CN116555114A - Ferment and application thereof, milk bean curd and preparation method thereof - Google Patents

Ferment and application thereof, milk bean curd and preparation method thereof Download PDF

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Publication number
CN116555114A
CN116555114A CN202310552636.6A CN202310552636A CN116555114A CN 116555114 A CN116555114 A CN 116555114A CN 202310552636 A CN202310552636 A CN 202310552636A CN 116555114 A CN116555114 A CN 116555114A
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China
Prior art keywords
milk
starter
lactococcus lactis
curd
fermentation
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Inventor
孟和毕力格
刘文俊
王记成
陈永福
王艺璇
苏馨
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Inner Mongolia Agricultural University
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Inner Mongolia Agricultural University
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N1/00—Microorganisms, e.g. protozoa; Compositions thereof; Processes of propagating, maintaining or preserving microorganisms or compositions thereof; Processes of preparing or isolating a composition containing a microorganism; Culture media therefor
    • C12N1/20—Bacteria; Culture media therefor
    • 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
    • A23C19/00—Cheese; Cheese preparations; Making thereof
    • A23C19/02—Making cheese curd
    • A23C19/032—Making cheese curd characterised by the use of specific microorganisms, or enzymes of microbial origin
    • A23C19/0323—Making cheese curd characterised by the use of specific microorganisms, or enzymes of microbial origin using only lactic acid bacteria, e.g. Pediococcus and Leuconostoc species; Bifidobacteria; Microbial starters in general
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12R—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES C12C - C12Q, RELATING TO MICROORGANISMS
    • C12R2001/00—Microorganisms ; Processes using microorganisms
    • C12R2001/01—Bacteria or Actinomycetales ; using bacteria or Actinomycetales
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12R—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES C12C - C12Q, RELATING TO MICROORGANISMS
    • C12R2001/00—Microorganisms ; Processes using microorganisms
    • C12R2001/01—Bacteria or Actinomycetales ; using bacteria or Actinomycetales
    • C12R2001/46—Streptococcus ; Enterococcus; Lactococcus
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P60/00—Technologies relating to agriculture, livestock or agroalimentary industries
    • Y02P60/80—Food processing, e.g. use of renewable energies or variable speed drives in handling, conveying or stacking
    • Y02P60/87—Re-use of by-products of food processing for fodder production

Abstract

The invention belongs to the technical field of traditional dairy product production, and particularly relates to a starter and application thereof, and a milk bean curd and a preparation method thereof. The invention provides a starter comprising lactococcus lactis (lactococcus lactis) and Lactobacillus paracasei (Lactobacilli sp. Casei); the viable count of the lactococcus lactis is more than or equal to 2.5X10 6 CFU/mL; the viable count of the cheese bacillus paracasei is more than or equal to 2.5X10 5 CFU/mL. The fermented bean curd prepared by the starter of the invention contains higher content of ketone compounds such as 2-heptanone, 2-nonanone and acetoin, and has unique fruit fragrance and cream fragrance. The fermented milk curd prepared by the starter does not harden in taste in the storage process, has enhanced toughness strength and reduced brittleness index, and improves the texture characteristics of the fermented milk curd.

Description

Ferment and application thereof, milk bean curd and preparation method thereof
Technical Field
The invention belongs to the technical field of dairy products, and particularly relates to a starter and application thereof, and a milk bean curd and a preparation method thereof.
Background
A milk bean curd, mongolian "huge milk De", is a traditional dairy product prepared from fresh milk as raw material by filtering, naturally fermenting until it is coagulated yogurt, collecting the milk oil layer floating on the surface, heating the lower layer curd to form flocculent curd block, removing whey, thermally deforming the solid substances such as milk protein into a viscous state, and molding. It is reported as "Hurood" in inner mongolia in china, which is called "milk bean curd" because its appearance is similar to that of ordinary bean curd, but it does not contain any bean component.
The milk bean curd is a dairy product with high protein content, the content of the milk bean curd is generally more than 30%, the protein is decomposed into peptone, peptide, amino acid, inorganic or organic compound and other small molecular substances under the action of microorganisms and enzymes, the milk bean curd is easy to digest and absorb by human bodies, and the milk bean curd is a good source of high-quality protein in diet. Meanwhile, the milk bean curd contains a large amount of calcium, phosphorus, sodium, potassium, magnesium, iron, zinc, fat-soluble vitamins, water-soluble vitamins and other nutrients, wherein the content of essential amino acids accounts for 36.10-37.75% of the total content of amino acids, and the milk bean curd is a comprehensive health food for providing high-quality proteins and enough calcium for human beings.
Until now, the preparation of milk tofu has been based on natural fermentation, with the fermenting microorganisms mainly coming from fresh, non-sterilized cow milk and fermentation vessels and environment. Due to the long-term fermentation of cow's milk, the environment and the natural choice in the container form the dominant lactic acid bacteria group, and the complex and diverse types of microorganisms exist in other groups, such as acid-resistant staphylococcus, saccharomycetes, mould and the like, so that the fermented bean curd quality and the flavor characteristics have large differences according to the personal habits and experiences of producers. The microbial groups participated in the natural fermentation of the milk tofu are complex, the microbial groups are greatly fluctuated and changed under the influence of environmental factors, and even some fungus microorganisms which are easy to cause the deterioration of the milk tofu exist, so that the milk tofu produced by the natural fermentation method has unstable flavor and poor taste.
Disclosure of Invention
The invention aims to solve the defects of the prior art, and provides a starter, which can produce substances with flavors of esters, alkanes, alkenes, acids and alcohols when used for preparing the milk bean curd, and the milk bean curd has stable flavor and good taste.
The invention provides a starter comprising lactococcus lactis (Lactococcus lactis) IMAU12063 and Lactobacillus paracasei (Lacticaseibacillus sp.) IMAU12062; the effective viable count of lactococcus lactis in the starter is more than or equal to 2.5X10 6 CFU/mL; the effective viable count of the Lactobacillus paracasei in the starter is more than or equal to 2.5X10 5 CFU/mL；
The preservation number of the lactococcus lactis IMAU12063 is CGMCC NO.26949; the preservation number of the Lactobacillus paracasei IMAU12062 is CGMCC NO.26948.
