CN110604181A - Garlic-flavor fermented bean curd with low bacillus cereus and preparation method thereof - Google Patents
Garlic-flavor fermented bean curd with low bacillus cereus and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a low-waxy bacillus fermented bean curd and a preparation method thereof. The preparation method comprises selecting undamaged and unmolded soybeans, soaking in water, grinding into thick liquid, filtering to obtain raw soybean milk, and cooking to obtain cooked soybean milk; then dispersing the garlic essential oil in the bean curd yellow serofluid or the cooked soybean milk cooled to room temperature; adding bean curd yellow serofluid into cooked soybean milk at 83-90 deg.C, adding dispersed Bulbus Allii essential oil, controlling the concentration of Bulbus Allii essential oil to 6-20mg/L, stirring, standing and curdling; squeezing and cutting after the soybean milk is completely solidified to form a white bean curd blank; fermenting mucor earlier to obtain a blank, adding salt to pickle the blank to obtain a salty blank, and fermenting later to obtain the low waxy bacillus fermented bean curd; the number of bacillus cereus in the fermented bean curd is less than 105CFU/g, and the garlic essential oil can adjust bacterial colony structure in the fermented bean curd fermentation process, improve the safety performance and potential probiotic performance of the fermented bean curd, and does not influence the normal fermentation process of the fermented bean curd.
Description
Technical Field
The invention relates to a preparation method of fermented bean curd, in particular to low-waxy bacillus fermented bean curd and a preparation method thereof, and specifically relates to application of plant essential oil in fermented bean curd production, so that proliferation of the low-waxy bacillus fermented bean curd is controlled.
Background
The bacillus cereus is a common food-borne conditioned pathogen, produces spores, is difficult to inactivate, and has extensive growth environment and wide distribution. In addition, Bacillus cereus can produce toxins, and improper consumption of food contaminated with Bacillus cereus can cause diarrhea, emesis, etc., usually when the amount exceeds 105cfu/g is regarded as inedible.
The fermented bean curd is a traditional fermented bean product in China, is a seasoning food with unique flavor and is cooked by long-lasting mildew and salt pickling of bean curd, and is popular with vast consumers at home and abroad. In recent years, a great deal of research has shown that various microorganisms appear in the process of making fermented bean curd. Through the fermentation and biotransformation of microorganisms, the protein in the bean curd is converted into small molecular polypeptide and free amino acid, the oil in the bean curd is converted into short chain fatty acid ester, and the glycoside type soybean isoflavone is converted into aglycone type isoflavone. Moreover, some active substances of the B family vitamins are generated newly. Therefore, the fermented bean curd not only contains rich amino acid flavor components and volatile ester flavor components, but also contains a large amount of functional components with physiological activity, such as peptides, isoflavone, vitamins and the like, and is a seasoning food with good flavor and function.
At present, the fermented bean curd is generally fermented by inoculating mucor, but because the fermentation process is open, microorganisms in the environment still enter and participate in fermentation and biotransformation in a large amount. It is worth noting that fermented bean curd is different from traditional fermented seasonings such as soybean paste and soy sauce, and because of unique organoleptic texture requirements, the fermented bean curd is not sterilized at high temperature before being delivered from a factory, so that the fermented bean curd finished product often has high number of living microorganisms, wherein the number of bacillus cereus is often up to or more than 105cfu/g, cancellationThe physical health of the consumers poses a potential threat and also seriously affects the export trade of such ethnic foods. Therefore, finding and exploring effective control methods for bacillus cereus has become a focus of general attention in the industry.
Disclosure of Invention
The invention aims to provide a low-bacillus cereus fermented bean curd without adding chemical agents and a preparation method thereof aiming at the problems in the prior art, so that the content of bacillus cereus in the fermented bean curd is stably controlled to be 105And the safety risk of the preserved beancurd food is reduced below CFU/g.
