Food sterilization technology can generally be divided into heating sterilization technology, chemical sterilization technology, radiation sterilization technology (gamma ray, microwave, infrared, etc.), filtration sterilization method, and sterilization technology combining heating and other means according to the sterilization method. The pasteurization method refers to a relatively low-temperature heat treatment method that ensures the original flavor of the food, but the sterilization is not thorough enough. Below, we will introduce various sterilization methods for food:

(1) Ultra high pressure sterilization technology: food ultra-high pressure sterilization (high hydrostatic pressure sterilization) is to put food materials into liquid medium (usually edible oil, glycerin, oil and water lotion) after being packaged in a certain way, and make them reach the sterilization requirements after acting for a certain time under the pressure of 100-1000 MPa. The basic principle of sterilization is the lethal effect of pressure on microorganisms, mainly achieved by disrupting the activity of cell membrane inhibitory enzymes and affecting the replication of genetic material such as DNA. Under a pressure of 400-600 MPa, it can kill bacteria, yeast, and mold, avoiding the adverse changes caused by general high-temperature sterilization. Therefore, it can better maintain the inherent color, aroma, and taste of food and achieve the effect of extending the shelf life.

(2) Low temperature sterilization: Low temperature sterilization is a heating method that partially sterilizes microorganisms present in food. Usually, temperatures below 100 ℃ are used. Due to the high residual bacteria in food after low-temperature sterilization, processing techniques such as refrigeration, fermentation, addition of additives, and deoxygenation are used to extend the shelf life of the product. This method is mainly applicable to acidic foods with a pH below 4.5 and foods that undergo strong heating treatment, which will significantly reduce their quality. In recent years, this method has also been applied to milk and products with shorter shelf lives.

(3) Pasteurization method: Pasteurization refers to a relatively low temperature heat treatment method, usually carried out at a temperature below the boiling point of water. It is an ancient technology, first developed by French doctor Pasteur in the 19th century, and still has certain practical value today.

Pasteurization is the earliest sterilization method that uses hot water as a heat transfer medium. The sterilization conditions are 61-63 ℃ for 30 minutes, or 72-75 ℃ for 10-15 minutes. When heating, it should be noted that the surface temperature of the material is 4-5 ℃ lower than the internal temperature; In addition, when bubbles are generated on the surface, it is difficult for the foam part to meet the sterilization requirements. This sterilization method, due to the long required time, discontinuous production process, and prolonged heating, can easily cause changes in certain thermosensitive components, and the sterilization is not ideal.

(4) Ultra high temperature instant sterilization: Ultra high temperature sterilization, abbreviated as UHT sterilization. The general heating temperature is 125-150 ℃, and the heating time is 2-8 seconds. The sterilization process in which the product meets commercial aseptic requirements after heating is called UHT sterilization. This sterilization method can achieve the sterilization purpose in an instant, with particularly good sterilization effect, almost reaching or approaching sterilization requirements, and causing minimal chemical changes. It has the advantages of improving processing capacity, saving energy, reducing equipment volume, stabilizing product quality, and can implement on-site non disassembly cyclic cleaning of equipment.

(5) Microwave sterilization: Microwave sterilization is the process of treating food with microwaves to inactivate or kill microorganisms in the food, thereby extending its shelf life. On the one hand, when microwaves enter the interior of food, molecules such as water molecules in the food constantly change their orientation, causing a sharp increase in the temperature of the food and achieving the effect of sterilization. On the other hand, the non thermal effect of microwave energy plays a special role in sterilization that conventional physical sterilization does not have. Under the action of a certain intensity of microwave field, bacterial cells change their biological arrangement and movement patterns, while absorbing microwave energy to heat up, causing proteins in the body to undergo both non thermal and rotational effects, resulting in changes or destruction of their spatial structure, leading to protein denaturation and ultimately loss of biological activity. Therefore, microwave sterilization mainly involves the mutation and destruction of proteins and physiologically active substances in microorganisms under the action of microwave thermal and non thermal effects, leading to cell death.

(6) Ultraviolet sterilization: The sterilization effect of ultraviolet radiation is to promote the degeneration of cytoplasm. When microbial cells inhale ultraviolet radiation, they undergo chemical changes in intracellular components, especially nucleic acids and plasma proteins, due to photochemical reactions, resulting in cytoplasmic degeneration. Especially inhibiting DNA replication and cell division, causing damage or even death to microbial cells. The ultraviolet radiation with a wavelength of 250-260 nm has the strongest bactericidal effect.

(7) Ozone sterilization: Ozone is a light purple gas with a special fishy odor that exists at room temperature and freezing temperature. It partially dissolves in water and its solubility increases with decreasing temperature; At room temperature, it can self degrade and produce a large amount of free radicals, with the most significant being hydroxide radicals, thus possessing strong oxidizing properties.

(8) High voltage electric field pulse sterilization is the process of placing food in an instantaneous high voltage electric field generated between two electrodes. High voltage electric pulses (HEEP) can damage the bacterial cell membrane, alter its permeability, and thus kill cells. It can meet the requirements of commercial sterility, especially suitable for heat sensitive foods, and has broad application prospects. Ultrasonic sterilization technology has achieved good results in sterilizing soy sauce. Pulse strong light sterilization technology uses strong white light flashing to sterilize. This technology only treats the surface of food, so it has little effect on the flavor and nutritional content of food. It can be used to extend the shelf life of food packaged with transparent materials and fresh food.

There are still many sterilization technologies in food engineering, such as chlorine dioxide sterilization technology, chlorine gas sterilization technology, electronic sterilization technology, heating and pressure combined sterilization technology, heating and chemical agents combined sterilization technology, heating and radiation combined sterilization technology, electrostatic sterilization technology, etc. These technologies are being researched and applied.