Preferably, the mass ratio of the lactococcus lactis to the lactobacillus paracasei is 1: (1-2).
The invention provides application of the starter in preparation of milk tofu.
Preferably, the starter is used alone or in combination with other commercial starter.
The invention provides a preparation method of milk bean curd, which comprises the following steps:
fermenting cow milk by using the starter according to the technical scheme to obtain a fermentation product;
and (3) discharging whey after the fermented product is curdled to obtain the milk bean curd.
Preferably, the temperature of the fermentation is 28-33 ℃, and the fermentation is stopped when the pH value of the fermentation product reaches 4.48-4.52.
Preferably, the mass ratio of the starter to the cow milk is 1:20 to 50.
Preferably, the temperature of the whey discharge is 43-47 ℃.
Preferably, the means for curd the fermentation product comprises: mixing the fermentation product with chymosin.
The invention provides the milk bean curd obtained by the preparation method of the technical scheme, which is characterized in that the flavor substances of the milk bean curd comprise one or more of 2-heptanone, 2-nonanone, acetoin, 3-methyl-butyraldehyde, heptanal and octanal.
The invention has the beneficial effects that: the starter provided by the invention comprises lactococcus lactis (Lactococcus lactis) and lactobacillus paracasei (Lactobacilli strarasei); the viable count of the lactococcus lactis is more than or equal to 2.5X10 6 CFU/mL; the viable count of the cheese bacillus paracasei is more than or equal to 2.5X10 5 CFU/mL; the lactococcus lactis comprises lactococcus lactis IMAU12063 with a preservation number of CGMCC NO.26949; the Lactobacillus paracasei comprises Lactobacillus paracasei IMAU12062 with a preservation number of CGMCC No.26948. The invention compounds lactococcus lactis and cheese bacillus paracasei, can generate rich esters, alkanes, alkenes, acids and alcohols in the fermentation process, and the prepared milk bean curd has good taste, and contains higher content of ketone compounds such as 2-heptanone, 2-nonanone and acetoin, thereby endowing the milk bean curd with unique fruit fragrance and cream fragrance. The milk tofu contains abundant 3-methyl-butyraldehyde, heptanal, octanal and other aldehyde compounds, which can produce pleasant aroma. Meanwhile, the milk bean curd is rich in esters, alkanes, alkenes, acids, alcohols and other compounds, and the milk bean curd is endowed with unique and stable flavor.
The common milk bean curd is easy to present the slag, the starter can improve the taste of the milk bean curd which is gradually hardened in the storage process, the slag does not appear, and meanwhile, compared with the commercial milk bean curd in the prior art, the prepared milk bean curd has the advantages of enhanced toughness strength after storage, reduced brittleness index, integrally improved texture of the milk bean curd and stable flavor of the milk bean curd.
Description of biological preservation
Lactococcus lactis (Lactococcus lactis) IMAU12063 was deposited in China general microbiological culture Collection center (CGMCC) with a accession number of CGMCC No.26949, accession number address: no. 1 and No. 3 of the north cinquefoil of the morning sun area of beijing city.
Cheese bacillus paracasei (lacticeibacillus sparasaei) IMAU12062, deposited in China general microbiological culture Collection center (ccmcc) under the accession number of CGMCC No.26948 at the accession number address: no. 1 and No. 3 of the north cinquefoil of the morning sun area of beijing city.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments will be briefly described below.
FIG. 1 shows the milk curds of the Lactobacillus lactis and Lactobacillus paracasei strains of example 1;
FIG. 2 shows the pH change during fermentation of lactococcus lactis in example 1;
FIG. 3 shows the change in titrated acidity during fermentation of lactococcus lactis in example 1;
FIG. 4 shows the pH change during fermentation of Lactobacillus paracasei in example 1;
FIG. 5 shows the change in titrated acidity during fermentation by Lactobacillus paracasei in example 1;
FIG. 6 shows the final viscosity (A) of the lactic acid bacterium strain fermented milk obtained in example 1;
FIG. 7 shows the results of the sensory evaluation test (B) of the fermentation end point of the lactic acid bacterium strain fermented milk in example 1;
FIG. 8 is a graph showing the results of pH and titrated acidity measurements of the fermentations during the fermentation of the starter-fermented milk of examples 2-9 and comparative example 1;
FIG. 9 shows sensory scoring results of the starter fermented milk of examples 2 to 9 and comparative example 1;
FIG. 10 is a graph showing the results of the total content change of each type of compound during storage of the fermented bean curd of example 10 and comparative example 2;
FIG. 11 is a graph showing the result of the change in the total amount of volatile matters during storage of the fermented bean curd of example 10 and comparative example 2;
FIG. 12 is a graph showing the results of various compound species during storage of the fermented bean curd of example 10 and comparative example 2;
FIG. 13 is a radar chart of an electronic nose sensor and a box-line graph analysis result during storage of the fermented bean curd prepared in example 10; a is an electronic nose detection flavor radar chart; and b is an electronic nose detection flavor box diagram.
Detailed Description
The invention provides a starter comprising lactococcus lactis (Lactococcus lactis) IMAU12063 and Lactobacillus paracasei (Lacticaseibacillus sp.) IMAU12062; the viable count of lactococcus lactis in the starter is more than or equal to 2.5X10 6 CFU/mL; the viable count of the Lactobacillus paracasei in the starter is more than or equal to 2.5X10 5 CFU/mL, the preservation number of the lactococcus lactis IMAU12063 is CGMCCNO.26949; the preservation number of the cheese-making bacillus paracasei IMAU12062 is CGMCCNO.26948.
