Oat fermented milk and preparation method thereof

Abstract

The present invention relates to the technical field of food processing, and in particular to an oat fermented milk and a preparation method thereof, comprising the following steps: preparing bacterial suspensions of TZ3-1-2, TG8-1-9 and QF-1-1 respectively; adding the bacterial suspension of TZ3-1-2 and the bacterial suspension of TG8-1-9 into oat juice for lactic acid bacteria fermentation to obtain a lactic acid bacteria fermentation product; adding the bacterial suspension of QF-1-1 into the lactic acid bacteria fermentation product for yeast fermentation to obtain a yeast fermentation product; performing post-ripening catalysis on the yeast fermentation product to obtain the oat fermented milk; the lactic acid bacteria TZ3-1-2 is Pediococcus pentosaceus ( Pediococcus pentosaceous ), the deposit number is CGMCC No.32259; the lactic acid bacteria TG8-1-9 is Lactobacillus plantarum ( Lactiplantibacillus plantarum ), the preservation number is CGMCC No. 32258. The present invention utilizes mixed bacteria fermentation and two-stage sequential fermentation technology to shorten the fermentation time and effectively make up for the deficiency of single fermentation, and finally obtains oat fermented milk with excellent taste and good tissue state in all aspects.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to oat fermented milk and a preparation method thereof. Background Art

[0002] oat( Avena sativa L.) is an annual plant of the genus Avena in the Poaceae family. It is mainly divided into two types: skin oats and naked oats. Skin oats are common cultivated oats, and naked oats are also called naked oats. Related studies have shown that eating oats will change genes related to cancer formation and protein production. In addition, oats are rich in vitamins and minerals. While promoting the health of the body, they can also promote fetal growth and development, participate in metabolism, and reduce systemic inflammation to fight diseases. Oats contain vitamin B1, vitamin B2, vitamin E, folic acid and fatty acids, which can promote blood circulation, help eliminate fatigue, relieve psychological stress, and contribute to the growth and development of the fetus. Oats also contain calcium, phosphorus, iron, zinc, manganese and other minerals, which can prevent osteoporosis and anemia and promote wound healing. Oats contain antioxidants, have excellent antioxidant properties, and can eliminate free radicals in the body. Other studies have shown that fermented oat products also have a positive effect on obesity by inhibiting fat production and regulating lipid metabolism.

[0003] Methods to improve the nutritional value of grains include cooking, grinding, and fermentation. Studies have shown that bioactive substances in grain bran tend to bind to complex cell wall structures, and traditional processes have certain limitations in this regard. However, microbial fermentation technology can effectively solve this problem. Fermentation is the most economical and simplest way to improve the nutritional value and functional quality of oats. During the fermentation process, the glycosidic bonds of some substrates, such as polyphenols and flavonoids, are hydrolyzed by the β-glucosidase of lactic acid bacteria, releasing and increasing their concentration, thereby increasing the potential value of oat fermented beverages. Oat fermented milk fermented from pure oat matrix is ​​rich in nutrition, has a good taste, is suitable for vegetarians and diabetics, and provides a new choice for patients with lactose intolerance and allergies. However, oats are usually fermented with lactic acid bacteria or yeast alone, and the fermented taste is not good. Therefore, it is urgent to provide a new method for preparing oat fermented milk with good taste and flavor. Summary of the invention

[0004] In order to solve the defect of poor taste of oats fermented with a single bacteria in the prior art, the present invention provides an oat fermented milk and a preparation method thereof.

[0005] The technical solution adopted by the present invention is:

[0006] The present invention provides a method for preparing oat fermented milk, comprising the following steps:

[0007] The invention discloses a method for preparing a suspension of lactic acid bacteria TZ3-1-2, a suspension of lactic acid bacteria TG8-1-9 and a suspension of yeast QF-1-1; adding the suspension of lactic acid bacteria TZ3-1-2 and the suspension of lactic acid bacteria TG8-1-9 to oat juice for lactic acid bacteria fermentation to obtain a lactic acid bacteria fermentation product; adding the suspension of yeast QF-1-1 to the lactic acid bacteria fermentation product for yeast fermentation to obtain a yeast fermentation product; performing post-ripening catalysis on the yeast fermentation product to obtain the oat fermented milk; the lactic acid bacteria TZ3-1-2 is Pediococcus pentosaceus ( Pediococcus pentosaceus ), deposited in the General Microbiological Center of China Microbiological Culture Collection Committee, with the deposit number CGMCC No.32259; the lactic acid bacteria TG8-1-9 is Lactobacillus plantarum ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.32258.

[0008] Preferably, the bacterial concentration of the lactic acid bacteria TZ3-1-2 bacterial suspension and the lactic acid bacteria TG8-1-9 bacterial suspension is 10 9 CFU / mL, the conditions for the lactic acid bacteria fermentation are: fermentation temperature is 31°C~37°C, inoculation amount is 0.2%~0.5%, and fermentation time is 4h~6h.

[0009] Preferably, the conditions for the lactic acid bacteria fermentation are: fermentation temperature is 35° C., inoculation amount is 0.3%, and fermentation time is 5 h.

[0010] Preferably, the yeast QF-1-1 bacterial suspension has a bacterial concentration of 10 9 CFU / mL, the yeast fermentation conditions are: fermentation temperature is 24°C~30°C, inoculation amount is 0.03%~0.05%, and fermentation time is 2h~4h.

[0011] Preferably, the yeast fermentation conditions are: fermentation temperature is 30° C., inoculation amount is 0.05%, and fermentation time is 4 hours.

