Aerobic bacteria and solids in a three-tank, two-pass, counterflow scalder

Scald water and whole carcass rinse samples were collected on 9 different d in a commercial broiler processing plant operating adjacent lines that processed birds from the same flock simultaneously. A conventional, single-tank, two-pass scalder was installed on one line and the other line had a three-tank, two-pass, counterflow scalder in which water mixed across the two lines of carcasses within each tank. Water samples from the turn around point in each tank were analyzed for aerobic bacteria and suspended solids. At the same time that water samples were taken, six carcasses were removed from the processing line immediately after feather removal and rinsed in 100 mL of phosphate-buffered saline; recovered rinse solution was analyzed for aerobic bacteria using a most probable number procedure. Estimated numbers of aerobic bacteria were significantly reduced in the third tank of the counterflow scalder compared to the second tank, or compared to the single tank of the conventional scalder. Despite the differences in aerobic bacteria between scald tanks, numbers of aerobic bacteria in carcass rinses were not affected by scalder design. Organic and total solids were significantly reduced in the third tank of the counterflow scalder compared to the first and second tanks, and in the third tank of the counterflow scalder compared to the conventional scalder. Solids in the third (final) tank of the counterflow scalder were reduced by about 70% compared to the conventional scalder.