In the invention, the mass ratio of the lactococcus lactis to the Lactobacillus paracasei in the starter is preferably 1: (1-2), more preferably 1: (1 to 1.5), more preferably 1:1.
the lactococcus lactis IMAU12063 has a preservation number of CGMCC NO.26949, latin name of Lactococcus lactis, and a cheese sample separated from tin Lin Guole allied areas is separated, identified and stored by a key laboratory of the university of inner Mongolia agricultural "Dairy biotechnology and engineering" education department, and the 16S rRNA sequence sequencing information of the lactococcus lactis IMAU12063 is OQ694910. The optimal growth temperature of IMAU12063 is 30-37 ℃, and the IMAU12063 has good growth in milk, high acid production speed, good curd property and good adhesion property. The lactic acid lactococcus IMAU12063 has good acid production performance, the single bacteria fermentation reaches the fermentation end point for 12 hours, the viscosity value is higher and reaches more than 700 Pa.S, which indicates that the fermented dairy product has higher protein content and nutritive value.
The collection number of the cheese bacillus paracasei IMAU12062 is CGMCC NO.26948, the Latin name is Lacticaseibacoil sparacasei, a cheese sample separated from Shangrilla is separated, identified and stored by a key laboratory of the university of inner Mongolia agricultural "Dairy biotechnology and engineering" education department, and the 16S rRNA sequence sequencing information is OQ694911. The IMAU12062 has an optimal growth temperature of 30-37 ℃, is suitable for the requirement of accumulating more flavor substances by low-temperature fermentation of the fermented milk of the milk bean curd, has good growth in milk, moderate acid production speed and good curd property. The lactobacillus paracasei IMAU12062 has good acid production performance, moderate fermentation speed and intermediate viscosity value, and the single-strain fermentation reaches the fermentation end point for 16 hours, and the viscosity value is about 500 Pa.S.
The invention also provides application of the starter in preparation of the milk tofu. The starter can improve the flavor and quality of the traditional milk tofu. The invention aims to provide two strains of lactic acid bacteria, namely lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062, which are used as starter strains for fermenting milk in the production process of the milk bean curd to compound the lactic acid bacteria, aiming at the current situation that the milk bean curd is produced by natural fermentation and has potential quality, safety and flavor problems.
The invention provides a starter, which comprises lactococcus lactis (Lactococcus lactis) and lactobacillus paracasei (Lactobacilli sp.asaei), and the preparation method of the starter preferably comprises the steps of mixing and applying the starter, preferably the lactococcus lactis (Lactococcus lactis) and the lactobacillus paracasei (Lacticaseibacillus paracasei), and more preferably the lactococcus lactis (Lactococcus lactis) bacterial suspension and the lactobacillus paracasei (Lactobacilli sp.asaei) bacterial suspension.
The preparation method of the lactococcus lactis suspension preferably comprises the following steps: inoculating lactococcus lactis into sterile liquid MRS culture medium, and performing activation culture to obtain bacterial mud, mixing the bacterial mud with PBS solutionThe bacterial suspension is obtained. The effective viable count of the lactococcus lactis suspension is preferably 0.75X10 7 ～5×10 7 CFU/mL, more preferably 2.5X10 7 CFU/mL。
The preparation method of the lactobacillus paracasei bacterial suspension preferably comprises the following steps: inoculating the cheese bacillus paracasei into a sterile liquid MRS culture medium for activation culture to obtain bacterial mud, and mixing the bacterial mud with PBS solution to obtain bacterial suspension. The effective viable count of the Lactobacillus paracasei bacterial suspension of the present invention is preferably 0.75X10 7 ～5×10 7 CFU/mL, more preferably 2.5X10 7 CFU/mL。
In the present invention, the composition of the MRS medium is preferably: each liter comprises 10g of soybean peptone, 5g of beef extract, 4g of yeast powder, 20g of glucose, 1mL of tween-80, 2g of disodium hydrogen phosphate, 5g of anhydrous sodium acetate, 2g of triamine citrate, 0.02g of manganese sulfate, 0.1g of magnesium sulfate, 15g of agar powder and 1L of sterile distilled water; the pH of the MRS medium is preferably 6.20. The MRS culture medium is preferably sterilized at 121 ℃ for 15min and then used.
The temperature of the activation culture is preferably 37 ℃, and the time of the activation culture is preferably 24 hours. The invention preferably carries out centrifugation on the culture solution obtained after the activation culture to obtain a precipitate, wherein the precipitate is bacterial mud. The rotational speed of the centrifugation is preferably 2800-3200 r/min, more preferably 3000r/min, and the time of the centrifugation is preferably 8-12 min, more preferably 10min. The PBS solution of the invention is preferably prepared from NaCl, na 2 HPO 4 、KH 2 PO 4 And water. In the PBS solution of the invention, the mass concentration of NaCl is preferably 8g/L, na 2 HPO 4 Preferably 1.4g/L, KH 2 PO 4 Preferably 0.24g/L.
The starter culture of the invention can be preferably used alone or in combination with other strains or starter culture. In the present invention, the starter preferably further includes use in combination with other commercial starter; the commercial starter is preferably one comprising YF-L904 (trade name: hansen Co., ltd., denmark)Chr.Hansen YF-L904 Thermophilicculture, size 25X 200U). The commercial starter of the present invention is preferably used in an amount of 0.001% to 0.003% by mass, more preferably 0.0015% by mass, of the milk raw material.
In the embodiment of the invention, when the starter is combined with commercial starter to prepare the milk tofu, the acid production can be further improved, and the prepared milk tofu has better taste.
The invention provides a preparation method of milk bean curd, which comprises the following steps:
fermenting cow milk by using the starter according to the technical scheme to obtain a fermentation product;
and (3) discharging whey after the fermented product is curdled to obtain the milk bean curd.
The starter is used for fermenting cow milk to obtain a fermentation product.
The invention preferably comprises the steps of sterilizing the cow milk before fermentation, cooling and mixing with anhydrous calcium chloride to obtain premix. In the present invention, the sterilization preferably comprises pasteurization; the temperature of the pasteurization is preferably 75℃and the time is preferably 15min. The cow milk of the present invention is preferably whole cow milk. The sterilization of the cow milk can avoid the pollution of cow milk mixed bacteria when the cow milk is used for preparing the milk curd, so that the flavor of the milk curd is stable. The addition amount of the anhydrous calcium chloride is preferably 0.02% (w/w) of the mass of the cow milk after sterilization, and the anhydrous calcium chloride improves the coagulability of the cow milk. The invention preferably cools the sterilized cow milk to 30-33 ℃ and then adds anhydrous calcium chloride.