[0012] Preferably, the post-ripening catalytic conditions are 4° C., 24 h.

[0013] Preferably, the culture medium for preparing the lactic acid bacteria TZ3-1-2 bacterial suspension and the lactic acid bacteria TG8-1-9 bacterial suspension is MRS medium; the culture medium for preparing the yeast QF-1-1 bacterial suspension is YEPD medium.

[0014] Preferably, the oat juice is prepared by adding water to the oat flour hydrolyzed by α-amylase, mixing and sterilizing.

[0015] Preferably, the material-liquid ratio of the oat flour hydrolyzed by α-amylase to water is 300 g:1 L.

[0016] The present invention also provides oat fermented milk prepared by the preparation method of the present invention.

[0017] The biomaterial sample preservation information involved in the present invention is as follows:

[0018] TG8-1-9, the proposed taxonomic name is Lactobacillus plantarum ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration on October 18, 2024, with the deposit number CGMCC No.32258, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0019] TZ3-1-2, the proposed taxonomic name is Pediococcus pentosaceus ( Pediococcus pentosaceus ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration on October 18, 2024, with the deposit number CGMCCNo.32259, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention provides a method for preparing oat fermented milk, comprising the following steps: preparing TZ3-1-2 bacterial suspension, TG8-1-9 bacterial suspension and QF-1-1 bacterial suspension respectively; adding the TZ3-1-2 bacterial suspension and the TG8-1-9 bacterial suspension into sterilized oat juice for lactic acid bacteria fermentation to obtain a lactic acid bacteria fermentation product; adding the QF-1-1 bacterial suspension into the lactic acid bacteria fermentation product for yeast fermentation to obtain a yeast fermentation product; performing post-ripening catalysis on the yeast fermentation product to obtain the oat fermented milk; the lactic acid bacteria TZ3-1-2 is Pediococcus pentosaceus ( Pediococcus pentosaceus ), deposited in the General Microbiological Center of China Microbiological Culture Collection Committee, with the deposit number CGMCC No.32259; the lactic acid bacteria TG8-1-9 is Lactobacillus plantarum ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.32258.

[0022] The present invention uses sensory score as the final evaluation standard, utilizes mixed bacteria fermentation and two-stage sequential fermentation technology to ferment pure oats, shortens the fermentation time, and ultimately obtains oat fermented milk with excellent taste and good tissue state in all aspects, laying a certain foundation for its broad market development.

[0023] The oat fermented milk prepared in the present invention has 36 volatile substances, mainly aldehydes, alcohols and acids, which can give the oat fermented milk a unique flavor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The results of the antagonism experiment between lactic acid bacteria and yeast are shown in Figure 2. A shows the state diagram of YEPD culture medium after 24 hours; B shows the state diagram of MRS culture medium after 24 hours.

[0025] Figure 2 This is a graph showing the results of pH and total acid determination in oat fermented milk prepared by lactic acid bacteria at different fermentation temperatures.

[0026] Figure 3 This is a graph showing the results of sugar determination of soluble solids and β-glucan content in oat fermented milk prepared by lactic acid bacteria at different fermentation temperatures.

[0027] Figure 4 This is a graph showing the sensory evaluation scores of oat fermented milk prepared by lactic acid bacteria at different fermentation temperatures.

[0028] Figure 5 The results of pH and total acid determination in oat fermented milk prepared with lactic acid bacteria suspensions with different inoculation amounts.

[0029] Figure 6 The results of sugar determination of soluble solids and β-glucan content in oat fermented milk prepared with different inoculation amounts of lactic acid bacteria suspension.

[0030] Figure 7 This is a graph showing the sensory evaluation scores of oat fermented milk prepared with different inoculation amounts of lactic acid bacteria suspension.

[0031] Figure 8 This is the result of measuring pH and total acid in oat fermented milk prepared by lactic acid bacteria at different fermentation times.

[0032] Fig. 9 This is a graph showing the results of sugar determination of soluble solids and β-glucan content in oat fermented milk prepared with lactic acid bacteria at different fermentation times.

[0033] Fig.10 Results of sensory evaluation of oat fermented milk prepared by lactic acid bacteria at different fermentation times.

[0034] Fig.11 This is the result of measuring pH and total acid in oat fermented milk prepared by yeast at different fermentation temperatures.

[0035] Fig.12 This is a graph showing the results of sugar determination of soluble solids and β-glucan content in oat fermented milk prepared by yeast at different fermentation temperatures.

[0036] Fig.13 This is a graph showing the sensory evaluation scores of oat fermented milk prepared by yeast at different fermentation temperatures.

[0037] Fig.14 This is the result of measuring pH and total acid in oat fermented milk prepared with different inoculation amounts of yeast suspension.

[0038] Fig.15 The results of sugar determination of soluble solids and β-glucan content in oat fermented milk prepared with different inoculation amounts of yeast suspension.

[0039] Fig.16 This is a graph showing the sensory evaluation scores of oat fermented milk prepared with different inoculation amounts of yeast suspension.

[0040] Fig.17 This is the result of measuring pH and total acid in oat fermented milk prepared by yeast at different fermentation times.

[0041] Fig.18 This is the result of sugar determination of soluble solids and β-glucan content in oat fermented milk prepared by yeast at different fermentation times.

[0042] Fig.19 This is a graph showing the sensory evaluation scores of oat fermented milk prepared with yeast at different fermentation times.

[0043] Fig. 20 This is the result of the determination of ABTS and DPPH free radical scavenging rates.