Garlic is a common seasoning in daily life, is also called garlic bulb, single-bulb garlic, calabash and calabash garlic, belongs to the allium genus of the liliaceae family, and has unique pungent smell. The garlic can be extracted by methods such as steam distillation and the like to obtain substances with high concentration of aroma and volatility, namely the garlic essential oil. The garlic essential oil contains various sulfur compounds, such as alliin, allicin, ajoene and the like, has very outstanding inhibiting or killing effects on bacteria, fungi, viruses and the like, and is a natural preservative. However, the garlic essential oil has strong pungent smell, and the person skilled in the art generally believes that the garlic essential oil has negative influence on the flavor when being applied to the fermented bean curd, and meanwhile, the garlic essential oil has strong volatility and the bacteriostatic effect is difficult to stabilize and last. In addition, the preserved beancurd is a solid gel food, and the garlic essential oil is difficult to permeate from the outside and can also influence the application effect of the preserved beancurd.
The invention discovers for the first time that the soybean protein can wrap the garlic essential oil and uniformly disperse the garlic essential oil into the bean curd blank, so that the volatility and the pungent smell of the garlic essential oil are reduced, but the slowly released garlic essential oil still has strong permeability, can damage the cell membrane of the bacillus cereus, inhibit the growth and the reproduction of the bacillus cereus and effectively reduce the number of the bacillus cereus in the fermentation process of the fermented bean curd; the invention also discovers that the garlic essential oil can adjust the flora structure of bacteria in the fermented bean curd fermentation process, improve the safety performance and the potential probiotic function of the fermented bean curd, does not influence the normal fermentation process of the fermented bean curd, and does not have adverse influence on the taste and smell of the fermented bean curd. On the basis, the invention applies the garlic essential oil to the production of the fermented bean curd for the first time.
The invention defines the key control point of bacillus cereus in the production process of fermented bean curd, and the effectiveness, accessibility and selectivity of the bacteriostatic concentration of garlic essential oil. Firstly, the invention discovers that the key control point of the bacillus cereus in the production process of the fermented bean curd is the early fermentation stage. The fermented bean curd production comprises early fermentation and later fermentation, wherein the early fermentation mainly refers to the cultivation of mucor at the temperature of 20-30 ℃, and the later fermentation refers to the biotransformation effect in the salted bean curd blanks. Since bacillus cereus is widely distributed in the environment and has strong stress resistance to heat, acid, salt and alcohol, the bacillus cereus can be massively propagated in the early fermentation process and survive in the later fermentation process as long as a small amount of bacillus cereus exists in the bean curd blank.
Secondly, although the garlic essential oil has strong bacteriostatic ability, the garlic essential oil also has strong volatility, and if the garlic essential oil cannot be stabilized in a system, the effective bacteriostatic concentration of the garlic essential oil can be rapidly reduced. According to the invention, the garlic essential oil is wrapped by the hydrophobic inner core of the soybean protein and is dispersed into the bean curd blank during curdling, so that the garlic essential oil is slowly and continuously released in the early fermentation process, the effective antibacterial concentration of the garlic essential oil is ensured, and the pungent smell of the garlic essential oil is avoided.
Third, garlic essential oil can inhibit the growth of various microorganisms including pathogenic bacteria and fungi, and thus it is important to obtain a selective inhibitory concentration. The invention defines an ideal essential oil concentration, can effectively inhibit the growth of the bacillus cereus, and does not influence the activities of a normal leavening agent and beneficial microorganisms.
The purpose of the invention is realized by the following technical scheme.
A preparation method of low-waxy bacillus fermented bean curd comprises the following steps:
(1) preparing soybean milk: selecting undamaged and unmolded soybeans, adding water for soaking, grinding into thick liquid, filtering to obtain raw soybean milk, and boiling the thick liquid to obtain cooked soybean milk;
(2) preparing essential oil bean curd: dispersing garlic essential oil in bean curd yellow serofluid or cooked soybean milk cooled to room temperature; adding bean curd yellow serofluid into cooked soybean milk at 83-90 deg.C, adding dispersed Bulbus Allii essential oil, controlling the concentration of Bulbus Allii essential oil to 6-20mg/L, stirring, standing and curdling; squeezing after the soybean milk is completely solidified, cooling, and cutting the bean curd to form white bean curd blanks;
(3) preparing a salty blank: inoculating Mucor spore to the white bean curd blank, placing into a fermentation room, and performing primary fermentation at 22-29 deg.C for 30-48 hr until the bean curd surface is full of mycelia to form blank; rubbing hair, adding salt, and pickling for 10-24hr to obtain salty blank;
(4) and (3) later-stage fermentation: adding the salty blank into the soup, sealing, and fermenting for 30-90 days to obtain low-Bacillus cereus fermented bean curd with Bacillus cereus number less than 105CFU/g。
In order to further achieve the aim of the invention, preferably, the soaking in water is carried out by adding water with the mass 6-10 times of that of the soybeans and soaking for 10-16h at normal temperature.
