Periodic graphics: The chemistry of canning | September 12, 2016 Issue - Vol. 94 Issue 36 | Chemical & Engineering News
Volume 94 Issue 36 | p. 29
Issue Date: September 12, 2016

Periodic graphics: The chemistry of canning

Chemical educator and Compound Interest blogger Andy Brunning packs in the science involved in preserving your home-grown fruits and veggies
By Andy Brunning
Department: Science & Technology
News Channels: Analytical SCENE, Biological SCENE, Organic SCENE
Keywords: canning, canned goods, acidity, botulinum, citric acid, fruits, vegetables, pH

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To see more of Brunning’s work, go to To see all of C&EN’s Periodic Graphics, visit

This article has been translated into Spanish by and can be found here.

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Steve Stewart (September 12, 2016 2:10 PM)
Are tomatoes considered to be low acid foods?
Andy Brunning (September 13, 2016 5:30 PM)
They're pretty much on the borderline. I've included them as low acid foods here because they can require addition of acid to be below pH 4.6. An element of safe advice here too – I don't want to go telling people tomatoes are always high acid foods when some varieties may not be!
Steve Stewart (September 15, 2016 11:45 AM)
Years of pH readings from thousands of tons of processing tomatoes in CA average below 4.6. This information is available from the Processing Tomato Advisory Board, I guess there is the chance for some being above 4.6.
Cody L Custis (September 12, 2016 2:25 PM)
Interesting to think that the C. Botulinum spores are common (even in soil), but without the proper conditions to germinate, they are harmless.
irenanesic (September 21, 2016 8:36 AM)
there are no high-acid and low acid food or anything else.

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