pH of Common Foods

What is pH?

Regarding many of the food safety interventions practiced by many meat processors, a pH fluctuation is often used to to kill bacteria.  Just what is pH and how does it impact various foods?  In the technical sense, this is pH:

\mathrm{pH} = - \log_{10}(a_{\textrm{H}^+}) = \log_{10}\left(\frac{1}{a_{\textrm{H}^+}}\right)

I also realize that this only means something to people who get really jazzed about pH (such as me).  The majority of people probably just care to know that pH is simply a reference for how acidic or alkaline something is.  The pH of food is an incredibly important property.  Not only does it impact a product’s flavor in many way (lemon juice would’t be lemon juice if it didn’t have a relatively low pH), but it also impacts a foods functionality.  pH is very relevant to protein function — it effects how proteins are folded and interact with one another.  pH also outside of a given bacteria’s “comfort zone” means that a tweak in pH, often just a temporary tweak at that, is enough to kill it.  The meat generally buffers the pH swing such that the end pH of the product is hardly changed at all.  An exception, of course, is fermented products like pepperoni or Lebanon bologna for which the reduced pH (acidic) is desired.

Below are some illustrations of the pH scale in relation to different consumer products as well as various foods.  Briefly, pH becomes “basic” or “alkaline” as the pH moves above 7 (which is neutral), whereas pH becomes “acidic” as it moves below 7.

A generic pH scale with reference points of various consumer products. Source: Wikipedia

This image is not one I created and does contain many inaccurate points about meat ... the normal pH of beef, pork and lamb is usually in the neighborhood of 5.6-5.8. I decided to show this image (source: theinformationnetwork.com) to illustrated the wide range in pH among some common foods. Some of the pH differences have likely been exaggerated.

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