It is well known that no matter what foods must be guaranteed to be free of pathogenic microorganisms and other toxic substances, this is the most important thing. Under the premise of meeting this requirement, we should try our best to meet other requirements for food. Although a small amount of non-pathogenic microorganisms enter the human body after oral administration, it does not cause any harm to the human body. However, if there are a small amount of non-pathogenic microorganisms in the soy milk, it will grow and grow under the appropriate temperature conditions, eventually leading to the rancid precipitation of the soy milk. Conducive to preservation. If there are a large number of non-pathogenic microorganisms in soy milk, it is not only difficult to preserve, but also a large amount of bacteria in the body can cause gastrointestinal infection and disease. From the perspective of production hygiene, soy milk contains a lot of bacteria, which is the result of serious pollution in the production process or prolonged reproduction and growth, and is a sign of product failure. Therefore, the heat sterilization of soy milk must be carried out; however, in order to ensure the flavor quality of soy milk, the sterilization temperature and time must be selected. Long-term sterilization at high temperature promotes Maillard reaction, which not only causes nutrient loss of soy milk, but also causes poor color and flavor deterioration. In severe cases, the additive fails and the stability of soy milk decreases.
How to achieve the purpose of sterilization and soy milk can meet the nutritional and flavor requirements of people, and it is necessary to select the sterilization method according to the characteristics of the product. Commonly used heat sterilization methods are as follows:

1. Low-temperature long-term sterilization method (LTLT): Low-temperature long-time sterilization method is a long-standing pasteurization method. Usually, soybean milk is heated to 60-70 ° C for 30 minutes, so it is also called retention sterilization method. This sterilization method can kill all pathogenic bacteria, but its bactericidal effect can only reach less than 99%, and it is not easy to kill thermophilic bacteria and spores, and some lactic acid bacteria can also remain.

2. High temperature short time sterilization method (HTST): high temperature short time sterilization method is rapid pasteurization method, adopting

80-85 ° C 10-15 seconds, or 75-78 ° C 15-40 seconds of sterilization method, its bactericidal effect is better than the low temperature long-term method, and less damage to the soy milk ingredients, but can not kill all microorganisms The purpose is to remove pathogenic bacteria. Low-temperature long-term sterilization is a batch process. High-temperature short-time sterilization is usually carried out in a plate heat exchanger. It is widely used in the production of heat-sensitive foods. The products obtained by these two methods still contain microorganisms, storage and processing. Keep refrigerated.

Soymilk sterilized by the above two methods is generally called sterilized soy milk. Companies that produce and sell fresh milk can produce sterile soy milk. Because the production of sterilized soy milk can simplify the production process and packaging materials, without adding stabilizers, emulsifiers and other additives, the cost is greatly reduced, and the damage of soy milk quality by high temperature sterilization is avoided. But soy milk is a very nutritious food, and it is in neutral condition, microbial

Easy to grow and multiply, as long as a small amount of microorganisms remain in the soy milk, it will grow and grow quickly when the temperature is right. In most cases, the acid is first produced, so that the protein in the soy milk is solidified and then spoiled. Qualified disinfected soy milk can only be stored for 1 day (24 hours) at room temperature (20 °C). It can be stored under low temperature (4-8 °C) for 3-5 days. Therefore, disinfected soy milk must be sold. Production, production on the same day, sold out on the same day. Before leaving the factory, be sure to put it in a refrigerated (5-10 ° C) warehouse, which is especially important in the summer.

3. High temperature maintenance sterilization method: The sterilization temperature of this method is 121 ° C, the steam pressure is 0.14 MPa, the sterilization time is 20-30 minutes (packaged soy milk), in fact, at 121 ° C, 4-5 All heat-resistant spores can be killed in minutes, but the sterilization time should be extended appropriately considering the heat transfer time required for the packaging material and the presence of protective substances in the soy milk. Maintaining sterilization kills all microorganisms that can be grown, and the products obtained are commercially sterile, that is, microorganisms that are free of toxins, free of pathogenic bacteria, and free of reproductive capacity under normal storage and distribution conditions. . Therefore, its storage and transportation sales do not require refrigeration.

4. Ultra-high temperature transient (UHT) sterilization method: The sterilization temperature of this method is 138-150 ° C, the steam pressure is 0.5 MPa, and the sterilization time is only a few seconds. UHT is the commercial sterility of the product by brief, high-intensity heating.

