CN111903761A - Yoghourt with antioxidant function and preparation method thereof - Google Patents
Yoghourt with antioxidant function and preparation method thereof Download PDFInfo
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- CN111903761A CN111903761A CN202010830221.7A CN202010830221A CN111903761A CN 111903761 A CN111903761 A CN 111903761A CN 202010830221 A CN202010830221 A CN 202010830221A CN 111903761 A CN111903761 A CN 111903761A
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Images
Classifications
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23C—DAIRY PRODUCTS, e.g. MILK, BUTTER OR CHEESE; MILK OR CHEESE SUBSTITUTES; MAKING THEREOF
- A23C9/00—Milk preparations; Milk powder or milk powder preparations
- A23C9/12—Fermented milk preparations; Treatment using microorganisms or enzymes
- A23C9/13—Fermented milk preparations; Treatment using microorganisms or enzymes using additives
- A23C9/1307—Milk products or derivatives; Fruit or vegetable juices; Sugars, sugar alcohols, sweeteners; Oligosaccharides; Organic acids or salts thereof or acidifying agents; Flavours, dyes or pigments; Inert or aerosol gases; Carbonation methods
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
- A23V2400/00—Lactic or propionic acid bacteria
- A23V2400/11—Lactobacillus
- A23V2400/137—Delbrueckii
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
- A23V2400/00—Lactic or propionic acid bacteria
- A23V2400/11—Lactobacillus
- A23V2400/169—Plantarum
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
- A23V2400/00—Lactic or propionic acid bacteria
- A23V2400/21—Streptococcus, lactococcus
- A23V2400/249—Thermophilus
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- Life Sciences & Earth Sciences (AREA)
- Microbiology (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Polymers & Plastics (AREA)
- Dairy Products (AREA)
- Micro-Organisms Or Cultivation Processes Thereof (AREA)
Abstract
The invention belongs to the field of food, and particularly relates to yoghourt with an antioxidant function and a preparation method thereof. The method comprises the following steps: 1) preparing reduced milk; 2) homogenizing; 3) sterilizing; 4) and (3) enzymatic hydrolysis: adding trypsin into the reduced milk and hydrolyzing; 5) enzyme inactivation; 6) inoculating a microbial inoculum: proportionally mixing streptococcus thermophilus, lactobacillus delbrueckii subsp bulgaricus and lactobacillus plantarum freeze-dried powder, and inoculating the mixture into reduced milk; 7) subpackaging and fermenting; 8) and (5) after-ripening. The method uses lactobacillus plantarum with strong oxidation resistance to prepare the yoghourt by cooperating with lactobacillus with strong proteolytic ability for fermentation, and simultaneously uses protease to carry out proper enzymolysis on raw milk to improve the proteolytic degree of the raw milk, thereby not only solving the problem that the lactobacillus plantarum grows poorly in the milk, but also improving the oxidation resistance activity of the product. The selected fermentation strain has good viscosity-producing property, and the whey protein powder is matched to strengthen the raw milk, so that the curd effect and the sensory flavor property of the product can be guaranteed.
Description
Technical Field
The invention belongs to the field of food, in particular to the field of dairy product processing in the field of food, and particularly relates to yoghourt with an antioxidant function and a preparation method thereof.
Background
The yoghourt contains high-quality protein, multiple vitamins and carbohydrates, can supplement nutrients required by a human body, has the effects of enhancing the intestinal immunity, relaxing bowels and the like, is unique in flavor and convenient to eat, and is a fermentation product which is widely distributed in the world at present and is most popular with consumers. With the general improvement of the living standard of people, people pay more and more attention to the health and the functionality of foods, and the yoghourt is used as a natural fermented food and is a good carrier for developing foods with probiotic functions.
Under normal conditions, a human body has a complete oxidation-antioxidation balance mechanism, and if the balance is changed due to the pathological changes of the body or the toxic influence of the external environment, active oxygen (ROS) and other free radicals generated by the body cannot be eliminated, so that the harmful influence is generated on the body. Taking the exogenous antioxidant substances can cause other various diseases such as arthritis, cancer, hypertension and the like, and the search for natural and high-cost-performance food antioxidants to protect cells from the influence of ROS is extremely important. At present, the antioxidation of lactobacillus has been proved, and the antioxidation mode mainly includes the elimination of free radicals, the chelation of metal ions, the improvement of the activity of antioxidant enzyme, etc.
China has abundant lactobacillus resources, such as lactobacillus plantarum widely existing in fermented foods such as salted pickles and fermented meat, has the effects of reducing cholesterol, reducing blood sugar, inhibiting obesity, resisting oxidation, adsorbing heavy metals and the like, and is gradually applied to fermented products due to good probiotic characteristics. However, lactobacillus plantarum lacks a complete proteolytic system, has poor protein hydrolysis capability and poor growth in cow milk, and needs to be added with additional probiotic factors and nutrients or to be fermented with lactobacillus with strong proteolytic capability to prepare yoghourt.
Disclosure of Invention
The invention aims to provide yoghourt with an antioxidant function and a preparation method thereof, aiming at the problems in the prior art. The method uses lactobacillus plantarum with strong oxidation resistance to prepare the yoghourt by cooperating with lactobacillus with strong proteolytic ability for fermentation, and simultaneously uses protease to carry out proper enzymolysis on raw milk to improve the proteolytic degree of the raw milk, thereby not only solving the problem that the lactobacillus plantarum grows poorly in the milk, but also improving the oxidation resistance activity of the product. The selected fermentation strain has good viscosity-producing property, and the whey protein powder is matched to strengthen the raw milk, so that the curd effect and the sensory flavor property of the product can be guaranteed.