Preferably, the pulping is to take soaked wet soybeans and carry out pulping according to the mass volume ratio of the wet soybeans to water of 1:6-1:10, wherein the mass unit is Kg, and the volume unit is L.
Preferably, the cooking pulp is cooked for 10-20min at 95-100 ℃.
Preferably, the yellow serofluid of bean curd is formed by naturally acidifying at 20-35 deg.C for 24-60 hr.
Preferably, the cutting is to cut the bean curd into standard size.
Preferably, the step of inoculating the mucor spores to the white bean curd blank is to uniformly place the white bean curd blank in a clean food steamer and uniformly spray pure mucor on the surface of the white bean curd blank.
Preferably, the relative humidity of the early fermentation is 70% -95%; the hair twisting is to twist the hypha of the blank to wrap the blank, and salt is added to ensure that the salt content of the blank reaches 8-12 wt%.
Preferably, the soup is prepared from salt, wine and spices.
A low Bacillus cereus fermented bean curd is prepared by the above method, and the number of Bacillus cereus in fermented bean curd is less than 105CFU/g。
Compared with the prior art, the invention has the following advantages:
1) the invention stably controls the content of the bacillus cereus in the finished product of the fermented bean curd to be 105The food safety risk of the preserved beancurd is reduced below CFU/g, and the requirement of outputting the preserved beancurd is met.
2) The method reduces the bacillus cereus, has small influence on the total countable bacterial colony number and the total countable fungal colony number in the fermented bean curd, and does not influence the normal fermentation of the fermented bean curd.
3) The invention has certain optimization effect on the bacterial structure in the fermented bean curd fermentation process, and reduces the relative abundance of the latent harmful bacteria acinetobacter in the fermentation process; the relative abundance of four types of lactic acid bacteria, namely lactococcus, Weissella, leuconostoc and lactobacillus, in the prepared fermented bean blank, salty blank and samples at the middle and later post-maturation stages of the after-ripening is high.
4) The invention reduces bacillus cereus and simultaneously does not influence the change of polar metabolites in the fermented bean curd fermentation process and the formation of volatile flavor components in the after-ripening process.
5) According to the invention, the garlic essential oil is applied to the front end of the fermented bean curd production, namely the essential oil is dispersed into the soybean milk and is carried into a bean curd blank body by wrapping the hydrophobic inner core of the soybean protein, so that the essential oil is uniformly and stably dispersed into the bean curd, and the stability and the effective concentration of the essential oil are ensured; the contact obstacle of the essential oil and the bacillus cereus in the bean curd blank is avoided; the stage of fermentation culture of the mucor at the early stage is also the growth stage of the bacillus cereus, the bacillus cereus mainly exists in vegetative cells, the formed spores are the least and the most sensitive to external conditions, and the effect of inhibiting the growth and the reproduction of the bacillus cereus by using the garlic essential oil is obvious.
Detailed Description
The present invention will be further illustrated by the following examples for better understanding, but the examples should not be construed as limiting the scope of the present invention in any way.
In the following examples and comparative examples:
1) detection method of bacillus cereus
The detection method of the bacillus cereus in the fermented bean curd is tested according to GB 4789.14-2014 Bacillus cereus test for food microbiology test.
2) Volatile aroma component analysis
Volatile aroma components in the fermented bean curd are analyzed by a solid phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) method. A100 μm PDMS extraction fiber head (SPME) was aged at the injection port (270 ℃) for 30 min. 5.0g of fermented bean curd 1:1 was weighed out and mixed with distilled water and added to a 25mL headspace bottle. Heating at 60 deg.C, heating for 10min, inserting SPME needle, adsorbing for 45min, and analyzing with GC/MS chromatograph. Gas chromatography conditions: the temperature of the sample inlet and the temperature of the sample inlet are 250 ℃; temperature rising procedure: keeping the temperature at 50 ℃ for 2min, then increasing the temperature to 110 ℃ by a program of 5 ℃/min, keeping the temperature for 8min, increasing the temperature to 240 ℃ by a program of 15 ℃/min, and keeping the temperature for 5 min. The split ratio is 20: 1; mass spectrum conditions: the interface temperature of the mass spectrometer is 250 ℃; the ion source temperature is 230 ℃; the temperature of the quadrupole rods is 150 ℃; ionization mode: EI; scanning mode: full scan, mass number range: 33 to 400 m/z; solvent retardation: 0.1 min.
