Soycheese, also known as fermented bean curd, is one of my country’s famous specialty fermented foods and has a production history of thousands of years. There are products with different characteristics in various places. It is a delicious, unique and nutritious food. It mainly uses soybeans as raw material and is refined through soaking, grinding, dough making, culture, pickling, ingredients, and fermentation. Become.

1. Fermentation types of fermented bean curd

According to the production process, there are four types of bean curd fermented: ① Pickled fermented bean curd ② Mucor fermented bean curd ③ Rhizopus fermented bean curd ④ Bacterial fermented bean curd.

1. Pickled fermented bean curd: Add water to boil the tofu base, then add salt to marinate it, put it in a jar, add auxiliary materials, and ferment into fermented bean curd. The characteristics of this processing method: the tofu base is directly put into the jar without fermentation (no pre-fermentation), undergoes post-fermentation, and matures relying on the microorganisms brought in the auxiliary materials. Its disadvantages are insufficient protease, long fermentation time, low amino acid content, and poor color and aroma, such as Sitangchang fermented bean curd and Hunan Zili mold-free bean curd.

2. Mucor fermented bean curd: Cultivate Mucor with tofu base, called pre-fermentation, so that white mycelium can grow all over the surface of the tofu base, forming a tough skin film, accumulating protease, and creating conditions for the later fermentation of pickling and loading. .

Mucor requires lower temperatures for growth, and its optimal growth temperature is around 16°C. Generally, Mucor fermented bean curd can only be produced under low temperature conditions in winter. The traditional process uses Mucor mold in the air and inoculates it naturally, which requires about 10-15 days of cultivation (suitable for family workshop production). Pure Mucor can also be cultured, artificially inoculated, and cultured at 15-20°C for 2-3 days.

3. Rhizopus-type fermented bean curd: Using high-temperature-resistant Rhizopus mold, pure bacterial culture, artificial inoculation, fermented bean curd can also be produced in the high temperature season of summer, but the rhizopus hyphae are thin, light gray, protease and The peptidase activity is low, and the shape, color, flavor and physical and chemical quality of the fermented bean curd produced are not as good as Mucor fermented bean curd.

Based on the above advantages and disadvantages, after experiments, mixed strains of bacteria are used to brew fermented bean curd, which can not only increase its flavor. It can also reduce the amount of liquor in the auxiliary materials, reduce costs and improve economic benefits. The best ratio of Mucor and Rhizopus sinensis is 7:3.

2. Strain culture method

1. Test tube slant inoculation medium: 15g peptone, 1.5g agar, 2g water, 100ml PH6

Potato culture medium can also be used : Wash the potatoes, peel them, weigh 20g and cut them into small slices, add water and boil for 15-20 minutes, filter with gauze, remove the residue and take the filtered juice, add water to make it 100ml, add 2g agar, boil and dissolve, add 2g glucose and mix well. , divide into test tubes (the filling volume is 1/5 of the test tube), plug with cotton plugs, wrap and sterilize, place on an inclined plane, inoculate Mucor (or Rhizopus) at 15-20°C (Rhizopus 28-30°C) and culture for 3 In about days, it is the test tube strain.

2. Erlenmeyer flask bacterial culture medium: 100g bran, 1g peptone, 100ml water, dissolve peptone in water, then mix with bran and put into an Erlenmeyer flask. 500ml Erlenmeyer flask contains 50g culture material. Put a cotton plug in it, sterilize it and shake it while it is hot. After cooling, add a small piece of test tube strain and culture it at 25-28°C. After 2-3 days, it will be full of hyphae and have a large number of spores for later use.

Equipment used: High-pressure sterilization pot, wall temperature incubator, ultra-clean workbench... Sterilization conditions: Use high-pressure sterilization pot, sterilize at 0.1Mpa for 45-60 minutes

Preparation of tofu base→pre-fermentation→post-fermentation→packing (or bottling)→finished product

Preparation of tofu base: Prepare the tofu base It is the basis for improving the quality of bean curd. The production of tofu blank is the same as that of ordinary tofu, except that the brine is slightly older, the pressing time is longer, and the water content of the tofu blank is lower.

The production of tofu paste is divided into processes such as soaking beans, grinding pulp, filtering residue, dotting pulp, squatting, pressing and shaping, and cutting into pieces.

(1) Soaking of soybeans: The water temperature, time and water quality of soaking beans will all affect the quality of soaked beans. The temperature of the water for soaking the beans should be below 25°C. If the temperature is too high, the water for soaking the beans will easily become acidic, which is detrimental to the extraction of soy protein. In summer, the temperature is high, so the water needs to be changed multiple times to lower the temperature.

