The behaviour of Salmonella enteritidis phage type 4 in home‐made mayonnaise was studied. Samples of mayonnaise were prepared with different pH values using wine vinegar or lemon juice in order to bring down the pH to 5,4.5,4 and 3.6, inoculate and incubated at 4, 24 and 35d̀C for 5 days. The results showed a better bactericidal activity of the vinegar (acetic acid) than the lemon juice (citric acid), both of these acids being more active at higher temperatures. For preventing salmonellosis transmission by home‐made mayonnaise the use of vinegar as an acidulant in order to achieve a pH between 3.6 and 4 and storage in a warm place is recomme