A preparation method of yoghourt with an antioxidant function comprises the following steps:
(1) preparation of reduced milk: preparing the skim milk powder and water into reduced milk according to a proportion, heating the reduced milk to 50-60 ℃, adding sucrose and whey protein powder, and stirring and mixing the materials for 20-25min at a rotation speed of 180-200 r/min.
Preferably, the skim milk powder and water are prepared into reduced milk according to the mass ratio of 9-11: 85-100; the addition amount of the sucrose is 5-9% by the total mass of the skim milk powder and the water; the addition amount of whey protein powder is 0.5-2%.
(2) Homogenizing the reduced milk with homogenizer at 60-65 deg.C for 3-5min under 20-25 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 85-95 deg.C for 5-30min, and rapidly cooling to 35-40 deg.C to obtain reduced milk;
(4) and (3) enzymatic hydrolysis: adding trypsin into the reduced milk, and hydrolyzing at 35-40 deg.C for 20-25 min.
Preferably, trypsin is added in an amount of 2-3mg per 100-105g of reduced milk.
(5) Enzyme inactivation: heating hydrolyzed reduced milk in 95-100 deg.C water bath for 5-7min, rapidly cooling to 38-43 deg.C, and keeping the temperature;
(6) inoculating a microbial inoculum: mixing streptococcus thermophilus, lactobacillus delbrueckii subsp bulgaricus and lactobacillus plantarum freeze-dried powder in proportion to obtain a composite yogurt starter; and (3) inoculating the compound yogurt starter into the reduced milk obtained in the step (5) according to the amount of 0.02-0.1% under the aseptic condition, and uniformly mixing.
Preferably, the number of viable bacteria in the freeze-dried powder of streptococcus thermophilus, lactobacillus delbrueckii subsp bulgaricus and lactobacillus plantarum is 1.0 multiplied by 1010-3.0×1010CFU/g。
Preferably, the freeze-dried powder of the streptococcus thermophilus, the lactobacillus delbrueckii subsp bulgaricus and the lactobacillus plantarum is mixed according to the mass ratio of 0.9-1.2:0.1-0.3: 0.1-0.5.
(7) Subpackaging and fermenting: subpackaging the inoculated reduced milk into sterile glass fermentation bottles and sealing the bottles; then placing the fermentation bottle in a constant temperature incubator at 38-43 ℃ for culturing for 5-8 h;
(8) after-ripening: taking out after the fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 2-4 ℃ for after-ripening fermentation for 24-48h to obtain the finished product.
The streptococcus thermophilus has strong protein hydrolysis capacity and good viscosity-producing characteristic, and the concentration of free amino nitrogen of the yogurt prepared independently is more than 7.5-8mmol/L and the viscosity of the yogurt is more than 5000mPa & s.
The Lactobacillus delbrueckii subspecies bulgaricus has strong proteolysis capability, and the free amino nitrogen concentration of the yogurt prepared by the Lactobacillus delbrueckii subspecies bulgaricus is more than 7.5-8 mmol/L.
The Lactobacillus plantarum DPPH free radical clearance rate is more than 80-85%, the hydroxyl free radical clearance rate is more than 55-60%, and the superoxide anion free radical clearance rate is more than 55-60%.
The yoghourt prepared by the method has high protein hydrolysis degree of viable count of lactic acid bacteria, remarkably improved ABTS free radical scavenging capacity, DPPH free radical scavenging capacity and hydroxyl free radical scavenging capacity, and strong antioxidant activity.
The positive effects of the invention are as follows:
the method utilizes lactobacillus with strong protease activity and lactobacillus plantarum to cooperatively ferment the yoghourt, and simultaneously utilizes protease to carry out proper enzymolysis on raw material milk, thereby effectively solving the problem that lactobacillus plantarum grows poorly in milk. The enzymolysis can improve the hydrolysis degree of the raw milk protein and produce more micromolecular polypeptide and amino acid. The streptococcus thermophilus has proteolytic enzyme, can hydrolyze milk protein, and can rapidly grow and produce acid in the initial milk environment; lactobacillus bulgaricus also has strong proteolytic ability, and can hydrolyze casein to produce polypeptide. The polypeptides and amino acids can be utilized by the lactobacillus plantarum, and the purpose of promoting the lactobacillus plantarum to grow in milk is achieved.
The lactobacillus plantarum fermented yoghourt with strong antioxidant activity obtained from the pickle can obviously improve the antioxidant activity of the yoghourt. The characteristic research shows that the DPPH free radical scavenging capacity, the hydroxyl free radical scavenging capacity and the superoxide anion scavenging capacity of the yoghourt are obviously improved.
And thirdly, the yoghourt prepared by the method not only has a strong antioxidation function, but also has a good curd effect and a good sensory flavor characteristic. The addition of proteases hydrolyzes part of the casein and whey proteins and may adversely affect the curding effect of the yogurt. The streptococcus thermophilus selected by the method has good viscosity-producing characteristics, and the milk curd effect of the product can be guaranteed by reinforcing the raw milk with the whey protein powder. The obtained product has the advantages of thick and smooth texture, proper sour and sweet taste and no difference in overall flavor characteristics with yoghourt without lactobacillus plantarum.
