In this month’s installment of Periodic Graphics in C&EN, we’re talking canning chemistry. When you’re canning vegetables and making chutneys, why does the acidity matter, and what’s the importance of temperature in the canning process? This graphic takes a brief look – see the full graphic over on the C&EN site.
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3 replies on “The Chemistry of Canning – in C&EN”
Two questions:
1) The Acidity pane says “low-acid foods need to have acid added (..)”, but the High-acid foods pane mention “Fruits and foods with added acid”. Is this right? I feel it is inverted, but I could be wrong.
2) The temperature range has a 5-60°C; shouldn’t it be 20-60°C (or another range starting after 20°C)?
Hi Ricardo, thanks for the questions – hopefully I can clarify!
1) This is correct. It’s intended to imply foods such as pickles, etc, which already have acid added. I think it would be clearer with a comma after fruits, perhaps, though that may have been omitted due to the C&EN style. Can’t remember if it was there before edits or not!
2) The danger zone temperature is from 5–60˚C. This, it’s worth noting, is for perishable foods before preserving. Once foods are canned, they should be stored in the optimum temperature range, 5–20˚C. Since they have been sterilised, there is no danger of microorganisms continuing to grow, even if the storage temperature is within the danger zone. Again, I can see how this one could be misconstrued – it was something we discussed in the editing process, but perhaps it can be made clearer still.
Hope that helps!
Thank you! These points indeed clarified things. 🙂