3) Sensory flavor evaluation: the score was made on a 9 point scale, with 1 point being the worst and 9 points being the best. 30 panelists were invited to score the odor, appearance, taste, texture and overall acceptability of the samples in a 20 ℃ environment.
Comparative example: conventional fermented bean curd
The first step is as follows: preparation of fermented bean curd
Soaking soybean at 23-26 deg.C for 12hr, pulping, filtering to obtain soybean milk, and decocting to 100 deg.C. Adding 25Kg of bean curd yellow serofluid naturally acidified for 2 days at the temperature of 23-26 ℃ into 100Kg of the above hot soybean milk, stirring, pressing after curding, and cutting into blocks to obtain white bean curd blanks. Cleaning the fermentation room in advance and keeping the white blank dry, inoculating mucor spores into the white blank, and fermenting at the early stage (24-26 ℃ for 36 hours) to obtain a blank full of white hyphae. Rubbing hair, adding salt, and pickling for 12hr to obtain salty blank; bottling the salty blank, filling the soup (water 70%, edible alcohol 18%, salt 8%, and chili powder 4%), and fermenting at later stage for 45 days to obtain basically mature fermented bean curd product.
The second step is that: bacillus cereus number analysis
Respectively collecting 5g of the white blank, the blank and the salty blank, and the fermented bean curd samples fermented for 15 days, 30 days and 45 days at the later stage, analyzing the number of bacillus cereus according to a national standard method, and finding that the number of bacillus cereus is 9.23 multiplied by 10 respectively2、1.80×106、9.77×105、 4.74×105、2.17×105、1.89×105cfu/g sample.
From the data, the number of the bacillus cereus in the white blank of the bean curd is not high and is only 2 orders of magnitude of 10, but the bacillus cereus grows logarithmically in the early fermentation stage, and the number of the bacillus cereus reaches 6 orders of 10 after the early fermentation is finished. Due to the strong stress resistance of the bacillus cereus, the number of the bacillus cereus is reduced by 1 order of magnitude after the bacillus cereus is prepared into salty blanks, and the bacillus cereus is kept unchanged in the later fermentation process of 45 days. Therefore, the early fermentation stage is a key point for controlling the number of bacillus cereus in the fermented bean curd product.
The third step: analysis of volatile Components
The fermented bean curd samples are collected, volatile aroma components of the fermented bean curd samples are analyzed by GC-MS, and 12 kinds of fatty acid ethyl esters are detected in total, wherein the fatty acid ethyl esters include short-chain fatty acid ethyl esters with fruit fragrance, such as ethyl valerate (0.98%), ethyl caproate (2.97%), ethyl heptanoate (1.32%).
The fourth step: structural analysis of flora
The above-mentioned fermented bean curd samples were collected for sequencing of 16s rDNA V3-V4 region. It was found that fermented bean curd mainly consisted of bacteria of Acinetobacter (11%), Lactobacillus (16%), Leuconostoc (20%), Weissella (10%), Tetragenococcus (21%), and the like.
The fifth step: sensory evaluation
Sensory evaluation was performed on the above fermented bean curd samples, and the results showed that the overall acceptability was 8.57, with an odor score of 8.50, an appearance score of 8.43, a taste score of 8.78, and a texture score of 8.55.
