retort machine principle
The principle of the sterilizer is to use the characteristics of bacterial proteins to deteriorate under high temperature and high pressure to make the bacteria lose vitality or reproductive ability. It is not 100% to eliminate bacteria, so the food has a shelf life after sterilization. After a period of time, the bacteria will grow and grow under suitable conditions.
In order to better understand the principle of the retort machine, it is necessary to distinguish the meaning of sterilization, disinfection and sterilization.
Sterilization: A measure that uses strong physical and chemical factors to permanently lose all microorganisms inside and outside of any object to its ability to grow and reproduce, called sterilization.
Disinfection: A method of killing pathogenic microorganisms, but not necessarily killing bacterial spores. Chemical methods are often used to achieve disinfection.
Sterilization: refers to the process of killing pathogenic bacteria in objects, but the objects also contain non-pathogenic bacteria such as spores and thermophiles. The difference between sterilization and sterilization is here.
Sterilize to eliminate all fungi.
Heat sterilization The heat sterilization method uses high temperature to denature all proteins in the microbial cells, and the enzyme activity disappears, causing the cells to die. There are usually dry heat, moist heat, and intermittent heat sterilization.
Dry heat sterilization
The flame burning method or the hot air sterilization method in the oven is called dry heat sterilization. The metalware or the cleaned glassware is placed in an electric oven and maintained at 150-170 ° C for 1-2 hours to achieve thorough sterilization (including spores of bacteria).
Incineration or combustion is one of the most thorough dry heat sterilization methods, and its application range is limited to inoculation rings, sterilization of inoculation needles or materials with pathogens, burning of animal carcasses, etc.
Wet heat sterilization Sterilize with boiling water, steam and steam.
Pasteurization: Because it was first used by the French microbiologist Pasteur for the disinfection of fruit wine, hence the name. This is a low-temperature disinfection method for liquid flavored foods or seasonings that are not suitable for high temperature sterilization such as milk, beer, fruit wine or soy sauce.
Pasteurization is wet heat sterilization
There are two ways to do this.
1 classic low temperature holding method (LTH): treatment at 61.7 ~ 62.8 ° C for 30 minutes;
2 More modern high temperature transient method (high temperatureshorttime or flushpoint, HTST): 15 minutes at 71.6 ° C or slightly higher temperature. Among the above methods, steam sterilization is best, and it can be sterilized by atmospheric pressure steam or in a high pressure steamer (usually 1 kg/cm).
2) Sterilization, the vapor temperature can reach 121 °C, and all the heat-resistant spores can be killed within 30 minutes. However, some substances that are easily destroyed by high pressure, such as certain sugars or organic nitrogen compounds, should be sterilized at a pressure of 0.6 kg/cm 2 (110 ° C) for 15 to 30 minutes.
Boiling disinfection method: using a method of boiling at 100 ° C for several minutes, generally used for disinfection of drinking water.
Intermittent sterilization Intermittent sterilization is a method of steam sterilization once a day for 3 days. This method is applicable to substances that cannot withstand temperatures above 100 °C and some sugar or protein substances.
It is usually sterilized by steam for 1 hour under normal atmospheric pressure. The sterilization temperature does not exceed 100 ° C, and does not cause damage to substances such as sugars, but the spores that are germinated during the intermittent culture can be killed to achieve the purpose of thorough sterilization.
Radiation sterilization A method of sterilizing by radiation under certain conditions. More commonly used are ultraviolet rays, others have ionizing radiation (rays speed up neutrons, etc.). Lasers with wavelengths between 25,000 and 80,000 nanometers also have strong bactericidal power and are most effective at wavelengths of 26,500 nanometers. Radiation sterilization is limited to a certain material, and it is difficult to use it widely because of the complicated equipment required.
Osmotic pressure sterilization
Osmotic sterilization is a method of sterilizing using a high osmotic pressure solution. In a high concentration of salt or sugar solution, the cells undergo plasmolysis due to dehydration, and normal metabolism cannot be performed, resulting in the death of microorganisms.
Chemical reagent sterilization
Most chemicals have a bacteriostatic action at low concentrations and a bactericidal effect at high concentrations. Commonly used 5% carbolic acid, 70% ethanol and ethylene glycol. The chemical bactericide must be volatile to remove any residual material from the sterilized material. Commonly used reagents for chemical sterilization include surface disinfectants, antimetabolites (sulfonamides, etc.), antibiotics, and biopharmaceutical antibiotics, which are synthetic secondary metabolites or artificial derivatives in the process of microbial or other biological life activities. They can inhibit or infect the life activities of their organisms (including pathogens, viruses, cancer cells, etc.) at very low concentrations and can therefore be used as excellent chemotherapeutic agents. retort machine is the most commonly used heat sterilization method. It is safe and reliable, and is especially safe for food. It is widely used.
Definition of bactericidal strength (F) The heating time required to kill a certain concentration of microorganisms under a certain temperature of lethal temperature (minutes) The corresponding temperature change (°C) TZ value of the Z value thermal lethal time according to 10 times change The inherent characteristics of microorganisms, the Z value of different microorganisms is different from the relationship between F0 and Dr; F0=Dr(loga-logb)=nDr
Relationship between F value and Z value: F=t×10(T-121.1)/Z
t: set holding time T: set holding temperature t: actual sterilization time T: actual sterilization temperature
The meaning of the formula: It can be determined that the sterilization time required to achieve the same or equivalent sterilization intensity at a fixed sterilization temperature can be achieved at a fixed sterilization time to achieve the same or equivalent sterilization intensity. Relationship between sterilization temperature and L value
t: actual sterilization time (minutes) T: actual sterilization time (°C)