When managing the cold chain, most attention is usually paid once carcasses leave the chiller. Birds are kept within a temperature range that retards bacterial growth, so delivering a product with the necessary shelf life.
However, there several complementary activities that should be monitored if the aim of achieving a good shelf life is to be successfully achieved.
It is worth remembering that a live bird has a body temperature of 40-42C. Post-slaughter, however, the carcass temperature falls. Slaughtered birds lose about 3 percent of their body weight through loss of blood, and this blood loss brings the carcass temperature down to about 38C.
It is also worth keeping in mind the relationship between body temperature and bacterial growth. At 38C, bacterial growth takes place in 15 minutes. At 21C, it takes an hour; at 10C, 2 hours; at 4C, 8 hours; and at 0C, it is slowed to 20 hours.
Given the above, it becomes obvious that processing must be completed without delay, so that birds reach the prechiller within approximately 18 minutes of slaughter.
During scalding, it is essential that any foam -- which is formed by protein in blood plasma mixing with the hot and agitated water -- that accumulates on the water is removed if sanitary conditions are to be maintained.
Should this foam be left in place, material from the esophagus and intestines, which can be rich in pathogens such as Salmonella and Campylobacter, can build up, and this can lead to cross-contamination.
While it is important to remove foam, it is also important to ensure that the water in the tank is replenished. There should be at least one liter of water per bird entering the scalder. Adding water is important for two reasons: It replaces water that has stuck to feathers -- it has been calculated that this can be as much as 60 percent -- but it also helps to keep the bacterial concentration in the water down; it should not be allowed to rise above 40 percent.
Plucking also can have an influence on shelf life. The water used during plucking should be warm, i.e. with a temperature of 34-38C. The pressure of the rubber fingers needs to be carefully adjusted to ensure that not too much pressure is applied, which can result in the contents of the cloaca being evacuated. Should this occur, fecal matter can be deposited in the open follicles once feathers have been removed. During chilling, the follicles will close, trapping and any fecal contamination inside.
Care must also be taken during the evisceration process. Ensuring good feed withdrawal will help to reduce bacterial contamination at this stage, regardless of whether a short or long feed withdrawal has been followed.
The quality of feed withdrawal is important to reduce the risk of bacterial contamination in the processing plant, irrespective of whether a short or long feed withdrawal is implemented. Following a short feed withdrawal, should the crop break, any feed contained therein, and accompanying pathogens, are evacuated. With a long feed withdrawal, the weakening of the intestines - the result of the loss of the mucosa and sub-mucosa - can result in them breaking, leading to serious contamination with feces.
Washing the carcasses, both internally as externally, will help to reduce contamination, as will brushing them. Brushing is effective in removing any residual fecal matter that may have stuck to the skin. It is important that quality control staff check carcasses before they enter the prechiller.
Particular care also needs to be paid at chilling. The length of time spent in the prechiller and chiller the must comply with time established by each individual company. Prechiller time tends to be between 20 and 45 minutes, while time in the chiller varies between 30 minutes and as much as two hours. This longer period occurs when chilling is used to shorten the time that carcasses are kept in cold storage to achieve appropriate rigor mortis.
The water temperature in the prechiller and chiller should be kept within the parameters set by the individual plant or by the health authorities. In many countries, prechiller water is kept at room temperature. However, if the temperatures should be below 24C, warmer water should be added to avoid the carcasses suffering a sudden temperature change, which can damage muscle fibers, so negatively affecting the quality and yield from the processed birds.
Any application of disinfectants during processing must be carried out in the correct manner. A wide range of products is available, and selection will depend on the regulations in place in each country.
Attention also needs to be paid to controlling carcass temperature when birds are exiting the chiller, as it should be kept below 4 C. This not only helps to minimize water loss but also impedes bacterial growth.
The packing, cut-up and deboning sections, which are temperature controlled, are usually kept at a temperature of 8-10C. Care needs to be taken that no bottlenecks occur at this stage, as this will not only result in a loss of water from the bird, the carcass temperature will start to rise, so encouraging bacterial growth.
Packing and storage
When birds are stored in the cold room, they must be positioned in such a way as to facilitate the free movement of air. Additionally, the temperature must remain constant as, should changes occur, bacterial growth will be favored.
When trucks are loaded, the decks must be properly temperature controlled, with a maximum temperature of 10 C, and vehicles must be closely joined to the loading bays.
Trucks must be brought to the correct temperature before they are loaded with birds. The person responsible for authorizing loading needs to check this and, additionally, ensure that the container complies with sanitary and atmosphere requirements.
Once the trucks have been loaded, the data log must be started so that a record is kept of the environmental conditions throughout the journey. Once deliveries have been completed, data needs to be reviewed to ensure that there were no major fluctuations.
It is also worth keeping in mind that, once the day’s operations have been completed, cleaning staff must do a thorough job in ensuring that plant and equipment are properly cleaned and disinfected. A lack of attention at this stage can make the difference between a product that has a good shelf life and one that has a short shelf life.
In summary, to ensure that the cold chain functions as well as it possibly can, possibilities for bacterial growth, and a consequent reduction in shelf life, should be kept to a minimum.