Scientific Abstract:
This research project addressed a critical knowledge gap surrounding the disposal of pig carcasses subjected to gas-filled or water-based foam depopulation methods in the United States. Since the rendering industry’s hesitancy to accept foam-depopulated pig carcasses is due to uncertainties about potential residues in rendered products, three foams were fully characterized to find compounds that were suitable as markers for the detection of foam residues in pig tissues. The foams were then used to humanely kill experimental groups of pigs with nitrogen-gas-filled foam. Tissues from foamed pig carcasses, snout, ears, skin, and feet, were collected, weighed, and cooked at times, temperatures, and conditions to simulate rendering to determine if any residues persist in rendered products. To determine if cooking eliminated or reduced the levels of foam, as ascertained by the detection of the suitable identified ion chemical markers, samples were tested in triplicate as raw and after cooked. Cooking was conducted in a commercial stove in a meat science laboratory at conditions that mirrored rendering, with tissues being primed with hot yellow pork grease and cooked to pathogen-killing temperatures for a sufficient duration (130°C (265°F) for 75 minutes). Raw samples and cooked tissues, after removing from fat, were extracted, and tested for the presence of the chemical ion markers using light chromatography-mass spectroscopy (LC-MS) at a food research laboratory. Levels obtained by LC-MS were adjusted for tissue weights to calculate mg/g of the identified marker of foam/tissue. Results of LC-MS demonstrated that after cooking tissues at conditions equivalent to rendering, foam residue chemical marker levels were reduced 3-fold, often to levels below detectable limits. Positive control ear sections soaked in water-based foams had detectable foam residue chemical markers at minimal levels in the raw samples that were reduced or non-detectable after cooking. There were low or non-detectable levels of foam residue chemical markers in both the raw and cooked samples for two of the three foams. After cooking, the skin, the largest organ of the body and the organ in most contact with foam, from foamed carcasses, had levels that ranged from non-detectable (*) to 0.02 (0.01 mg/g average). Since the majority of the cooked samples tested had no to minimally detectable chemical markers of foam residues, it may be possible in the future to implement procedures to prevent even low-level foam residues, such as rinsing the external surfaces of the carcasses of pigs humanely killed by foaming before grinding and rendering. If carcasses of foamed pigs can be rendered, the cost-savings and resource-sparing would be substantial and limit the additional losses due to depopulation by providing an alternative method of disposal.
