The meaning of sterilization of canned food is to kill all microorganisms in the food. However, there is a difference between the so-called "sterilization" of canned food and the sterilization in bacteriology. The latter refers to absolute sterility, [therefore the term "sterilization" is used. word. If the sterilization of canned food really reaches this level, the sterilization temperature and time will be greatly increased. This will inevitably affect the quality of food. That is to say, the flavor and nutrition of the food are reduced, and the edible value is even lost. In order to ensure the color, aroma, taste and nutritional value of food, the sterilization of raw food can only require that the food will not contain pathogenic bacteria harmful to human health after being heated to a certain extent. At the same time, it can inhibit the activity of non-pathogenic microorganisms that cause food spoilage under normal storage conditions. In order to achieve the shelf life specified for canned storage. This sterilization of canned food is also called "commercial sterilization" 
There are many factors that affect the sterilization effect of cans, such as the degree of contamination of food before sterilization, food ingredients, heat transfer, initial temperature of cans, etc. A brief introduction to each is as follows:
1. The degree of contamination of food before sterilization. From raw material processing to filling and sterilization, food will be contaminated by microorganisms to varying degrees. The higher the contamination rate, the longer the time required for sterilization at the same temperature. Different types of microorganisms have different degrees of heat resistance. Yeast can be killed at 40 or 70°C. Thermophilic bacteria can be killed at 75-80°C. Clostridium botulinum type A and B spores need to be heated at 100°C for 6 hours or at 120°C for 4 minutes. die. The more microbial spores, the higher the temperature required for sterilization and the longer the sterilization time. 2. Food ingredients. Canned foods contain sugar, salt, protein, fat and other foods that can affect the heat resistance of microorganisms and contain phytoncides, such as : Chili peppers, onions, etc. have the effect of inhibiting or killing microorganisms. 
The acidity in food has a great influence on the heat resistance of microorganisms. Undissociated organic acid molecules can easily penetrate into the living cells of bacteria and dissociate into ions, thereby transforming the internal reactions of the cells and causing cell death. Therefore, foods with high acidity can generally be sterilized at a lower temperature and for a shorter time.
3. Heat transfer
When cans are heated and sterilized, the main modes of heat transfer are conduction and convection ① Types and types of can containers: tin-plated thin steel cans transfer heat faster than glass cans, and small cans transfer heat faster than large cans. For cans of the same volume, flat cans transfer heat faster than short cans.
② Type of food and canning status: Liquid food transfers heat quickly, but the heat transfer speed of sugar liquid, salt water or seasoning liquid decreases as its concentration increases. Solid foods such as lunch meat, crab meat, etc. have a slow heat transfer rate. Bulk food with soup transfers heat faster than without soup. Larger blocks conduct heat more slowly than smaller blocks. Tight cans transfer heat more slowly.
③ The form of the retort and the position of the can in the retort: Rotary sterilization has a greater effect and shorter time than stationary sterilization. The canned food is placed far away from the air inlet pipe in the sterilizing pot. When the temperature in the pot has not reached equilibrium, the heat transfer is relatively slow. The amount of air removed from the pot, the accumulation of condensed water, and the structure of the sterilization basket all affect the sterilization effect.
4. Initial temperature of cans. The center temperature of cans before sterilization is closely related to the sterilization effect. Before sterilization, the initial temperature of the food in the can should be increased (for example, the temperature of the food and soup should be increased during canning, and sterilization should be carried out in time after exhaust and sealing). This is more important for cans that are not prone to convection and have slow heat transfer.The canned sterilization process has strict requirements and has different process curves for different varieties. It can be divided into four stages of heating, heating, insulation and cooling in chronological order. Different stages have different requirements for temperature, time, pressure, etc. At present, Most cans are sterilized by steam heating and cold water cooling, and the main sterilization equipment is a sterilization retort machines.
Canned sterilization process requirements are as follows:
(1) Preheating stage: Steam circulation is required to quickly heat the material, and the temperature in the kettle is required to rise to 100 C to 106 C within 5 to 6 minutes.
(2) Heating stage: The temperature in the kettle is raised at a certain rate to 121 Co in about 10 minutes.
(3) Heat preservation stage: Keep the gold temperature at 121C. The heat preservation time generally ranges from 15-30 minutes depending on the type of material.
(4) Cooling stage: reduce the kettle temperature from 121C to below 40C within a certain period of time. A very important requirement at this stage is to keep the pressure inside the kettle basically unchanged. However, while adding cold water to cool down the kettle, the pressure inside the kettle is often greatly affected. Once a large amount of cold water is injected into the kettle, it will cause
The CU pressure drops rapidly and needs to be controlled in time. In addition, there are also corresponding requirements for cooling time. 
The optimal pH for most microorganisms is in the range of 6-7. In acidic and highly acidic foods, the heat resistance of microorganisms and their spores is greatly reduced. Therefore, the corresponding sterilization temperature of food with different acidity is also different. At present, canned food heating and sterilization temperatures can be roughly divided into two categories:Low-temperature sterilization method: Some foods, such as fruits and some vegetable foods, cannot withstand high temperatures. When heated at high temperatures, the tissue shape of fruits and vegetables becomes soft. The color, aroma and flavor are reduced. Therefore, for this type of highly acidic food, the temperature can be lower than 100 C, and the time depends on the variety and specifications. Usually between 10-30 minutes. However, this temperature and time cannot achieve the purpose of "commercial sterilization" for low-acid canned fruits and vegetables. In order to maintain food quality and achieve sterilization purposes, the low-temperature gap sterilization method can be used, that is, the cans are first sterilized at 60-70°C. After taking it out, place it at room temperature for a certain period of time to allow the remaining microorganisms in the tank to multiply and develop. The cans are then sterilized at low temperatures to achieve the purpose of commercial sterilization.2. High-temperature sterilization method for canned meat, aquatic products and certain vegetables. This type of low-acid food requires higher temperatures because its microorganisms are highly resistant to heat. Usually above 100C, up to 121C. The time should also be extended accordingly. Approximately 60-90 minutes. Long-term sterilization of certain foods will cause great losses in product quality and nutritional content. For this reason, high-temperature short-time sterilization method is also used in the canning industry. The temperature is greater than 121°C, and the commonly used ones are 127C and 135°C. The maximum time is 150C, which takes a few minutes to a few seconds. This kind of sterilization is suitable for fluid foods and rotating sterilization. The installed can has the best sterilization effect.Zhucheng City Jinding Food Machinery Co., Ltd. established in 1996, the company has formed a complete operating system integrating raw material supply, product development, process design, experimental design, finished product inspection, storage and transportation and technical services.We can offer a wide range of sterilization retorts autoclave machines and canning line system, Sumpot team has extensive experience to provide a high-quality solution for pouch loading unloading system; provide professional support and guidance from installation to maintenance and after-sales-service; Sumpot retorts and canning line are made with high-quality components, to reduce the need for costly repairs or replacements.
The types of sterilizing retort suitable for canned sterilization include: double-layer water immersion sterilizing retorts, water spray retorts, steam retorts, steam air retorts etc. The details should be determined according to the outer packaging form of the can. For example, glass bottles should choose an interheating chamber. Cold spray sterilization retorts, etc.
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