Fully cooked, ready-to-eat products continue to increase in popularity among consumers because of their convenience. However, cooking these products requires careful control during the manufacturing process to ensure that the product is not overcooked or undercooked. While overcooking can cause quality deterioration, undercooking can create an unsafe product.
"Food safety is a critical issue, so producers often compensate for natural variability in the product and in the measurement process by overcooking products,” says John Stewart, a senior research engineer in the Georgia Tech Research Institute, Atlanta. “But overcooking wastes energy, degrades product quality, lowers the maximum throughput rate of the production line and decreases product yield.”
At typical production rates of 6,000 lb/hr, the losses from overcooking can have a significant financial impact on producers. Currently, after meat products travel through an oven for cooking, producers randomly test samples with thermocouple insertion probes to ensure that the product reaches the minimum required cooking temperature.
To minimize both undercooking and overcooking, Stewart and his GTRI colleagues built a system that measures the surface temperature and three-dimensional shape of every piece of meat before it enters the oven. Researchers focused on analyzing the product before it goes into the oven because at that stage, there still is time to make changes to the cooking time or temperature to be sure all pieces are cooked adequately, Stewart says. “Once the product comes out of the oven, it’s too late to correct any undercooking.”
The system consists of two commercially available cameras - a wide-area three-dimensional camera and an infrared camera - mounted above a 48" wide processing conveyor belt. Locating individual pieces of meat on the conveyor belt can be challenging because producers often place products very close together to maximize throughput. In addition, thermal cameras sometimes view the product and conveyor belt temperatures as close to the same, which provides little contrast.
By measuring the three-dimensional profile of the meat, the screening system can identify individual products and detect arrangement issues such as overlapping product. Once individual product shapes have been measured, they are compared with a library of previously recorded cooking results for meat products with a similar shape and a cook profile that matches the current oven-cook profile. Thermal heat and mass transfer models, along with the current oven-cook profile, are used to determine whether a particular product will reach the desired end-point temperature.
“The system predicts the percentage of product that will be overcooked and identifies individual pieces of meat or arrangements of products that are likely to undercook,” Stewart says. “In the future, a producer might use this information to fine-tune the product arrangement before it reaches the oven.”
The three-dimensional profiling system and models have been tested using chicken breast filets, and the researchers plan to test the system in a local plant this year. GTRI principal research engineer Wayne Daley and Georgia Tech undergraduate students Chris McClannahan and John Turgeson also contributed to the research.