Example 1: garlic essential oil fermented bean curd 1
The first step is as follows: preparation of fermented bean curd
(1) Preparing soybean milk: selecting undamaged and unmoulded soybeans, adding 6 times of water by mass, soaking for 12 hours at normal temperature (22-25 ℃), taking soaked wet soybeans, and mixing the soaked wet soybeans according to the mass volume ratio of the wet soybeans to the water of 1:10 grinding into thick liquid with a mass unit of Kg and a volume unit of L, filtering to obtain raw soybean milk, and cooking the raw soybean milk at 95-100 ℃ for 15min to obtain cooked soybean milk;
(2) preparing essential oil bean curd: dispersing 8mg of garlic essential oil in 10L of cooked soybean milk cooled to room temperature, and stirring thoroughly to obtain garlic essential oil soybean milk for later use. Naturally acidifying at 23-26 deg.C for 2 days to obtain bean curd yellow water 25Kg, adding into cooked soybean milk at 85-88 deg.C 100Kg, adding dispersed Bulbus Allii essential oil soybean milk, slowly stirring, standing and curding; squeezing the soybean milk in a box after the soybean milk is completely solidified, and cutting the soybean milk into standard soybean milk white blanks added with the garlic essential oil after cooling;
(3) early-stage fermentation: cleaning and keeping the bean curd white blank dry in advance in a fermentation room, uniformly placing the bean curd white blank in a clean food steamer, uniformly spraying pure mucor on the surface of the bean curd white blank in the fermentation room, performing early-stage fermentation for 36 hours (relative humidity is 80-95%) at the temperature of 24-26 ℃, and forming a blank after hypha grows on the surface of the bean curd; twisting the mycelium of the blank, wrapping the blank, placing in a basin regularly, adding salt layer by layer to make the salt content of the blank reach 10 wt%, and pickling for 12hr to obtain salty blank;
(4) and (3) later-stage fermentation: filling the salty blank into a glass bottle, filling soup (70% of water, 18% of edible alcohol, 8% of salt and 4% of chilli powder), sealing and fermenting for 45 days at the later stage to obtain the low-waxy bacillus fermented bean curd.
The second step is that: bacillus cereus number analysis
Respectively collecting the white blank, the blank and the salty blank of the bean curd and 5g of fermented bean curd samples fermented for 15 days, 30 days and 45 days at the later stage, analyzing the number of bacillus cereus according to a national standard method, and finding that the number of bacillus cereus is 1.28 multiplied by 10 respectively2、2.15×105、 5.68×104、4.74×104、4.65×104、3.90×104cfu/g sample.
From the aboveThe test data show that the number of Bacillus cereus is reduced by an order of magnitude compared to the prior art (comparative example) by the application of garlic essential oil, the number of which in the product is 105The sample is less than cfu/g, and the guide requirement of the ready-to-eat food for the hong Kong food circle administration is met.
The third step: analysis of volatile Components
The fermented bean curd samples are collected, volatile aroma components of the fermented bean curd samples are analyzed by GC-MS, and 12 kinds of fatty acid ethyl esters are detected in total, wherein the fatty acid ethyl esters include short-chain fatty acid ethyl esters with fruit fragrance, such as ethyl valerate (2.99%), ethyl caproate (5.38%) and ethyl heptanoate (2.07%). In addition, 2 garlic essential oil components characteristic of diallyl disulfide and diallyl sulfide were detected in the fermented bean curd samples.
From the above test data, it can be seen that the fermented bean curd has higher content of volatile aroma components and has light garlic fragrance through the application of garlic essential oil, compared with the prior art (comparative example), so that the flavor of the product is richer.
The fourth step: structural analysis of flora
The above-mentioned fermented bean curd samples were collected for sequencing of 16s rDNA V3-V4 region. The fermented bean curd is mainly composed of bacteria such as lactobacillus (20%), leuconostoc (34%), Weissella (20%), lactococcus (9%) and the like.
From the above test data, it can be seen that compared with the prior art (comparative example), by using the garlic essential oil, the proportion of acinetobacter in the fermented bean curd is reduced to 6%, while the proportion of lactobacillus, leuconostoc, weissella, lactococcus and the like with probiotic function is up to 83%, so that the safety and functionality of the product are further improved.
In order to verify the inhibition effect of the garlic essential oil on bacillus cereus, 20mg of tetracycline is used as a positive control, a filter paper sheet method is adopted to test the antibacterial activity, and the inhibition effects of clove, rosemary, cinnamon, pepper and garlic essential oil on bacillus cereus are respectively tested, so that the result shows that the diameter of the inhibition zone of the tetracycline is 25mm, and the diameters of the inhibition zones of the above essential oil are respectively 19mm, 13mm, 31mm, 30mm, 0mm and 90 mm. Tests show that the garlic essential oil has a far better inhibiting effect on bacillus cereus than clove, rosemary, cinnamon and pepper.
