pH level (Acidity)pH is a measure of how acidic something is, and it runs on a scale of 0 to 14. Anything lower than 7 is considered acid and anything higher than 7 is considered base or alkaline. A value of 7 would be considered neutral. Ordinary water, for example, has a pH of 7.
As it turns out, bacteria can't stand anything too acidic or too alkaline. For bacteria to thrive, the pH environment needs to be neutral. Well, guess what foods fall into that category? Yep — animal based products like seafood, meat, poultry, eggs and milk.
By contrast, most vegetables and pasta have a very high pH when uncooked, but turn neutral — hence, more hazardous — when cooked. Highly acidic foods such as citrus, tomatoes, apples, vinegar, berries and so on, are relatively unattractive to bacteria from a pH standpoint. They'll grow, it just takes a lot longer.
ConclusionsIt may seem like there are a lot of ways to control the growth of bacteria in our food — and technically, it's true. But we can't control time. It keeps ticking away no matter what.
And while we can change the moisture and acidity levels of foods, relying on that method alone would mean eating a lot more chicken jerky and pickled eggs. For that reason, temperature really is the most crucial element in controlling the spread of food-borne illness.
Here's a table showing the key temperatures of the Temperature Danger Zone.