A food product is more or less acidic, and its acidity is measured in the amount of H + ions.
An environment with a pH of 7.0 is exactly neutral. Foods with a pH below 7.0 are acidic; a pH above 7.0 is alkaline. The lower the pH, the higher the acidity; the higher the pH, the lower the acidity.
Why does acidity increase conservation?
To multiply, bacterias need an environment whose pH is between 5.5 and 6.5, so close to neutrality. The majority of foods are in these values. When a portion of food becomes acidic, the bacteria will stop their development, that’s why a product is considered stable for a pH lower than 4,5.
What are the ways to lower the pH?
The decrease in pH, and therefore the increase of the acidity of food, is done by additions of vinegar or citrus juice such as lemon. It will, therefore, be preferable to offer lemon pies (pH = 4.2) in the summer menus rather than pastries made with pastry cream or whipped cream (pH between 6 and 6.5), the risk of multiplication of bacteria will be much lower. This parameter is important when outside temperatures are high!