(2) Squeezing and cutting: After squatting, the tofu will sink and the yellow pulp will become clear. Press until the tofu base has a moisture content of 65-70% and a uniform thickness. After pressing and shaping, cut into small pieces (4×4×1.6cm).

Preliminary fermentation: Preliminary fermentation is a molding process, that is, the process of cultivating Mucor or Rhizopus in the tofu base. The result of fermentation is that the tofu base is covered with mycelium, forming a soft, dense and tough skin film and accumulating A large amount of protease is used to slowly hydrolyze the protein in the later fermentation. In addition to selecting excellent bacterial strains, it is also necessary to master the growth rules of Mucor and control conditions such as culture temperature, humidity, and time.

(1) Inoculation: Place the divided tofu base into a steamer grid or wooden frame bamboo bottom. The tofu base needs to be placed on its side, leaving space (about 1cm) between the rows to facilitate ventilation and heat dissipation. Adjusting the temperature is conducive to the growth of Mucor mold. Add 400ml of cold boiled water to each flask, break the mycelium with a bamboo stick, shake well, filter with gauze, add 400ml of cold boiled water to the filter residue, wash once, filter, mix the two filtrates to make a spore suspension. Spray inoculation can be used, or the tofu base can be soaked in bacterial solution and taken out immediately after soaking to prevent water from infiltrating into the base and increasing the water content to affect the growth of mucor mold. Generally, 100kg of soybean tofu is inoculated with the seed liquid in two Erlenmeyer flasks. In high-temperature seasons, a little vinegar can be added to the bacterial liquid to make the bacterial liquid acidic (PH4) to inhibit the growth of miscellaneous bacteria. Or inoculate the grown bran koji, dry it at low temperature and grind it into bacterial powder. Use a fine sieve to sift the dried bacterial powder on the tofu base. It must be uniform and there is bacterial powder on each side. The inoculation amount is 1% of the weight of soybeans. (Family workshop-style production can also directly use Mucor and Rhizopus in the air for natural inoculation, but it requires a clean natural culture room with a relatively stable and well-controlled temperature).

(2) Culture: Stack the culture plates high, cover them with an empty plate, and moisten them with a wet cloth around them. In spring and autumn, the culture temperature is generally around 20°C, and the culture time is 48 hours. In winter, the room temperature is kept at 16°C, and the culture time is 72 hours. hour, the temperature is high in summer, the room temperature is 30℃, and the culture is 30 hours. (If natural inoculation is used, the required time is longer, about 10-15 days in winter) The termination of fermentation depends on the maturity of Mucor. Generally, when producing green cubes, the mold will be slightly tender, and when the hyphae grow into white cotton-like shapes, That’s it. At this time, the activity of Mucor protease has not yet reached its peak, and the protein decomposition should not be too strong, otherwise the tofu will be broken (because the fermentation of stinky tofu is strong in the later stage). Red bean curd is slightly older in the early fermentation stage and is light yellow in color.

The growth and development changes of Mucor in the early stage of fermentation can be roughly divided into three stages: spore germination stage, mycelial growth stage, and spore formation stage. (Note: When mycelium begins to grow on the surface of the tofu base, that is, after plush-like mycelium grows, the cage must be turned, usually about three times)

(3) Pickling the base: when the bacteria When the silk begins to turn light yellow and a large number of gray-brown spores are formed, it is time to loosen the cage, open the window for ventilation, cool down the flowers, stop mold, promote Mucor to produce protease, end the early fermentation after 8-10 hours, and immediately Rub the hair and marinate. To enter the pickling process, first separate the interdependent mycelium and wipe it with your hands to wrap it around the tofu base. Put it into a large vat for marinating. At the bottom of the large vat, there is a hole in the middle about 20cm away from the bottom of the vat. Place the blanks on a round wooden board with a diameter of about 15 cm, and arrange them along the wall of the tank to the center. They should be arranged tightly with each other. When pickling the blanks, be careful to keep the side without mycelium growing to the side and not facing downwards to prevent the finished product from deforming. . Use the layered salting method to pickle the dough, increase the amount of salt in layers, and finally sprinkle a layer of covering salt. For each thousand pieces (4 × 4 × 1.6 cm), 6 kg of salt is used in spring and autumn, 5.7 kg of salt in winter, and 6.2 kg of salt in summer. The pickling time is about 7 days in winter, about 5 days in spring and autumn, and about 2 days in summer. The NaCl content of the pickled blanks is required to be 12-14%. After pickling, the blanks must be pressed 3 to 4 days later, that is, salt water is added and the noodles are marinated. The pickling time is about 3-4 days. After the salting is completed, open the bottom port of the tank, release the salt water and leave it overnight to allow the salt to dry and shrink.

