regularly to detect the absorbance.

[0062] Figure 1 is the antibacterial effect diagram of measuring the total colony count by the optical density method, Figure 2 is the pH value change diagram. Figure 1 and Figure 2 From the comparison data, it can be seen that both sourdough 1 and sourdough 2 have good inhibitory effects on bacteria, especially on acid-producing bacteria, and maintain the pH value stability of the system.

[0063] Example 4

[0064] Application experiment in bread:

[0065] Raw material weighing (high-gluten flour, 45% ice water, 14% granulated sugar, 7% syrup, 15% margarine, 2% milk powder, 1.2% dry yeast, 1% salt, 0.1% bread improver (LV Wei Kang compound enzyme preparation emulsifier LBM-MB802); in experimental group 1, sourdough 1 was added, in experimental group 2, sourdough 2 was added, and experimental group 3 was used as the blank group without addition. The addition ratio of each raw material is based on the weight of the flour), put into the mixing tank for stirring (using the method of adding oil later), take out the dough after it is whipped in place, relax for 10 min, divide the dough into 420 g per piece, proof for the second time for 5 min, shape and put into the mold or on the tray, proof under the conditions of 38 °C and RH 85%, put into the oven after proofing in place, bake at 192 °C / 212 °C for 43 min for top and bottom heat, cool the bread, slice, and seal the package. Regularly count the number of moldy bread and detect the total number of colonies.)

[0066] Figure 3 It is a comparison chart of the anti-mold effect in bread toast, Figure 4 It is a comparison chart of the total number of colonies in bread toast. According to Figure 3 and Figure 4 it can be seen that when 4 g / kg (calculated based on the total amount of the dough) of sourdough 1 and sourdough 2 are added, they both have good antibacterial and anti-mold effects on the bread, and the anti-mold effect of sourdough 1 is better than that of sourdough 2.)

[0067] Example 5

[0068] Application experiment in cakes:

[0069] The cake production process is as follows:

[0070] Component A (400 g whole eggs, 200 g fine sugar, 2 g compound acidity regulator (0.8 g citric acid, 1.2 g δ-glucono-lactone), 3 g salt; in experimental group 1, sourdough 1 was added, in experimental group 2, sourdough 2 was added, and experimental group 3 was used as the blank group without addition (the addition amount is based on the total amount of the finished product), stir and mix evenly at low speed, add Component B (250 g low-gluten flour, 25 g cake improver (LV Wei Kang compound enzyme preparation emulsifier LBM-CHM0908), sifted) and stir and mix evenly at low speed, add Component C (40 g sorbitol, 15 g glycerol, 40 g SP) and stir and mix evenly at low speed, whip at high speed, add Component D (100 g soybean oil) and stir and mix evenly at low speed, pour into the baking tray, bake at 190 °C / 170 °C for 26 min for top and bottom heat. After baking, cool, seal the package, store at 30 °C, regularly observe the number of moldy samples, and detect various indicators.)

[0071] Figure 5 It is a comparison chart of the total number of colonies in the application in cakes, Figure 6 It is a comparison chart of the anti-mold effect in the application in cakes, Figure 7 It is a result chart of the DPPH free radical scavenging and ORAC oxygen radical absorption capacity in cakes. According toFigures 5 to 7 The results show that when 5 g / kg (calculated based on the total amount of the cake) of sourdough 1 and sourdough 2 are added, they have good antibacterial and mold-proof effects on the cake. Among them, the mold-proof effect of sourdough 1 is better than that of sourdough 2; the antibacterial effect of sourdough 2 is slightly better than that of sourdough 1. At the same time, sourdough has good antioxidant effects, and its ability to scavenge DPPH free radicals and absorb ORAC oxygen free radicals in the cake is far better than that of the blank group, which can greatly reduce the oxidative rancidity of the cake and improve the food safety and appearance.

[0072] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing sourdough, characterized in that: The following steps are involved: Mixing grain powder and water to obtain grain slurry; mixing the grain slurry with a thermostable α-amylase, liquefying, and first sterilizing to obtain a sterile grain slurry; The composite bacteria are mixed with sterile grain slurry for fermentation; the composite bacteria include lactic acid bacteria, yeast and propionibacterium; during the fermentation process, a sterilizing composite enzyme is added; the composite enzyme includes ligninase, β-glucosidase, phospholipase, ligninase, pectinase, phytase and aminopeptidase; After fermentation, a second sterilization is carried out, and the filtrate is filtered, collected, concentrated, and dried to obtain sour dough.

2. The preparation method according to claim 1, characterized in that: The cereal flour includes one or more of rice flour, wheat flour, millet flour, soybean flour, corn flour, sorghum flour, millet flour and millet flour.

3. The preparation method according to claim 1, characterized in that: The lactic acid bacteria include Lactococcus lactis subsp. lactis and / or Lactobacillus plantarum; the propionibacterium includes Propionibacterium freudenreichii and / or Propionibacterium acidipropionici; and the yeast includes Pichia pastoris and / or Saccharomyces cerevisiae.

4. The preparation method according to claim 1 or 3, characterized in that: Based on the mass of the sterile grain slurry, the addition amount of lactic acid bacteria is 0.5-1.5%, the addition amount of yeast is 0.2-2.0%, and the addition amount of propionibacterium is 0.8-3.0%; the viable count of the lactic acid bacteria is greater than 1.5×10 9 CFU / g; the number of viable yeast cells> 2×10 9 CFU / g; the number of viable Propionibacterium> 1×10 9 CFU / g.

5. The preparation method according to claim 1, characterized in that: The addition amount of ligninase is 1 to 10 ppm, the addition amount of β-glucosidase is 10 to 50 ppm, the addition amount of phospholipase is 1 to 20 ppm, the addition amount of xylanase is 1 to 15 ppm, the addition amount of pectinase is 1 to 20 ppm, the addition amount of phytase is 1 to 5 ppm, and the addition amount of aminopeptidase is 1 to 10 ppm.

6. The preparation method according to claim 1, characterized in that: The fermentation temperature is 25-40° C.; the fermentation time is 90-200 hours; and the fermentation stirring rate is 0-100 rpm.

7. The preparation method according to claim 1, characterized in that: During the fermentation process, the pH value is controlled to be 4.0-8.

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8. Sourdough prepared by the method according to any one of claims 1 to 7.

9. A food quality preservation product, characterized in that: The invention comprises sour dough prepared by the preparation method according to any one of claims 1 to 7 and auxiliary materials.

10. Use of the sourdough prepared by the preparation method according to any one of claims 1 to 7 in food preservation and / or anti-oxidation.

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