Poor harvesting and handling of chickens can result in bruises and other damage to birds, thus devaluing the carcass.
Each and every day, the processing industry sends large amounts of chicken that could be sold for human consumption to the rendering plant, where it is transformed into meal and fat.
To counter this costly situation, some processing plants have tightened controls, in an attempt to send to the rendering plant only those materials that should be sent there – i.e., material that is unfit for human consumption.
There are, of course, many materials that originate at the processing plant that should be sent for rendering. For example:
- Blood
- Feathers
- Viscera unsuitable for human consumption
- Birds that are dead on arrival
- Small chickens – under 800 grams
- Birds with pododermatitis problems
- Livers and hearts condemned because of sanitary problems
- Condemned parts due to quality issues: red neck, bruises and trauma
- Bones from the deboning machine
While the above should find their way to the rendering plant, other materials are also sent there, too, and these can include meat that should be classified as Grade A. For example:
- Whole and parts of birds
- Offal, either complete or partial
- Product returns from customers
- Products that have been damaged while stored
In addition to organic material, if a processing plant is poorly controlled, other materials can find their way to the rendering plant, and these might include rubber gloves, bags, rubber fingers and even knives. Any of these objects can have serious consequences for the quality of meal produced.
Communication
Rendering operations tend to be carried out in two ways: either close to the processing plant, making rendering the last stage in the broiler production business; or as a third-party service, where the operator receives raw material from a number of different processing plants.
It is important that there are good lines of communication between the processing plant and whoever may be carrying out rendering operations. In particular, communications needs to be frequent enough so that information can be easily exchanged, problems identified, and the yields of both operations maximized. Perhaps surprisingly, communication can be particularly poor when both activities are carried out by the same company.
I have seen in many plants that feedback is often partial and sporadic, rather than being established as part of everyday working practice. It is somewhat of a contradiction that within “poultry integrators,” where there should be good communication to allow the various stages of broiler production to be modified to maximize the quantity and quality of production, that not only waste is sent for rendering.
In order to minimize what ends of up at the rendering plant, it is worth looking in more detail at the types of material that are sent to the rendering plant and what acceptable levels for these types of material might be.
Chickens dead on arrival
Dead on arrival birds result in a loss of 85 percent of saleable meat – the carcass and the giblets. In hot climates, dead on arrival birds should not be in excess of 0.7 percent of the total number of birds received in a day, while in cold climates the amount should be below 0.5 percent.
Expressed in numerical terms, imagine that a plant slaughters 100,000 chickens each day. Dead on arrival as a result of climate should not be above 70 birds in hot climates and be below 50 birds each day in cold countries.
Bruises and trauma
When bleeding is not properly carried out, the value of birds is again reduced.
Birds can be bruised when they are poorly harvested on the farm. In addition, bruising can also happen in the receiving area of the processing plant and when hanging onto the overhead conveyor.
Processing
The first area during processing that should be producing raw material for rendering is the slaughter and bleeding tunnel. Some 45-50 percent of a bird’s blood is drained at this stage – some 7 percent of total body weight.
However, if this process is not carried out properly, and chickens have not been properly bled, they may enter the scalder alive, with death resulting by drowning rather than by anoxia. When this occurs, the performance of the processing plant goes down and the volume of material sent for rendering increases.
The amount of waste produced at scalding can also increase if birds are kept for too long in the scalding tank. Over-scalding can result in the loss of 85 percent of meat suitable for human consumption.
A similar situation can occur during plucking. Carcasses may fall from the plucking line for a variety of reasons. If there is inadequate infrastructure to prevent them being removed along with the feathers, quality carcasses may be lost to the rendering process, increasing costs for the processing plant. Under normal conditions, only the feathers should be sent to rendering at this stage, accounting for 5.5 percent of total live weight.
The next stage in the process is evisceration, where giblets are removed from the carcass for either human consumption or industrial use. Once removed, giblets need to be sent to the chiller as quickly as possible to prevent the growth of bacteria. When this does not occur, the 6.5 percent that should be sent to rendering – i.e. the crop, trachea, upper-intestinal tract, spleen, vent, etc. – increases to include the liver, head, gizzard and neck.
When birds have undergone a long feed withdrawal, an issue that rises is the adhesion of the gizzard cuticle, and this results in costly additional removal costs. This can also result in meat entering the wastewater that leaves the processing plant and can build up in the filters through which this water passes.
While demand for paws from China has allowed this part of the bird to be commercialized, a large number are still lost due to fungal infections, and this results in extra material entering the rendering process.
Rendering plants ought really to be receiving only those waste products that are produced under normal conditions. This can be summarized as blood, feathers and innards, which account for some 15 percent of the bird.
Daily amounts processed
The wet percentages processed depend on each plant and its particular processes for the transport of subproducts, the amount of water used, its equipment, and the conscientiousness of the processor in understanding that water must be removed at the processing plant.
As a percentage of the total number of birds processed, processing plants should receive no more than the following of saleable product:
- Drowned chickens 0.07
- Bruised birds 0.03
- Poorly bled 0.03
- Over-scalded 0.01
- Damaged at plucking 0.02
- Condemned giblets 0.005
- Losses during processing 0.005
- Total 0.17
As a final thought, it would be worth considering whether the water used in the chillers, which is rich in residues, could, through careful filtration, supply an additional rich subproduct. Renderers should keep a careful eye on this possibility. Achieving this would also reduce wastewater treatment costs.