Introduction:
Soybean milk, also known as sufu, is one of the famous fermented foods in China, which has a production history of thousands of years. Different places have different products, which are delicious, distinctive and nutritious. They are mainly made of soybeans, which are refined through soaking, pulping, blank making, bacterial culture, embryo preservation, ingredients and jar fermentation.
1. Fermentation types of sufu
According to the production technology, there are four types of fermented sufu: ① pickled sufu; ② Mucor fermented bean curd; ③ Rhizopus sufu; ④ Bacterial sufu.
1. Pickling sufu: Boil tofu with water, then marinate it with salt, put it in a jar, add auxiliary materials, and ferment it into sufu. This processing method is characterized in that the bean curd blank is directly put into a vat without fermentation (no pre-fermentation), then fermented, and matured by microorganisms brought in by auxiliary materials. Its disadvantages are insufficient protease, long fermentation time, low amino acid content and poor color and fragrance, such as Rusi sugar factory sufu and Hunan Gigi Lai mildew-free sufu.
2. Mucor fermented bean curd: Mucor is cultured with bean curd blank, which is called pre-fermentation, so that white hyphae are spread all over the surface of bean curd blank, forming tough skin membrane and accumulating protease, creating conditions for post-fermentation of pickling and canning.
The growth temperature of Mucor is low, and the optimum growth temperature is about 65438 06℃. Generally, Mucor fermented bean curd can only be produced at low temperature in winter. Traditional technology uses Mucor in the air to inoculate naturally, which takes about 10- 15 days (suitable for family workshop production). Mucor can also be cultured, inoculated artificially, and cultured at 15-20℃ for 2-3 days.
3. Rhizopus-type sufu: It can be produced by high-temperature resistant Rhizopus after pure bacterial culture and artificial inoculation, but Rhizopus is fine and light gray, with low protease and peptidase activities, and the shape, color, flavor and physical and chemical quality of the produced sufu are not as good as those of Mucor.
Combined with the above advantages and disadvantages, through experiments, fermented bean curd with mixed strains can not only increase its flavor. It can also reduce the amount of white wine in the auxiliary materials, reduce the cost and improve the economic benefits. The best ratio of Mucor to Rhizopus chinensis is 7: 3.
Second, the strain culture method
1. Test tube slant inoculation medium: maltose 15g peptone 1.5g agar 2g water 100mlPH6.
You can also use potato culture medium: listen carefully, peel potatoes, weigh 20g and cut into small slices, add water to boil for15-20min, filter with gauze, remove residues and take filtrate, add water to 100ml, add 2g agar, add 2g glucose after boiling, mix well, and sub-package test tubes (capacity is 65438+ 0/5 of test tubes).
2. triangle flask culture medium: wheat bran 100g peptone 1g water 100ml, dissolve peptone in water, then mix it with wheat bran, put it into a triangle flask, put 50g culture medium into a 500ml triangle flask, plug it with a cotton plug, shake it while it is hot, cool it, and inoculate a small piece of test-tube strain.
Equipment used: clean workbench of autoclave wall temperature incubator ... sterilization conditions: autoclave, 0. 1Mpa for 45-60 minutes.
Third, the brewing process of sufu
Tofu blank making → pre-fermentation → post-fermentation → canning (or bottling) → finished product.
Making bean curd cake: Making bean curd cake is the basis of improving the quality of fermented bean curd. The production of bean curd cake is the same as that of ordinary bean curd cake, except that the brine is a little old, the pressing time is longer and the water content of bean curd cake is lower.
The production of tofu brain blank is divided into: soaking beans, grinding pulp, filtering residue, sorting, squatting, pressing and forming, cutting into pieces and other processes.
(1) Soaked beans: The water temperature, time and quality of soaked beans will affect the quality of soaked beans. The water temperature of soaking beans should be below 25℃. If the temperature is too high, the soaked water will turn sour easily, which is not conducive to extracting soybean protein. The temperature is high in summer, so it is necessary to change the water several times to cool down.
