Step 2 soak. The quality of soybean soaking directly affects the quality of tender tofu. Soybeans must be soaked after the juice and lime soil are cleaned. Different kinds of soybeans have different water absorption, different expansion speed and different temperature and water temperature in winter, so the requirements of soaking time and soaking degree of soybeans are different in each season. The general soaking time and degree are shown in the following table:
season
Temperature (℃)
Water temperature (℃)
Soaking time (hours)
Soaking degree
winter
20～22
There is a yellow concave surface of110 in the center of the watercress joint surface.
Early winter and early spring
10
10
12～ 14
There is a yellow concave surface of110 ~115 in the center of watercress noodles.
Spring and Autumn Period
24
twenty
10～ 1 1
There is a yellow concave surface of 1/5 in the center of the watercress joint surface.
summer
30～40
25～30
6～7
There is a 3/ 10 yellow concave surface in the center of the watercress joint surface.
On the one hand, the heat generated when the soybean is crushed makes the protein thermally denatured, and the viscosity is reduced; on the other hand, the soybean is soaked enough, the viscosity of the soybean paste is small, and the solidified soybean milk is not scraped; moreover, the shaping and kneading of tender tofu do not need dehydration, so the soaking of soybean is different from the soaking of other varieties, and the time is shortened, and the degree of expansion is slightly less.
The results of the above soaking can definitely ensure that the tender tofu is tender in texture, strong in water retention, good in elasticity, bright in knife section, and porous and bubbly when eaten, which lays a good foundation for softness and strength, and will never reduce the yield, on the contrary, the yield will increase slightly. The degree of soybean soaking is not enough, and the extraction amount of protein is relatively reduced, the yield is reduced, and the quality is poor. The degree of soybean soaking is too high. Although the extraction amount of protein is high, the acidity leads to the decrease of viscosity, and the structure of soybean milk coagulum is crisp and hydrophobic, and the product quality is naturally poor. Soybeans are soaked to the required degree, and they need to be washed with water after being fished out before they can be crushed to make soybean milk, which is a must for sanitary quality.
3. Make soybean milk. (1) Soybean is crushed into paste. Coarse grinding and low protein extraction. If the paste is too fine, the fine bean dregs can't be filtered out and mixed in the soybean milk. These will reduce the quality of finished products. Generally, 70 ~ 80 mesh grinding is suitable. The eyelet of silk or nylon skirt bag for pulp filtration is preferably140 ~150 mesh.
(2) The added water must be boiling water. Although the number of times of adding water is different, the total amount of water added is 9 times the weight of dried beans, which refers to ordinary tender tofu, and Hunan tofu is 8 times. When too much water is added, the concentration of soybean milk is low, and the soybean milk condensate is in an obvious network state, which is highly hydrophobic. When too little water is added, the concentration of soybean milk is high, the water content of soybean milk condensate is low, and the protein cohesion is strong. In these two cases, the tender tofu is hard and fragile, the knife section has burrs, and the eating board is hard and tastes bad.
(3) The soybean milk must be boiled within 5 ~10 minutes, and the shorter the time, the better. The temperature must be above 92℃, the protein heat denaturation is complete, and the soybean milk is completely solidified. The temperature is not enough, the thermal denaturation of protein is not complete, the coagulation of soybean milk is not complete, the tender tofu is easy to disperse into paste, and the color is red. Soybean milk is not boiled, and its saponin and anti-pancreatic egg enzyme are not destroyed. Eating this soybean milk and tofu made of it can cause indigestion, poisoning and diarrhea for weak people.
(4) After the soybean milk is boiled, the temperature is high, the coagulation effect of the coagulant is fast, and the condensate is hydrophobic, so the tender tofu is slightly hard. For example, if the temperature of soybean milk is low, the coagulation effect of the lower coagulant is slow, the coagulation result will be incomplete, and it is water-containing and hydrophobic, and tofu can only be made after dehydration. This kind of tofu is neither old nor tender, neither fish nor fowl nor tender. The optimum temperature of soybean milk during solidification is about 75℃.
