Modelling the pH of mayonnaise by the ratio of egg to vinegar

The relationship between the ingredients and pH of home-made mayonnaise and its safety has been investigated. It has been found that the pH of mayonnaise is mainly determined by the ratio of egg to vinegar and drops as the ratio decreases. Although egg yolk, egg white and whole egg have different pH values, they have an identical effect on the pH of mayonnaise when the ratio is less than 2.5. Salt and sugar decrease while oil, mustard and pepper increase the pH of mayonnaise. A formula to estimate pH of a mayonnaise recipe is proposed and validated. By using the validated formula and a safe pH value (4.10 or 4.00) for mayonnaise, it is concluded that a mayonnaise recipe is safe only if its ratio of egg to vinegar is equal to or less than its safe ratio. To make safe mayonnaise in the kitchen, it is recommended that at least 20 ml vinegar (6% w/v acetic acid) per fresh egg yolk, 40 ml per fresh egg white or 60 ml per fresh whole egg should be used. After preparation, the product should be held at 20°C or above for at least 48 h before refrigeration or consumption.