[0044] Fig.21 The results of the indole test. A to C are: positive control, negative control and QE-1-12.

[0045] Fig. 22 The results of nitrate reductase activity test. A~C are positive control, negative control and QE-1-12.

[0046] Fig.23 This is the result of amino acid decarboxylase activity test. A to C are positive control, negative control and QE-1-12 respectively. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific examples, but it should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0048] The inventive concept of the present invention is as follows:

[0049] Fermentation is the most economical and simplest way to improve the nutritional value and functional quality of oats. Fermentation can improve the bland taste and flavor of oats and give them a special aroma and flavor. The bacteria contained in the fermented oat milk on the market are mainly lactic acid bacteria. The taste of single lactic acid bacteria fermentation is monotonous and the probiotic effect on the human body is similar.

[0050] Based on this, the present invention provides a preparation method of oat fermented milk, comprising the following steps: preparing TZ3-1-2 bacterial suspension, TG8-1-9 bacterial suspension and QF-1-1 bacterial suspension; adding TZ3-1-2 bacterial suspension and TG8-1-9 bacterial suspension to sterilized oat juice for lactic acid bacteria fermentation to obtain lactic acid bacteria fermentation products; adding QF-1-1 bacterial suspension to the lactic acid bacteria fermentation products for yeast fermentation to obtain yeast fermentation products; performing post-ripening catalysis on the yeast fermentation products to obtain the oat fermented milk; the lactic acid bacteria TZ3-1-2 is Pediococcus pentosaceus ( Pediococcus pentosaceus ), deposited in the General Microbiological Center of China Microbiological Culture Collection Committee, with the deposit number CGMCC No.32259; the lactic acid bacteria TG8-1-9 is Lactobacillus plantarum ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.32258.

[0051] The present invention can reduce the acid production of oat milk, improve the taste, increase the content of flavor substances such as alcohols and esters through double-bacteria fermentation, and double-bacteria fermentation accelerates the conversion of fermentable sugars, greatly reduces the level of digestible carbohydrates, and improves the functional value of active ingredients.

[0052] Since the plant lactobacillus ( Lactiplantibacillus plantarum ) ， The biological material of reference is TG8-1-9, so in the present invention, the plant lactobacillus ( Lactiplantibacillus plantarum ) is referred to as TG8-1-9; the Pediococcus pentosaceus of the present invention ( Pediococcus pentosaceus ), the reference biological material is TZ3-1-2, so in the present invention, the plant lactobacillus ( Lactiplantibacillus plantarum ) is referred to as TZ3-1-2.

[0053] 1. Experimental materials:

[0054] (1) Yeast:

[0055] Yeast QF-1-1 was isolated from Baotou, Inner Mongolia and was identified as abnormal Wickham yeast ( Wickerhamomyces anomalus), abnormal Wickham yeast is widely used as an aroma-producing yeast in fermented foods and fermented feed such as liquor, wine, soy sauce, vinegar, bread, etc. The abnormal Wickham yeast in the present invention has been evaluated for safety, proving that the yeast is safe and can be used in the preparation of fermented foods. Yeast QF-1-1 is disclosed in an article by Liu Yadong, Wang Suhe, He Min, et al. Reference: Liu Yadong, Wang Suhe, He Min, et al. High-throughput screening and identification of yeasts that tolerate and adsorb heavy metal Pb~(2+) [J]. Journal of Chinese Institute of Food Science and Technology, 2020, 20(06): 246-255. DOI: 10.16429 / j.1009-7848.2020.06.030.

[0056] (2) Lactic acid bacteria:

[0057] Lactobacillus TG8-1-9 is a plant lactobacillus ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.32258.

[0058] Lactic acid bacteria TZ3-1-2, Pediococcus pentosaceus ( Pediococcus pentosaceus ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.32259.

[0059] Lactobacillus plantarum ( Lactiplantibacillus plantarum ) RJ1-1-4 and Lactococcus lactis ( Lactococcus ) milk fat subspecies TG7-1-6, disclosed in the reference: "Zhong Huachen, Zhang Yue, Gu Yue, et al. Screening, identification and exopolysaccharide secretion conditions of high-yielding biomembrane lactic acid bacteria [J]. Journal of Chinese Institute of Food Science and Technology, 2021, 21(07): 76-86. DOI: 10.16429 / j.1009-7848.2021.07.010.".

[0060] (3) Preparation of culture medium and oatmeal juice:

[0061] The preparation of MRS medium and YEPD medium shall comply with the quality requirements of GB 4789.28-2024 National Food Safety Standard Food Microbiology Examination Culture Medium and Reagents.

[0062] The formula of MRS medium per liter is: 10g peptone, 5g beef extract powder, 20g yeast extract powder, 2g dipotassium hydrogen phosphate heptahydrate, 2g triammonium citrate, 5g ammonium acetate trihydrate, 0.05g magnesium sulfate heptahydrate, 1mL Tween 80, and water as the solvent.

[0063] The formula of YEPD medium per liter is: 10g yeast extract, 20g peptone, 20g glucose, and water as solvent.

[0064] Preparation of oat juice: add 300g of oatmeal powder hydrolyzed by α-amylase to 1L of water, stir and mix for 5min using a wall breaker, and sterilize at 95°C. The oatmeal powder hydrolyzed by α-amylase is Gate hydrolyzed oatmeal powder purchased from Taobao.

