Look at the canned food packaging process (on)

Look at the canned food packaging process (on)

Canned packaging containers mainly use tinplate cans, thin-walled glass jars, retort pouches, empty metal cans and empty glass jars, which can be purchased directly from designated manufacturers. The retort pouches can be purchased from prefabricated bags or directly from canning production plants. Empty cans should be inspected before use. It is required that the cans are neat, the welds are completely uniform, the edges of the cans and can ends are not chipped or deformed, and there is no rust and tin removal on the tinned sheets. The glass jar should be neatly shaped, the jar mouth is smooth and smooth, no gap, uniform thickness, no bubbles and cracks in the glass. Some empty cans should be cleaned before being filled, and it should not be left for a long time after cleaning to avoid re-contamination. The production process of canned foods varies with the variety and variety of raw materials, but the basic packaging process is generally: filling, exhausting, sealing, sterilization, cooling, and each process has factors that cause canned food to deteriorate. The main influencing factors are analyzed as follows:

Filling process?

Filling is the loading of the contents into an empty can container. When filling, there must be a certain head gap in the can, the size of which directly affects the capacity of the food in the tank, the degree of vacuum and the deformation of the can after sterilization. If the headspace is too small, the pressure increases due to the expansion of the food during heat sterilization, which tends to cause the bottom cover of the can to protrude outward, and cracks occur; if the headspace is too large, the pressure inside the can is greatly reduced after sterilization and cooling, often the can The body is sunken itself. In addition, due to the large headspace, there is more air in the tank, which is likely to cause oxidative discoloration of the food. The size of the headspace is slightly different depending on the type of raw material, the shape of the tank, and the state of the raw material. Generally, the top gap is 6-8 mm when the can is filled. Keep the edge of the tank clean and dry when filling and salting. Do not stick the raw material or salt to the tank and affect the seal. ?

The can filling is generally performed by a rotary cup type can or a drum type vibration canning, both of which are volumetric. The reason for the unsatisfactory filling amount is that the capacity of the measuring cup is not adjusted correctly, the feeding of the hopper is too slow or unstable, the loading surface of the hopper is too low, the feeding tube is too small, the material flow is unsatisfactory, and the feeding tube and the measuring cup are different. Waiting will make the measuring cups unsatisfactory. If the running speed of the machine is too fast, the speed of the material falling from the hopper will cause the material to be recirculated and the filling amount will be too much; if the measuring cup expansion mechanism is improperly adjusted, it will cause excessive reflow; if the container is not in contact with the feeding tube, the beat is not allowed. If the container is too small or the material sticks to the material tube, the feed delay will cause the material to overflow. ?

Exhaust process?

Exhaust is to remove the air contained in the canned food tissue as much as possible after the food is filled, so that the canned body does not cause excessive pressure in the tank due to thermal expansion of the air during heat sterilization, so that the can body is deformed or the can seam is loose; At the same time, a certain degree of vacuum is formed in the tank, which can inhibit the activity of aerobic microorganisms remaining in the tank, reduce the oxidative corrosion of the tank wall and reduce the oxidation loss of nutrients (especially vitamin C), and better preserve the canned food. The color, fragrance and taste. It is generally required to vent the center temperature in the sealed tank to 70 degrees Celsius to 80 degrees Celsius. ? Tinplate cans are usually vacuumed - the container and contents are placed in a closed volume, the vacuum volume is used to evacuate the closed volume, the air density in the volume is reduced, the vacuum is obtained after sealing, or the steam injection method - with a certain temperature The steam injection bottle mouth of a certain pressure, after the sealing, the steam condenses to form a certain vacuum. Glass bottle cans are commonly used for thermal exhausting method - heating the container and contents before sealing, so that the air density in the bottle is reduced, heat sealed, and vacuum is obtained after cooling. The retort pouch is vacuumed. In order to effectively remove the air in the tank without affecting the quality of the contents, attention should be paid to the venting: the varieties with slow heat transfer should be reheated before refilling, and hot water can be added, and boiling water is added. Exhaust and extend the exhaust time appropriately. The exhaust process must prevent vapor condensation from dripping into the tank. When using the vacuum pumping method, the degree of vacuuming should be controlled according to the shape of the pot, the variety, and the temperature of the added soup. The variety with the soup, the degree of vacuum is too high, the soup is easy to be extracted, too low and often cause insufficient vacuum in the tank. Generally, it is preferred to control the degree of vacuum 40-66.7kga. ? When heating and exhausting, if the exhaust temperature is too high, it will cause the material in the tank to be soft and the net weight is insufficient; if the exhaust is insufficient, the vacuum in the tank is too low, which may cause corrosion of the canned cover, the false expansion tank and the can bone. It can not effectively inhibit the growth of aerobic bacteria remaining in the tank, and will affect the pressure difference inside the tank when the can is sterilized and cooled, and indirectly affect the leakage when the can is sterilized. The main reason is that the temperature of the steam or hot water used does not meet the requirements. ? When vacuuming and exhausting, the main cause of insufficient vacuum is: the pumping rate of the vacuum pump is reduced; the gas path is seriously leaking or the pumping pipe is filled; the vacuum device is out of order; the sealing rubber ring inside the glass cap is damaged. ?

Sealing process?

The sealing is to maintain the vacuum in the packaging container. The food is isolated from the external environment and is no longer caused by the pollution of the outside air and microorganisms. The quality of the sealing does not meet the requirements, and the food will be in contact with the air and oxidized and deteriorated. The tinplate sealing method is a double crimping method in which two pre-flanged can bodies are crimped and hooked to the inner side of the flange-shaped can lid by two wrapping rollers having different groove shapes. The glass jar is mainly screw-sealed - using a jaw, a friction wheel or a friction belt, the metal cap with the claw is rotated relative to the glass bottle with the spiral flange at the mouth and moved axially along the spiral to The top sealant is pressed tightly against the end of the bottle to form a seal. Soft cans are mainly sealed with heat seals. The problems of sealing quality are as follows:

(1) Reasons why the double-side sealing is not strict:

False roll - the curling body hook and the cover hook are not engaged. The problem is the flanging damage caused during the transportation and conveying of the can body. The shape of the can body is not qualified, the rounded edge of the can is defective or damaged, and the can is sealed. The cover is not aligned with the can body, etc. ?

Large sag - when the can is sealed, the edge of the can body or the lid of the can is severely touched, so that the can body and the can lid are not hooked together, and the can body is exposed at the lower part of the hem, because the can body is transported. The flanging damage caused during the conveying process is unsatisfactory in the shape of the flange of the can body, the rounded edge of the can lid is damaged or the rounded edge is too large, and the can lid is not aligned with the can body when sealing. ?

Skip--Because the seam is thicker at the weld, the sealing roller is skipped when it passes through the can weld, and the crimp is not pressed. The reason is that the sealing machine runs too fast, and the two sealing wheel buffer springs are too soft. The seam of the can body is too thick. ?

The crimping is not complete - the partial crimping is not fully compressed due to the slipping of the can lid on the indenter or the poor rotation of the sealing roller, etc., which is characterized in that a part of the bead has a normal thickness and a part is super thick. The reason is that the tray pressure is too small, the size or taper of the can lid and the indenter is not suitable, the indenter is worn, the height of the indenter shaft is improperly adjusted, the spacing between the trays is too large, the tray spring is out of order, and the oil is on the indenter or the tray. The indenter is tilted in the axial direction, and the positioning is not allowed.