How to make hand-ground dried tofu?

Sensory requirements: bright color, uniform particle size, full grains, less than 2% impurities, less than 5% discolored cotyledons, less than 2% moldy diseased grains and less than 65,438+00% broken grains.

2. The crude protein content is more than 34%, and the moisture content is less than 16% (Note: soybeans with this moisture content cannot be stored for a long time. )

Neither Chen Dadou nor dried bean curd is suitable for making dried bean curd. Due to the long storage time, some protein was consumed by life activities, especially after high temperature season, fat oxidation and protein denaturation, the processed tofu was rough, inelastic, poor in water retention and dark in color. The protein part of dried beans denatured during drying, which affected the yield of tofu.

4. Iron beans should not be used too much and should be less than 1%. Iron beans refer to soybeans that absorb water very slowly or do not absorb water. It needs to be judged by soaking experiment.

Second, the white embryo production part

1. Soybean pretreatment: remove impurities in soybeans, such as soil, sand, stones, metals and grass seeds. And wash off some microorganisms on the surface of soybean to prevent soybean from deteriorating during soaking. It needs to be rinsed until the water becomes clear.

2. Soaking and washing: Soak 500 kilograms of soybeans with 1 0,000 kilograms of water, and the volume of the container needs 1.5 cubic meters. The yield of tofu soaked in soft water is higher than that of well water or river water. Criteria for judging the suitability for soaking: the seeds fully expand without wrinkling after absorbing water, and the epidermis falls off less than 20%. After bean separation, there is no yellow heart, no whitening, the central part is fine and concave, no sour taste, and the pH is 6.0-7.0. Washing function: reduce the acidity of soaked soybeans, improve the hygiene and safety of products and ensure the quality of products. Refer to bean soaking process:

Seasonal water temperature/℃

Spring and autumn15-2010-12

Summer 20-35 6-8

Winter 5- 15 13- 18

3) Beating: 1 kg of soaked soybeans is added with 2.5 kg of water. In order to improve the extraction rate of protein, the process of adding water for many times, grinding for many times and separating slurry and residue is usually adopted. It is required that the slurry is fine without residue, and the slurry and residue should be rubbed by hand, without juice flowing and sticky hands. The protein content of bean dregs is less than 2.6%. The amount of water added during separation is 4 to 6 times that of soybean. The amount of water added should be constant, so as to avoid the excessive fluctuation of soybean milk concentration, which will affect the product quality of subsequent processes. After the ground soybean milk enters the storage tank, two thousandths of defoamer should be added. Particle size standard during grinding: less than or equal to 1mm after grinding, less than or equal to 0.5mm after large grinding, and 15um after small grinding.

4) Boiling and filtration: The purpose of boiling is to denature protein by heating, at the same time, destroy the activity of enzymes in raw materials, improve the digestibility of protein, eliminate anti-nutritional factors in soybeans, remove the beany smell, and also play a role in sterilization. At present, the continuous pulping process is usually adopted, which requires the temperature of the first tank to be 40℃, the second tank to be 60℃, the third tank to be 80℃ and the last tank to be 96- 100℃. The pressure is less than 0. 1 MPa. The filter screen is required to be 200-250 mesh/inch. Bean dregs that cannot pass through the filter screen will generally return to the pulping process for re-grinding.

5) Pulping and brain squatting: Pulping, also known as brain making and flower making, is a key process in the production of tofu. It is mainly the process of adding coagulant to cooked soybean milk according to a certain proportion and method, adjusting the pH value of soybean milk to the isoelectric point of protein, and transforming soybean protein sol into gel, that is, soybean milk into tofu (also known as tofu). Salt water is often used as coagulant in the production of dried bean curd, among which magnesium salt has fast coagulation speed and low yield of soybean protein, but it has good flavor; Calcium salt is relatively slow, the solidification process is relatively easy to control, and the yield of tofu is high. The concentration of brine is often 14- 17 wave magnesium. In the process of bittern lighting, bittern should not be discharged too quickly, and the flow rate should be balanced. When you put the brine, you should observe it while stirring. If it is too old, the water will run fast when squeezing, and the tofu will be rough, too tender and sticky, and it will be difficult to squeeze if it runs slowly. Generally, the temperature of sizing is 80-85℃, and it is impossible to directly order sizing when the temperature is above 95℃. The concentration of soybean milk should be 7-8Bé. There is a process for hot soybean milk to achieve complete solidification after adding coagulant evenly, which is called squatting. Squatting time is generally10-15 minutes.

6) brain breaking, boxing and squeezing: brain breaking means breaking tofu formed by pulping. The size of the brain block should be 0.5-0.8 cm. When packaging, tofu brain should be evenly distributed on the wrapping cloth, and the packaging should be tight, otherwise there will be more rotten edges and great waste. The purpose of squeezing is to make the partially dispersed protein in tofu coagulate and adhere better, so that the internal tissue of bean products is tight, and at the same time, the water discharged by squeezing is forced to be discharged through the wrapping cloth, thus making the tofu white embryo meet the requirements. Extrusion requires gradual pressurization to discharge the yellow slurry. The embryo skin of dried bean curd will be very hard, and the yellow slurry inside will not be exhausted, forming a small cavity inside, which is honeycomb-shaped, but the dried bean curd is bad and soft. Pressing must have a certain temperature, generally 65-70℃, so it should be pressed in time after packaging. Reference technology: pressing time is 20-25min, moisture content of white embryo is 60-65%, and pressure is 1-3 MPa.

7) Stripping and molding (slicing): The cut embryo should be moved to a ventilated place in time for cooling to avoid spoilage.

Second, the dry embryo production part

8) blanching and marinating: the purpose of blanching is to remove the fabric and connection lines on the surface of the embryo and remove the hard skin on the surface, so that the surface of dried tofu is smoother and easier to taste and color when marinating. Reference process of alkali scalding: wet embryo 75 kg, water 200 kg, alkali 500 g, boiled in boiling water for 2 minutes.

Reference process of marinating: 5-5.5% bittern salt, marinating time is 30-45 minutes. When marinating, the steam pressure is less than 0.2mPa. In the process of marinating, it should be stirred at regular intervals to make the color of marinating uniform.

9) Baking: Reference process: temperature 80- 100℃, time 20 minutes. The water content of dry embryo is 50-55%, and the salt content of dry embryo is 1.7-2.2%.