[0065] 2. The mutual influence of lactic acid bacteria and yeast growth is as follows:

[0066] Lactobacillus plantarum TG8-1-9 and Pediococcus pentosaceus TZ3-1-2 were inoculated into YEPD medium containing abnormal Wickham yeast QF-1-1; abnormal Wickham yeast QF-1-1 was inoculated into MRS medium containing Lactobacillus plantarum TG8-1-9 and Pediococcus pentosaceus TZ3-1-2, and co-cultured them respectively to observe whether there was an inhibitory effect.

[0067] The results are as follows Figure 1 As shown, there was no obvious inhibition zone around the Oxford cup, and both yeast and lactic acid bacteria grew vigorously, indicating that there was no inhibition between them. These three strains can be co-cultured for subsequent fermentation tests.

[0068] 3. Analysis of the quality and functional characteristics of oat fermented milk, as follows:

[0069] (1) Determination of nutritional components:

[0070] Determine the pH value, total acid content, protein content, fat content, and reducing sugar content of oat fermented milk. The pH value is determined using a pH meter; the total acid content is determined by the titration method in accordance with GB12456-2021; the soluble solids are determined using an Abbe refractometer; the protein content is determined by the Kjeldahl nitrogen determination method in accordance with the national standard GB5009.4-2016; the fat content is determined by the Rozsko-Try method in accordance with the national standard GB5009.4-2016; and the reducing sugar content is determined by the DNS colorimetric method.

[0071] (2) Determination of functional ingredients:

[0072] 1) Determination of polyphenol content: refer to the method in the article by Hidvegi M et al., Hidvegi M, Tomoskozine RF, Lapis K, et al. Immunostimulatory and metastasisinhibiting fermented vegetalmaterial: US Patent 6, 355. 474[P]. 2002-3-12.

[0073] 2) Determination of flavonoid content: refer to the method in the article by Tai Xianquan et al., Tai Xianquan, Li Hongli, Li Dongbo, et al. Study on sensory evaluation of litchi wine based on fuzzy comprehensive evaluation method [J]. Journal of Southwest Agriculture, 2016, 29(6): 1443-1447.

[0074] 3) Determination of β-glucan content: refer to the method in the article by Zhang Huijie et al., Zhang Huijie. Comparative study on the effects of three kinds of grain germination on the quality of fermented glutinous rice in pastoral areas [D]. Inner Mongolia: Inner Mongolia Agricultural University, 2018.

[0075] (3) Antioxidant capacity analysis:

[0076] 1) Determination of DPPH free radical scavenging effect: The DPPH free radical scavenging rate detection kit was used.

[0077] 2) Determination of ABTS scavenging effect: The operation was carried out according to the total antioxidant capacity T-AOC detection kit of Beijing Solebow Technology Co., Ltd.

[0078] 4. Data processing and analysis:

[0079] There were 3 biological replicates in each group, and data statistical analysis was performed using Excel, SPSS27.0 and other software, and the obtained data were graphed using Origin 2021 software.

[0080] V. Product sensory evaluation method:

[0081] The present invention adopts a consumer test method, selects 12 volunteers to form a sensory evaluation panel, randomly codes the samples, and tastes them at room temperature. The scoring criteria are shown in Table 1 below, and the sum of the scores of the four indicators of the product is the final sensory evaluation score.

[0082] Table 1 Sensory rating table

[0083]

[0084] Example 1

[0085] A method for preparing oat fermented milk, comprising the following steps:

[0086] Step 1: Activation of the strain, as follows:

[0087] The lactic acid bacteria TZ3-1-2, lactic acid bacteria TG8-1-9 and yeast QF-1-1 preserved in glycerol were thawed and inoculated into MRS and YEPD liquid culture media with an inoculation volume fraction of 2%, respectively. The lactic acid bacteria were cultured at 37°C for 24 h, and the yeast was cultured on a shaker at 30°C for 24 h. Single colonies were picked and inoculated into MRS and YEPD liquid culture media, respectively, and cultured for 18 h and 14 h, respectively, to obtain activated strains for preparing bacterial suspensions. The remaining bacterial liquid was mixed with glycerol in a certain proportion and inoculated, and stored at -80°C for subsequent use.

[0088] Step 2: Preparation of bacterial suspension, as follows:

[0089] Preparation of lactic acid bacteria suspension: TZ3-1-2 and TG8-1-9 were inoculated in MRS liquid medium at a volume fraction of 2% and activated for 3 generations, and then diluted with 0.85% saline to OD 595nm The value is 1.0, which is 10 9 The test solution with a concentration of about CFU / mL is used for subsequent tests.

[0090] Preparation of yeast suspension: Yeast QF-1-1 was inoculated with 2% volume fraction in YEPD liquid medium for activation for 3 generations, and then diluted with 0.85% physiological saline to OD 630nm The value is 1.0, which is 10 9 The test solution with a concentration of about CFU / mL is used for subsequent tests.

[0091] Step 3: Lactic acid fermentation, as follows:

[0092] 100 mL of oat juice was measured and sterilized at 95°C for 5 min, and then lactic acid bacteria suspension was added for fermentation. The inoculation amount of lactic acid bacteria suspension was 0.3%, the fermentation temperature was 35°C, and the fermentation time was 5 h to obtain lactic acid bacteria fermentation products. The mass ratio of TZ3-1-2 and TG8-1-9 in the lactic acid bacteria suspension was 1:2.

[0093] Step 4: Yeast fermentation, as follows:

[0094] Yeast suspension was added to the lactic acid bacteria fermentation product for fermentation. The inoculation amount of the yeast suspension was 0.05% of the volume of the lactic acid bacteria fermentation product. The fermentation temperature was 30° C. and the fermentation time was 3 h to obtain the yeast fermentation product.