(2) Squeeze and cut into pieces: after squatting, the tofu flower sinks and the yellow slurry water is clarified. It is appropriate to squeeze the bean curd cake with water content of 65-70% and uniform thickness, and cut it into (4×4× 1.6㎝) small pieces after squeezing.
Pre-fermentation: pre-fermentation is a moldy process, that is, the process of cultivating Mucor or Rhizopus in tofu blank. The result of fermentation is that the bean curd blank is covered with hyphae, forming a soft, delicate and tough skin membrane, accumulating a large amount of protease, and slowly hydrolyzing protein in the later fermentation. In addition to selecting excellent strains, it is necessary to master the growth law of Mucor and control the culture conditions such as temperature, humidity and time.
(1) Inoculation: Put the diced bean curd blank into a steamer grid or a bamboo chassis with wooden frame. The bean curd blank should be placed on its side, leaving a space between rows (about 1㎝) for ventilation and heat dissipation, and adjusting the temperature, which is beneficial to the growth of Mucor. Add 400ml of cold boiled water into each triangular flask, break the mycelium with a bamboo stick, shake it evenly, filter it with gauze, rinse the filter residue with 400ml of cold boiled water, filter it, and mix the filtrates twice to make spore suspension. Spray inoculation can be used, or tofu blank can be soaked in bacterial liquid and taken out immediately after soaking, so as to prevent water from soaking into the blank and increase the water content to affect the growth of Mucor. General 100㎏ bean curd blank was inoculated with two triangular bottles of seed liquid. In high temperature season, a little vinegar can be added to the bacterial liquid to make it acidic (PH4) to inhibit the growth of miscellaneous bacteria. Or inoculate that grown bran koji, drying at low temperature, grin into bacterial powder, and sieving the dried bacterial pow on the bean curd blank with a fine sieve, wherein each side of the bacterial powder is required to be uniform, and the inoculation amount is 65,438+/-0% of the weight of soybean. Family workshop production can also directly use Mucor and Rhizopus in the air for natural inoculation, but it needs a clean and well-controlled natural culture room.
(2) culture: stack the culture plates, cover the upper plate, and keep it moist with a wet cloth. The temperature in spring and autumn is generally around 20℃, and the culture lasts for 48 hours. In winter, the room temperature is 65438 06℃, and the culture time is 72 hours. In summer, the temperature is high, the room temperature is 30℃, and the culture is 30 hours. (If natural inoculation is adopted, it will take a long time, about 10- 15 days in winter). Fermentation termination depends on the maturity of Mucor. Generally, the green formula is moldy, and it is enough for the mycelium to grow into white cotton wool. At this time, the protease activity of Mucor has not reached the peak, and the protein decomposition will not be too strong, otherwise it will lead to the breaking of tofu (because the stinky tofu is fermented strongly in the later period). Red sufu is slightly older and yellowish in the early stage of fermentation.
The growth and development of Mucor in the early stage of fermentation can be roughly divided into three stages: spore germination stage, mycelium growth stage and spore formation stage. (Note: When hyphae begin to grow on the surface of tofu brain blank, that is, after hairy hyphae grow, the cage should be turned over, usually about three times. )
(3) Blank brewing: When the hyphae begin to turn pale yellow and a large number of grayish brown spores are formed, you can loosen the cage, open the window for ventilation, cool the flowers, prevent mildew and promote Mucor to produce protease. After 8- 10 hour, after the early fermentation is finished, the wool is rubbed and pickled immediately. In the process of pickling, first separate the connected hyphae, knead and wrap the tofu blank by hand, and then put it in a vat for pickling. The bottom of the cylinder is about 20㎝ away from the bottom of the cylinder, and a circular wooden board with a hole in the middle with a diameter of about 15㎝ is added. Put the blanks on the board and arrange them along the cylinder wall to the center, which should be closely arranged with each other. When pickling the blank, attention should be paid to making it short. The blank is salted in layers, and the salt content is increased in layers. Finally sprinkle a layer of covering salt. Every thousand cubic meters (4×4× 1.6㎝) is 6㎝ in spring and autumn, 5.7㎝ in winter and 6.2㎝ in summer. The curing time is about 7 days in winter, 5 days in spring and autumn and 2 days in summer. The content of NaCl in the cured blank should be 12- 14%, and the blank should be pressed 3-4 days after curing, that is, salt water is added to the surface of the blank, and the curing time is about 3-4 days. After pickling is completed, open the through hole at the bottom of the tank, let out salt water, and leave it overnight to dry and shrink the salt blank.