The method for testing the antibacterial activity by the filter paper sheet method comprises the following steps:
activating Bacillus cereus in nutrient broth culture medium (beef extract 3g, peptone 10g, sodium chloride 5 g; distilled water 1L (nutrient agar culture medium added with 0.7-2% agar based on nutrient broth culture medium), sterilizing at 121 deg.C for 15min), and standing for 2-3 generations.
The antibacterial activity of the garlic essential oil is detected by adopting a filter paper sheet method. A suspension containing 1% Bacillus cereus (10)8CFU/mL) were poured into sterilized dishes and, after they had set, three 6mm diameter sterile filter paper discs were placed on agar plates at equal distances. mu.L of the suspension was injected onto filter paper sheets, incubated at 37 ℃ for 24 hours, and the size of the zone of inhibition was recorded, and 3 replicates were set for the experiment.
The invention also tests the effect of garlic essential oil on the growth of mucor: collecting potato glucose agar culture medium, subpackaging in 100ml triangular flask, adding Bulbus Allii essential oil with concentration of 60, 120, 180 μ g/Kg, respectively, pouring onto flat plate, coating with Mucor AS 3.2778, culturing at 28 deg.C for 48hr, observing Mucor growth, and finding no abnormality.
Potato dextrose agar medium: 200g of cleaned and peeled potatoes are cut into small pieces, boiled with water and filtered by eight layers of gauze. While heating the filtrate, 20g of agar and 20g of glucose were added, and the mixture was stirred well. After slightly cooling, the water is replenished to 1000 ml, and the mixture is sterilized for 15min at 121 ℃.
The embodiment analyzes the bacteriostatic concentration of the garlic essential oil:
1) preparing a bacillus cereus suspension: adding 50mL of nutrient broth culture medium into a 100mL triangular flask, sterilizing at 121 ℃ for 15min, inoculating Bacillus cereus (CMCC63302) strain, culturing at 37 ℃ overnight, and storing in a refrigerator at 4 ℃ for later use.
2) And (3) analyzing the bacteriostatic concentration of the garlic essential oil: adjusting the concentration of Bacillus cereus in the nutrient broth to 107CFU/mL. Taking 10mL sterile test tubes, adding 5mL nutrient broth culture medium containing bacteria, and adjusting garlic essence in the culture mediumOil concentrations were 1000, 500, 250, 125, 62.50, 31.25, 15.62, 7.81 and 3.90. mu.g/Kg. All nutrient broth media were incubated at 37 ℃ for 24 hr. The minimum concentration at which no growth of bacillus cereus was observed was recorded as the minimum inhibitory concentration of the essential oil. The result shows that the minimum inhibitory concentration of the garlic essential oil to the bacillus cereus can be as low as 62.5 mug/Kg.
It should be noted that the effect of the test of example 1 on examples 2 and 3 is the same and is not repeated one by one.
Example 2: garlic essential oil fermented bean curd 2
The first step is as follows: essential oil fermented bean curd production and preparation
(1) Preparing soybean milk: selecting undamaged and unmolded soybeans, adding 8 times of water by mass, soaking for 10 hours at normal temperature, taking soaked wet soybeans, grinding the wet soybeans into thick liquid according to the mass-to-volume ratio of the wet soybeans to the water of 1:8, wherein the mass unit is Kg and the volume unit is L, filtering to obtain raw soybean milk, and cooking the raw soybean milk at 95-100 ℃ for 10 minutes to obtain cooked soybean milk;
(2) preparing essential oil bean curd: dispersing 12mg of garlic essential oil in 5Kg of bean curd yellow serofluid, naturally acidifying at 28-35 deg.C for 24hr to obtain the final product; adding 20Kg of bean curd yellow serofluid into 100Kg of cooked soybean milk at 83-90 deg.C, adding bean curd yellow serofluid dispersed with garlic essential oil, stirring, standing and curding; squeezing the soybean milk in a box after the soybean milk is completely solidified, and cutting the bean curd into bean curd white blanks with standard specification and added with garlic essential oil after cooling;
(3) early-stage fermentation: cleaning and keeping the bean curd white blank dry in advance in a fermentation room, uniformly placing the bean curd white blank in a clean food steamer, uniformly spraying pure mucor on the surface of the bean curd white blank in the fermentation room, performing early-stage fermentation for 30 hours (relative humidity is 85-95%) at the temperature of 26-28 ℃, and forming a blank after hypha grows on the surface of the bean curd; twisting the mycelium of the blank, wrapping the blank, placing in a basin regularly, adding salt layer by layer to make the salt content of the blank reach 12 wt%, and pickling for 10hr to obtain salty blank;
(4) and (3) later-stage fermentation: filling the salty blank into a glass bottle, filling soup (70% of water, 17.5% of edible alcohol, 7.5% of salt and 4% of chili powder), sealing and fermenting for 60 days at the later stage to obtain the low-waxy bacillus fermented bean curd.
