The difference between pasteurization and high temperature sterilization

Pasteurization, also known as low-temperature disinfection, cold sterilization, etc., is a disinfection method that uses lower temperatures to kill germs and keep the flavor of nutrients in articles unchanged. It is often used to define heat treatment methods that need to kill a variety of pathogens. Let's take a look at the difference between pasteurization and high-temperature sterilization.

Working principle of pasteurization

Pasteurization is to heat the mixed raw materials to 68 °70 ℃, and keep this temperature for 30 minutes after rapid cooling to 4 °5 ℃, because the general lethal point of bacteria are 68 ℃ and time below 30 minutes, so the mixed raw materials after this method can kill pathogenic bacteria and the vast majority of non-pathogenic bacteria, the mixed raw materials suddenly cool after heating, sharp hot and cold changes can also promote the death of bacteria.

The difference between pasteurization and high temperature sterilization

1. Sterilization temperature and time: pasteurized milk was pasteurized at a lower temperature, and ultra-high temperature sterilized milk was sterilized at more than 135℃ for several seconds.

2. Flavor: pasteurized milk tastes fresh and close to raw milk, while ultra-high temperature pasteurized milk has cooked milk or steamed taste.

3. Nutrition: there is less nutritional damage in pasteurized milk and more in ultra-high temperature sterilized milk, mainly micronutrients such as vitamins, but there is no significant difference in main nutrients such as protein, fat and lactose.

4. Storage conditions and shelf life: pasteurized milk can be stored at 2: 8 ℃ for 3-10 days, ultra-high-temperature sterilized milk can be stored for 3-6 months at room temperature, and bagged ultra-high-temperature sterilized milk can be stored for 1.5 months.

5. Foreign consumption: pasteurized milk is the main consumption type, while ultra-high temperature sterilized milk is secondary or less consumption.

Alternative methods of pasteurization

1. Ultra-high temperature sterilization: with the progress of technology, people also use ultra-high temperature sterilization (UHT ultra-high temperature instant sterilization, more than 100℃, but the heating time is very short, little damage to nutrients) to deal with milk. The shelf life of milk treated in this way will be longer, and most of the carton-packed milk we see is in this way.

2. Sterilization and storage technology: the biological effect of pulse discharge is used to sterilize in liquid medium. the sterilization equipment is generally composed of two parts: the pulse discharge power supply which supplies energy and the sterilization room where liquid materials are sterilized directly. when sterilizing by pulse discharge, the liquid material is placed as a dielectric in the gap between the two electrodes of the sterilization room or flows continuously through the gap between the two electrodes of the sterilization room. When the two electrodes are added with a pulsed electric field of a certain intensity and frequency, a very strong biological effect is produced in the liquid material to kill the bacteria.

3. Electrolytic sterilization: in a conductive solution, there are two kinds of redox reactions caused by the exchange of electrons at the interface between the electrode and the solution, one of which occurs under the action of external electric energy. one is excited by external light, heat or other forms of energy without external power supply.

4. Ac electric sterilization: generally refers to the method of killing microbial bacteria in liquid materials of fruit and vegetable juice by low-frequency alternating current below hundreds of hertz, in which there is an extended use method, which uses the thermal effect of alternating current, also known as resistance heating technology, which uses the resistance thermal effect of continuous flow of conductive liquid to heat, in order to achieve the purpose of sterilization.

5. Ultrasonic sterilization: make use of the cavitation effect, mechanical effect, chemical effect, thermal effect, dispersion effect, sound flow effect, capillary effect and thixotropic effect of ultrasonic wave in solid, liquid and gas. a series of reactions to achieve sterilization.

6. Laser sterilization: laser is not only an electromagnetic wave, but also a kind of energy flow (photon flow). Sterilization using the working principle of some special biological effects (chemical reaction, thermal effect, electronic effect, pressure effect, biological stimulation effect) produced by laser sterilization.

7. Pulsed strong light sterilization: the use of strong white light flash technology for sterilization, this technology is generally used to deal with food surface sterilization, can prolong the shelf life of prepackaged food with transparent materials.

8. Magnetic field sterilization: both constant magnetic field and pulsed magnetic field can effectively inhibit the growth of some microorganisms and bacteria. When reaching a certain intensity of magnetic field, biological macromolecules such as enzymes, amino acids, nucleic acids and proteins are inactivated and bacteria are killed by inhibiting the free radical activity of food and affecting the activity of proteins and enzymes.

9. Microwave sterilization

The thermal effect of ① microwave energy: under the action of a certain intensity microwave field, insects and bacteria in food will heat up due to the phenomenon of molecular polarization, resulting in protein denaturation and loss of biological activity. The thermal effect of microwave mainly plays the role of rapid heating and sterilization.

Non-thermal effect of ② microwave energy: high-frequency electric field also changes its membrane potential and polar molecular structure, resulting in the variation of proteins and physiologically active substances in microorganisms, resulting in loss of vitality or death. It plays a special role in sterilization that conventional physical sterilization does not have, and it is also one of the causes of bacterial death.