Post-fermentation

Post-fermentation is a process that uses the mucor mold growing on the tofu base and the action of various microorganisms in the ingredients to mature the fermented bean curd and form the color, aroma and taste, including packaging. Processes such as altar setting, soup filling, and storage.

(1) Load the jar, take out the salt blank, drain the salt water, and put it into the jar. Do not pack it too tightly, so as not to affect the later fermentation and make the fermentation incomplete. There is a sandwich in the middle, and put the salt into the jar. The blanks are arranged in order, flattened by hand, and ingredients are added in layers, such as a little red yeast rice, noodle koji, and red pepper powder. After filling, pour in the soup.

(2) Pour the ingredients into the soup. Pour the prepared soup into the jar or bottle. The amount of filling depends on the variety you need, but it should not be too full to prevent the fermented soup from gushing out. Outside the altar or bottle.

The preparation of fermented bean curd soup depends on different ingredients, resulting in various varieties and flavors of fermented bean curd.

Red bean curd soup: 3kg red yeast rice, 1.2kg noodle yeast, 12.5kg rice wine, soak for 2-3 days, grind into a paste and then add 57.8kg rice wine and 4kg white sugar. In order, add 150g of curved surface, 1-2 lotus leaves, 150g of salt for cover, and 150g of soju for cover. The production process of red yeast rice: Since the production process of red yeast rice is quite complicated and not suitable for family workshop production, it is generally available on the market and will not be discussed in detail here.

Green fermented bean curd soup: use 450g of cold boiled water, 75g of yellow slurry water, and then add the brine and salt water. The concentration used is about 8%, and 50g of shochu is added to each jar.

White fermented bean curd soup: Use 16% salt water to prepare 12-degree rice wine as the soup (the amount of wine is generally 2-4%). ??You can also add a little yellow syrup water in seasons with higher temperatures. to add flavor.

Spicy fermented bean curd soup: for 1,000 pieces, use 9kg of 46% soju, about 0.9kg of chili powder, about 10kg of 12% sweet wine, about 1kg of red yeast rice, 1.2kg of white sugar, and 10g of MSG. .

Preparation of ingredients: Use a unique mixed spice seasoning. The ratio of the mixed spice seasoning is: 1 kg of mixed spice seasoning, 0.20 kg of galangal, and chili powder (the chili powder must be fine and not moldy) , high quality) 0.50kg, 0.12kg of Sichuan peppercorns, 0.04kg of Zanthoxylum bungeanum bark, 0.04kg of cinnamon bark, 0.03kg of licorice, 0.03kg of sesame seeds (requires that Zanthoxylum bungeanum, Zanthoxylum bungeanum, Zanthoxylum bungeanum, Zanthoxylum bungeanum, cinnamon bark, and licorice root must be dried and ground before adding), white sugar 0.04 kg (if the soup is spicy fermented bean curd soup, you don’t need to add it), MSG 0.02kg (if the soup is spicy fermented bean curd soup, you don’t need to add it). Mix the above ingredients together and mix well, add a little boiling oil or white wine, or add a little yellow slurry water to adjust the humidity.

(3) Seal and store, fill the altar with soup and then cover it (it is recommended to use a porcelain altar and add one or two washed and dried lotus leaves to the bottom of the altar, and then cover the mouth of the altar with a lotus leaf) , then seal it with cement or pig blood mixed with plaster of paris. When stored at room temperature, it usually takes more than 3 months to reach the quality of fermented bean curd. Green and white fermented fermented bean curds only need 1 to 2 months to mature due to their higher water content.

Note: The jars must be sterilized with boiling water and then drained and cooled to room temperature before being loaded into the jars.

Quality requirements for fermented bean curd

According to the ministry-issued standards SB-80 "Quality Standard for Red Bean Curd", SB76-80 "Quality Standard for White Bean Curd", SB77-80 "Quality Standard for Green Bean Curd" Standard" and the national food hygiene standard GB2712-81 "Hygiene Standard for Fermented Soy Products".

1. Sensory indicators

*** Same indicators: delicious taste, salty and palatable, no peculiar smell, neat and uniform block shape, fine texture and no impurities.

Red fermented bean curd: red or maroon on the surface, apricot yellow on the inside, with a fat and wine aroma.

White fermented bean curd: milky yellow, with the unique aroma of white fermented bean curd.

Green fermented bean curd: green bean color with special aroma of green fermented bean curd.

2. The approximate value of microbial indicator E. coli (individuals/100g) is less than 30.