After the premix is obtained, the premix is preferably mixed with a starter for fermentation to obtain a fermentation product.
In the present invention, the starter is preferably inoculated in the form of a starter bacterial suspension. The starter bacterial suspension comprises a lactococcus lactis bacterial suspension and a Lactobacillus paracasei bacterial suspension.
In the invention, the mass ratio of the starter to the cow milk is preferably 1:20 to 50, more preferably 1:50. the fermentation temperature of the present invention is preferably 28 to 33 ℃, more preferably 29 to 31 ℃, and still more preferably 30 ℃. The invention preferably stops fermentation when the pH value of the fermentation product reaches 4.48-4.52 in the fermentation process. The pH of the fermentation product of the present invention is selected to promote subsequent curd of the fermentation product.
After the fermented milk is obtained, the fermented milk is preferably mixed with chymosin to obtain a fermented milk after curd. The amount of chymosin to be added in the present invention is preferably 0.001g chymosin per 1kg fermented milk. The enzyme activity of chymosin of the present invention is preferably 1 to 2U, more preferably 1.3U. The chymosin is preferably placed for 55-65 min, more preferably 60min, and then slowly heated after being added, and the effect of the chymosin is favorable for forming stable coagulum by milk tofu while the chymosin fully plays a role. The slow heating according to the invention is preferably carried out at a temperature rise of 5℃every 30 min. The temperature after heating in the present invention is preferably 29 to 31 ℃, more preferably 30 ℃. Preferably, the curd stops at a pH of 4.5.+ -. 0.02 in the fermented milk of the present invention. The pH value is selected to ensure the activity of lactobacillus and make the yoghurt have good flavor. The acidity of the fermented milk after curd according to the present invention is preferably controlled to 50 to 55℃T, more preferably 53℃T.
After the fermented milk after curd is obtained, whey is discharged from the fermented milk after curd, and the milk curd is obtained. In the present invention, the temperature of the whey to be discharged is preferably 43 to 47 ℃, more preferably 45 ℃. The method for discharging whey is not particularly limited, and a conventional method is adopted. After whey is preferably discharged, the coagulum is filled into a die to be pressed and shaped, so that the milk bean curd finished product is obtained. The press-shaping method is not particularly limited, and a conventional method is adopted.
The invention also provides the milk bean curd obtained by the preparation method of the technical scheme, and the flavor substances of the milk bean curd comprise one or more of 2-heptanone, 2-nonanone, acetoin, 3-methyl-butyraldehyde, heptanal and octanal. The milk bean curd obtained by the preparation method disclosed by the invention is rich in one or more of 2-heptanone, 2-nonanone, acetoin, 3-methyl-butyraldehyde, heptanal and octanal. The content of 2-heptanone in the milk bean curd prepared in the invention (measured directly after the preparation of example 10) is 5.0-5.20 mug/L, the content of 2-nonanone is 2.0-2.32 mug/L, the content of acetoin is 4.62-4.82 mug/L, the content of 3-methyl-butyraldehyde is 0.13-0.15 mug/L, the content of heptanal is 0.18-0.22 mug/L, and the content of octanal is 0.10-0.12 mug/L. The milk bean curd prepared by the invention has good stability, is stored for 14 days at the temperature of 4 ℃, the content of 2-heptanone in the milk bean curd is 3.18-3.30 mug/L, the content of 2-nonanone is 1.13-1.15 mug/L, the content of acetoin is 4.01-4.13 mug/L, the content of 3-methyl-butyraldehyde is 0.03-0.05 mug/L, the content of heptanal is 0.38-0.40 mug/L, and the content of octal is 0.17-0.19 mug/L.
The invention screens and obtains a lactobacillus lactis IMAU12063 and a lactobacillus paracasei IMAU12062, and the two lactobacillus are compounded according to a proportion to be used as a starter for fermenting whole milk and preparing the milk bean curd, and the fermented bean curd has better texture and flavor characteristics than the milk bean curd prepared by natural fermented milk. The invention can shorten the fermentation time of cow milk, has controllable fermentation process, takes acetaldehyde, diacetyl, acetoin and the like as main flavor substances of the fermented milk, gives the special flavor characteristics of the traditional milk bean curd, improves the sanitary quality and safety of the milk bean curd, and makes up the defect that the natural fermentation of raw milk is only controlled by experience in the traditional milk bean curd manufacturing process.
The technical solutions provided by the present invention are described in detail below with reference to the drawings and examples for further illustrating the present invention, but they should not be construed as limiting the scope of the present invention.
Example 1
Screening of fermented milk strains suitable for fermented milk tofu
MRS liquid medium: 10g of soybean peptone, 5g of beef extract, 4g of yeast powder, 20g of glucose, 801mL of tween-801, 2g of disodium hydrogen phosphate, 5g of anhydrous sodium acetate, 2g of triamine citrate, 0.02g of manganese sulfate, 0.1g of magnesium sulfate, 15g of agar powder, 1L of distilled water for constant volume, adjusting the initial pH value to 6.20, and sterilizing at 121 ℃ for 15min.
10% skim milk medium: 10g of skim milk powder, 90mL of distilled water, heating to 50 ℃ for full dissolution, packaging into test tubes or triangular flasks, and sterilizing at 115 ℃ for 10min.
Full-fat raw milk: the whole raw milk without sterilization treatment is purchased from the dairy laboratory of the university of inner Mongolia.
The lactococcus lactis and the Lactobacillus paracasei are separated from cheese samples in different areas of China, and are separated, identified and preserved by a key laboratory of the university of inner Mongolia agricultural "Dairy biotechnology and engineering" education department. The identification of the strain adopts a 16SrRNA gene sequence comparison method.