Drawings
FIG. 1 is a bar graph showing the types and amounts of flavor components of products prepared in example 1 and comparative example 1.
FIG. 2 is a graph showing the relative content of flavor components in the products prepared in example 1 and comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments for the purpose of making the objects, technical solutions and advantages of the present invention more apparent, but it should not be construed that the scope of the above-described subject matter of the present invention is limited to the following examples. Various substitutions and alterations can be made without departing from the technical idea of the invention as described above, according to the common technical knowledge and conventional means in the field, and the scope of the invention is covered.
In the present document,% represents wt% unless otherwise specified; the raw materials used are all commercial products unless otherwise specified.
In the following examples, lyophilized powder of each strain was prepared by the prior art.
The method for evaluating the proteolytic ability of the streptococcus thermophilus strain and the lactobacillus delbrueckii subsp bulgaricus strain and the method for evaluating the viscosity property of the streptococcus thermophilus strain in the application are as follows:
(1) strain activation: inoculating corresponding strain into MRS culture medium, activating for three generations, centrifuging the third generation strain culture solution (4500rpm, 10min, 4 deg.C), collecting thallus, suspending with sterile physiological saline to obtain thallus suspension, and standing at 4 deg.C.
(2) Preparing fermented milk: sterilizing skim milk at 95 deg.C for 5min, cooling to 43 deg.C, inoculating bacterial suspension, fermenting in 43 deg.C constant temperature incubator for 7 hr, and taking out.
(3) Determination of proteolytic Capacity: mixing 450uL of yogurt sample with 900uL of 0.75mol/L trichloroacetic acid solution, standing for 10min, centrifuging at 4500rpm and 4 ℃, and collecting supernatant for later use. And (3) putting 0.15mL of supernatant and 3mL of o-phthalaldehyde reaction liquid into a quartz cuvette, uniformly mixing, reacting for 2min, measuring the light absorption value at 340nm, and comparing with a standard curve to obtain the concentration of free amino nitrogen.
(4) And (3) measuring the viscosity-generating property: the viscosity of the unstirred yoghurt is measured by a viscometer at room temperature, the rotating speed of a rotor is 15r/min, and the value of the 30 th s is selected as the apparent viscosity of the yoghurt.
The lactobacillus plantarum is derived from Sichuan pickle and has strong antioxidant activity, wherein the DPPH free radical clearance rate is more than 80-85%, the hydroxyl free radical clearance rate is more than 55-60%, and the superoxide anion free radical clearance rate is more than 55-60%. The method for evaluating the antioxidant capacity of the strain comprises the following steps:
(1) sample pretreatment: inoculating activated lactobacillus into liquid culture medium according to 1% inoculum size, culturing for 24h, centrifuging the culture solution (10000rpm, 5min, 4 deg.C) to obtain supernatant and cell precipitate. The supernatant was filtered through a 0.22 μm microfiltration membrane filter.
(2) And (3) measuring antioxidant activity: the DPPH radical clearance, hydroxyl radical clearance, superoxide anion radical clearance of the filtrate were measured by methods reported in the literature.
The lactobacillus plantarum strain used in the following examples can be screened from kimchi by the existing screening method, and the streptococcus thermophilus and lactobacillus bulgaricus strain can be screened from yogurt by the existing screening method, but the screened strains must meet the following requirements: the streptococcus thermophilus has strong protein hydrolysis capability and good viscosity-producing characteristic, and the concentration of free amino nitrogen of the yogurt prepared by the streptococcus thermophilus is more than 7.5-8mmol/L and the viscosity of the yogurt is more than 5000mPa & s.
The Lactobacillus delbrueckii subspecies bulgaricus strain has strong proteolysis capability, and the free amino nitrogen concentration of the yogurt prepared by the strain is more than 7.5-8 mmol/L.
The DPPH free radical clearance rate of the lactobacillus plantarum strain is more than 80-85%, the hydroxyl free radical clearance rate is more than 55-60%, and the superoxide anion free radical clearance rate is more than 55-60%.
The strains required above can also be screened by the following specific steps:
1. screening of Streptococcus thermophilus and Lactobacillus bulgaricus
(1) Strain activation: a plurality of Streptococcus thermophilus strains and a plurality of Lactobacillus bulgaricus strains are separated from the milk product by a conventional method and then preserved in a laboratory for standby. Respectively selecting 45 strains of streptococcus thermophilus and 21 strains of lactobacillus bulgaricus from strains preserved in a laboratory, inoculating the strains and the strains into an MRS liquid culture medium to activate three generations, taking a third generation strain culture solution to centrifuge (4500rpm, 10min, 4 ℃) and collecting thalli, suspending the thalli by using sterile physiological saline to prepare a thalli suspension, and placing the thalli suspension at 4 ℃ for later use.
(2) Preparing fermented milk: sterilizing skim milk at 95 deg.C for 5min, cooling to 43 deg.C, inoculating bacterial suspension, fermenting in 43 deg.C constant temperature incubator for 7 hr, and taking out.