Late fermentation
Post-fermentation is the process of using Mucor growing on tofu blank and various microorganisms in ingredients to make sufu mature and form color, fragrance and taste, including canning, soup filling and storage.
(1) Take out the salt blank from the cylinder, drain the salt water and put it into the cylinder in several places. When filling, it should not be too tight. After the late fermentation was not affected, the fermentation was incomplete and there was a sandwich in the middle. Arrange the salt blanks in turn, flatten them by hand, add ingredients in layers, such as a little red yeast, flour koji and red pepper powder, and fill them with soup.
(2) Pour the ingredients into a jar or bottle. The amount of stuffing depends on the variety you need, but it should not be too full to avoid the fermented soup pouring out of the jar or bottle.
The production of fermented bean curd soup has formed various varieties and flavors of fermented bean curd due to different ingredients.
Red bean curd soup: red koji 3㎏, flour koji 1.2㎏, yellow rice wine 12.5㎏, soaked for 2-3 days, ground into slurry, and then added with yellow rice wine 57.8㎏ and white sugar 4㎏. Add curved surface 150g, lotus leaf 1-2, covering salt 150g and covering shochu 150g in turn. Production technology of monascus: Because the production technology of monascus is quite complicated, it is not suitable for family workshop production, and it is generally available in the market, so I will not discuss it in detail here.
Soup of Fangqing sufu: 450g of cold boiled water, 75g of yellow serous water, supplemented by Hua Mao bittern and brine, with a concentration of about 8%, and 50g of shochu is added to each tank.
White bean curd soup base: 12 degree rice wine takes 16% salt water as the soup base (the amount of wine is generally 2-4%), and a little yellow slurry water can be added to enhance the flavor in high temperature season.
Spicy sufu soup: 1, 000 pieces of 46-degree shochu 9㎏, Chili powder 0.9㎏, liqueur 12 ㎏, Redmi 1㎏, sugar 1.
Preparation of ingredients: use a unique mixed spice seasoning, in which the proportion of mixed spice seasoning is: 1㎏, and in the mixed spice seasoning, 0.20㎏ of galangal and 0.50㎏ of Chili powder (fine powder, no mildew and high quality). 0. 12㎏ Zanthoxylum bungeanum, 0.04㎏ Cinnamomum cassia, 0.03㎏ Glycyrrhiza uralensis, 0.03㎏ Sesame (Zanthoxylum bungeanum, Cinnamomum cassia and Glycyrrhiza uralensis must be dried and crushed before adding) and 0.04㎏ sugar. Mix all the above materials together and stir well. Add a little boiling oil or white wine, or add some yellow syrup to adjust the humidity.
(3) Seal the jar, store it, fill it with soup and cover it (it is recommended to use a porcelain jar, add one or two washed and dried lotus leaves to the bottom of the jar, and then cover it with lotus leaves), and then seal it with cement or pig blood mixed with cooked gypsum. Generally, it takes more than 3 months for sufu to be stored at room temperature to reach its quality. Because of the high water content, Fangqing and Baifang sufu only need 1~2 months to mature.
Note: the jar should be disinfected with boiling water and cooled to room temperature before it can be put into the jar.
Quality requirements of tofu milk
According to the ministerial standards SB-80, SB76-80, SB77-80 and GB 27 12-8 1 fermented bean products.
1, sensory index
* * * Same index: delicious, salty and palatable, with no peculiar smell, neat and uniform lump, delicate texture and no impurities.
Red sufu: the surface is red or jujube red, and the inside is apricot yellow, with fat and wine fragrance.
White sufu: milky yellow, with the unique aroma of white sufu.
Green sufu: bean blue, with a special aroma of green sufu.
2. The approximate value of microbial indicator coliforms (each/100g) is less than 30.
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