A dual cooling tunnel arrangement for cooling viscous heated fluid foodstuffs in flexible bags. The flexible bags containing the heated fluids are received on pivoted wire carriers which are driven by an endless chain through an upper cooling tunnel in a first direction and returned through a second cooling tunnel in the opposite direction. In each cooling tunnel, a cooling water spray is directed on the bags in the carriers as the carriers are slowly rocked, causing the fluid in each bag to flow to different areas of the bag, altering its shape, to produce enhanced heat transfer rates and a more uniform temperature distribution throughout the fluid during cooling.