Review: Fate of pathogens in home-made mayonnaise and related products

Home-made mayonnaise has been associated with outbreaks of food-poisoning due mainly to Salmonella and in some cases eggs have been shown to be the principal source of infection. The survival of Salmonella spp., Clostridium perfringens and Staphylococcus aureus in mayonnaise is influenced by the pH of the mayonnaise and the choice of the acidulant used in preparation. Acetic acid (vinegar) is more germicidal than citric acid (lemon juice). It is recommended that mayonnaise is prepared with vinegar to a pH of 4·1 or less. The addition of garlic or mustard to mayonnaise at concentrations of 0·3-1·5% (w/w) results in an increase in the death rate of Salmonella enteritidis. Salt, on the other hand, has a protective effect on S. enteritidis survival at similar concentrations. The type of oil and vinegar used in mayonnaise preparation also influences the death rate. Storage of mayonnaise at refrigeration temperatures protects Salmonella spp. from acidulants and therefore a holding time of 24 h at 18-22°C is advised before refrigeration. The presence of vegetable material in the mayonnaise has the effect of reducing the toxicity of mayonnaise by absorbing acetic acid.