[0095] Step 5: After fermentation is completed, the yeast fermentation product is refrigerated at 4° C. for 24 hours for post-ripening catalysis to obtain oat fermented milk.

[0096] Embodiment 2~embodiment 4

[0097] A method for preparing oat fermented milk is as follows:

[0098] In Example 2 to Example 4, the fermentation temperatures of the lactic acid bacteria in step 3 are 31° C., 33° C. and 37° C., respectively, and the other conditions are exactly the same as in Example 1.

[0099] Comparative Example 1 and Comparative Example 2

[0100] A kind of preparation method of oat fermented milk

[0101] In Comparative Examples 1 and 2, the fermentation temperatures of the lactic acid bacteria in step 3 were 39° C. and 41° C., respectively, and the other conditions were exactly the same as those in Example 1.

[0102] The fermentation temperature affects the growth of the strain to a certain extent and ultimately determines the flavor of the product. The choice of fermentation temperature mainly depends on the characteristics of the fermentation substrate and the fermentation strain. Figure 2~Figure 4 As the fermentation temperature of oat fermented milk increases, its pH value continues to decrease, the total acid content continues to increase, and the soluble solid content decreases significantly, p<0.05, because lactic acid bacteria use sugars in oat juice for growth and fermentation. As the fermentation temperature of lactic acid bacteria increases, the content of β-glucan decreases, and the decrease is only 7.2%. Based on the sensory score, 35℃ was selected as the fermentation temperature of lactic acid bacteria.

[0103] Embodiment 5~embodiment 7

[0104] A method for preparing oat fermented milk is as follows:

[0105] In Examples 5 to 7, the inoculation amounts of the lactic acid bacteria suspension in step 3 were 0.2%, 0.4% and 0.5%, respectively, and the other conditions were exactly the same as in Example 1.

[0106] Comparative Example 3 and Comparative Example 4

[0107] A method for preparing oat fermented milk is as follows:

[0108] In Comparative Examples 3 and 4, the inoculation amounts of the lactic acid bacteria suspension in step 3 were 0.6% and 0.7% respectively, and the other conditions were exactly the same as those in Example 1.

[0109] From Example 5 to Example 7, Comparative Example 3 to Comparative Example 4, it can be seen that Figure 5~Figure 7 , with the increase of lactic acid bacteria inoculation amount, the pH value of oat fermented milk decreased, the total acid value continued to rise, and the content of soluble solids and β-glucan also decreased slightly. Too much lactic acid bacteria inoculation amount is not conducive to forming a good taste. On the contrary, too little lactic acid bacteria inoculation amount will inhibit the acid production of lactic acid bacteria due to its unfavorable growth environment. Based on the comprehensive sensory score, 0.3% was selected as the lactic acid bacteria inoculation amount.

[0110] Embodiment 8~embodiment 9

[0111] A method for preparing oat fermented milk is as follows:

[0112] In Example 8 to Example 9, the fermentation time of the lactic acid bacteria suspension in step 3 is 4 h and 6 h respectively, and the other conditions are exactly the same as in Example 1.

[0113] Comparative Example 5~Comparative Example 7

[0114] A method for preparing oat fermented milk is as follows:

[0115] In Comparative Examples 5 to 7, the fermentation time of the lactic acid bacteria suspension in step 3 is 3 h, 7 h and 8 h, and the other conditions are exactly the same as those in Example 1.

[0116] From Example 8 to Example 9, Comparative Example 5 to Comparative Example 7, it can be seen that Figure 8~Figure 10 , the content of soluble solids and β-glucan decreased slightly. As the fermentation time increases, lactic acid bacteria continue to produce acid. When the fermentation time is too short, due to insufficient acid production by lactic acid bacteria, the acidity of oat fermented milk is insufficient, the overall sensory perception is sweet and greasy, and the ester substances produced are insufficient, so the sensory score is low. The highest score of the comprehensive sensory score is 87.3±1.27 points, and 5h is selected as the fermentation time of lactic acid bacteria.

[0117] Embodiment 10~embodiment 12

[0118] A method for preparing oat fermented milk is as follows:

[0119] In Examples 10 to 12, the yeast fermentation temperatures in step 4 are 24° C., 26° C. and 28° C., and the other conditions are exactly the same as in Example 1.

[0120] Comparative Example 8 and Comparative Example 9

[0121] A method for preparing oat fermented milk is as follows:

[0122] In Comparative Examples 8 and 9, the yeast fermentation temperature in step 4 is 32° C. and 34° C., and other conditions are exactly the same as those in Example 1.

[0123] From Example 10 to Example 12, Comparative Example 8 and Comparative Example 9, it can be seen that Figure 11~Figure 13, if the yeast culture temperature is too high, it will cause the denaturation and inactivation of proteins and nucleic acids. If the culture temperature is too low, the enzyme activity will be inhibited, the metabolic activity of the cells will be weakened, and the growth will slow down. As the yeast fermentation temperature increases, the pH value continues to decrease and the total acid value continues to increase. β-glucan remains basically unchanged as the yeast fermentation temperature increases. The soluble solids content continues to decrease. The higher the yeast fermentation temperature, the higher the yeast content, and the carbon source required for its growth also increases. The sensory score shows a trend of first increasing and then decreasing with the increase of fermentation temperature, reaching the maximum at 30°C, so 30°C is taken as the optimal fermentation temperature for yeast.