Aiming at 56 lactococcus lactis and 24 lactobacillus paracasei strains in traditional dairy products separated from different areas and stored in a lactobacillus strain resource library of a dairy biotechnology and engineering major laboratory of the university of inner Mongolia agriculture, a skim milk culture medium fermentation experiment is adopted to screen strains with excellent fermentation characteristics. The specific experimental method is as follows: inoculating 56 lactococcus lactis and 34 Lactobacillus paracasei into liquid MRS culture medium, culturing at 37deg.C for 24 hr, activating to culture for three generations, inoculating activated bacteria liquid into 10% sterilized skim milk culture medium according to the mass ratio of 2%, culturing at 30deg.C for 24 hr, and observing. The curds of the strains are shown in FIG. 1 and Table 1, and the pH and titrated acidity of the strains are measured every 2 hours during fermentation of the strains, and the results are shown in FIGS. 2 to 3 and Table 1.
TABLE 1 lactococcus lactis and Lactobacillus paracasei pH and curd Condition
From FIGS. 1 to 5 and Table 1, it can be seen that 47 strains of 56 strains of lactococcus lactis grew in skim milk and were able to curd, and 19 strains of 24 strains of Lactobacillus paracasei grew in skim milk and were able to curd, within a 24-hour fermentation time (see FIG. 1). Wherein 11 lactococcus lactis strains are fermented in skimmed milk for 12h to enable the pH value to approach 4.5 (see figure 2), and give out natural fragrance of yogurt, and have curd phenomenon; 6 strains of Lactobacillus paracasei had a pH of approximately 5.0 at 12h of fermentation (see FIG. 4) and started to exhibit the curd phenomenon. Among 11 lactococcus lactis, 4 strains of IMAU12063, IMAU81310, IMAU81321 and IMAU81309 have pH value of skim milk of about 5.2 at 8 hr fermentation, and have titrated acidity of about 88℃T after 12 hr (see FIG. 3 and Table 2). Of the 6 strains of Lactobacillus paracasei, strains IMAU12062, IMAU50903, IMAU50897 reached about 86℃T in titrating acidity to the end of fermentation (see FIG. 5 and Table 3). Among the numerous ferments, lactococcus lactis IMAU12063, IMAU81310, IMAU81321, IMAU81309 and 3 strains of Lactobacillus paracasei IMAU50897, IMAU50903, IMAU12062 had an acidity of 86℃to 88℃in skim milk, and the fermented milk produced was excellent in acidity.
TABLE 2 measurement of lactococcus lactis acidity (TA) at various fermentation times
TABLE 3 measurement of Lactobacillus paracasei acidity (TA) at various fermentation times
Time (h) IMAU50903 IMAU50921 IMAU12062 IMAU50896 IMAU50897 IMAU50918
0 24±1.2 16±0.7 22±0.9 18±1.2 20±0.9 20±0.9
2 24±0 20±0.9 24±0 20±0.9 24±1 24±1
4 24±1.2 22±0.6 24±1.2 24±1 26±0.9 24±0.7
6 24±10.9 24±1 28±0.9 26±0.7 28±1 24±0.9
8 34±0.9 32±0.9 36±1 34±0.9 36±1 36±0.9
10 52±0.6 46±0.9 52±1 44±1 50±0.6 44±1
12 62±1 54±1 60±1.2 56±1 58±0.9 52±1
14 74±1 64±1 72±0.9 66±0.9 70±1.2 68±1.2
16 84±0.6 74±0.7 84±0.9 80±0.9 78±0.9 76±1.2
17 88±1 82±0.9 90±1 86±1 86±0.9 82±0.9
After the 4 strains of lactococcus lactis IMAU12063, IMAU81310, IMAU81321, IMAU81309 and 3 strains of Lactobacillus paracasei IMAU50897, IMAU50903 and IMAU12062 reached the fermentation end, the viscosity was measured by a DV2T viscometer and sensory evaluation of the fermented milk was carried out in accordance with GB 19302-2010 national food safety standard fermented milk, using the above-mentioned lactococcus lactis IMAU12063, IMAU81310, IMAU81321, IMAU81309 and 3 strains of Lactobacillus paracasei IMAU50897, IMAU50903 and IMAU12062, respectively, in a 10% sterilized skim milk medium, the results are shown in FIG. 7 and Table 4.
TABLE 4 sensory scores of fermented milks
Strain name Smell (30 minutes) Taste (30 min) Texture, color (20 minutes) Mouthfeel (30 minutes) Total score (30 score)
IMAU12062 26.375±1.57 26.25±1.29 16.5±0.86 16.625±0.69 85.75±2.05
IMAU50897 22.25±1.29 23.25±0.58 14.75±1.56 15±0.70 75.25±1.32
IMAU81309 20.125±1.16 20.625±1.72 17.25±0.66 16.5±0.70 69.25±2.23
IMAU12063 17.625±0.85 20±0.86 16.5±1.11 15.125±0.78 74.5±1.36
IMAU81310 17±0.70 19±1.22 16.875±0.92 15.375±0.85 68.25±2.24
As can be seen from FIG. 6, the lactic acid bacterium IMAU12063 has better acid production performance and higher viscosity value, which reaches more than 700 Pa.S; the acid production performance of the Lactobacillus paracasei IMAU12062 is better, the fermentation speed is moderate, the viscosity value is centered and is about 500 Pa.S, and the strain is superior to other strains (see figure 6). The acid-producing performance, the viscosity of fermented milk and the sensory evaluation of the strain are comprehensively compared and analyzed through the experiment, and from 7 strains, lactococcus lactis IMAU12063, IMAU81310, IMAU81309 and 3 strains of Lactobacillus paracasei IMAU50897, IMAU50903 and IMAU12062 are screened for sensory scores, wherein the sensory score of lactococcus lactis IMAU12063 is 74.5 minutes, and the sensory score of Lactobacillus paracasei IMAU12062 is 85.75 minutes, as shown in figure 7.
Biological preservation is carried out on lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062, the preservation number of the lactococcus lactis IMAU12063 is CGMCC NO.26949, and the preservation number of the Lactobacillus paracasei IMAU12062 is CGMCC NO.26948.