The second step is that: bacillus cereus assay
Collecting the fermented bean curd sample, and analyzing Bacillus cereus according to national standard method, wherein the number of Bacillus cereus is 1.28 × 104cfu/g sample.
The third step: sensory evaluation
Sensory evaluation was performed on the above fermented bean curd samples, and the results showed an overall acceptability of 8.64, with an odor score of 8.72, an appearance score of 8.38, a taste score of 8.93, and a texture score of 8.54.
Example 3: garlic essential oil fermented bean curd 3
The first step is as follows: essential oil fermented bean curd production and preparation
(1) Preparing soybean milk: selecting unbroken and unmolded soybeans, adding 10 times of water by mass, soaking for 16h at normal temperature (20-23 ℃), pulping the soaked wet soybeans according to the mass-to-volume ratio of the wet soybeans to the water of 1:6, wherein the mass unit is Kg and the volume unit is L, filtering to obtain raw soybean milk, and cooking the soybean milk for 20min at the temperature of 95-100 ℃ to obtain cooked soybean milk;
(2) preparing essential oil bean curd: dispersing 16mg of garlic essential oil in 25Kg of bean curd yellow serofluid, and naturally acidifying the bean curd yellow serofluid at 20-23 deg.C for 48hr to obtain the final product; adding bean curd yellow serofluid dispersed with garlic essential oil into 100Kg cooked soybean milk at 83-90 deg.C, stirring, and standing for curding; squeezing the soybean milk in a box after the soybean milk is completely solidified, and cutting the soybean milk into bean curd white blanks with standard specification and added with garlic essential oil after cooling;
(3) early-stage fermentation: cleaning the fermentation room in advance and keeping the bean curd blank dry, uniformly placing the bean curd blank in a clean food steamer, uniformly spraying pure mucor on the surface of the bean curd blank in the fermentation room, performing early fermentation at the temperature of 22-25 ℃ for 36hr (relative humidity of 70% -88%), and forming a blank after hypha grows on the surface of the bean curd; twisting the mycelium of the blank, wrapping the blank, placing in a basin regularly, adding salt layer by layer to make the salt content of the blank reach 8 wt%, and pickling for 24hr to obtain salty blank;
(4) and (3) later-stage fermentation: filling the salty blank into a glass bottle, filling soup (70% of water, 17.5% of edible alcohol, 7.5% of salt and 4% of chilli powder), sealing and fermenting for 90 days at the later stage to obtain the low-waxy bacillus fermented bean curd.
The second step is that: bacillus cereus assay
Collecting the fermented bean curd sample, and analyzing Bacillus cereus according to national standard method, wherein the number of Bacillus cereus is 4.33 × 104cfu/g sample.
As can be seen from the above examples, garlic essential oil has excellent anti-bacillus cereus properties compared to other essential oils. In the practical application of the fermented bean curd production, the garlic essential oil is added at the front end of the fermented bean curd production, so that the number of bacillus cereus in each production stage can be obviously reduced, and the number of bacillus cereus in the fermented bean curd product is stabilized at 105The safety of the fermented bean curd is improved when the concentration of cfu/g is less than that of cfu/g (examples 1 to 3). In addition, while bacillus cereus is reduced, the garlic essential oil has a certain optimization effect on the bacterial structure in the fermented bean curd fermentation process, and the safety and the potential probiotic function of the fermented bean curd are further improved (example 1). In addition, the garlic essential oil has no adverse effect on the flavor, and the sensory evaluation result shows that the garlic essential oil fermented bean curd has higher overall acceptability.