4. Solidification operation jujube pulp washing. Nanjing tender tofu has such characteristics, and the main key is to adopt the method of pulp washing, so that the solidification effect is good and the quality can be guaranteed. The relationship has the following five aspects: (1) The coagulant jujube gypsum solution must be beaten. Gypsum powder is mixed evenly with a little raw soybean milk. It must be dry and not thin. It usually takes an hour to hammer it in a mortar. It is important to mix and hammer quickly, which will slow down the swelling of gypsum and affect the solidification effect. After plastering, the gypsum should be diluted with water, and the concentration of 8% is better to remove coarse impurities. Gypsum is white and transparent fiber gypsum, and the solidified substance of soybean milk is quite scraping, elastic and strong in binding force. Other kinds of gypsum are not as effective as it.
(2) The correct rushing angle must be mastered in pulp flushing. A small amount of soybean milk and gypsum solution (referred to as slurry paste for short) for slurry flushing is washed down against the wall of the slurry container at an angle of15 ~ 35, and the slurry paste smoothly rushes down the wall to the bottom of the device, impulsive soybean milk to turn up, turn up and down, and all of them are turned over to be evenly mixed with gypsum, with good solidification effect. Part of the grout flushed at an angle less than15 will rush out of the container, the impulse will be weakened, the dosage of gypsum will be reduced, and the setting will be incomplete. Due to the reaction of the wall, the slurry injected at an angle of 40 ~ 50 degrees splashes around, and most of the slurry bounces back to the middle and upper layers of the washed soybean milk, and only a small part of the slurry rushes to the bottom, so the impulse is too small, the soybean milk can't turn up, the gypsum is unevenly mixed and sinks, and the solidification is partially incomplete and partially overdone. The bigger the angle, the worse the effect.
The amount of soybean milk below 7.5 kg is small, so it is good to pour gypsum liquid into the bottom of the container and flush all soybean milk at once.
(3) The dosage of gypsum is generally 2.4 ~ 2.6% of the weight of dried beans. The amount of gypsum is small, the amount of calcium ion bridging is not enough, the bonding force between protein is weak, and the solidification is not completely semi-condensed. When the amount of gypsum is large, the effect of calcium ion is relatively enhanced, and the connection between protein is rapid and strong, and the structure of the solidified substance is loose and hydrophobic, so the solidification is too much.
(4) Mastering the impulse, even if the angle of grouting and the dosage of gypsum can be mastered, the impulse is very important. The impulse is small, the soybean milk turns slowly and stands fast, the gypsum sinks, and the bottom layer is strengthened by calcium ions, which leads to excessive solidification and incomplete upper layer. If the impulse is large, the soybean milk will turn over quickly and stand slowly. If it reaches the initial setting state and cannot stand, the solidification will fail.
After the pulp washing, it stops turning in about 20 seconds and reaches the initial setting in 30 ~ 50 seconds. As a result, moderate setting has the best effect, and the quality and output are both beautiful. The time required by the two requirements is not enough, the solidification is excessive, and the solidification of the excess is incomplete. The correct method of pulping is to use the minimum amount of gypsum and the maximum impulse when the angle is correct, and the initial setting time of soybean milk is about 40 ~ 50 seconds.
(5) The standing time must be about 30 minutes, otherwise, all previous efforts will be wasted. Because, although the soybean milk is initially solidified, the denaturation and connection of protein are still going on, and the organizational structure is still being formed. It will take some time for the soybean milk to be completely solidified and the structure to be stable. Don't dehydrate when making tender tofu, so let it stand for a long time. That's the reason. The standing time is short, the structure is fragile, the dehydration is fast, and the tender tofu is not tender and bright without water retention, but becomes thick and hard. After standing for a long time, the temperature of the solidified matter is reduced, the binding force is poor, and it is not dehydrated. The tender tofu is too tender and fragile, and the molding is unstable. It is fragile and cannot be sliced into pieces when eaten.
The tender tofu made by incomplete or excessive solidification has poor quality and low yield. The incomplete yield is reduced by10 ~15%, and the excessive yield is reduced by10 ~ 20%.