(3) Determination of proteolytic Capacity: mixing 450uL of yogurt sample with 900uL of 0.75mol/L trichloroacetic acid solution, standing for 10min, centrifuging at 4500rpm and 4 ℃, and collecting supernatant for later use. And (3) putting 0.15mL of supernatant and 3mL of o-phthalaldehyde reaction liquid into a quartz cuvette, uniformly mixing, reacting for 2min, measuring the light absorption value at 340nm, and comparing with a standard curve to obtain the concentration of free amino nitrogen.
(4) And (3) measuring the viscosity-generating property: the viscosity of the unstirred yoghurt is measured by a viscometer at room temperature, the rotating speed of a rotor is 15r/min, and the value of the 30 th s is selected as the apparent viscosity of the yoghurt.
(5) Determination of excellent strains: the streptococcus thermophilus strain 1 with strong protein hydrolysis capability and good viscosity-producing property is obtained by screening, and the free amino nitrogen concentration of the yogurt prepared by the streptococcus thermophilus strain is more than 7.5-8mmol/L and the viscosity is more than 5000mPa & s by determination. The strain of Streptococcus thermophilus is numbered PCFM 195.
After screening, Lactobacillus bulgaricus strain 1 with strong proteolytic ability is obtained, and the free amino nitrogen concentration of the yogurt prepared independently is more than 7.5-8 mmol/L. The strain number of the strain of Lactobacillus bulgaricus is PCFM 178.
2. Screening of Lactobacillus plantarum having antioxidant Property
(1) Strain activation and treatment: separating 32 strains of Lactobacillus plantarum from Sichuan pickle, activating twice in liquid MRS culture medium, taking the third generation culture solution, inoculating into liquid MRS culture medium according to the inoculum size of 1%, culturing at 37 deg.C for 24 h. Centrifugation (10000rpm, 5min, 4 ℃) was then carried out to obtain supernatant and cell pellet. The supernatant was filtered through a 0.22 μm microfiltration membrane filter.
(2) And (3) measuring antioxidant activity: the DPPH radical clearance, hydroxyl radical clearance, superoxide anion radical clearance of the filtrate were measured by methods reported in the literature. (3) Determination of lactobacillus plantarum strain with strong antioxidant activity: screening to obtain Lactobacillus plantarum 1 strain with strong antioxidant activity, wherein DPPH free radical clearance rate is more than 80-85%, hydroxyl free radical clearance rate is more than 55-60%, and superoxide anion free radical clearance rate is more than 55-60%. The strain number of the lactobacillus plantarum strain is PCFM 108.
Example 1:
a preparation method of yoghourt with an antioxidant function comprises the following steps:
(1) preparation of reduced milk: 100g of skim milk powder and 900g of water are weighed to prepare reduced milk, and then the reduced milk is heated to 60 ℃.6 percent of sucrose and 1 percent of whey protein powder are respectively added according to the mass of the reduced milk, and then the mixture is stirred for 20min at 200 r/min.
(2) Homogenizing: homogenizing the reduced milk with homogenizer at 60 deg.C for 3min under 20 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 90 deg.C for 10min, and rapidly cooling to 37 deg.C.
(4) And (3) enzymatic hydrolysis: adding trypsin at a ratio of 2mg enzyme per 100g reduced milk, and hydrolyzing at 37 deg.C for 20 min.
(5) Enzyme inactivation: immediately heating in 100 deg.C water bath for 5min after hydrolysis, rapidly cooling to 43 deg.C, and keeping the temperature for use.
(6) Inoculating a microbial inoculum: the number of viable bacteria is 1.0 × 1010CFU/g freeze-dried powder of streptococcus thermophilus, the viable count is 1.0 multiplied by 1010The number of the freeze-dried powder and the viable bacteria of the CFU/g lactobacillus delbrueckii subspecies bulgaricus is 1.0 multiplied by 1010And (3) mixing the freeze-dried powder of the CFU/g lactobacillus plantarum according to the mass ratio of 1:0.2:0.2 to obtain the compound yoghurt starter. And (3) weighing 1g of the compound yogurt starter, inoculating the compound yogurt starter into the reduced milk under an aseptic condition, and uniformly mixing. .
(7) Subpackaging and fermenting: and (3) subpackaging the inoculated reduced milk into sterile glass fermentation bottles, sealing the bottles, and culturing the bottles in a constant-temperature incubator at 43 ℃ for 6 hours.
(8) After-ripening: taking out after fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 4 ℃ for after-ripening fermentation for 24h to obtain the finished product.
Example 2:
a preparation method of yoghourt with an antioxidant function comprises the following steps:
(1) preparation of reduced milk: weighing 110g of skim milk powder and 850g of water to prepare reduced milk, and heating to 55 ℃.5 percent of sucrose and 0.5 percent of whey protein powder are added according to the mass of the reduced milk, and then the mixture is stirred for 20min at 200 r/min.
(2) Homogenizing: homogenizing the reduced milk with homogenizer at 60 deg.C for 3min under 20 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 85 deg.C in water bath for 30min, and rapidly cooling to 37 deg.C.
(4) And (3) enzymatic hydrolysis: adding trypsin at a ratio of 3mg enzyme per 100g reduced milk, and hydrolyzing at 37 deg.C for 25 min.
(5) Enzyme inactivation: immediately heating in 95 deg.C water bath for 7min after hydrolysis, rapidly cooling to 42 deg.C, and keeping the temperature for use.