The invention takes the natural plant essential oil garlic essential oil as the bacteriostatic agent, and does not use artificially synthesized medicines. The method can effectively reduce the number of bacillus cereus at each stage in the fermented bean curd fermentation process, adjust the bacterial colony structure in the fermented bean curd fermentation process, and improve the safety performance and potential probiotic function of the fermented bean curd. The invention does not influence the normal fermentation process of the fermented bean curd and does not have adverse effect on the taste and smell of the fermented bean curd.
It should be noted that the present invention is not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations and simplifications which are made without departing from the spirit and principle of the present invention should be regarded as equivalent alternatives, which are included in the protection scope of the present invention.
Claims (10)
1. A preparation method of low-waxy bacillus fermented bean curd is characterized by comprising the following steps:
(1) preparing soybean milk: selecting undamaged and unmolded soybeans, adding water for soaking, grinding into thick liquid, filtering to obtain raw soybean milk, and boiling the thick liquid to obtain cooked soybean milk;
(2) preparing essential oil bean curd: dispersing garlic essential oil in bean curd yellow serofluid or cooked soybean milk cooled to room temperature; adding bean curd yellow serofluid into cooked soybean milk at 83-90 deg.C, adding dispersed Bulbus Allii essential oil, controlling the concentration of Bulbus Allii essential oil to 6-20mg/L, stirring, standing and curdling; squeezing, forming and cutting after the soybean milk is completely solidified to form a white bean curd blank;
(3) preparing a salty blank: inoculating Mucor spore to the white bean curd blank, placing into a fermentation room, and performing early-stage fermentation at 22-29 deg.C for 30-48h until the bean curd surface is full of mycelia to form a blank; rubbing hair, adding salt, and pickling for 10-24hr to obtain salty blank;
(4) and (3) later-stage fermentation: adding the salty blank into the soup, sealing, and fermenting for 45-90 days to obtain low-Bacillus cereus fermented bean curd with Bacillus cereus number less than 105CFU/g。
2. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the soaking in water is carried out by adding water 6-10 times of the weight of the soybeans and soaking for 8-16h at normal temperature.
3. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the pulping is to pulp soaked wet soybeans according to the mass volume ratio of the wet soybeans to water of 1:6-1:10, wherein the mass unit is Kg, and the volume unit is L.
4. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the pulp cooking is carried out at 95-100 deg.C for 10-20 min.
5. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the yellow serofluid of bean curd is obtained by naturally acidifying at 20-35 deg.C for 24-60 hr.
6. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the cutting is to cut the bean curd into standard size.
7. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the inoculation of the Mucor spores on the white bean curd blanks is to uniformly place the white bean curd blanks in a clean food steamer and uniformly spray pure Mucor on the surfaces of the white bean curd blanks.
8. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the relative humidity of the early fermentation is 70-95%; the hair twisting is to twist the hypha of the blank to wrap the blank, and salt is added to ensure that the salt content of the blank reaches 8-12 wt%.
9. The method for preparing a bacillus cereus-low fermented bean curd according to claim 1, wherein: the soup is prepared from salt, wine and spices.
10. A low Bacillus cereus fermented bean curd, characterized in that it is prepared by the method of any one of claims 1 to 9, and the number of Bacillus cereus in the fermented bean curd is less than 105CFU/g。
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| KR20040072459A (en) * | 2003-02-13 | 2004-08-18 | 대한민국(관리부서:산림청 임업연구원) | antibiotic composition and antibiotic material containing essential oil Extracts of Eucalyptus globulus |
| CN107873857A (en) * | 2017-11-22 | 2018-04-06 | 桂林国农生态农业有限公司 | The manufacture craft of low-salt flavor fermented bean curd |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20040072459A (en) * | 2003-02-13 | 2004-08-18 | 대한민국(관리부서:산림청 임업연구원) | antibiotic composition and antibiotic material containing essential oil Extracts of Eucalyptus globulus |
| CN107873857A (en) * | 2017-11-22 | 2018-04-06 | 桂林国农生态农业有限公司 | The manufacture craft of low-salt flavor fermented bean curd |
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| 吴克刚等编著: "《食品微胶囊技术》", 31 July 2006, 北京：中国轻工业出版社 * |
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