Example 2
Example 1 the resulting and biologically deposited formulation of lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062 was subjected to a milk fermentation test.
1. Inoculating lyophilized preserved strain lactococcus lactis IMAU12063 into sterile liquid MRS culture medium (composition same as in example 1), activating culture at 37deg.C for 24 hr, centrifuging at 3000r/min for 10min to remove supernatant, mixing the precipitate with PBS solution (8 g/LNaCl, 1.4g/L Na) 2 HPO 4 And 0.24g/L KH 2 PO 4 ) Evenly mixing to prepare the survival bacterial count of 2.5 multiplied by 10 7 The CFU/mL lactococcus lactis IMAU12063 bacterial suspension is placed in a refrigerator at 4 ℃ for later use.
Inoculating lyophilized preserved strain Lactobacillus paracasei IMAU12062 into sterile liquid MRS culture medium, activating culture at 37deg.C for 24 hr, centrifuging at 3000r/min for 10min to remove supernatant, mixing the precipitate with PBS solution (8 g/LNaCl, 1.4g/L Na 2 HPO 4 And 0.24g/L KH 2 PO 4 ) Evenly mixing to prepare the number of viable bacteriaIs 2.5X10 7 The CFU/mL strain of Lactobacillus paracasei IMAU12062 is preserved in a refrigerator at 4deg.C for use.
2. The raw milk 20kg is pasteurized (75 ℃ for 15 min) and then cooled to 30 ℃ and then is inoculated with 0.4kg of compound fermentation inoculant. The composition of the compound fermentation inoculant is 0.0003kg of commercial starter (YF-L904) and 0.3997kg of starter of the invention. The mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension in the starter culture is 1:1, and the effective viable count of the original lactococcus lactis IMAU12063 bacterial suspension is 2.5X10 7 The effective viable count of CFU/mL and original Lactobacillus paracasei IMAU12062 bacterial suspension was 2.5X10 7 CFU/mL。
3. After inoculation, the fermentation was carried out at a constant temperature of 30℃for about 6 hours, and the fermentation end was reached at pH=4.5.+ -. 0.02, and the inoculation types and inoculation amounts of the specific starter were shown in Table 2.
Example 3
The only difference from example 2 is the number of viable bacteria available for the starter of the present invention. In the starter culture of the invention, the mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension is 1:1, and the original effective viable count of the lactococcus lactis IMAU12063 is 1.75X10 7 CFU/mL and Acetobacter paracasei IMAU12062 with an initial effective viable count of 0.75X10 7 CFU/mL. The composition of the starter culture was 0.0003kg of a commercial starter culture (YF-L904) and 0.3997kg of a starter culture of the present invention.
Example 4
The only difference from example 2 is the number of viable bacteria available for the starter of the present invention. In the starter culture of the invention, the mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension is 1:1, and the effective viable count of the original lactococcus lactis IMAU12063 is 1.25X10 7 CFU/mL and effective viable count of 1.25X10 of Lactobacillus paracasei IMAU12062 7 CFU/mL. The composition of the starter culture was 0.0003kg of a commercial starter culture (YF-L904) and 0.3997kg of a starter culture of the present invention.
Example 5
The only difference is that the hair of the present invention is as in example 2The effective viable count of the ferment is different. The starter culture of the invention consists of lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062, wherein the mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension is 1:1, and the effective viable count of the original lactococcus lactis IMAU12063 is 2 multiplied by 10 7 CFU/mL and effective viable count of 0.5X10 of the original Lactobacillus paracasei IMAU12062 7 CFU/mL. The composition of the compound fermentation inoculant is 0.0003kg of commercial starter (YF-L904) and 0.3997kg of starter of the invention.
Example 6
The only difference from example 2 is that the compounded starter culture only contains the starter of the invention. The starter culture of the invention consists of lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062, wherein the mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension is 1:1, and the effective viable count of the original lactococcus lactis IMAU12063 is 5 multiplied by 10 7 CFU/mL and effective viable count of Lactobacillus paracasei IMAU12062 in the original starter culture of 5X 10 7 CFU/mL. The addition amount of the starter of the invention was 0.4kg.
Example 7
The difference is that the compound fermentation inoculant only contains the starter of the invention, the starter of the invention consists of lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062, the mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension is 1:1, and the effective viable count of the original lactococcus lactis IMAU12063 is 3.5X10 7 CFU/mL and effective viable count of 1.5X10 of Acetobacter paracasei IMAU12062 7 CFU/mL. The addition amount of the starter of the invention was 0.4kg.
Example 8
The difference is that the compound fermentation inoculant only contains the starter of the present invention as in example 2. The starter culture consists of lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062, wherein the mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension is 1:1, and the raw milk is obtainedThe effective viable count of the acid coccus IMAU12063 is 2.5X10 7 CFU/mL and effective viable count of original Lactobacillus paracasei IMAU12062 of 2.5X10 7 CFU/mL. The addition amount of the starter of the invention was 0.4kg.
Example 9
The difference is that the compound fermentation inoculant only contains the starter of the present invention as in example 2. The starter culture of the invention consists of lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062, wherein the mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension is 1:1, and the effective viable count of the original lactococcus lactis IMAU12063 is 4.0x10 7 CFU/mL and effective viable count of original Lactobacillus paracasei IMAU12062 of 1.0X10 7 CFU/mL. The addition amount of the starter of the invention was 0.4kg.
Comparative example 1
The difference from example 2 is that the compounded starter culture contained only commercial starter culture YF-L904, which was purchased from Hansen Co., inc. of Denmark; the amount of YF-L904 added was 0.0006kg.
The specific compositions of the added starter of examples 2 to 9 and comparative example 1 are shown in Table 5.
