 In 1976 there were serious salmonellosis outbreaks on four flights to and from Spain which caused 500 cases and 6 fatalities.In the US, 404 people became ill and nine died in a New York City hospital due to hospital-prepared mayonnaise.In all salmonellosis cases, the major reason was inadequate acidification of the mayonnaise, with a pH higher than the recommended upper limit of 4.1, with acetic acid as the main acidifying agent.