[0124] Example 13 and Example 14

[0125] A method for preparing oat fermented milk is as follows:

[0126] In Example 13 and Example 14, the inoculation amount of the yeast suspension in step 4 is 0.03% and 0.04%, respectively, and the other conditions are exactly the same as those in Example 1.

[0127] Comparative Example 10~Comparative Example 12

[0128] A method for preparing oat fermented milk is as follows:

[0129] In Comparative Examples 10 to 12, the inoculation amount of the yeast suspension in step 4 was 0.01%, 0.02%, and 0.06%, and the other conditions were exactly the same as those in Example 1.

[0130] It can be seen from Example 13, Example 14 and Comparative Examples 10 to 12 that Figure 14~Figure 16 , as the yeast inoculation amount increases, the pH value of oat fermented milk continues to decrease, and the total acid continues to increase. β-glucan remains basically unchanged with the increase of yeast inoculation amount, and the content of soluble solids continues to decrease. When the yeast inoculation amount is very small, the number of live yeast cells is not large, and the ethanol content produced is relatively small, resulting in few esters or aldehydes produced. As the inoculation amount increases, the number of live yeast cells also increases, the alcohol taste produced will be stronger, and the sensory score will also decrease. When the inoculation amount is 0.05%, the sensory score is the largest, so 0.05% is the optimal inoculation amount of yeast.

[0131] Example 15 and Example 16

[0132] A method for preparing oat fermented milk is as follows:

[0133] In Example 15 and Example 16, the fermentation time of yeast in step 4 is 2 hours and 4 hours, and other conditions are exactly the same as in Example 1.

[0134] Comparative Example 13~Comparative Example 15

[0135] A method for preparing oat fermented milk is as follows:

[0136] In Comparative Examples 13 to 15, the fermentation time of the yeast in step 4 is 1 h, 5 h, and 6 h, and the other conditions are exactly the same as those in Example 1.

[0137] It can be seen from Example 15, Example 16 and Comparative Examples 13 to 15 that Figure 17~Figure 19 , with the increase of yeast fermentation time, the pH value of oat fermented milk continued to decrease, and the total acid continued to increase. β-glucan remained basically unchanged with the increase of yeast inoculation amount, and the content of soluble solids continued to decrease. The results showed that with the increase of fermentation time, the sensory score increased first and then decreased, reaching a peak of 88.2±0.25 points at 3h; with the extension of fermentation time, the content of ethanol and lactic acid also continued to increase. On the contrary, due to the short fermentation time, the alcohol content was too low, and less ester substances were produced, affecting the sensory quality of the product. In summary, 3h was selected as the optimal fermentation time for yeast.

[0138] Comparative Example 16

[0139] A method for preparing oat fermented milk is as follows:

[0140] Step 1 and step 2 are exactly the same as those in Example 1. Step 3 is firstly subjected to yeast fermentation, and step 4 is subjected to lactic acid bacteria fermentation, followed by post-ripening. The conditions of yeast fermentation, lactic acid bacteria fermentation and post-ripening are exactly the same as those in Example 1.

[0141] Comprehensive Example 1 and Comparative Example 16, comparing two different fermentation processes, it can be seen that in the process of lactic acid bacteria fermentation followed by yeast fermentation, lactic acid bacteria first fermentation causes the pH of oat fermented milk to decrease, limiting the rapid growth of yeast and also limiting the rapid accumulation of ethanol. In the process of lactic acid bacteria fermentation followed by yeast fermentation, a certain amount of acid combined with a small amount of ethanol can give the product a unique fragrance, and the highest sensory score is 81.3±0.88 points. In the process of yeast fermentation followed by lactic acid bacteria fermentation, since yeast first ferments to produce a large amount of ethanol, after lactic acid bacteria are introduced, a large amount of ethanol cannot be combined with a small amount of acid to produce aromatic substances, thereby adversely affecting the taste and flavor of oat fermented milk, and the maximum sensory score is 74.3±0.93 points, which is lower than the sensory score of lactic acid bacteria fermentation followed by yeast fermentation. By comparing the pH value, total acid, β-glucan, soluble solids content and sensory scores of the two different fermentation processes, there was no significant difference in β-glucan and soluble solids between the two. According to the sensory score as one of the most important indicators for measuring the flavor substances of the product, the present invention selects the fermentation process of lactic acid bacteria fermentation followed by yeast fermentation to develop oat fermented milk.

[0142] Example 17 and Example 18

[0143] A method for preparing oat fermented milk is as follows:

[0144] In Example 17 and Example 18, the mass ratio and specific gravity of TZ3-1-2 and TG8-1-9 in step 3 are as shown in Table 2, and the other conditions are exactly the same as in Example 1.

[0145] Comparative Example 17 to Comparative Example 22

[0146] A method for preparing oat fermented milk is as follows:

[0147] In Comparative Examples 17 to 22, the mass ratios and specific gravities of TZ3-1-2 and TG8-1-9 in step 3 are shown in Table 2, and the other conditions are exactly the same as those in Example 1.

[0148] Table 2 Ratio of the amount of two lactic acid bacteria added

[0149]

[0150] Note: Different lowercase letters indicate significant differences between different proportions, p<0.05.

[0151] Taking into account the color, texture, smell and taste of the oat fermented milk, the oat fermented milk fermented with the two strains in Example 1 is more outstanding overall, so the optimal ratio of the two lactic acid bacteria is determined to be TZ3-1-2:TG8-1-9=1:2.

