The research reinforces the 20-year-old European food industry 'CIMSCEE Code' for mathematically predicting the shelf-life of sauces and pickles that use acetic acid.
Work in the applied microbiology department at Lund university found that a small amount of acetic acid actually increased the amount of toxin from the harmful bacteria in the food.
However, if a large amount was added, as is traditional in dressings, sauces, cheeses and pickles, the bacteria did not survive, said researcher Nina Wallin Carlquist.
Carlquist studied the bacteria: Staphylococcus aureus and Campylobacter jejuni in boiled and smoked ham, in Serrano ham and in salami. It only took a few hours for the bacteria to multiply in the boiled and smoked ham, but a week in the Serrano ham. They did not survive at all in salami.