TABLE 5 preparation of different groups of ferments
Test example 1
(1) The fermentation characteristic indexes of examples 2 to 9 and comparative example 1 were measured every 2 hours during the fermentation after inoculation until the pH value of the fermented milk was 4.48 to 4.52, and the results of the fermentation characteristic measurement are shown in FIG. 8A and B, table 6 and Table 7. The group E produced acid energy is best in the four groups (B, C, D, E) without commercial starter, and the group F and group I produced acid energy is better in the four groups (F, G, H, I) with commercial starter.
TABLE 6 titrated acidity during fermentation of the fermented milks of examples 2-9 and comparative example 1
Time (h) A B C D E F G H I
0 18±1.08 18±0.91 18±0.91 18±1.13 20±1.92 18±1.21 20±1.27 18±0.98 18±1.08
2 24±0.90 22±0.93 22±0.92 22±1.20 29±0.91 30±1.14 34±1.12 36±1.20 34±1.08
4 56±1.03 34±1.39 32±1.24 28±1.20 42±1.01 56±1.20 56±1.21 60±1.14 60±1.20
6 68±1.02 52±1.28 44±1.28 54±1.15 64±1.03 74±1.18 68±1.09 72±1.24 74±1.20
8 78±0.90 62±0.92 62±1.12 66±1.08 76±1.02 86±1.08 76±0.90 80±1.02 86±1.18
10 84±1.19 78±0.91 82±1.01 82±0.91 84±1.14 90±1.10 86±00.90 86±1.021 92±1.13
TABLE 7 pH during fermentation of fermented milk of examples 2 to 9 and comparative example 1
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(2) After fermentation to a pH of 4.48 to 4.52, sensory scores and volatile flavor measurements were made for comparative example 1, example 6, example 5 and example 2.
The determination adopts a solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method, and the specific method is as follows: SPME condition: 5g of milk bean curd sample is taken and put into a 15mL extraction bottle, and is subjected to water bath in a water bath kettle with the temperature of 50 ℃ for 30min, and an extraction head is inserted into the extraction bottle for extraction after water bath, wherein the extraction condition is 65 ℃ for 60min.
GC conditions: the column temperature program was as follows using a DB-WAX capillary column (30 m. Times.0.25 mm,0.25 μm): the initial column temperature was 35℃for 3min, raised to 100℃at a rate of 5℃per minute for 3min, then raised to 150℃at a rate of 5℃per minute, finally raised to 230℃at a rate of 8℃per minute for 3min, with the carrier gas being He and the flow rate being 1mL/min. And the sample injection is not split.
MS conditions: the mass scanning range m/z is 20-350.
The measurement results are shown in FIG. 9 and Table 8. As can be seen from fig. 8, 9 and table 8, the pH value of the compound strain of example 2 after 4 hours of fermentation is lower than 5.0 in the rapid fermentation stage, the titrated acidity is 55°t, and after the fermentation is continued for 10 hours, rich flavor substances are formed, and the combination is more suitable for preparing fermented milk of milk tofu.
TABLE 8 identification of volatile flavor compounds in fermented milks prepared with different fermenters
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Note that: -means that the substance is not detected
As can be seen from table 3 and fig. 8 to 9, the sensory scores of the fermented milk of example 2 are superior to those of other experimental groups, and the fermented milk of example 2 contains abundant volatile flavor substances, including ethyl acetate, ethyl caproate, vinyl formate and the like, which can modify and improve the flavor and mouthfeel of the fermented milk, so that the optimal combination of the compound ferment is obtained by screening: the effective viable count of the original lactococcus lactis is 2.5X10 7 CFU/mL, the effective viable count of the raw cheese sticks is 2.5X10 7 CFU/mL, the mass ratio (w/w) of added commercial starter to cow's milk was 0.0015%.
EXAMPLE 10 use of lactococcus lactis IMAU12063 and Lactobacillus paracasei IMAU12062 in the preparation of milk tofu
Sterilizing the whole raw milk by a pasteurization method (75 ℃ for 15 min), cooling to about 32-33 ℃, adding 0.02% of anhydrous calcium chloride, and adding a compound fermentation inoculant. The compound fermentation inoculant consists of a commercial starter (YF-L904) and the starter of the invention. The mass ratio of the lactococcus lactis IMAU12063 bacterial suspension to the Lactobacillus paracasei IMAU12062 bacterial suspension in the starter culture is 1:1, and the effective viable count of the lactococcus lactis IMAU12063 bacterial suspension is 2.5X10 7 The effective viable count of CFU/mL and Lactobacillus paracasei IMAU12062 bacterial suspension was 2.5X10 7 CFU/mL；
The compound fermentation inoculant is mixed with full-fat raw milk, namely the mass ratio of the compound fermentation inoculant consisting of the fermentation inoculant and the commercial fermentation inoculant to the mass of the full-fat raw milk is 1:50, the commercial starter in the compound starter is 0.0015% (w/w) of the mass of full-fat raw milk, the mixture is stirred and mixed uniformly, then the mixture is fermented at a constant temperature of 30 ℃, the pH value of the mixture is detected over time, when the pH value reaches 4.5+/-0.02, chymosin with the concentration of 0.001g/kg is added, the mixture is kept stand for 60 minutes, the enzyme activity of chymosin is 13 ten thousand U, then the mixture is slowly heated to form curd, the acidity is controlled at 50-55 ℃, whey is discharged at 45 ℃, and the curd is put into a die after being continuously discharged, and is pressed and shaped, thus obtaining the milk curd product.
Comparative example 2
The method for preparing the milk curd comprises the steps of taking fresh cow milk, naturally standing and fermenting the fresh cow milk to form curd, scraping cream floating on the surface layer, heating the rest curd in a pot until flocculent coagulum is separated to remove whey, continuously heating and kneading the milk curd until the milk curd is in a wireform, filling the milk curd into a mould, and cooling the milk curd.
Test example 2
The texture, volatile flavor and odor of the fermented milk curd of storage period were evaluated while comparing the texture and volatile flavor of the fermented milk curd prepared in example 10 with those of the commercial fermented milk curd of comparative example 2.
