Effects of processing and cooking on PBB residues.

To study the effect of processing on polybrominated biphenyl (PBB) levels, milk from four dairy herds containing less than 0.3 ppm (fat basis) of physiologically incorporated PBBs was presented individually into cream, skim milk, butter, and stirred curd cheese. Pasteurized and freeze-dried whole milk, skim milk, and cream, spray-dried whole milk and skim milk, and condensed whole milk were also made. PBBs were concentrated in the high-fat products. Spray-drying reduced PBBs in whole milk and skim milk while pasteurization, freeze-drying, aging of cheese, and condensation were not effective. To study the effect of cooking on PBB levels, thigh meat, thigh skin, drumstick and breast (with skin) from half of chickens fed PBBs were analyzed raw, and pieces from the other halves were analysed following separate pressure cooking. The level of PBBs expressed as parts per million on a solids basis was lower in the cooked sample than in the corresponding raw piece and part of the PBBs lost were found in the drip. Recoveries of PBBs in cooked tissue and broth ranged from 68.1% in the thigh skin to 84.6% in the drumstick, with approximately two-thirds of the recovered PBBs found in the cooked meat itself. Therefore, pressure cooking resulted in a loss ranging from 36% for the drumstick to 53% for the thigh skin.