[0152] Comparative Example 23

[0153] A method for preparing oat fermented milk is as follows:

[0154] The lactic acid bacteria strains used in this comparative example are: Lactobacillus plantarum ( Lactiplantibacillus plantarum ) RJ1-1-4 and Lactococcus lactis ( Lactococcus ) milk fat subspecies TG7-1-6, the mass ratio of RJ1-1-4 and TG7-1-6 is 1:2. Other conditions are exactly the same as in Example 1.

[0155] Different lactic acid bacteria strains have a decisive influence on the flavor of fermented products. By comparing Example 1 and Comparative Example 23, it can be seen that under the same fermentation conditions, the oat fermented milk product prepared in Comparative Example 23 has a pH value of 4.91, a total acid of 1.78g / L, an acetaldehyde content of 8.25mg / L, and a diacetyl content of 7.13mg / L. The acid production capacity of the comparative example is weak, the fermentation speed is slow, and the ratio of acetaldehyde to diacetyl is small, and the product flavor is poor. While the oat fermented milk product prepared in Example 1 has acetaldehyde and diacetyl in a suitable range, with an acetaldehyde content of 10.22mg / L and a diacetyl content of 3.03mg / L. The sense of harmony of flavor is related to the ratio of acetaldehyde and diacetyl. When the ratio of the two is greater than 3:1, the greater the ratio, the better the product flavor.

[0156] The oat fermented milk obtained in Example 1 was subsequently analyzed as follows:

[0157] (1) Determination of nutritional components of oat fermented milk.

[0158] The pH, total acid, soluble solids, protein, fat and reducing sugar of oat fermented milk were measured. The results are shown in Table 3.

[0159] Table 3 Nutritional content

[0160]

[0161] As shown in Table 3, after fermentation, the pH value decreased, the total acid increased, the reducing sugar content decreased, and the soluble solids decreased compared with those before fermentation. This is because lactic acid bacteria and yeast use carbohydrates in oat juice to produce acid.

[0162] (2) Determination of functional components of oat fermented milk.

[0163] The contents of β-glucan, polyphenols and flavonoids in oat fermented milk were measured, and the results are shown in Table 4.

[0164] Table 4 Content of various functional ingredients

[0165]

[0166] As shown in Table 4, the content of β-glucan decreased after fermentation, from 673±3.00 mg / L to 533±2.00 mg / L, a decrease of 26%. The content of polyphenols increased after fermentation, from 0.52±0.03 mg / mL to 0.75±0.02 mg / mL, an increase of 29.2%, and the content of flavonoids increased after fermentation, from 0.33±0.02 mg / mL to 0.53±0.03 mg / mL, an increase of 44.2%.

[0167] (3) Analysis of the antioxidant capacity of oat fermented milk.

[0168] like Fig. 20 The results showed that with the extension of fermentation time, the ABTS free radical scavenging rate and DPPH free radical scavenging rate both increased. After reaching the fermentation end point, the scavenging rates of the two were 43% and 40%, respectively, proving that with the increase of flavonoids content, the antioxidant capacity of the product also increased. The stronger the antioxidant capacity, the more stable the product system.

[0169] (4) Analysis of flavor substances in oat fermented milk.

[0170] 1) Analysis of organic acid content in oat fermented milk.

[0171] As shown in Table 5, a total of 17 organic acids were measured, of which 7 organic acids had no significant changes before and after fermentation, p>0.05, 6 organic acids had significant changes, p<0.05, and 4 organic acids had extremely significant changes, p<0.01. Comparing before and after fermentation, the increase in the content of different organic acids from high to low was lactic acid, fumaric acid, pantothenic acid, phenyllactic acid, L-pyroglutamic acid and vanillic acid, which increased by 465.06μg / mL, 92.95μg / mL, 7.3μg / mL, 1.71μg / mL, 0.69μg / mL and 0.27μg / mL, respectively. The increase in the content of 6 different organic acids can give oat fermented milk a better sensory experience and improve product quality and antioxidant properties.

[0172] Table 5 Changes in organic acid content before and after fermentation

[0173]

[0174] Note: “**” indicates extremely significant, p<0.01; “*” indicates significant, p<0.05; “-” indicates not detected.

[0175] 2) Analysis of volatile flavor compounds in oat fermented milk.

[0176] The most widely used flavor substance separation and determination method, gas chromatography-mass spectrometry, is used to determine the flavor substances in oat fermented milk at the molecular level.

[0177] As shown in Table 6, the contents of 14 flavor substances before and after fermentation are significantly different, and aldehydes, alcohols and acids are the most abundant among all volatile compounds. The increase in the content of flavor substances can provide oat fermented milk with a more pleasant aroma and enhance the richness of the product's aroma. Among the alcohol substances, the content of trans-2-nonene-1-ol, which provides a violet aroma, is the highest at 7.16±0.08ng / mL. Among the aldehyde substances, the content of 2,4-decadienal, which has an orange aroma, is the highest at 23.46±0.47ng / mL. Among the acid substances, the content of dodecanedioic acid is the highest at 9.89±0.61ng / mL. Among the ketone substances, the content of 3-octen-2-one, which has the smell of sweet cream, lavender, mushrooms, butter, and coconut, is the highest at 5.98±0.23ng / mL. The contents of these substances are significantly increased before and after fermentation, p<0.05.

[0178] Table 6 Quantitative table of volatile flavor substances

[0179]

[0180] Note: "*" indicates significant, p<0.05, which are differential flavor metabolites.

[0181] The safety evaluation of the abnormal Wickham yeast, Metschnikowia chrysoperlae, QF-1-1, is as follows:

[0182] (1) Test results of harmful metabolites of test strains.