1. The texture of the fermented bean curd prepared according to the present invention and commercial products were examined using a ta.xt.plus texture analyzer, and the test results are shown in table 9. As can be seen from Table 9, the soft milk curd prepared by the method has better softness when preserved at a constant temperature of 4 ℃, the taste of the soft milk curd which is gradually hardened in the storage process is improved, the toughness strength is enhanced, the brittleness index is reduced, and the texture of the soft milk curd is integrally improved compared with that of the soft milk curd prepared by the comparative example 2.
TABLE 9 results of texture measurement during storage period of milk tofu
2. And (3) detecting and analyzing the volatile flavor substances of the fermented milk curd in the storage period by using a solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) technology. The volatile flavor substances of the fermented bean curd prepared in example 10 were analyzed at storages 0d, 1d, 7d and 14d, respectively, and the results are shown in fig. 10 to 12 and table 10. As can be seen from fig. 10 to 12 and table 10, the milk tofu contains higher content of ketone compounds such as 2-heptanone, 2-nonanone and acetoin, so that the milk tofu is endowed with unique fruit fragrance and cream fragrance. Contains abundant 3-methyl-butyraldehyde, heptanal, octanal and other aldehyde compounds, and can produce pleasant fragrance. Meanwhile, the milk bean curd is rich in esters, alkanes, alkenes, acids, alcohols and other compounds, and the milk bean curd is endowed with unique and stable flavor.
TABLE 10 identification of volatile flavor compounds in milk tofu during storage
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Note that: -means that the substance is not detected; DJ represents a commercially available conventional milk curd stored for 7 days.
3. The smell was measured using a PEN3 type electronic nose, the set parameter was an automatic cleaning time of 100s, a sample measurement time of 90s, and the change of the smell component during storage was performed on the fermented bean curd prepared in example 10, and the results are shown in fig. 13 and table 11. In FIG. 13, W1C represents an aromatic compound, W5S represents a nitroxide compound, W3C represents an amine and a partial aromatic compound, W6S represents a hydride compound, W5C represents an olefin, an aromatic, a polar molecule, W1S represents an alkane compound, W1W represents a sulfur compound, W2S represents an alcohol and a partial aromatic compound, W2W represents an aromatic compound, a sulfur organic compound, W3S represents an alkane and an ester. As can be seen from fig. 13, the nitrogen oxides, ammonia, alkane aromatics, organosulfides aromatics, alcohols, aldehyde ketones, alkanes contents in the milk tofu were relatively stable during storage, indicating that the odor was relatively stable.
TABLE 11 electronic nose sensor Radar image and Box Pattern analysis results during storage of milk tofu
Compounds of formula (I) 0d 1d 7d 14d
W1C 1.2382 1.6994 2.00725 1.8936
W5S 1.1949 1.28735 1.28865 1.3091
W3C 0.8423 0.8567 0.8854 0.8956
W6S 1.2678 1.28815 1.40455 1.32275
W5C 0.89535 0.9196 0.9507 0.9641
W1S 1.49895 1.4982 1.4374 1.3437
W1W 0.66035 0.69515 0.75615 0.7721
W2S 1.42075 1.3975 1.3518 1.3187
W2W 0.94505 0.9779 1.03975 0.9918
W3S 1.2764 1.32815 1.36775 1.3896
In conclusion, the fermented milk curd prepared by the starter does not become hard gradually in the storage process, meanwhile, the toughness strength is enhanced, the brittleness index is reduced, and the texture of the fermented milk curd is integrally improved. The prepared milk bean curd contains higher content of ketone compounds such as 2-heptanone, 2-nonanone and acetoin, and unique fruit fragrance and cream fragrance are provided for the milk bean curd. Contains abundant 3-methyl-butyraldehyde, heptanal, octanal and other aldehyde compounds, and can produce pleasant fragrance. Meanwhile, the milk bean curd is rich in esters, alkanes, alkenes, acids, alcohols and other compounds, so that the milk bean curd is endowed with unique and stable flavor and good taste.
Although the foregoing embodiments have been described in some, but not all, embodiments of the invention, it should be understood that other embodiments may be devised in accordance with the present embodiments without departing from the spirit and scope of the invention.

Claims (10)

1. A starter culture comprising lactococcus lactis (lactococcus lactis) IMAU12063 and lactobacillus paracasei (lacteceibacillus paracasei) IMAU12062; the effective viable count of lactococcus lactis in the starter is more than or equal to 2.5X10 6 CFU/mL; the effective viable count of the Lactobacillus paracasei in the starter is more than or equal to 2.5X10 5 CFU/mL；
The preservation number of the lactococcus lactis IMAU12063 is CGMCCNO.26949; the preservation number of the lactobacillus paracasei IMAU12062 is CGMCCNO.26948.
2. The starter according to claim 1, wherein the mass ratio of the lactococcus lactis to the lactobacillus paracasei is 1: (1-2).
3. Use of a starter according to claim 1 or 2 for the preparation of a milk curd.
4. Use according to claim 3, wherein the starter is used alone or in combination with other commercial starter.
5. The preparation method of the milk bean curd is characterized by comprising the following steps of:
fermenting cow milk with the starter according to claim 1 or 2 to obtain a fermentation product;
and (3) discharging whey after the fermented product is curdled to obtain the milk bean curd.
6. The process according to claim 5, wherein the fermentation is carried out at a temperature of 28 to 33℃and the fermentation is stopped when the pH of the fermentation product reaches 4.48 to 4.52.
7. The preparation method according to claim 5, wherein the mass ratio of the starter to the cow's milk is 1:20 to 50.
8. The method according to claim 5, wherein the temperature of the whey discharged is 43-47 ℃.
9. The method according to claim 5, wherein the means for forming the curd of the fermentation product comprises: mixing the fermentation product with chymosin.
10. The milk curd obtained by the method according to any one of claims 5 to 9, wherein the flavor substance of the milk curd comprises one or more of 2-heptanone, 2-nonanone, acetoin, 3-methyl-butyraldehyde, heptanal and octanal.
CN202310552636.6A 2023-05-17 2023-05-17 Ferment and application thereof, milk bean curd and preparation method thereof Pending CN116555114A (en)

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