(6) Inoculating a microbial inoculum: the number of viable bacteria is 3.0 × 1010The freeze-dried powder and viable count of the CFU/g streptococcus thermophilus are 3.0 multiplied by 1010CFU/g's Deshi milk strawThe number of lyophilized powder and viable bacteria of the Bulgaria subspecies is 3.0 × 1010And (3) mixing the freeze-dried powder of the CFU/g lactobacillus plantarum according to the mass ratio of 0.9:0.2:0.5 to obtain the compound yoghurt starter. 0.2g of the compound yoghourt starter is weighed and inoculated into the reduced milk under the aseptic condition, and the mixture is uniformly mixed.
(7) Subpackaging and fermenting: and (3) subpackaging the inoculated reduced milk into sterile glass fermentation bottles, sealing the bottles, and culturing the bottles in a constant-temperature incubator at 42 ℃ for 5 hours.
(8) After-ripening: taking out after fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 4 ℃ for after-ripening fermentation for 24h to obtain the finished product.
Example 3:
a preparation method of yoghourt with an antioxidant function comprises the following steps:
(1) preparation of reduced milk: weighing 90g of skim milk powder and 1000g of water to prepare reduced milk, and heating to 60 ℃.9 percent of sucrose and 2 percent of whey protein powder are added according to the mass of the reduced milk, and then the mixture is stirred for 20min at 200 r/min.
(2) Homogenizing: homogenizing the reduced milk with homogenizer at 65 deg.C for 5min under 25 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 95 deg.C in water bath for 5min, and rapidly cooling to 40 deg.C.
(4) And (3) enzymatic hydrolysis: adding trypsin at a ratio of 2mg enzyme per 100g reduced milk, and hydrolyzing at 40 deg.C for 20 min.
(5) Enzyme inactivation: immediately heating in 100 deg.C water bath for 5min after hydrolysis, rapidly cooling to 38 deg.C, and keeping the temperature for use.
(6) Inoculating a microbial inoculum: the number of viable bacteria is 2.0 × 1010The freeze-dried powder and viable count of the CFU/g streptococcus thermophilus are 2.0 multiplied by 1010The number of the freeze-dried powder and the viable bacteria of the CFU/g lactobacillus delbrueckii subspecies bulgaricus is 2.0 multiplied by 1010And (3) mixing the freeze-dried powder of the CFU/g lactobacillus plantarum according to the mass ratio of 1.2:0.2:0.1 to obtain the compound yoghurt starter. 0.6g of the compound yoghourt starter is weighed and inoculated into the reduced milk under the aseptic condition, and the mixture is uniformly mixed.
(7) Subpackaging and fermenting: and (3) subpackaging the inoculated reduced milk into sterile glass fermentation bottles, sealing the bottles, and culturing the bottles in a constant-temperature incubator at 38 ℃ for 8 hours.
(8) After-ripening: taking out after fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 4 ℃ for after-ripening fermentation for 24h to obtain the finished product.
The storage stability of the yoghurts prepared in examples 1, 2 and 3 was evaluated:
storing the yogurt product at 4 deg.C for 20 days, sampling at 0, 5, 10, 15, and 20 days, and measuring acidity by phenolphthalein indicator method, with the results shown in Table 1.
TABLE 1 acidity Change during storage of yoghurts
The results show that the acidity of the yoghurt is increased with the prolongation of the storage time, and post-acidification phenomenon is generated. The optimal edible acidity of the yoghourt is 80-120 DEG T, and the acidity of the product is lower than 120 DEG T in the whole storage period, which indicates that the product has good storage stability.
Comparative example 1: the preparation of yoghurt was carried out as in example 1, with the only difference that no lactobacillus plantarum was added.
A preparation method of yogurt comprises the following steps:
(1) preparation of reduced milk: 100g of skim milk powder and 900g of water are weighed to prepare reduced milk, and the reduced milk is heated to 60 ℃.6 percent of sucrose and 1 percent of whey protein powder are added according to the mass of the reduced milk, and then the mixture is stirred for 20min at 200 r/min.
(2) Homogenizing: homogenizing the reduced milk with homogenizer at 60 deg.C for 3min under 20 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 90 deg.C in water bath for 10min, and rapidly cooling to 37 deg.C.
(4) And (3) enzymatic hydrolysis: adding trypsin at a ratio of 2mg enzyme per 100g reduced milk, and hydrolyzing at 37 deg.C for 20 min.
(5) Enzyme inactivation: immediately heating in 100 deg.C water bath for 5min after hydrolysis, rapidly cooling to 43 deg.C, and keeping the temperature for use.
(6) Inoculating a microbial inoculum: the number of viable bacteria is 1.0 × 1010The freeze-dried powder and the viable count of the CFU/g streptococcus thermophilus are 1.0 multiplied by 1010And (3) mixing the freeze-dried powder of the CFU/g lactobacillus delbrueckii subspecies bulgaricus according to the mass ratio of 1:0.2 to obtain the compound yoghurt starter. Weighing 1g of the compound yogurt starter, inoculating the compound yogurt starter into the reduced milk under an aseptic condition, and uniformly mixing.
(7) Subpackaging and fermenting: and (3) subpackaging the inoculated reduced milk into sterile glass fermentation bottles, sealing the bottles, and culturing the bottles in a constant-temperature incubator at 43 ℃ for 6 hours.
(8) After-ripening: taking out after fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 4 ℃ for after-ripening fermentation for 24h to obtain the finished product.