[0183] Indole test: refer to the test method of Chen Nannan et al. Chen Nannan, Hou Meiru, Wang Yan, et al. Study on the stability of Bacillus amyloliquefaciens SSY1 strain [J]. Chinese Journal of Microecology, 2017, 29(01): 1-5. The results are as follows Fig.21 As shown, no red ring appeared in QF-1-1 and the negative control group, but a red ring appeared in the positive control group strain Escherichia coli, indicating that QF-1-1 did not produce indole substances.

[0184] (2) Nitrate reductase activity detection.

[0185] Refer to the experimental method in the article "Research Progress of Microbial Nitrite Reductase" by Zhang Qingfang, Li Meiyu, Wang Xiaohui, et al., published in Microbiological Bulletin, 2019, 46(11): 3148-3157. The results are as follows Fig. 22 As shown, the test strain and the negative control group were colorless, which was a negative reaction, and the Escherichia coli in the positive control group turned red, which was a positive reaction, indicating that the nitrate reductase in the QF-1-1 metabolite was inactive or did not contain nitrate reductase.

[0186] (3) Aminodecarboxylase activity detection.

[0187] Refer to the test method of the paper "Safety Evaluation of Enterococcus Lactic Acid Bacteria in Mare's Milk and Its Products in Pastoral Areas of Inner Mongolia" published by Wang Mengjiao et al. in 2014. The results are as follows Fig.23 As shown, the test strain and the negative control group were yellow, indicating a negative reaction, and the positive control group Escherichia coli was purple, indicating a positive reaction, indicating that the metabolites of QF-1-1 did not contain amino acid decarboxylase and would not produce cadaverine, putrescine, and spermine.

[0188] (4) Drug resistance test.

[0189] The drug resistance of the test strains was tested by E-test method, and the drugs included amphotericin B, itraconazole, fluconazole and voriconazole.

[0190] The drug sensitivity results were determined according to the Candida susceptibility test standards recommended by the Clinical and Laboratory Standards Institute (CLSI). The results are shown in Table 7: QF-1-1 was resistant to itraconazole and amphotericin B, intermediate to fluconazole, and sensitive to voriconazole.

[0191] Table 7 Analysis of drug sensitivity test results

[0192]

[0193] Note: S: sensitive; I: intermediate; R: resistant.

[0194] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0195] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing oat fermented milk, characterized in that: The following steps are involved: Prepare a lactic acid bacteria TZ3-1-2 bacterial suspension, a lactic acid bacteria TG8-1-9 bacterial suspension and a yeast QF-1-1 bacterial suspension; The lactic acid bacteria TZ3-1-2 bacterial suspension and the lactic acid bacteria TG8-1-9 bacterial suspension were added into oat juice for lactic acid bacteria fermentation to obtain lactic acid bacteria fermentation products. The bacterial concentration of the lactic acid bacteria TZ3-1-2 bacterial suspension and the lactic acid bacteria TG8-1-9 bacterial suspension was 10 9 CFU / mL, the conditions for the lactic acid bacteria fermentation are: fermentation temperature of 31°C to 37°C, inoculation amount of 0.2% to 0.5%, and fermentation time of 4h to 6h; The yeast QF-1-1 bacterial suspension was added to the lactic acid bacteria fermentation product for yeast fermentation to obtain the yeast fermentation product. The bacterial concentration of the yeast QF-1-1 bacterial suspension was 10 9 CFU / mL, the yeast fermentation conditions are: fermentation temperature is 24°C~30°C, inoculation amount is 0.03%~0.05%, and fermentation time is 2h~4h; Post-ripening and catalyzing the yeast fermentation product to obtain the oat fermented milk; The preparation method is used to improve the nutrient content and antioxidant capacity of oat fermented milk, wherein the nutrient includes at least one of protein, polyphenols and flavonoids; The preparation method is used to increase the ratio of acetaldehyde to diacetyl in oat fermented milk, wherein the ratio of acetaldehyde to diacetyl is 3.37:1; The lactic acid bacteria TZ3-1-2 is Pediococcus pentosaceus ( Pediococcus pentosaceus ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number of CGMCC No.32259; The lactic acid bacteria TG8-1-9 is Lactobacillus plantarum ( Lactiplantibacillus plantarum ), deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC No.32258.

2. The preparation method according to claim 1, characterized in that The conditions of the lactic acid bacteria fermentation are: The fermentation temperature was 35°C, the inoculation amount was 0.3%, and the fermentation time was 5h.

3. The preparation method according to claim 1, characterized in that: The conditions of the yeast fermentation are: The fermentation temperature was 30°C, the inoculation amount was 0.05%, and the fermentation time was 4h.

4. The preparation method according to claim 1, characterized in that: The conditions for the post-ripening catalysis are 4° C., 24 h.

5. The preparation method according to claim 1, characterized in that: The culture medium for preparing the lactic acid bacteria TZ3-1-2 bacterial suspension and the lactic acid bacteria TG8-1-9 bacterial suspension is MRS culture medium; The culture medium for preparing the yeast QF-1-1 bacterial suspension is YEPD culture medium.

6. The preparation method according to claim 1, characterized in that: The preparation process of the oat juice is as follows: Add water to the oatmeal powder hydrolyzed by α-amylase, mix well, and sterilize.

7. The preparation method according to claim 6, characterized in that: The material-liquid ratio of the oat flour hydrolyzed by α-amylase to water is 300g:1L.

8. Oat fermented milk prepared by the preparation method according to claim 1.

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