Hog processors having problems dehairing hogs may find that it is the scalding-not the machinery-that is the problem.
An operations manager for a hog dehairing machinery manufacturer, which has been in business for more than 100 years, recommends that the scalding tub's water temperature be between 138 and 140 F. And, the hog scald time should range be between 61Ú2 and 7 minutes.
While conducting dehairing evaluations in hog plants in Iowa and Missouri, the manager discovered that plants that have dehairing problems generally exhibited uneven water temperatures in their scalding tubs.
"When you have an uneven temperature in the tub because of the misplacement of steam injection or recirculation problems, the tubs may have areas that vary in temperature as much as 2 to 3 F," he said. "When the carcasses pull through the scalding tub in such cases, the water will scald, set the hair, scald and set the hair again. This makes the hair harder to remove."
To ensure consistent water temperature during scalding, processors must have proper recirculation in the tub and must regulate the steam that goes into the heating system.
Hog processors should take care not to have the steam aimed directly into the flow of an oncoming carcass. This can cause one side to get hot spots through over-scalding.
During an evaluation, the manager also uncovered another generally shared problem related to temperature.
"The temperature of the water where the hog enters the tub has the tendency to drop," he pointed out. "A hog enters water, taking BTUs out of the water in order to bring the carcass up to scald temperature. So the infeed into the scald tub in many plants is not hot enough. The infeed into the tub should be a little hotter, maybe 141 F."
A number of hog processing plants in the United States are approaching, or exceeding 1,000 head per hour. Increasing speeds are causing hog processors to overrun the capacities of their dehairing equipment.
"Many hog processing plants have been set up with the biggest machine we make, which gives processors the capacity of 800 head per hour," the manager noted. "When processors start running faster speeds, they are overrunning the machine. Something has to suffer-and that is the quality of the hair removal."
Compensating line speeds
Processors can compensate for increased line speeds in a number of ways, including increasing the temperature in the scalding tub or changing the configuration of the internal parts of the dehairing machine to do a better scraping job.
"Many companies are having problems because they don't maintain the proper water temperature within the dehairing machine itself," he said. "They are trying to operate machines in 125 F water, which resets the hair as it goes through the machine. The water in the dehairing machine shouldn't be anymore than 2 F colder than your scalding temperature. It should be around 140 F."
Some companies allow the hogs to spend too much time-30 to 40 seconds-between exiting the scald tank and entering the dehairing machine.
Processors need to reduce that time to a minimum so carcasses don't cool off and lose surface temperature, which will reset the hair.
It is equally important that processors ensure their dehairing machines have the correct setting of spirals, scrapers (make sure they're stiff enough), shaft RPMs and water temperature in the dehairing machine. Maintenance of the recirculation system within the dehairing machine is also critical.