The latter two methods are high temperature pressure sterilization method, also known as steam sterilization method, which is characterized in that all microorganisms can be killed, if combined with aseptic packaging, or after packaging together with the packaging, sterilization, that is, no production Soymilk, choose a good insulation material, can be stored at room temperature for 3-5 months, no rancidity.

Each sterilization has a negative impact, and the product changes and thus affects its nutritional value and sensory properties. The effect of heat treatment on protein is more or less changed its properties (denaturation process is only related to the physical state of protein), its nutritional value does not actually change much; heating has little effect on amino acids in proteins, mainly lysine Loss, the situation is: pasteurization 1% -2%, keep sterilizing 6% -10%, ultra-high temperature (UHT) treatment 3% -4%; excessive heat treatment will lead to browning, reducing sugar involved in browning reaction There will be losses. Pasteurization and ultra-high temperature instant sterilization do not produce this change. However, at higher storage temperatures (35-40 ° C), browning may also occur; fat is generally not affected by heating in different sterilization processes; minerals are basically unaffected by bactericidal heat treatment And the content of soluble calcium and phosphate may be reduced; in all kinds of vitamins, vitamins are basically not affected by pasteurization and ultra-high temperature treatment; vitamins are kept stable during sterilization; vitamins are considered to be heated The amount of loss depends on the degree of heat treatment; the difference in Vitamin loss caused by pasteurization and ultra-high temperature treatment is very small; vitamins are easily affected by heat, especially during the sterilization process; folic acid is also very susceptible to The effect of heating, the amount of loss is basically equivalent to the case of vitamins. Both biotin and niacin are stable and have limited loss of heat during the sterilization process.

In the sterilization process, the sterilization temperature is low and takes a long time, and the loss rate of the heat sensitive component in the food increases as the temperature increases and the time increases. With the increase of sterilization temperature, the time required for sterilization is rapidly reduced, and the loss rate of heat sensitive components in foods will increase with the increase of sterilization temperature, but will decrease with the decrease of sterilization time, due to high temperature sterilization. The time required is very short, and the two are offset. The loss rate of the heat-sensitive component in the food during the sterilization process tends to decrease as the sterilization temperature increases. It is pointed out that when the sterilization temperature is 121 ° C, the spore killing time is 4 minutes, and the retention rate of a certain component is 70%. However, as the temperature increases, the spore killing time decreases sharply; on the contrary, the food ingredient retention rate rises sharply. When the sterilization temperature is 132 ° C, the retention rate of the component is 90%, and when the sterilization temperature is 150 ° C, the retention rate is above 98%.

High temperature short time sterilization must be a short time throughout the high temperature phase, not a short time at the highest temperature. Therefore, in the choice of equipment, it is necessary to enable the soy milk to raise the temperature to the highest sterilization temperature in an instant, and the end of the sterilization can simultaneously reduce the temperature to the connection and the direct heating.

The method of directly heating by steam generally preheats the soy milk to above 70, and then instantaneously mixes with the high-temperature steam to raise the temperature of the soy milk to the process sterilization requirement. After the time has elapsed, immediately inhale the vacuum tank and flash. Due to the heat of evaporation, the temperature of the soy milk is lowered to below 85 ° C in a very short time (10 seconds), and the condensed water mixed with the soy milk is evaporated, and the bad flavor in the soy milk can be effectively removed. This is by far the most effective method of combining soy milk sterilization and deodorization.

The direct current heating method is to pass the soy milk through the resistance tube while passing the current, and try to make the current mainly through the soy milk flowing through the tube instead of the outer wall, so that the soy milk is heated to 140 ° C in a very short time, this patent method Overcoming the indirect heating of the tube causes the temperature of the tube wall to be too high to cause scaling problems, and thus the difficulty of heat transfer and cleaning, and the thermal efficiency is extremely high, up to 80%.

Vitamin

Another benefit of vitamins for the human body is that it can help the growth and development of the human body to operate normally, especially for teenagers, vitamins are one of the essential nutrients in the growth process. For example, vitamin D can well adjust the metabolism of some trace elements in the human body, and can also promote the absorption of calcium by the human body, maintain bone health, and maintain a balance between the blood phosphorus level and the blood calcium level in the human body.

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