Sterilization techniques commonly used in food aseptic packaging

Superheated steam sterilization technology is also called dry heat sterilization. Is the use of high temperature superheated steam sterilization, that is, using the temperature of 130 degrees to 160 degrees of superheated steam spray sterilized items, a few seconds to complete the sterilization operation, the current superheated steam sterilization technology is only applicable to heat food packaging containers (such as metal products, glass products, etc.) sterilization. Metal can is one of the earliest packaging materials used in aseptic packaging, mainly divided into tin can and aluminum can. At present, the most advanced typical representative of aseptic packaging of metal can in the world is dole aseptic can system in the United States, which adopts this sterilization technology. The method is that when the empty tank passes through the sterilization chamber on the conveyor chain, the superheated steam is sprayed from top to bottom for 45 seconds, at which time the temperature of the tank rises to 221 ° F ~ 224 ° F, and the lid also USES the superheated steam of 287 ° F ~ 316 ° F to sterilize for 75 to 90 seconds, which is high enough to kill all heat-resistant bacteria. Because all containers and equipment are sterilized by superheated steam, the sterility is high, there is little air in the top gap inside the can, and it is in a high vacuum state, so the product is safe and reliable.

Resistance heating sterilization technology

Also known as ohmic sterilization, it is a new type of thermal sterilization technology that USES electricity to generate heat inside food to achieve the purpose of sterilization. It USES the electrode to direct the current into the human food, from the food's own dielectric property to generate heat, in order to achieve the purpose of sterilization. Resistance heating sterilization using the frequency of the alternating current (ac) of 50 hz ~ 60 hz, the applicability of the ohmic heating determined by the electrical conductivity of food materials, most use pump, dissolved salt ions and water content in more than 300% of food available resistance heating sterilization, and the effect is very good, and some of the fat, sugar, oil, add salt and treated water is not ionized food is not applicable to the technology. As a new and high technology, ohmic sterilization is applied to food containing grain, such as diced beef and diced carrot, which plays a key role in improving product health safety and flavor quality, facilitating process control and reducing operating cost.

Experiments conducted by APV Food Processing Center in the United Kingdom show that resistance heating has been successfully used to sterilize all kinds of food containing large particles and flake food, such as potato, carrot, mushroom, beef, chicken, flake apple, pineapple, peach, etc. For the food with particles (particle size less than 20mm), conventional heat exchanger indirectly heats and sterilizes the food. The heat is first transferred by the heating medium to the liquid in the food material through the partition wall, then by convection and conduction between the liquid and the solid particles to the solid particles, and finally the heat transfer inside the solid particles. Obviously, in order to achieve the sterilization temperature inside the particle, the surrounding food media must be overheated, which will inevitably lead to the soft texture and appearance of the food containing particles after sterilization, affecting the flavor and quality of the product. By using ohmic sterilization technology, the heating rate of particles can be close to that of liquid, and the heating rate can be faster than that of conventional heat transfer sterilization method (the heating rate of particles is about 1 ° F/s ~ 2 ° F/s) to obtain high quality products. Therefore, it is more suitable for continuous sterilization of acidic and low-acid food and food with granules.