In some cases cooker operators even had to run their hands through the processed material after it had cooled down to decide if it was ready, Peter Smith told the BSE inquiry in south London.
His testimony adds weight to the contention made by government scientists since December 1987 that inadequate heat treatment failed to kill off the BSE disease agent when infected animals were added to the cookers. The remains were then made into meat and bone meal which was added to cattle feed.
The parlous state of the cookers and the systems used to oversee them still existed in the late 1980s, when the epidemic was at its height, said Mr Smith, who worked at the Ministry of Agriculture, Fisheries and Food (Maff) veterinary investigations centre in Preston. He said there were still inadequate controls at 11 rendering plants which he checked in March and April 1988, three months after the official declaration about the cause of the epidemic.
"Control was left to the experience of the operator," Mr Smith concluded in 1988. "It is surprising the BSE problem has not arisen earlier if batch cooking is a suspect as it is."
The inquiry, set up to investigate the causes of the BSE epidemic and its handling, was adjourned until June. It is due to report to the Government by the end of the year.
n The first prosecution in England for serving beef on the bone has been suspended. Rother council in east Sussex has suspend its case against publican Alan Coomber pending the outcome of the appeal in a similar case in Scotland.