Comparative example 2: the preparation of yoghurt was carried out as in example 1, with the only difference that no trypsin was added.
A preparation method of yogurt comprises the following steps:
(1) preparation of reduced milk: 100g of skim milk powder and 900g of water are weighed to prepare reduced milk, and the reduced milk is heated to 60 ℃.6 percent of sucrose and 1 percent of whey protein powder are added according to the mass of the reduced milk, and then the mixture is stirred for 20min at 200 r/min.
(2) Homogenizing: homogenizing the reduced milk with homogenizer at 60 deg.C for 3min under 20 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 90 deg.C in water bath for 10min, rapidly cooling to 43 deg.C, and keeping the temperature for use.
(4) Inoculating a microbial inoculum: the number of viable bacteria is 1.0 × 1010The freeze-dried powder and viable count of the CFU/g streptococcus thermophilus are 1.0 multiplied by 1010The number of the freeze-dried powder and the viable bacteria of the CFU/g lactobacillus delbrueckii subspecies bulgaricus is 1.0 multiplied by 1010And (3) mixing the freeze-dried powder of the CFU/g lactobacillus plantarum according to the mass ratio of 1:0.2:0.2 to obtain the compound yoghurt starter. Weighing 1g of the compound yogurt starter, inoculating the compound yogurt starter into the reduced milk under an aseptic condition, and uniformly mixing.
(5) Subpackaging and fermenting: and (3) subpackaging the inoculated reduced milk into sterile glass fermentation bottles, sealing the bottles, and culturing the bottles in a constant-temperature incubator at 43 ℃ for 6 hours.
(6) After-ripening: taking out after fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 4 ℃ for after-ripening fermentation for 24h to obtain the finished product.
Comparative example 3: preparation of yoghurt was carried out as in example 1, except that Streptococcus thermophilus was not added.
A preparation method of yogurt comprises the following steps:
(1) preparation of reduced milk: 100g of skim milk powder and 900g of water are weighed to prepare reduced milk, and the reduced milk is heated to 60 ℃.6 percent of sucrose and 1 percent of whey protein powder are added according to the mass of the reduced milk, and then the mixture is stirred for 20min at 200 r/min.
(2) Homogenizing: homogenizing the reduced milk with homogenizer at 60 deg.C for 3min under 20 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 90 deg.C in water bath for 10min, and rapidly cooling to 37 deg.C.
(4) And (3) enzymatic hydrolysis: adding trypsin at a ratio of 2mg enzyme per 100g reduced milk, and hydrolyzing at 37 deg.C for 20 min.
(5) Enzyme inactivation: immediately heating in 100 deg.C water bath for 5min after hydrolysis, rapidly cooling to 43 deg.C, and keeping the temperature for use.
(6) Inoculating a microbial inoculum: the number of viable bacteria is 1.0 × 1010The number of the freeze-dried powder and the viable bacteria of the CFU/g lactobacillus delbrueckii subspecies bulgaricus is 1.0 multiplied by 1010And mixing the freeze-dried powder of the CFU/g lactobacillus plantarum according to the mass ratio of 1:0.2 to obtain the compound yoghurt starter. Weighing 1g of the compound yogurt starter, inoculating the compound yogurt starter into the reduced milk under an aseptic condition, and uniformly mixing.
(7) Subpackaging and fermenting: and (3) subpackaging the inoculated reduced milk into sterile glass fermentation bottles, sealing the bottles, and culturing the bottles in a constant-temperature incubator at 43 ℃ for 6 hours.
(8) After-ripening: taking out after fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 4 ℃ for after-ripening fermentation for 24h to obtain the finished product.
Comparative example 4: the fermentation strain is common strain
A preparation method of yogurt uses Streptococcus thermophilus, Lactobacillus delbrueckii subsp bulgaricus and Lactobacillus plantarum with the characteristics of: the yogurt prepared from Streptococcus thermophilus alone has free amino nitrogen concentration of less than 7.5mmol/L and viscosity of less than 5000 mPa.s, the yogurt prepared from Lactobacillus delbrueckii subsp bulgaricus alone has free amino nitrogen concentration of less than 7.5mmol/L, and the Lactobacillus plantarum has DPPH free radical clearance rate of less than 80%, hydroxyl free radical clearance rate of less than 55% and superoxide anion free radical clearance rate of less than 55%. The preparation method comprises the following steps:
(1) preparation of reduced milk: 100g of skim milk powder and 900g of water are weighed to prepare reduced milk, and the reduced milk is heated to 60 ℃.6 percent of sucrose and 1 percent of whey protein powder are added according to the mass of the reduced milk, and then the mixture is stirred for 20min at 200 r/min.
(2) Homogenizing: homogenizing the reduced milk with homogenizer at 60 deg.C for 3min under 20 MPa.
(3) And (3) sterilization: sterilizing the homogenized material liquid at 90 deg.C in water bath for 10min, and rapidly cooling to 37 deg.C.
(4) And (3) enzymatic hydrolysis: adding trypsin at a ratio of 2mg enzyme per 100g reduced milk, and hydrolyzing at 37 deg.C for 20 min.
(5) Enzyme inactivation: immediately heating in 100 deg.C water bath for 5min after hydrolysis, rapidly cooling to 43 deg.C, and keeping the temperature for use.
