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It takes some work to find a list of the actual pH of various foods. (Searches are confounded by a popular "alkaline diet" theory that the pH effect on a human body of consuming various foods is not a function of the pH of the food itself.)

It appears that almost all food has pH < 7.0 (most much lower), and I can't find any with pH > 7.5.

Is there a biochemical reason that there is no significantly alkaline food?

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  • $\begingroup$ Apparently lutefisk is edible with a pH well above 8. (Preparation pH is in the 11 to 12 range.) $\endgroup$ – Ed V Sep 7 at 21:22
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    $\begingroup$ Counting lutefisk a food is quite a stretch, as to me. Now to the point. Our world is acidic. An acid will stay unchanged for pretty long, but any alkaline solution will quickly get neutralized by $\ce{CO2}$. $\endgroup$ – Ivan Neretin Sep 7 at 21:44
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    $\begingroup$ Proteins don't like alkalines. Our world is an oxgen world. Oxidation of organic substrates gives acids. $\endgroup$ – Karl Sep 7 at 22:23
  • $\begingroup$ So no need to mention Icelandic Hákarl, which is reputedly high in ammonia content, but, properly prepared, is not poisonous! ;) $\endgroup$ – Ed V Sep 7 at 22:41
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    $\begingroup$ How about the common celery, which normally has a pH of 5.7 to 6.0 (see engineeringtoolbox.com/food-ph-d_403.html ). However, as it has a water content of 95% (per livescience.com/…. ), celery grown in alkaline soil and watered with alkaline water, may actually have a pH over 7. $\endgroup$ – AJKOER Sep 7 at 23:32
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Most people find alkaline taste bitter and "bad tasting". There are some exceptions; shellfish, particularly conch, may have a pH of more than 8.0. This is also the approximate pH of bile, which tastes particularly foul when retching.

Crackers made with baking powder or baking soda also may be somewhat alkaline, as is egg yolk.

However, your question is valid... why are the vast majority of foods neutral or somewhat acidic? Why do most enjoy the taste of grapes, plums and citrus fruits, which may have pH below 3.0? Does it have to do with metabolism? With the preservative effects of low pH?

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