The quality problems of canned food caused by low vacuum and expanding can are mainly caused by three aspects: bacterial, chemical and physical. The following are as follows:

 

1. Bacterial bulging tank

 

1. The common microbes of canned food corruption

 

(1) low acid and moderate acid canned foods (PH > 4.5)

 

(1) bacillus thermophilus: thermophilic, flat lid rancidity, acid production, no gas production or trace gas production (low vacuum);

 

2. Thermophilic clostridium difficile: thermophilic, gas producing, not producing H2S, producing acid and expanding tank;

 

3. Clostridium difficile: thermophilic, producing H2S, flat cover or light expansion (low vacuum), blackening;

 

C. Clostridium botulinum: thermophilic, anaerobic, toxin producing, acid producing, gas producing, H2S producing, expansion tank;

 

5. Sporotroph: thermophilic, anaerobic, non toxic, acid producing, gas producing, H2S producing, bulging, and smelly.

 

(2) acid canned food (PH3.7 ~ 4.5)

 

Bacillus coagulis: thermophilic, flat lid rancidity, acid production, no gas production;

 

2. Clostridium barosi, Clostridium butyricum: thermophilic, anaerobic fermentation, O2 (H2);

 

3. Bacillus subtilis, Bacillus subtilis, thermophilic, gas production, acid production, acetone production, ethanol production.

 

(3) high acid canned food (PH < 3.7)

 

Lactobacillus plantarum: thermophilic, non spore producing bacteria, producing acid, producing gas (CO2), expanding the tank;

 

Yeast: ethanol production, gas production (CO2), production of membrane;

 

3. Mold: the surface is long mouldy;

 

(4) pure yellow silk mold and snow white mildew: decomposing pectin, cracking fruit, fermenting gas production (CO2), expanding tank.

 

2. Causes and preventive measures caused by bacterial corruption

 

(1) Tight tinplate empty container, especially double crimping, resistance welding seam should meet the standard requirements, should not use semi-automatic resistance welding machine. The quality of the sealant should be superior, and the location and thickness of the injection should be up to the standard. The whole process of making cans should pay great attention to avoid scratching and scratching plates. Canned food factory should strictly check whether the flange is damaged before sealing, even if there are minor bumps should be removed to ensure that canned food to meet the sealing requirements.

 

The principle of canned food preservation depends on container seal, moderate sterilization, no need and no antiseptic, the finished product reaches commercial asepsis, and can be stored at normal temperature for a long time. Therefore, canned food is very strict in sealing requirements for containers. The container is an important component of canned food. It should be absolutely sealed. The air and microorganism outside the tank can't invade the tank, so that the canned food will not be polluted by two times, and it is corrupt.

 

(2) raw and auxiliary materials used in canned food should be fresh and thoroughly cleaned. Special attention should be paid to reducing the processing time of semi-finished products as far as possible. The raw material should be precooked until the time of sterilization should not exceed 2.5h, and the time of canned cover to the sterilization time should not exceed 30min. Bacteria can proliferate at this time, and the number of bacteria can increase to several hundred times to several hundred times. The more bacteria, the longer the same temperature required to sterilize; the more bacterial spores, the higher the temperature required to sterilize, the longer the sterilization time.

 

Taking Clostridium botulinum No.97 as an example, the time of killing all spores per milliliter at 100 C is as follows:

 

Each milliliter contains 100 times the number of spores to kill the time needed.

 

72 x 109230 ~ 240Min

 

65 x 10480 ~ 85min

 

32835 ~ 40min

 

Raw materials are not fresh, the temperature is high, and the semi-finished product backlog processing time is too long. The canned bone chicken can be produced in a factory. The processing time of the semi-finished product is too long, and it is separated for 145 minutes before being sterilized. Bacteria increased to 520 times the original level, of which Escherichia coli increased to 1600 times the original. As far as canned meat is concerned, the longer the half finished products are waiting for sterilization, the higher the temperature is, the higher the temperature is, the more fast the spoilage bacteria in the tank, such as the bacteria producing pinch bacteria or the weinsteiti, have been killed quickly, although they have been killed by sterilization, but the canned can have low vacuum or light expansion. A large number of dead bacteria can be observed under microscopically.

 

When canned food starts to be sterilized, the maximum tank capacity and initial temperature should be checked regularly. The original process regulations set the maximum amount of solid solids, such as in the actual operation of the amount of more than a lot of fashion tank, still use the original sterilization procedures, it is likely to have incomplete germicidal tank. Physical expansion can also occur due to excessive solid content.

 

It is very important to determine the initial temperature of germicidal sterilizing regularly. The initial temperature set by the sterilization procedure, such as the low initial temperature in the actual production, will produce an incomplete and corrupt bulging tank.

 

Canned sweet corn

 

The initial temperature is 71.1 C, so that the temperature of the center can reach 115 C, which requires 40min

 

The initial temperature is 21.1 C, so that the temperature of the center can reach 115 C, which requires 80min

 

(3) real tank equipment and equipment

 

The production equipment and tools of the tank workshop should be cleaned and disinfected immediately after the end of each production shift, and can be put into production after cleaning before the next production. All equipment must be loaded and unloaded for easy cleaning and disinfection. The weld of equipment and container should be smooth and smooth, so as not to breed bacteria.

 

It is not allowed to use wood, bamboo, cotton fiber and other materials, such as containers and tools. In wet conditions, microorganisms can breed in large quantities and pollute the processed food.

 

Strictly control the number of bacteria in the food tank before sterilization. After that, the bacteria should be measured regularly.