(6) Inoculating a microbial inoculum: the number of viable bacteria is 1.0 × 1010The freeze-dried powder and viable count of the CFU/g streptococcus thermophilus are 1.0 multiplied by 1010The number of the freeze-dried powder and the viable bacteria of the CFU/g lactobacillus delbrueckii subspecies bulgaricus is 1.0 multiplied by 1010And (3) mixing the freeze-dried powder of the CFU/g lactobacillus plantarum according to the mass ratio of 1:0.2:0.2 to obtain the compound yoghurt starter. Weighing 1g of the compound yogurt starter, inoculating the compound yogurt starter into the reduced milk under an aseptic condition, and uniformly mixing.
(7) Subpackaging and fermenting: and (3) subpackaging the inoculated reduced milk into sterile glass fermentation bottles, sealing the bottles, and culturing the bottles in a constant-temperature incubator at 43 ℃ for 6 hours.
(8) After-ripening: taking out after fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 4 ℃ for after-ripening fermentation for 24h to obtain the finished product.
Experiment 1:
the yogurt products prepared in example 1, comparative example 2, comparative example 3, and comparative example 4 were subjected to viable lactic acid bacteria counting, and the degree of proteolysis and antioxidant activity were measured:
the lactic acid bacteria quantity of the yoghourt is determined according to GB 4789.35-2016 food safety national standard food microbiology inspection lactic acid bacteria inspection. The antioxidant activity and the degree of proteolysis of the product were determined according to the methods reported in the literature, and the results are shown in Table 2.
TABLE 2 determination of lactic acid bacteria amount, degree of proteolysis and antioxidant Activity of the products
| Index (I) | Comparative example 1 | Comparative example 2 | Comparative example 3 | Comparative example 4 | Example 1 |
| Lactic acid bacteria (CFU/g) | 7.8×107 | 4.0×107 | 4.8×107 | 5.3×107 | 8.4×107 |
| Degree of proteolysis (mmol/L) | 10.1 | 6.7 | 8.2 | 7.5 | 10.6 |
| ABTS radical scavenging ability (%) | 30.6 | 42.8 | 48.3 | 33.9 | 68.5 |
| DPPH radical scavenging ability (%) | 47.3 | 63.1 | 65.6 | 52.7 | 75.4 |
| Hydroxy radical scavenging ability (%) | 17.9 | 33.6 | 38.0 | 24.4 | 58.2 |
The lactobacillus plantarum added in the comparative example 1 does not have strong antioxidant activity, and the antioxidant activity of the yoghurt product is obviously lower than that of the yoghurt product in the example 1 in the comparative example 4. Compared example 2 without adding trypsin for hydrolysis, compared example 3 without adding streptococcus thermophilus, the viable count and the proteolysis degree of the lactic acid bacteria are lower than those of example 1, and the oxidation resistance of the yoghourt product is poor. The result shows that the product of the invention has higher viable count of lactobacillus and protein hydrolysis degree, the ABTS free radical scavenging capacity, DPPH free radical scavenging capacity and hydroxyl free radical scavenging capacity (%) of the product are obviously improved, and the antioxidant activity is strong.
Experiment 2:
sensory evaluation was performed on the yogurt products prepared in example 1, comparative example 1 and comparative example 3:
the fermented and post-cooked product for 24 hours is evaluated by a specially trained evaluator, and 6 aspects of the color (20 points), the tissue state (20 points), the viscosity (10 points), the sour-sweet ratio (15 points), the milk flavor (20 points), the fermentation flavor (15 points) and the like of the product are evaluated for the yogurt in a sensory manner, and the total score is 100 points (table 3). The results are shown in Table 4.
TABLE 3 sensory Scoring criteria for products
TABLE 4 sensory Scoring results for the products
Comparative example 3, no streptococcus thermophilus is added, whey separation is generated, the taste is rough, the viscosity of the product is poor, and comparative example 4, the general bacterial strain is used, the tissue state and viscosity of the product are also poor, so that the method provided by the invention can effectively guarantee the curd effect of the product. Compared with the comparative example 1, the product of the invention is added with the lactobacillus plantarum, and after the enzyme hydrolysis treatment is carried out on the raw material milk, the product has certain influence on the tissue state and the viscosity of the yoghourt, the taste of the product is slightly sour, but the fermentation flavor is more intense. Therefore, the yoghourt product prepared by the method not only has stronger antioxidant function, but also has good sensory and flavor characteristics, and the sensory quality of the yoghourt product is not different from that of yoghourt without lactobacillus plantarum.
Experiment 3:
the yogurt products prepared in example 1 and comparative example 1 were subjected to volatile flavor component determination:
referring to the method reported in the literature, the volatile flavor components of the product were measured by a headspace solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method, and the results are shown in fig. 1 and 2. The results show that compared with the yoghourt without lactobacillus plantarum, the yoghourt has more types of flavor components, wherein the relative contents of ketones, alcohols and alkanes are higher, and the difference of the overall flavor characteristics is not great compared with the yoghourt without lactobacillus plantarum.
According to the experiments, the method provided by the invention utilizes the lactobacillus with strong protein hydrolysis capacity and viscosity producing property and the lactobacillus plantarum with antioxidant activity to cooperatively ferment the yoghourt, and simultaneously properly processes the raw material milk, so that the antioxidant activity of the yoghourt is improved, and the product has good storage stability, sensory quality and flavor characteristics, and the variety of the product is enriched.
The above examples are only preferred embodiments of the patent, but the scope of protection of the patent is not limited thereto. It should be noted that, for those skilled in the art, without departing from the principle of this patent, several improvements and modifications can be made according to the patent solution and its patent idea, and these improvements and modifications should also be considered as within the protection scope of this patent.
Claims (10)
1. A method for preparing yoghourt with antioxidant function is characterized by comprising the following steps:
(1) preparation of reduced milk: preparing reduced milk from the skim milk powder and water in proportion, heating the reduced milk to 50-60 ℃, adding sucrose and whey protein powder, and stirring and mixing the materials at the speed of 180-200r/min for 20-25 min;
(2) homogenizing: homogenizing the reduced milk with homogenizer at 60-65 deg.C for 3-5min under 20-25 MPa;
(3) and (3) sterilization: sterilizing the homogenized material liquid at 85-95 deg.C for 5-30min, and rapidly cooling to 35-40 deg.C to obtain reduced milk;
(4) and (3) enzymatic hydrolysis: adding trypsin into the reduced milk, and hydrolyzing at 35-40 deg.C for 20-25 min;
(5) enzyme inactivation: heating hydrolyzed reduced milk in 95-100 deg.C water bath for 5-7min, rapidly cooling to 38-43 deg.C, and keeping the temperature;
(6) inoculating a microbial inoculum: mixing streptococcus thermophilus, lactobacillus delbrueckii subsp bulgaricus and lactobacillus plantarum freeze-dried powder in proportion to obtain a composite yogurt starter; inoculating the compound yogurt starter in the reduced milk obtained in the step (5) in an amount of 0.02-0.1% under aseptic conditions, and uniformly mixing;
(7) subpackaging and fermenting: subpackaging the inoculated reduced milk into sterile glass fermentation bottles and sealing the bottles; then placing the fermentation bottle in a constant temperature incubator at 38-43 ℃ for culturing for 5-8 h;
(8) after-ripening: taking out after the fermentation is finished, immediately cooling in ice water bath, and then placing in a refrigerator at 2-4 ℃ for after-ripening fermentation for 24-48h to obtain the finished product.
2. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the skim milk powder and water are prepared into the reduced milk according to the mass ratio of 9-11: 85-100.
3. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the addition amount of the sucrose is 5-9% by the total mass of the skim milk powder and the water; the addition amount of whey protein powder is 0.5-2%.
4. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the number of viable bacteria in lyophilized powder of Streptococcus thermophilus, Lactobacillus delbrueckii subsp bulgaricus and Lactobacillus plantarum is 1.0 × 1010-3.0×1010CFU/g。
5. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the freeze-dried powder of the streptococcus thermophilus, the lactobacillus delbrueckii subsp bulgaricus and the lactobacillus plantarum is mixed according to the mass ratio of 0.9-1.2:0.1-0.3: 0.1-0.5.
6. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the streptococcus thermophilus has strong protein hydrolysis capacity and good viscosity-producing characteristic, and the concentration of free amino nitrogen of the yogurt prepared independently is more than 7.5-8mmol/L and the viscosity of the yogurt is more than 5000mPa & s.
7. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the Lactobacillus delbrueckii subspecies bulgaricus has strong proteolysis capability, and the free amino nitrogen concentration of the yogurt prepared by the Lactobacillus delbrueckii subspecies bulgaricus is more than 7.5-8 mmol/L.
8. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the Lactobacillus plantarum DPPH free radical clearance rate is more than 80-85%, the hydroxyl free radical clearance rate is more than 55-60%, and the superoxide anion free radical clearance rate is more than 55-60%.
9. The method for preparing yoghourt with antioxidant function according to claim 1, which is characterized by comprising the following steps: the amount of trypsin added is 2-3mg per 100-105g of reduced milk.
10. Yoghurt produced by the method according to any one of claims 1 to 9, wherein: the yoghourt prepared by the method has high protein hydrolysis degree of viable count of lactic acid bacteria, remarkably improved ABTS free radical scavenging capacity, DPPH free radical scavenging capacity and hydroxyl free radical scavenging capacity, and strong antioxidant activity.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113647458A (en) * | 2021-08-06 | 2021-11-16 | 皇氏集团华南乳品有限公司 | Mixed lactobacillus fermented milk with antioxidant function and preparation method thereof |
| WO2023008491A1 (en) * | 2021-07-27 | 2023-02-02 | 合同酒精株式会社 | Enzyme-containing composition, method for producing milk and method for producing fermented milk |
| CN115927117A (en) * | 2023-01-04 | 2023-04-07 | 兰州大学 | Lactobacillus plantarum and application thereof |
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| CN101006802A (en) * | 2007-01-26 | 2007-08-01 | 华南理工大学 | Preparation method of coagulated yoghurt containing rich active peptides |
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| WO2023008491A1 (en) * | 2021-07-27 | 2023-02-02 | 合同酒精株式会社 | Enzyme-containing composition, method for producing milk and method for producing fermented milk |
| CN113647458A (en) * | 2021-08-06 | 2021-11-16 | 皇氏集团华南乳品有限公司 | Mixed lactobacillus fermented milk with antioxidant function and preparation method thereof |
| CN115927117A (en) * | 2023-01-04 | 2023-04-07 | 兰州大学 | Lactobacillus plantarum and application thereof |
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